Patent Publication Number: US-10787465-B2

Title: Lanthanide toolbox for organelle specific molecular imaging with multi-color

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application claims priority from and the benefit U.S. Provisional Patent Application Ser. No. 62/579,915 filed on Nov. 1, 2017, the disclosure of which is hereby incorporated by reference in their entirety. 
    
    
     FIELD OF INVENTION 
     The present disclosure relates to a cyclen-based lanthanide complexes, which exhibit specific subcellular localization in the primary cilium. The present disclosure has applications in organelle specific imaging and/or tagging/pull down. 
     BACKGROUND OF INVENTION 
     The primary cilium is a solitary, non-motile microtubule-based organelle that protrudes outwards from the surface of most normal eukaryotic cells. Upon in-depth investigation, it has been found to participate actively in various intercellular signaling pathways in mammals, e.g. Hedgehog (Hh), Wingless (Wnt) and PDGFRa, for cell migration, homeostasis, and cell cycle regulation. It also functions as the multisensory antenna of the cells towards external stimuli, such as chemical, temperature, and pressure stimuli. 
     Recently, a renaissance on the research of its structure was initiated by substantial new and overwhelming evidence in support of its significant correlation with many human diseases and developmental disorders (collectively known as ciliopathies). For instance, dysfunctions of primary cilium signaling have been found to correlate strongly in human polycystic kidney diseases, epithelial ovarian cancer, as well as aberrant skeletal development; the absence of primary cilia and overexpression of proteins nearby have also well been observed throughout the stages of pancreatic, breast, and prostate tumorigenesis. 
     That said, very little have the roles of primary cilium been clearly and fully known so far, with the lack of direct and specific imaging methods, for example visible-to-near-infrared fluorescence imaging and magnetic resonance imaging, being a critical factor. There are so many organelle-specific markers currently available for mitochondria, Golgi apparatus, and lysosome; however, visualization of primary cilia, to date, can only be achieved through immunostaining using antibodies or green fluorescent proteins, as no primary cilium-specific probes have been reported in literature. Such two indirect means are always challenged with fixation and delivery issues, while auto-fluorescence is inevitable and the amount of information obtained through them is limited. 
     To address all the above problems, using a direct and specific imaging tool incorporated with lanthanide ions is a promising solution. The long emission lifetimes (micro to millisecond region), hypersensitive, sharp and fingerprint spectral profile of europium, paired with a time-gated system, can effectively eliminate the interfering autofluorescence as well as allowing the specific imaging of primary cattail in a time-resolved manner in vitro or in vivo. 
     Therefore, it turns out to be a need for simplicity of the design and synthesis of a complex which exhibits the specific subcellular localization in the primary cilium and is optionally capable of protein targeting, tagging and/or pull down. 
     Citation or identification of any reference in this section or any other section of this application shall not be construed as an admission that such reference is available as prior art for the present application. 
     SUMMARY OF INVENTION 
     Accordingly, provided herein are cyclen-based lanthanide complexes, which exhibit specific subcellular localization in the primacy cilium. The landthanide complexes provided herein can be used for primary cilium imaging as well as primary cilium tagging and/or pull down experiments. 
     In a first aspect, provided herein is a compound represented by formula (IV): 
                         
wherein m is an integer selected from 0, 1, 2 or 3;
 
X is a pharmaceutically acceptable anion;
 
Ln is Eu, Tb, Gd, Yb, Er, Dy, Sm, La, Ce, Pr, Nd, Pm, Tm or Y;
 
A 1  is C, N, or Si;
 
R 1 , R 2  and R 3  are independently selected from the group consisting of —N(R 12 ) 2 ;
 
                         
R 4 , R 5 , R 6 , R 7 , R 8 , R 9  and R 10  are independently selected from the group consisting of H, alkyl, —CF 3 , —OR 12 , and —N(R 12 ) 2 ;
 
R 11  is hydrogen, alkyl, aryl ether, —CO 2 R 13 ; or —NH(C═O)R 14 ;
 
R 12  and R 13  for each instance is independently selected from the group consisting of hydrogen and alkyl;
 
R 14  is alkyl, cycloalkyl, aryl, or heteroaryl; and
 
n is a whole number selected from 1-8, wherein one of R 1 , R 2  and R 3  is not N(R 12 ) 2 .
 
     In a first embodiment of the first aspect, provided herein is the compound of the first aspect, wherein R 1  and R 3  are independently —N(H)(alkyl). 
     In a second embodiment of the first aspect, provided herein is the compound of the first embodiment of the first aspect, wherein A 1  is C. 
     In a third embodiment of the first aspect, provided herein is the compound of the first embodiment of the first aspect, wherein n is 4, 5, or 6. 
     In a fourth embodiment of the first aspect, provided herein is the compound of the third embodiment of the first aspect wherein R 11  is —NH(C═O)Ar. 
     In a fifth embodiment of the first aspect, provided herein is the compound of the first aspect, wherein the compound is represented by the formula (V): 
                         
wherein m is an integer selected from 0, 1, 2 or 3;
 
X is a pharmaceutically acceptable anion;
 
Ln is Eu, Tb, Gd, Yb, Er, Dy, Sm, La, Ce, Pr, Nd, Pm, Tm or Y;
 
R 2  is selected from the group consisting of:
 
                         
R 12  for each instance is independently alkyl; and
 
n is a whole number selected from 1-8.
 
     In a sixth embodiment of the first aspect, provided herein is the compound of the fifth embodiment of the first aspect, wherein each instance of R 12  is tert-butyl. 
     In a seventh embodiment of the first aspect, provided herein is the compound of the sixth embodiment of the first aspect, wherein n is 4, 5, or 6. 
     In an eighth embodiment of the first aspect, provided herein is the compound of the first aspect, wherein the compound is selected from the group consisting of: 
                                           
wherein Ln is Eu, Tb, Gd, Yb, Er, Dy, Sm, La, Ce, Pr, Nd, Pm, Tm or Y; and
 
X is a pharmaceutically acceptable anion.
 
     In a ninth embodiment of the first aspect, provided herein is the compound of the first aspect, wherein the molecule selectively binds to primary cilium. 
     In a second aspect, provided herein is a method for imaging primary cilium in a biological cell comprising the steps of contacting the biological cell with the compound of the first aspect and imaging the biological cell. 
     In a first embodiment of the first aspect, provided herein is the method of the first aspect, wherein the imaging is performed using linear fluorescence microscopy using UV light excitation or a two-photon confocal laser scanning microscope. 
     In a second embodiment of the first aspect, provided herein is the method of the first aspect, wherein the imaging is done in living biological cells. 
     In a third aspect, provided herein is a method for preparing a compound of the eighth embodiment of the first aspect, comprising the step of 
     a) contacting a compound of formula (VI): 
                         
with a compound selected from the group consisting of:
 
                         
thereby forming the compound of the eighth embodiment of the first aspect.
 
     Throughout this specification, unless the context requires otherwise, the word “include” or “comprise” or variations such as “includes” or “comprises” or “comprising”, will be understood to imply the inclusion of a stated integer or group of integers but not the exclusion of any other integer or group of integers. It is also noted that in this disclosure and particularly in the claims and/or paragraphs, terms such as “included”, “comprises”, “comprised”, “comprising” and the like can have the meaning attributed to it in U.S. Patent law; e.g., they can mean “includes”, “included”, “including”, and the like; and that terms such as “consisting essentially of” and “consists essentially of” have the meaning ascribed to them in U.S. Patent law, e.g., they allow for elements not explicitly recited, but exclude elements that are found in the prior art or that affect a basic or novel characteristic of the present invention. 
     Furthermore, throughout the specification and claims, unless the context requires otherwise, the word “include” or variations such as “includes” or “including”, will be understood to imply the inclusion of a stated integer or group of integers but not the exclusion of any other integer or group of integers. 
     The term “alkyl” is art-recognized, and includes saturated aliphatic groups, including straight-chain alkyl groups, branched-chain alkyl groups, cycloalkyl (alicyclic) groups, alkyl substituted cycloalkyl groups, and cycloalkyl substituted alkyl groups, in certain embodiments, a straight chain or branched chain alkyl has about 30 or fewer carbon atoms in its backbone (e.g., C 1 -C 30  for straight chain, C 3 -C 30  for branched chain), and alternatively, about 20 or fewer. Likewise, cycloalkyls have from about 3 to about 10 carbon atoms in their ring structure, and alternatively about 5, 6 or 7 carbons in the ring structure. 
     The term “aryl” is art-recognized and refers to 5-, 6- and 7-membered single-ring aromatic groups that may include from zero to four heteroatoms, for example, benzene, naphthalene, anthracene, pyrene, pyrrole, furan, thiophene, imidazole, oxazole, thiazole, triazole, pyrazole, pyridine, pyrazine, pyridazine and pyrimidine, and the like. Those aryl groups having heteroatoms in the ring structure may also be referred to as “aryl heterocycles” or “heteroaromatics.” The aromatic ring may be substituted at one or more ring positions with such substituents as described above, for example, halogen, azide, alkyl, aralkyl, alkenyl, alkynyl, cycloalkyl, hydroxyl, alkoxyl, amino, nitro, sulfhydryl, imino, amido, phosphonate, phosphinate, carbonyl, carboxyl, silyl, ether, alkylthio, sulfonyl, sulfonamide, ketone, aldehyde, ester, heterocyclyl, aromatic or heteroaromatic moieties, —CF 3 , —CN, or the like. The term “aryl” also includes polycyclic ring systems having two or more cyclic rings in which two or more carbons are common to two adjoining rings (the rings are “fused rings”) wherein at least one of the rings is aromatic, e.g., the other cyclic rings may be cycloalkyls, cycloalkenyls, cycloalknyls, aryls and/or heterocyclyls. 
     Other definitions for selected terms used herein may be found within the detailed description of the present invention and apply throughout. Unless otherwise defined, all other technical terms used herein have the same meaning as commonly understood to one of ordinary skill in the art to which the present invention belongs. 
     Other aspects and advantages of the present invention will be apparent to those skilled in the art from a review of the ensuing description. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
       The patent or application file contains at least one drawing executed in color. Copies of this patent or patent application publication with color drawing(s) will be provided by the Office upon request and payment of the necessary fee. 
       The above and other objects and features of the present invention will become apparent from the following description of the present invention, when taken in conjunction with the accompanying drawings, in which: 
         FIG. 1A  shows the chemical structures and emission spectra of HGEu001 in aqueous solution (10 μM and λ ex =340 nm). 
         FIG. 1B  shows the chemical structures and emission spectra of HGEu002 in aqueous solution (10 μM and λ ex =340 nm). 
         FIG. 2A  shows Linear fluorescence microscopy images of the red emission from HGEu001 (dosage concentration=10 μM, λ ex =375 nm, band pass=610-630 nm) after 6 hours exposure in HeLa cells. 
         FIG. 2B  shows Linear fluorescence microscopy images of the red emission from HGEu001 (dosage concentration=10 μM, λ ex =375 nm, band pass=610-630 nm) after 6 hours exposure in HeLa cells. 
         FIG. 2C  shows Linear fluorescence microscopy images of the red emission from HGEu001 (dosage concentration=10 μM, λ ex =375 nm, band pass=610-630 nm) after 6 hours exposure in HeLa cells. 
         FIG. 2D  shows Linear fluorescence microscopy images of the GolgiTracker® Oregon Green (W6748, Wheat Germ Agglutinin) dosed in HeLa cells (50 nM, λ ex =488 nm, band pass=505-555 nm. 
         FIG. 2E  shows Linear fluorescence microscopy images of the LysoTracker® Green DND-26 (L-7526) dosed in HeLa cells (50 nM, λ ex =488 nm, band pass=505-555 nm). 
         FIG. 2F  shows Linear fluorescence microscopy images of the MitoTracker® Green FM (M-7514) dosed in HeLa cells (50 nM, λ ex =488 nm, band pass=505-555 nm). 
         FIG. 2G  shows Linear fluorescence microscopy merged images for  FIGS. 2A and 2D . 
         FIG. 2H  shows Linear fluorescence microscopy merged images for  FIGS. 2B and 2E . 
         FIG. 2I  shows Linear fluorescence microscopy merged images for  FIGS. 2C and 2F . 
         FIG. 3A  shows the two-photon time lapses in vitro images of HGEu001 in HeLa cells of which the images were taken at 3 hours incubation time points. The red emission of HGEu001 (arrows) is localized in primary cilium. 
         FIG. 3B  shows the two-photon time lapses in vitro images of HGEu001 in HeLa cells of which the images were taken at 6 hours incubation time points. The red emission of HGEu001 (arrows) is localized in primary cilium. 
         FIG. 3C  shows the two-photon time lapses in vitro images of HGEu001 in HeLa cells of which the images were taken at 18 hours incubation time points. The red emission of HGEu001 (arrows) is localized in primary cilium. 
         FIG. 3D  shows the two-photon time lapses in vitro images of HGEu001 in HeLa cells of which the images were taken at 24 hours incubation time points. The red emission of HGEu001 (arrows) is localized in primary cilium. 
         FIG. 3E  shows the overlay images of fluorescence channel shown in  FIG. 3A  and bright field channel (Dosed concentration=10 μM, λ ex =700 nm, filter Bandpass=550-665 nm). The red emission of HGEu001 (arrows) is localized in primary cilium. 
         FIG. 3F  shows the overlay images of fluorescence channel shown in  FIG. 3B  and bright field channel (Dosed concentration=10 μM, λ ex =700 nm, filter Bandpass=550-665 nm). The red emission of HGEu001 (arrows) is localized in primary cilium. 
         FIG. 3G  shows the overlay images of fluorescence channel shown in  FIG. 3C  and bright field channel (Dosed concentration=10 μM, λ ex =700 nm, filter Bandpass=550-665 nm). The red emission of HGEu001 (arrows) is localized in primary cilium. 
         FIG. 3H  shows the overlay images of fluorescence channel shown in  FIG. 3D  and bright field channel (Dosed concentration=10 μM, λ ex =700 nm, filter Bandpass=550-665 nm). The red emission of HGEu001 (arrows) is localized in primary cilium. 
         FIG. 4A  shows the co-staining experiments of red HGEu001 in fluorescence microscope with marked distance for primary cilium (Green line) (Dosed concentration 10 μM HGEu001, 6 hours incubation after GFP-ARL13B was transfected and expressed). 
         FIG. 4B  shows the green GFP-ARL13B in fluorescence microscope with marked distance for primary cilium (Green line). 
         FIG. 4C  shows the overlay of  FIGS. 4A and 4B  in fluorescence microscope with marked distance for primary cilium (Green line). 
         FIG. 4D  shows the intensity of HGEu001. 
         FIG. 4E  shows the co-staining experiments of red HGEu002 (control) in fluorescence microscope with marked distance for primary cilium (Green line) (Dosed concentration 10 μM HGEu002, 6 hours incubation after GFP-ARL13B was transfected and expressed). 
         FIG. 4F  shows the green GFP-ARL13B in fluorescence microscope with marked distance for primary cilium (Green line). 
         FIG. 4G  shows the overlay of  FIGS. 4E and 4F  in fluorescence microscope with marked distance for primary cilium (Green line). 
         FIG. 4H  shows the intensity of HGEu002. 
         FIG. 5A  shows the three dimensional in vitro imaging and emission spectra of 10 μM in xz plane for HGEu001 incubated in HeLa cells for 6 hours. (λ ex 700 nm). 
         FIG. 5B  shows the three dimensional in vitro imaging and emission spectra of 10 μM in xz plane for HGEu002 incubated in HeLa cells for 6 hours. (λ ex 700 nm). 
         FIG. 5C  shows the three dimensional in vitro imaging and emission spectra of 10 μM in xy plane for HGEu001 incubated in HeLa cells for 6 hours. (λ ex 700 nm). 
         FIG. 5D  shows the three dimensional in vitro imaging and emission spectra of 10 μM in xy plane for HGEu002 incubated in HeLa cells for 6 hours. (λ ex 700 nm). 
         FIG. 5E  shows the three dimensional in vitro imaging and emission spectra of 10 μM in xyz plane for HGEu001 incubated in HeLa cells for 6 hours. (λ ex 700 nm). 
         FIG. 5F  shows the three dimensional in vitro imaging and emission spectra of 10 μM in xyz plane for HGEu002 incubated in HeLa cells for 6 hours. (λ ex 700 nm). 
         FIG. 6A  shows the three dimensional (by z stack) two-photon confocal in vitro images of HGEu001 with co-localization of green GFP-ARL14B/GFP-IFT88/MitoTracker® Green FM (M-7514) in HeLa cells. (λ ex =700 nm) HeLa cells were first transfected with GFP-ARL13B/GFP-IFT88 or incubated with MitoTracker® Green FM (M-7514) for 15 minutes and further incubated 6 hours with 10 μM of HGEu001. 
         FIG. 6B  shows the three dimensional (by z stack) two-photon confocal in vitro images of HGEu002 (negative control) with co-localization of green GFP-ARL14B/GFP-IFT88/MitoTracker® Green FM (M-7514) in HeLa cells. (λ ex =700 nm) HeLa cells were first transfected with GFP-ARL13B/GFP-IFT88 or incubated with MitoTracker® Green FM (M-7514) for 15 minutes and further incubated 6 hours with 10 μM of HGEu002. 
         FIG. 6C  shows the three dimensional (by z stack) two-photon confocal in vitro images of Dark field of HGEu001 with co-localization of green GFP-ARL14B/GFP-IFT88/MitoTracker® Green FM (M-7514) in HeLa cells. (λ ex =700 nm) HeLa cells were first transfected with GFP-ARL13B/GFP-IFT88 or incubated with MitoTracker® Green FM (M-7514) for 15 minutes and further incubated 6 hours with 10 μM of HGEu001. 
         FIG. 6D  shows the three dimensional (by z stack) two-photon confocal vitro images of Dark field of HGEu002 (negative control) with co-localization of green GFP-ARL14B/GFP-IFT88/MitoTracker® Green FM (M-7514) in HeLa cells. (λ ex =700 nm) HeLa cells were first transfected with GFP-ARL13B/GFP-IFT88 or incubated with MitoTracker® Green FM (M-7514) for 15 minutes and further incubated 6 hours with 10 μM of HGEu002. 
         FIG. 7A  shows HPLC spectra of HGEu001. 
         FIG. 7B  shows HPLC spectra of HGEu002. 
         FIG. 8  shows HRMS(+ESI) spectrum of the complex HGEu001. (m/z calcd. for C47H65EuN9O4 [M−H2O−2H]+972.4372, found 972.4378, calcd. for C47H66ClEuN9O4 [M−H2O−H+Cl—]+1008.4139, found 1008.4119, calcd. for C47H67Cl2EuN9O4 [M−H2O+2O+2Cl]+1044.3905, found 1044.3882). 
         FIG. 9  shows HRMS(+ESI) spectrum of the complex HGEu002. (m/z calcd. for C48H65EuF3N9O4 [M−H2O−H] 2+  m/z=1041.4324/2=520.7162, found 520.7186. 
         FIG. 10  shows the absorption spectra of HGEu001 and HGEu002 in aqueous solution (10 μM). 
         FIG. 11A  shows the emission spectra of HGEu001 aqueous solution (10 μM, λ ex =340 nm). The spectra were recorded on Horiba Flurolog-3 spectrophotometer. The same emission bands and ratios obtained are compared with the emission spectra measured with Edinburgh instrument FLS920 spectrophotometer as in  FIGS. 1A-1B . 
         FIG. 11B  shows the emission spectra of HGEu002 aqueous solution (10 μM, λ ex =340 nm). The spectra were recorded on Horiba Flurolog-3 spectrophotometer. The same emission bands and ratios obtained are compared with the emission spectra measured with Edinburgh instrument FLS920 spectrophotometer as in  FIGS. 1A-1B . 
         FIG. 12A  shows the emission decay curve of the complex HGEu001 and in D 2 O and H 2 O. (λ em =614 nm.  5 D 0 → 7 F 2 . λ ex =355 nm). 
         FIG. 12B  shows the emission decay curve of the complex HGEu002 in D 2 O and H 2 O. (λ em =614 nm.  5 D 0 → 7 F 2 . λ ex =355 nm). 
         FIG. 13A  shows the raw data of cytotoxicity of HGEu001 in Table 3. 
         FIG. 13B  shows the raw data of cytotoxicity of HGEu002 in Table 3. 
         FIG. 14A  shows the two-photon time lapses in vitro images of HGEu002 in HeLa cells which the images were taken at 3 hours incubation time points; The red emission of HGEu002 is localized in cytoplasm. (In parallel with  FIG. 3A ). 
         FIG. 14B  shows the two-photon time lapses in vitro images of HGEu002 in HeLa cells which the images were taken at 6 hours incubation time points; The red emission of HGEu002 is localized in cytoplasm. (In parallel with  FIG. 3B ). 
         FIG. 14C  shows the two-photon time lapses in vitro images of HGEu002 in HeLa cells which the images were taken at 18 hours incubation time points; The red emission of HGEu002 is localized in cytoplasm. (In parallel with  FIG. 3C ). 
         FIG. 14D  shows the two-photon time lapses in vitro images of HGEu002 in HeLa cells which the images were taken at 24 hours incubation time points; The red emission of HGEu002 is localized in cytoplasm. (In parallel with  FIG. 3D ). 
         FIG. 14E  shows the overlay images of fluorescence channel shown in  FIG. 14A  and bright field channel (Dosed concentration=10 μM, λ ex =700 nm, filter Bandpass=550-665 nm); The red emission of HGEu002 is localized in cytoplasm. (In parallel with  FIG. 3E ). 
         FIG. 14F  shows the overlay images of fluorescence channel shown in  FIG. 14B  and bright field channel (Dosed concentration=10 μM, λ ex =700 nm, filter Bandpass=550-665 nm); The red emission of HGEu002 is localized in cytoplasm. (In parallel with  FIG. 3F ). 
         FIG. 14G  shows the overlay images of fluorescence channel shown in  FIG. 14C  and bright field channel (Dosed concentration=10 μM, λ ex =700 nm, filter Bandpass=550-665 nm); The red emission of HGEu002 is localized in cytoplasm. (In parallel with  FIG. 3G ). 
         FIG. 14H  shows the overlay images of fluorescence channel shown in  FIG. 14D  and bright field channel (Dosed concentration=10 μM, λ ex =700 nm, filter Bandpass=550-665 nm); The red emission of HGEu002 is localized in cytoplasm. (In parallel with  FIG. 3H ). 
         FIG. 15A  shows the three dimensional in vitro imaging of 10 μM in xz plan for HGEu001 incubated in MRC-5 cells with 6 hours. (λ ex =700 nm, In parallel with  FIG. 5A ). 
         FIG. 15B  shows the three dimensional in vitro imaging of 10 μM in xz plan for HGEu002 incubated in MRC-5 cells with 6 hours. (λ ex =700 nm, In parallel with  FIG. 5B ). 
         FIG. 15C  shows the three dimensional in vitro imaging of 10 μM in xy plan for HGEu001 incubated in MRC-5 cells with 6 hours. (λ ex =700 nm, In parallel with  FIG. 5C ). 
         FIG. 15D  shows the three dimensional in vitro imaging of 10 μM in xy plan for HGEu002 incubated in MRC-5 cells with 6 hours. (λ ex =700 nm, in parallel with  FIG. 5D ). 
         FIG. 15E  shows the three dimensional in vitro imaging of 10 μM in xyz plane for HGEu001 incubated in MRC-5 cells with 6 hours. (λ ex =700 nm, In parallel with  FIG. 5E ). 
         FIG. 15F  shows the three dimensional in vitro imaging of 10 μM in xyz plane for HGEu002 incubated in MRC-5 cells with 6 hours. (λ ex =700 nm, In parallel with  FIG. 5F ). 
         FIG. 16  shows H NMR spectrum of compound 2. (400 MHz, DMSO-d 6 ). 
         FIG. 17  shows C NMR spectrum of compound 2. (100 MHz, DMSO-d 6 ). 
         FIG. 18  shows H NMR spectrum of compound 3. (400 MHz, DMSO-d 6 ). 
         FIG. 19  shows C NMR spectrum of compound 3. (100 MHz, DMSO-d 6 ) 
         FIG. 20  shows H NMR spectrum of compound 4. (400 MHz, DMSO-d 6 ) 
         FIG. 21  shows C NMR spectrum of compound 4. (100 MHz, DMSO-d 6 ) 
         FIG. 22  shows H NMR spectrum of compound 5. (400 MHz, CDCl 3 ) 
         FIG. 23  shows C NMR spectrum of compound 5. (100 MHz, CDCl 3 ) 
         FIG. 24  shows H NMR spectrum of HGL001. (400 MHz, DMSO-d 6 ) 
         FIG. 25  shows C NMR spectrum of HGL001. (100 MHz, DMSO-d 6 ) 
         FIG. 26  shows H NMR spectrum of HGL002. (400 MHz, DMSO-d 6 ) 
         FIG. 27  shows C NMR spectrum of HGL002. (100 MHz, DMSO-d 6 ) 
         FIG. 28  shows molecular library of the europium complexes which have similar structures with HGEu001 for primary cilium specific imaging screening. 
         FIG. 29  shows the synthesis scheme (Scheme 1) of HGEu001 and its motif complex HGEu002: (a) (4-ethynylpyridin-2-yl)methanol, Pd(PPh 3 ) 4 , CuI, DIPEA THF; (b) MsCl, DIPEA, DCM; (c) cyclen, NaHCO 3 , CH 3 CN; (d) K 2 CO 3 , MeCN, 60° C.; (e) EuCl 3 .6H 2 O, MeOH, rt., 24 hours. 
         FIG. 30  shows the chemical structures of the new lanthanide complexes for organelle specific imaging. 
         FIG. 31 a    shows the absorption spectrum of HGEu001-Coumarin in aqueous solution (10 μM). 
         FIG. 31 b    shows the emission spectrum of HGEu001-Coumarin under excitation of 330 in aqueous solution (10 μM). 
         FIG. 31 c    shows the emission spectrum of HGEu001-Coumarin under excitation of 430 in aqueous solution (10 μM). 
         FIG. 32 a    shows the absorption spectrum of HGEu001-Por in aqueous solution (10 μM). 
         FIG. 32 b    shows the emission spectrum of HGEu001-Por under excitation of 330 in aqueous solution (10 μM). 
         FIG. 32 c    shows the emission spectrum of HGEu001-Por under excitation of 430 in aqueous solution (10 μM). 
         FIG. 33  shows the chemical structures of HGEu001-Biotin and HGEu001-EDECRIN for primary cilium related protein enrichment and labeling respectively. 
         FIG. 34  shows the SDS gel imaging of HGEu0001-Biotin and HGEu001-EDECRIN of cell lysate. 
         FIG. 35  shows the protein number that identified by proteomic analysis of proteins in SDS gels band. 44 primary cilium related proteins are identified by the two probes HGEu001-Biotin and HGEu001-EDECRIN. 
         FIG. 36  shows the mass spectrum of the observed peptide sequence ‘NSIMKCDVDIRKDLY ANTVLSGGTTMYPGIADR’ which labeled with HGEu001-EDECRIN from proteomic analysis. 
         FIG. 37 a    depicts an exemplary synthetic scheme for the preparation of the intermediate HGEu001-NH 2  that can be used in the preparation of HGEu001-Biotin, HGEu001-EDECRIN, HGEu001-Por, and HGEu001-Coumarin, wherein the synthetic steps call for: a) MsCl, DIPEA, DCM; b) NaHCO 3 , ACN; c) K 2 CO 3 , ACN; d) 6 M HO; e) EuCl 3 .6H 2 O. 
         FIG. 37 b    depicts an exemplary synthetic scheme for the preparation HGEu001-Biotin, HGEu001-EDECRIN, HGEu001-Por, and HGEu001-Coumarin from intermediate HGEu001-NH 2 , wherein the synthetic steps call for: f) Coumarin-NHS, DIPEA, DMSO; g) Por-NHS, DIPEA, DMSO; h) EDECRIN-NHS, DIPEA, DMSO; i) Biotin-NHS, DIPEA, DMSO. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Provided herein are compounds of formula (IV) and formula (V), which exhibit specific subcellular localization in the primary cilium with blue to deep red emission color under ultraviolet (UV)/visible/near infrared (NM) light excitation. The emission properties are tunable by the selection of the function group attached in the parent primary cilium marker (tris(N-(tert-butyl)acetamide) cy den-based lanthanide complexes (molecules of formula (I), (II), and (III))). The present disclosure has applications in organelle specific imaging and protein quantitative analysis. The compounds of formula (IV) and (V) are analogs of tris(N-(tert-butyl)acetamide) cyclen-based lanthanide complexes (molecules of formula (I), (II), and (III) described U.S. patent application Ser. No. 15/604,660, which is hereby incorporated in its entirety) and extend the utility of the molecules of formula (I), (II), and (III) and surprisingly maintain many of their advantageous properties, such as cilium binding specificity, specific subcellular localization, high water solubility, and high stability. 
     Molecules of formula (I) have been shown to be useful for imaging rod-like organelle in biological cells, wherein the molecule of formula (I) comprises: 
                         
wherein Ln is selected from Eu, Tb, Gd, Yb, Er, Dy, Sm, La, Ce, Pr, Nd, Pm, Tm and Y, X −  is selected from Cl − , NO 3   − , CH 3 COO − , ClO 4   −  or other anions; A 1  is selected from C, N or Si; R 1 , R 2  and R 3  are jointly or separately selected from NH(tert)Bu, OH −  or other amine; R 4 , R 5 , R 6 , R 7 , R 8 , R 9  and R 10  are jointly or separately selected from H, CF 3 , OMe, OEt, OH or NMe 2 ; R 11  is selected from alkyl, aryl ether, ester, amide or aromatic rings; m is an integer selected from 0, 1, 2 or 3. In particular embodiments, the derivatives of the molecule of the formula (I) can be represented by formula (II):
 
                         
wherein R 11  is selected from:
 
                         
and
 
wherein R 12 , R 13 , R 14 , R 15 , R 16 , R 17 , R 18 , R 19 , and R 20  are jointly or separately selected from H, CF 3 , OMe, OEt, OH or NMe 2 ; A 2  is selected from C, N, or Si. Alternatively, the corresponding substituents for X, A 2  and R n  (where n=4-20) in each of the derivatives can be defined as follows:
 
X=Cl, A 2 =C, R n =H ( n= 4-10, 12-16);  HGL001
 
X=Cl, A 2 =C, R n =H ( n= 4-10, 12-15), R 16 =CF 3 ;  HGL002
 
X=Cl, A 2 =C, R n =H ( n= 4-10, 12-15), R 16 =OMe;  HGL003
 
X=Cl, A 2 =C, R n =H ( n= 4-10, 12-15), R 10 =NMe 2 ;  HGL004
 
X=Cl, A 2 =N, R n =H ( n= 4-10, 12-15);  HGL005
 
X=Cl, R n =H ( n= 4-10, 17-19);  HGL006
 
X=Cl, R n =H ( n= 4-10), R 20 =OH;  HGL007
 
X=Cl, R n =H ( n= 4-10), R 20 =OEt;  HGL008
 
X=Cl, A 2 =C, R n =H ( n= 4-6, 8, 10, 12-16), R 7 =R 9 =OMe;  HGL009
 
X=Cl, A 2 =C, R n =H ( n= 4-6, 8, 10, 12-15), R 7 =R 9 =OMe, R 16 =CF 3 ;  HGL010
 
X=Cl, A 2 =C, R n =H ( n= 4-6, 8, 10, 12-15), R 7 =R 9 =R 16 =OMe;  HGL011
 
X=Cl, A 2 =C, R n =H ( n= 4-6, 8, 10, 12-15), R 7 =R 9 =OME, R 16 =NMe 2 ;  HGL012
 
X=Cl, A 2 =N, R n =H ( n= 4-6, 8, 10, 12-15), R 7 =R 9 =OMe;  HGL013
 
X=Cl, A 2 =C, R n =H ( n= 4-6, 8, 10, 17-19), R 7 =R 9 =OMe;  HGL014
 
X=Cl, A 2 =C, R n =H ( n= 4-6, 8, 10), R 7 =R 9 =OMe, R 20 =OH;  HGL015
 
X=Cl, A 2 =C, R n =H ( n= 4-6, 8, 10), R 7 =R 9 =OMe, R 20 =OEt;  HGL016
 
where Ln refers to lanthanide; OMe refers to a methoxy group; NMe 2  refers to a nitro-dimethyl group; OEt refers to ethoxy group.
 
     Additional analogs of the molecules (I), (II), and (III) have been developed that further extend the utility of these molecules as described herein. It has been surprisingly discovered that the molecules of (I), (II), and (III) can be modified to include reactive functionality capable of protein targeting/pull down or additional fluorescent groups expanding the excitation and emission wavelengths of the molecules, without impacting their ability to localize and selectively bind to cilium present in cells. 
     In a first aspect, provided herein is a compound represented by the formula (IV): 
                         
wherein in is an integer selected from 0, 1, 2 or 3;
 
X is a pharmaceutically acceptable anion;
 
Ln is Eu, Tb, Gd, Yb, Er, Dy, Sm, La, Ce, Pr, Nd, Pm, Tm or Y;
 
A 1  is C, N, or Si;
 
R 1 , R 2  and R 3  are independently selected from the group consisting of —N(R 12 ) 2 ;
 
                         
R 4 , R 5 , R 6 , R 7 , R 8 , R 9  and R 10  are independently selected from the group consisting of H, alkyl, —CF 3 , —OR 12 , and —N(R 12 ) 2 ;
 
R 11  is hydrogen, alkyl, aryl ether, —CO 2 R 13 ; or —NH(C═O)R 14 ;
 
R 12  and R 13  for each instance is independently selected from the group consisting of hydrogen and alkyl;
 
R 14  is alkyl, cycloalkyl, aryl, or heteroalyl; and
 
n is a whole number selected from 1-8, wherein one of R 1 , R 2  and R 3  is not N(R 12 ) 2 .
 
     In instances in which one of group member of R 1 , R 2  and R 3  is not N(R 12 ) 2 , the one group member of R 1 , R 2  and R 3  that is not is N(R 12 ) 2  is selected from the group consisting of: 
                         
and the remaining two group members of R 1 , R 2  and R 3  are each independently —N(R 12 ) 2 .
 
     In certain embodiments, R 1  and R 3  are independently —N(H)(alkyl); R 1  and R 2  are independently —N(H)(alkyl); or R 2  and R 3  are independently —N(H)(alkyl). 
     In certain embodiments, R 1  and R 3  are independently —N(H)(alkyl) and R 2  is selected from the group consisting of: 
     
       
         
         
             
             
         
       
     
     In certain embodiments, the compound of formula (IV) can be represented by the compound of formula (V): 
                         
wherein m is an integer selected from 0, 1, 2 or 3;
 
X is a pharmaceutically acceptable anion;
 
Ln is Eu, Tb, Gd, Yb, Er, Dy, Sm, La, Ce, Pr, Nd, Pm, Tm or Y;
 
R 2  is selected from the group consisting of:
 
                         
R 12  for each instance is independently alkyl; and
 
n is a whole number selected from 1-8.
 
     As used herein, the term “pharmaceutically acceptable anion” refers to the relatively non-toxic, organic or inorganic anions including, but are not limited to, chloride, bromide, iodide, perchlorate, carbonate, bicarbonate, sulfate, phosphate, monohydrogen phosphate, dihydrogen phosphate, metaphosphate, pyrophosphate, acetate, maleate, fumarate, formate, malonate, oxalate, lactate, tartrate, citrate, gluconate, mesylate, besylate, tosylate, succinate, and salicylate sulfate, sulfite, bisulfate, bisulfite, nitrate and nitrite. In certain embodiments, X is selected from the group consisting of chloride, nitrate, acetate, and perchlorate. 
     In certain embodiments, Ln is Eu, Tb, Gd, Yb, Er, Dy, Sm, La, Ce, Pr, Nd, Pm, Tm or Y, wherein Ln is in the +2, +3, or +4 oxidation state. In certain embodiments. Ln is selected from the group consisting of Eu(III), Tb(III), Gd(III), Yb(III), Er(III), Dy(III), Sm(III), La(III), Ce(III), Pr(III), Nd(III), Pm(III), Tm(III) and Y(III). In certain embodiments, Ln is Eu(III). 
     In certain embodiments, A 1  is C or N. In certain embodiments, A 1  is C. 
     In certain embodiments, n is a whole number selected from the group consisting of 2-8; 3-8; 4-8; 4-6; 5-8; 5-7; or 6-8. In certain embodiments, n is 6. 
     In certain embodiments, R 11  is —NH(C═O)Ar. In such embodiments, Ar can be represented by 
                         
wherein R 12 , R 13 , R 14 , R 15 , and R 16 , are independently selected from H, CF 3 , OMe, OEt, OH or NMe 2 ; or wherein A 2  is N, R 16  is absent; and A 2  is selected from C, N, or Si. In certain embodiments, R 12 , R 13 , R 14 , and R 15  are H; and R 16  is CF 3 , OMe, or NMe 2 .
 
In certain embodiments, R 12  is independently for each instance a C 1 -C 6  alkyl, such as methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, tert-butyl, n-pentyl, isopentyl, neopentyl, n-hexyl, 2-methylpentane, 3-methylpentane, 2,3-dimethylbutane, 2,2-dimethylbutane, and the like.
 
     In certain embodiments, the compound of formula (IV) is selected from the group consisting of: 
                                           
wherein Ln is Eu, Tb, Gd, Yb, Er, Dy, Sm, La, Ce, Pr, Nd, Pm, Tm or Y, wherein Ln is in the +2, +3, or +4 oxidation state; and X is chloride, bromide, iodide, perchlorate, carbonate, bicarbonate, sulfate, phosphate, monohydrogen phosphate, dihydrogen phosphate, metaphosphate, pyrophosphate, acetate, maleate, fumarase, formate, malonate, oxalate, lactate, tartrate, citrate, gluconate, mesylate, besylate, tosylate, succinate, and salicylate sulfate, sulfite, bisulfate, bisulfite, nitrate or nitrite. In certain embodiments, X is selected from the group consisting of chloride, nitrate, acetate, and perchlorate.
 
     In certain embodiments, the compound of formula (IV) is selected from the group consisting of: 
                                           
wherein Ln is Eu; and X −  is Cl − .
 
     In certain embodiments, there is provided a compound for imaging rod-like organelle in biological cells comprising any of the compounds described herein, wherein the rod-like organelle in biological cells is primary cilium. 
     In certain embodiments, there is provided a compound for imaging rod-like organelle in biological cells comprising any of the compounds described herein, wherein the imaging is done in living cells. 
     In certain embodiments, there is provided a compound for imaging rod-like organelle in biological cells comprising any of the compounds described herein, wherein the imaging is performed using a linear fluorescence microscopy under UV light excitation or a two-photon confocal laser scanning microscope. 
     In certain embodiments, there is provided a compound for imaging rod-like organelle in biological cells comprising a compound selected from the group consisting of: 
                                           
wherein Ln is Eu(III); and X is selected from the group consisting of chloride, nitrate, acetate, and perchlorate.
 
     In certain embodiments, there is provided a compound for imaging rod-like organelle in biological cells comprising a compound described herein, wherein the compound can selectively bind to proteins in cells. In certain embodiments, the protein is at least one primary cilium related protein. 
     In certain embodiments, there is provided a compound for imaging rod-like organelle in biological cells comprising a compound described herein being used for quantitative analysis of primary cilium related proteins. 
     In certain embodiments, there is provided a compound for imaging rod-like organelle in biological cells comprising a compound described herein being used as a disease diagnosis probes. 
     In certain embodiments, there is provided a compound for imaging rod-like organelle in biological cells comprising a compound described herein being used as an organelle targeting specific vector. 
     In certain embodiments, there is provided a compound for imaging rod-like organelle in biological cells comprising a compound described herein being conjugated with a drug for combined disease treatment. 
     In certain embodiments, a compound described herein is first dissolved in an aqueous solution before accumulating in the rod-like organelle in biological cells for imaging. 
     Also provided herein is a method for imaging rod-like organelle in biological cells comprising accumulating a compound described herein in the rod-like organelle in biological cells directly. In certain embodiments, the rod-like organelle in biological cells is primary cilium. 
     In certain embodiments, the imaging is performed using a linear fluorescence microscope under UV light excitation or a two-photon confocal laser scanning microscope. 
     In certain embodiments, imaging the rod-like organelles in biological cells is conducted in living cells. 
     In certain embodiments, there is provided a method for quantitatively analyzing primary cilium related proteins comprising accumulating a compound described herein in the rod-like organelle in biological cells directly. 
     In certain embodiments, there is provided a method for diagnosing primary cilium related disease comprising using a compound described herein as a disease diagnosis probe. 
     In certain embodiments, there is provided a method for targeting primary cilium in biological cells comprising using a compound described herein as an organelle targeting specific vector or agent. 
     In certain embodiments, there is provided a method for treating primary cilium related disease comprising administering a compound described herein in conjugation with a drug for combined treatment. 
     The presently claimed invention is further illustrated by the following experiments or embodiments which should be understood that the subject matters disclosed in the experiments or embodiments may only be used for illustrative purpose but are not intended to limit the scope of the presently claimed invention: 
     Materials and Methods 
     Synthesis and Characterization of HGEu001 and HGEu002 
     General Information for the Synthesis. 
     Tetrahydrofuran (THF), dichloromethane (DCM), acetonitrile (CH 3 CN) and N,N-diisopropylethylamine (DIPEA) were dried over calcium hydride (CaH 2 ). All reactions were carried out with anhydrous solvents under nitrogen atmosphere, unless otherwise specified. All the reagents were obtained commercially with high quality and used without further purification. Reactions were monitored by thin-layer chromatography (TLC) which was carried out on silica gel plates (0.25 mm, 60F-254) by using UV light as visualizing method. Flash column chromatography was carried out on 200-300 mesh silica gel.  1 H and  13 C NMR spectra were recorded on a 400 ( 1 H: 400 MHz,  13 C: 100 MHz) spectrometer. The following abbreviations were used to explain the multiplicities: s=singlet, d=doublet, t=triplet, q=quartet, dd=doublet of doublets, m=multiplet, br=broad. High resolution mass spectra were obtained from an ESI or MALDI-TOF mass spectrometer. The synthetic route for the primary cilium specific probe HGEu001 and its motif complex. HGEu002 is shown in  FIG. 29 . 
     Synthesis of N-(4-iodophenyl)-4-(trifluoromethyl)benzamide (Compound 2) 
     The solution of 4-iodoaniline (5 g, 46.23 mmol) and DIPEA (13.42 mL, 77.06 mmol) in DCM (200 mL), 4-(trifluoromethyl)benzoyl chloride (5.72 mL, 38.53 mmol) was added dropwise at 0° C. in 30 min. The resulting solution was stirred for 12 hours at room temperature. The solvent of the resulting mixture was concentrated to 100 mL, and the white precipitate was collected as product after filtration. (13.41 g, 34.29 mmol, yield=89%)  1 H NMR (400 MHz, DMSO-d 6 ): δ10.57 (s, 1H), 8.13 (d, J=4 Hz, 2H), 7.92 (d, J=4 Hz, 2H), 7.72 (d, J=4 Hz, 2H), 7.63 (d, J=4 Hz, 2H); ( FIG. 16 )  13 C NMR (100 MHz, DMSO-d 6 ): δ164.5, 138.6, 138.5, 137.3, 131.6, 131.3, 128.6, 125.4, 125.3, 125.2, 122.5, 87.9; ( FIG. 17 ) HRMS (MALDI-TOF) m/z calcd. for C 14 H 10 F 3 INO [M+H] +  391.9759 found 391.9761. 
     Synthesis of N-(4-((2-(hydroxymethyl)pyridin-4-yl)ethynyl)phenyl)benzamide (Compound 3) 
     (4-ethynylpyridin-2-yl)methanol (0.92 g, 6.8 mmol) was added into the solution of N-(4-iodophenyl)benzamide (Compound 1) (3.36 g, 10.4 mmol), Pd(PPh 3 ) 2 Cl 2  (136 mg, 0.21 mmol), CuI (80 mg, 0.42 mmol) and DIPEA (2.0 mL) in freshly distilled THF (200 mL). The resulting mixture was stirred at 45° C. for 6 hours under protection of N 2  gas. Silica gel flash column chromatography (DCM:MeOH=30:1) of the concentrated residue gave a white solid as the product. (2.16 g, 6.4 mmol, yield=94%)  1 H NMR (400 MHz, DMSO-d 6 ): δ10.49 (s, 1H), 8.52 (d, J=2 Hz, 1H), 7.96 (d, J=4 Hz, 2H), 7.90 (dd, J 1 =4 Hz, J 2 =8 Hz, 2H), 7.63-7.60 (m, 3H), 7.57-7.53 (m, 3H), 7.38 (d, J=2 Hz, 1H), 5.52 (br, 1H), 4.58 (s, 2H); ( FIG. 18 )  13 C NMR (100 MHz, DMSO-d 6 ): δ165.8, 162.5, 148,9, 140.4, 134.7, 132.4, 131.8, 130.8, 128.4, 127.7, 123.2, 121.4, 120.1, 115.9, 93.6, 86.6, 63.9, 53.5; ( FIG. 19 ) HRMS (MALDI-TOF) m/z calcd. for C 21 H 17 N 2 O 2  [M+H] +  329.1290 found 329.1295. 
     Synthesis of N-(4((2-(hydroxymethyl)pyridin-4-yl)ethynyl)phenyl)-4-(trifluoro methyl) benzamide (Compound 4) 
     (4-ethynylpyridin-2-yl)methanol (1.13 g, 8.52 mmol) was added into the solution of N-(4-iodophenyl)-4-(trifluoromethyl)benzamide (Compound 2) (4 g, 10.22 mmol), Pd(PPh 3 ) 4  (197 mg, 0.17 mmol), CuI (65 mg, 0.34 mmol) and DIPEA (20 mL) in freshly distilled THF (200 mL), The resulting mixture was stirred at 45° C. for 6 hours under protection of N 2  gas. Silica gel flash column chromatography (DCM:MeOH=30:1) of the concentrated residue gave a white solid as the product. (3.10 g, 7.84 mmol, yield=92%)  1 H NMR (400 MHz, DMSO-d 6 ): δ10.71 (s, 1H), 8.52 (d, J=4 Hz, 1H), 8.15 (d, J=4 Hz, 2H), 7.93 (d, J=4 Hz, 2H), 7.90 (d, J=4 Hz, 2H), 7.64 (d, J=4 Hz, 2H), 7.55 (s, 1H), 7.36 (d, J=2 Hz, 1H), 5.54 (t, J=4 Hz, 1H), 4.14 (d, J=2 Hz, 2H); ( FIG. 20 )  13 C NMR (100 MHz, DMSO-d 6 ): δ164.7, 162.5, 148.9, 140.0, 138.5, 132.5, 131.7, 131.3, 130.70, 128.7, 125.4, 125.2, 123.2, 122.5, 121.4, 120.2, 116.3, 93.4, 86.6, 63.9; ( FIG. 21 ) HRMS (MALDI-TOF) m/z calcd. for C 22 H 16 F 3 N 2 O 2  [M+H] +  397.1164 found 397.1168. 
     Synthesis of 2,2′,2″-(1,4,7,10-tetraazacyclododecane-1,4,7-triyl)tris(N-(tert-butyl) acetamide) (Compound 5) 
     2-promo-N-(tert-butyl)acetamide (10.1 g, 52.2 mmol) was added into the solution of 1,4,7,10-tetraazacyclododecane (3.0 g, 17.4 mmol) in anhydrous acetonitrile (80 mL), followed by NaHCO 3  (21.9 g, 261 mmol). The resulting solution was stirred at room temperature for 24 hours. After filtration of the resulting mixture, filtrate was concentrated and recrystallized from hot water to obtain a white solid as the product. (4.8 g, 8.7 mmol, yield=50%)  1 H NMR (400 MHz, CDCl 3 ): δ6.78 (s, 1H), 6.68 (s, 2H), 3.05 (s, 4H), 3.05 (s, 2H), 2.70 (m, 16H), 1.37 (s, 18H) 1.36 (s, 9H); ( FIG. 22 )  13 C NMR (100 MHz, CDCl 3 ): δ170.1, 170.0, 60.5, 59.6, 53.4, 52.9, 52.3, 51.1, 50.9, 46.7, 28.9, 28.8; ( FIG. 23 ) HRMS (MALDI-TOF) m/z calcd. For C 26 H 54 N 7 O 3  [M+H] +  512.4288 found 512.4285. 
     Synthesis of 2,2′,2″-(10-((4-((4-benzamidophenyl)ethynyl)pyridin-2-yl)methyl)-1,4,7,10-tetranzacyclododecane-1,4,7-triyl)tris(N-(tert-butyl)acetamide) (HGL001) 
     Methanesulfonyl chloride (0.22 mL, 2.73 mmol) was added into a stirred solution of N-(4((2-(hydroxymethyl)pyridin-4-yl)ethynyl)phenyl)benzamide (Compound 3) (300 mg, 0.91 mmol) in anhydrous DCM (150 mL) and DIPEA (1.59 mL, 9.11 mmol). The resulting mixture was stirred at room temperature for 3 hours. The solution was then washed with saturated NaHCO 3  solution, saturated NH 4 Cl solution and brine. The organic layer was dried over anhydrous Na 2 SO 4  and concentrated to give a pale yellow solid as the intermediate compound, (4-((4-benzamidophenyl)ethynyl)pyridin-2-yl)methyl methanesulfonate, which was directly used in the next step without further purification. The pale yellow solid was dissolved in dry CH 3 CN (50 mL). 2,2′,2″-(1,4,7,10-tetraazacyclododecane-1,4,7-triyl)tris(N-(tert-butyl)acetamide) (Compound 5, 0.50 g, 0.61 mmol) and anhydrous K 2 CO 3  (1.26 g, 9.1 mmol) added. The resulting mixture was stirred at 50° C. for 12 hours under N 2  gas. The solids were filtered off, and the filtrate was concentrated. Silica gel flesh column chromatography (CH 2 Cl 2 :MeOH=12:1) of the residue gave a pale yellow solid as the product (378 mg, 0.46 mmol, yield=75%).  1 H NMR (400 MHz, DMSO-d 6 ): δ10.53 (s, 1H), 8.38 (d, J=2 Hz, 1H), 7.97 (d, J=4 Hz, 2H), 7.94 (d, J=4 Hz, 2H), 7.83 (br, 2H), 7.60-7.53 (m, 7H), 7.38 (d, J=2 Hz, 1H), 3.66 (br, 2H), 3.20-2.07 (m, 22 J), 1.30 (s, 9H), 1.22 (s, 18H); ( FIG. 24 )  13 C NMR (100 MHz, DMSO-d 6 ): δ170.5, 169.9, 165.9, 158.7, 149.0, 140.5, 134.7, 132.3, 131.8, 131.1, 128.5, 128.2, 127.8, 125.1, 123.5, 120.1, 115.9, 93.9, 86.3, 58.1, 57.9, 57.2, 50.4, 50.3, 28.3, 28.1; ( FIG. 25 ) HRMS (MALDI-TOF) m/z calcd. for C 47 H 68 N 9 O 4  [M+H] +  822.5394, found 822.5390. 
     Synthesis of 2,2′,2″-(10((4-((4-(4-(trifluoromethyl)benzamido)phenyl)ethynyl)pyridin-2-yl)methyl)-1,4,7,10-tetraazacyclododecane-1,4,7-triyl)tris(N-(tert-butyl)acetamide) (HGL002) 
     Methanesulfonyl chloride (0.18 mL, 2.28 mmol) was added into a stirred solution of N-(4-((2-(hydroxymethyl)pyridin-4-yl)ethynyl)phenyl)-4-(trifluoromethyl)benzamide (Compound 4) (300 mg, 0.76 mmol) in anhydrous DCM (150 mL) and DIPEA (1.33 mL, 7.61 mmol).The resulting mixture was stirred at room temperature for 3 hours. After that the solution was then washed with saturated NaHCO 3  solution, saturated NH 4 Cl solution and brine. The organic layer was dried over anhydrous Na 2 SO 4  and concentrated to give a pale yellow solid as the intermediate compound, (4-((4-(4-(trifluoromethyl)benzamido)phenyl)ethynyl)pyridin-2-yl)methyl methanesulfonate, which was directly used in the next step without further purification. The pale yellow solid was dissolved in dry CH 3 CN (50 mL). 2,2′,2″-(1,4,7,10-tetraazacyclododecane-1,4,7-triyl)tris(N-(tert-butyl)acetamide) (Compound 5, 0.42 g, 0.51 mmol) and anhydrous K 2 CO 3  (1.05 g, 7.6 mmol) were added. The resulting mixture was stirred at 50° C. for 12 hours under N 2  gas. The solids were filtered off, and the filtrate was concentrated. Silica gel flesh column chromatography (CH 2 Cl 2 :MeOH=12:1) of the residue gave a pale yellow solid as the product (354 mg, 0.40 mmol, yield=78%).  1 H NMR (400 MHz, DMSO-d 6 ): δ10:78 (s, 1H), 8.38 (d, J=2 Hz, 1H), 8.18 (s, 1H), 8.16 (s, 1H), 7.91 (d, J=4 Hz, 4H), 7.82 (br, 2H), 7.62 (d, J=8 Hz, 2H), 7.57 (d, J=4 Hz, 2H), 7.39 (d, J=2 Hz, 1H), 3.71 (br, 2H), 2.87-2.17 (m, 22H), 1.29 (s, 9H), 1.27 (s, 18H); ( FIG. 26 )  13 C NMR (100 MHz, DMSO-d 6 ): 170.5, 169.8, 164.7, 158.6, 148.9, 140.1, 138.4, 132.3, 131.6, 131.3, 131.0, 128.7, 125.4, 125.2, 125.1123.4, 122.5, 120.2, 116.2, 93.7, 86.4, 58.1, 57.9, 57.2, 54.9, 50.4, 50.3, 49.4, 28.3, 28.1; ( FIG. 27 ) HRMS (MALDI-TOF) m/z calcd. for C 48 H 67 F 3 N 9 O4 [M+H] +  890.5268 found 890.5264. 
     Synthesis of Complex HGEu001 
     Europium (III) chloride hexahydrate (77 mg, 0.21 mmol) was added to the solution of the ligand (HGL001, 0.20 mmol) in MeOH/H 2 O (100 mL, v:v=1:1). The resulting solution was maintained in a pH range of 6.0-6.5 with NaOH solution (0.4 M) and stirred at room temperature for 24 hours. The solvents were removed under vacuum; the residue was dissolved in 1 mL of methanol and dropped into ethyl ether (50 mL). The precipitates were filtered, washed with diethyl ether and dried under vacuum at room temperature. White solids were collected as the products. (222 mg, 0.19 mmol, yield=90%). HRMS (+ESI) m/z calcd. for C 40 H 65 EuN 9 O 4  [M−H 2 O−2H] +  972.4372, found 972.4378, calcd. for C 47 H 66 ClEuN 9 O 4  [M−H 2 O−H+Cl − ] +  1008.4139, found 1008.4119, calcd. for C 47 H 67 Cl 2 EuN 9 O 4  [M−H 2 O+2Cl] +  1044.3905, found 1044.3882 ( FIG. 8 ) HPLC characterization: Retention time=15.20 min. (Table 1 and  FIGS. 7A-7B ). The chemical structure of HGEu001 can be represented by the following formula: 
                         
wherein X is H; Ln is Eu.
 
     Synthesis of Complex HGEu002 
     HGEu002 was obtained from ligand HGL002 with same procedures as HGEu001 (204 mg, 0.19 mmol, yield=95%). HRMS (+ESI) m/z m/z calcd. for C 48 H 65 EuF 3 N 9 O 4  [M−H] 2+  m/z=1041.4324/2=520.7162, found 520.7186. ( FIG. 9 ); HPLC characterization: Retention time=15.36 min, (Table 1 and  FIGS. 7A-7B ). The chemical structure of HGEu002 can be represented by the formula (II), wherein X is CF 3 ; Ln is Eu. 
     
       
         
           
               
             
               
                 TABLE 1 
               
             
            
               
                   
               
               
                 Solvent gradient of HPLC for the characterization 
               
               
                 of HGEu001 and HGEu002. 
               
            
           
           
               
               
               
            
               
                 Time/min 
                 0.05% TFA in water/% 
                 0.05% TFA in CH 3 CN/% 
               
               
                   
               
            
           
           
               
               
               
            
               
                 0.0 
                 90 
                 10 
               
               
                 5 
                 90 
                 10 
               
               
                 15 
                 40 
                 60 
               
               
                 20 
                 90 
                 10 
               
               
                 25 
                 90 
                 10 
               
               
                   
               
               
                 Flow rate = 1 mL/min 
               
            
           
         
       
     
     Synthesis of Complex of HGEu001-Coumarin 
     An exemplary synthesis of HGEu001-Coumarin, HGEu001-Por, HGEu001-EDECRIN and HGEu001-Biotin is shown in  FIGS. 37 a  and 37 b   . Referring to  FIG. 37 a   , Compound 6 was obtained by mesylating the chromophore alcohol Compound 3 and it was used in the next step without purification. Monoalkylation of 2,2′-(1,4,7,10-tetraazacyclododecane-1,7-diyl)bis(N-(tert-butyl)acetamide) (Compound 7) with Compound 6 afforded Compound 8 with an overall yield of 52% over the first two steps. Compound 8 was then reacted with Compound 9 under basic conditions to afford Compound 10 in a yield of 71%. Compound 10 was then deprotected by reaction with 1 M HCl in dioxane to afford the key intermediate HGL001-NH 2  in a yield of 97%. Europium (III) complexation of HGL001-NH 2  obtained the europium (III) complex HGEu001-NH 2 . Finally, the lanthanide complexes HGEu001-Coumarin, HGEu001-Por, HGEu001-EDECRIN, and HGEu001-Biotin were obtained by reaction of HGEu001-NIH with the corresponding n-hydroxysuccinimide (NHS) esters: Coumarin-NHS (reaction f,  FIG. 37 b   ), Por-NHS (reaction g,  FIG. 37 b   ), EDECRIN-NHS (reaction h,  FIG. 37 b   ), and Biotin-NHS (reaction i,  FIG. 37 b   ), respectively. 
     HGEu001-Coumarin, HGEu001-Por, HGEu001-EDECRIN, and HGEu001-Biotin were each characterized by high resolution mass spectroscopy (HRMS). The results of these tests are shown below and confirm that the desired products were synthesized. 
     HGEu001-NH 2 . Yield=96%; HRMS (+ESI) m/z calcd. for C 49 H 70 EuN 10 O 4  [M−H 2 O−2H] +  1015.4794, found 1015.4783. 
     HGEu001-Coumarin. Yield=87%; HRMS (+ESI) m/z calcd. for C 63 H 84 EuN 11 O 7  [M−H 2 O−H] +  12.59.5767/2=629.7883, found 629.7886. 
     HGEu001-Por. Yield=90%; HRMS (+ESI) m/z calcd. for C 103 H 116 EuN 14 O 14  [M−H 2 O−H] 2+  1925.8008/2=962.9004, found 962.9009. 
     HGEu001-EDECRIN. Yield=85%; HRMS (+ESI) m/z calcd. for HGEu001-Biotin. Yield=92%; HRMS (+ESI) m/z calcd. for C 59 H 85 EuN 12 O 6 S [M−H 2 O−H] 2+  1242.5648/2=621.2824, found 621.2819. 
     Photophysical Studies 
     UV-Visible absorption spectra in the spectral range 200 to 1100 nm were recorded by an HP Agilent UV-8453 Spectrophotometer. The emission spectra and the emission decay lifetimes of HGEu001 and HGEu002 were measured by Horiba Fluorolog-3 spectrophotometer and also measured by Edinburgh instrument ELS920 spectrophotometer for cross checking. (Two spectrophotometers are equipped with a 450 W continuous xenon lamp for steady state emission measurement, 60 W xenon flashlamp for emission life time measurement and an UV-Vis PMT detector—Hamamatsu—R 928  cooled 216 at −20° C.) 
     Stability Test Via Europium Emission Titration 
     Kinetic stability of the europium complexes were conducted to investigate the stability of the complexes in the diluted solution and in the present of 100 times of [EDTA] 2−  and Ca 2+ . EDTA was chose as a competitive ligand for the Eu 3+  ion. Ca 2+  cation serves as competitive ions for the ligand which can bind to the cyclen based macrocyclic ligand. 10 μM of europium complex was co-incubated 1 mM of EDTA or Ca 2+  at room temperature, and the europium emission spectra were measured at different time point (1, 24 and 48 hours). 
     Materials 
     Tissue Culture 
     Human cervical cancer HeLa cells were grown in Dulbecco&#39;s Modified Eagle Medium (DMEM). Human lung normal diploid fibroblasts MRC-5 and neuroblastoma cells SK-N-SH were provided by Cell resource center of Shanghai Institute of Biological Sciences, Chinese Academy of Sciences; and cultured in MEM (GIBCO 41500034); Human derived liver cells QSG-7701 cells were grown in RPMI-1640 (GIBCO 31800022); all cells were supplemented with 10% (v/v) fetal bovine serum, 1% penicillin and streptomycin at 37° C. and 5% CO 2 . 
     MTT Cell Cytotoxicity Assays 
     HeLa, SKA-SH, QSG-7701 or MRC-5 cells treated with testing complexes for 24 hours were further incubated with MTT, 3-(4,5-dimethylthiazol-2-yl)-2 and 5-diphenyltetrazolium bromide (0.5 mg; ml) for 4 hours, to produce formazan during cell metabolism. Then, formazan was thoroughly dissolved by dimethyl sulfoxide (DMSO), and the absorbance of solutions was measured in Bio-Rad iMark microplate reader (570 nm). Quadruplicates were performed. Data analysis and plotting were operated by the GraphPad Prism 5 software. 
     Two-Photon Confocal in Vitro Imaging 
     Cells were seeded on coverslip in 35-mm culture dishes overnight. And then incubated with HGEu001 or HGEu002 (10 μM) for 6 hours, and the cells were washed by PBS 3 times before imaging. For the two-photon time lapses in vitro images of HGEu001 and HGEu002 were observed with different incubation time (3, 6, 18 and 24 hours). Then the unabsorbed complexes were washed out with PBS buffer and the cells were subject to microscopic imaging. The in vitro imaging of HGEu001 and HGEu002 were undertaken on a linear fluorescence microscopy under 375 nm UV light excitation or a confocal laser scanning microscope, Leica TCS SP8, equipped with a Ti:sapphire laser (Libra II, coherent). The excitation beam produced by 690 nm to 1080 nm (fs laser) was focused on the adherent cells through a 63× oil immersion objective. 
     3D images obtained by the Z-stacks form the two-photon confocal microscopy and the 3D reconstruction was done with built-in programs of Leica TCS SP8 confocal microscope. 
     Co-Localization Imaging 
     (a) 3D Co-Localization Imaging of HGEu001 and HGEu002 with Primary Cilia Markers ARTL13B and IFT88. 
     Full length ARTL13B (ADP-ribosylation factor-like protein 13B) was PCR amplified from cDNA library and inserted into multiple cloning sites (MCS) of pEGFP-C3 (CLONETECH, #6082-1) using restriction digestion sites of XhoI/EcorI for GFP-ARTL13B expression. The positive recombinant was selected through kanamycin proved by sequencing. Plasmid mEmerald-IFT88-N-18 (intraflagellar transport protein 88 homolog) expressing GFP-IFT88 was a gift from Michael Davidson (Addgene plasmid #54125). Plasmids were amplified in  E. coli  (DH5α) and purified using a StarPrep Plasmid Miniprep Kit (Genstar). Both GFP-ARL13B and GFP-ITF88 for primary cilium tracking were expressed in HeLa cells through lipofectamine2000 (Cat. No.11668-019, Invitrogen) mediated transfection. Briefly, a 3.5 cm dish of HeLa cells (with 70-80% confluent) was transfected with 4 μg DNA plus 4 μL lipotectamine2000 mixture according to the manufacturer instructions. After incubation for 8 hours, 10 μM of HGEu001 or HGEu002 were added and incubated for 6 hours. 
     (b) Co-Localization Imaging of HGEu001 and HGEu002 with Organelles. 
     Live cell labeling probes of organelles (mitochondria, lysosome and Golgi apparatus) MitoTracker® Green FM (M-7514), LysoTracker® Green DND-26 (L-7526) and GolgiTracker® Oregon Green (W6748, Wheat Germ Agglutinin) were respectively purchased from ThermoFisher Scientic Inc. and stocked in −20° C. 
     Three dishes of HeLa cells (1×10 5 ) were first incubated with 10 μM HGEu001/HGEu002 for 6 hours. Then organelles probes (50 nM, each) were added in parallel to the cells and further incubated for 15 minutes. The cells were washed by PBS 3 times before imaging on the linear fluorescence microscopy. Under the excitation of UV light (375 nm) emission from the channel (610-630 nm) were collected for the emission signals from HGEu001/HGEu002. Under 488 nm blue light excitation, imaging channel in the range between 505 and 555 nm were collected from the emission signal of organelles dyes. 
     Absorption and Emission Spectra of HGEu001-Coumarin and HGEu001-Por 
     UV-Visible absorption spectra of HGEu001-Coumarin and HGEu001-Por were recorded by an HP Agilent UV-8453 Spectrophotometer. The emission spectra of HGEu001-Coumarin and HGEu001-Por were measured by Horiba Fluorolog-3 spectrophotometer, which was equipped with a 450 W continuous xenon lamp and a UV-Vis PMT detector—Hamamatsu—R928 cooled 216 at −20° C. for steady state emission measurement. 
     Protein Enrichment Using HGEu001-Biotin and HGEu001-EDECRIN. 
     a) Protein Labeling Using HGEu001-EDECRIN 
     HGEu001-EDECRIN was reacted with cell lysate at 4° C./16° C./37° C. for 10 min. The protein mixture was then treated with SDS-PAGE loading buffer. The resulting mixture were boiled for 10 min and centrifuged at 14000 rpm for 5 minutes. Then the protein mixture was loaded onto one well of a gel and separated by SDS-PAGE using a Hoefer SE400 Vertical Electrophoresis System (18×16 cm). The gel was stained with Coomassie brilliant blue 6250 and imaged. Florescence images of the gel were taken under UV light excitation. The fluorescent protein band was excised and then destained in 50% (v/v) acetonitrile, dehydrated with gradient acetonitrile (50-70%) and then cysteine-alkylated by dithiothreitol/iodoacetamide. MS compatible peptides of each of the bands were generated by In-Gel trypsin digestion (Trypsin Gold, V5280, Mass Spectrometry Grade 100 mg (1 vial), Promega) at 37° C. for 16 hours and extracted using 70% acetonitrile (with 0.02% trifluoroacetic acid) three times. The extracts were combined and vacuum dried, resuspended in LC buffer (95% H2O, 5% acetonitrile, 0.1% formic acid) and readied for mass spectrometry analysis. 
     b) Protein Pull-Down Using HGEu001-Biotin 
     HGEu001-Biotin was incubated with cell lysate at 37° C. for 10 min, HGEu001-Biotin binding protein was enriched using Monomeric Avidin UltraLink resin using home-made micro-columns. The proteins were further analyzed by SDS-Gel analysis. Since the amount of enriched protein was too small, there was no one clear band could be seen by coomassie blue staining method. The protein band, which had the same position with fluorescent band of HGEu001-EDECREN labeling and imaging assay as describe above, was excised and further treated for nLC-MS/MS analysis. 
     Results 
     Two europium complexes HGEu001 and HGEu002 were synthesized by similar procedures as shown in Scheme 1 ( FIG. 29 ). Recrystallization of the crude europium complexes with diethyl ether gave HGEu001 and HGEu002 in a yield of ˜95%. All the intermediates were well characterized by  1 H-NMR,  13 C-NMR and HRMS. The europium complexes, HGEu001 and HGEu002, were purified and verified by high-performance liquid chromatography and HRMS ( FIGS. 7A-7B, 8-9 ). The strong absorption bands of the complex HGEu001 in water can be found peaking at 340 nm (ε&gt;20,000 cm −1 , Table 2), corresponding to the π→π* transition ( FIG. 10 ). 
     The photo-physical properties of HGEu001 and HGEu002 were recorded in aqueous solution and have similar europium emission quantum yields (ϕ=˜10%). The five europium f-f emission  5 D 0 → 7 F J  bands (J=0-4) were observed and the ratio of these f-f transition intensity is consistent with literature reports of a typical cyclen-based europium complexes with a D2h symmetry ( FIGS. 1A-1B ,  FIGS. 11A-11B  and Table 2). Showing similar molecular structures and photo-physical properties, the toxicity of HGEu001 and HGEu002 is also similarly low in HeLa, SK-N-SH, QSG-7701 and MRC-5 cells (IC50 are ˜390-440 μM, Table 3). However, the in vitro subcellular localization of HGEu001 and HGEu002 is vastly different, especially HGEu001—the red emission of HGEu001 in vitro did not correlate with common commercial organelle-specific markers, such as mitochondria, lysosome and Golgi apparatus in fluorescence microscopy ( FIGS. 2A-2I ). 
     
       
         
           
               
             
               
                 TABLE 2 
               
             
            
               
                   
               
               
                 Photophysical properties of the europium 
               
               
                 complexes HGEu001 and HGEu002. 
               
            
           
           
               
               
               
               
               
               
               
            
               
                   
                 λ max / 
                 ε/M −1   
                 τ(H 2 O)/ 
                 τ(D 2 O)/ 
                   
                 Φ L   Eu / 
               
               
                 Complex 
                 nm  [a]   
                 cm −1    [a]   
                 ms  [b]   
                 ms  [b]   
                 q [c]   
                 %  [d]   
               
               
                   
               
            
           
           
               
               
               
               
               
               
               
            
               
                 HGEu001 
                 327 
                 23400 
                 0.56 
                 1.78 
                 0.9 
                 10.5 
               
               
                 HGEu002 
                 327 
                 22200 
                 0.56 
                 1.78 
                 0.9 
                 10.3 
               
               
                   
               
               
                   [a]  Absorption coefficient in H 2 O, 298K; 
               
               
                   [b]  Europium emission decay in FIGS. 12A-12B (λ em  = 614 nm.  5 D 0 → 7 F 2 . λ ex  = 340 nm); 
               
               
                   [c] Derived hydration numbers, q (±20%) q = 1.2[(k(H 2 O) k(D 2 O)) − (0.25 + 0.07x)] (k = τ −1 , x = number of carbonyl-bound amide NH oscillators); 
               
               
                   [d]  Overall europium emission quantum yield in H 2 O, by-integrated sphere. 
               
            
           
         
       
     
     
       
         
           
               
             
               
                 TABLE 3 
               
             
            
               
                   
               
               
                 Cytotoxicity of the complexes HGEu001 and HGEu002 against 
               
               
                 HeLa, SK-N-SH, QSG-7701 find MRC-5 cell line. (IC 50 /μM) 
               
            
           
           
               
               
               
               
               
               
            
               
                   
                 Complex 
                 HeLa 
                 SK-N-SH 
                 QSG-7701 
                 MRC-5 
               
               
                   
                   
               
            
           
           
               
               
               
               
               
               
            
               
                   
                 HGEu001 
                 411 
                 389 
                 395 
                 395 
               
               
                   
                 HGEu002 
                 417 
                 437 
                 410 
                 402 
               
               
                   
                   
               
               
                   
                 Incubation time = 24 hours; Raw data are shown in FIGS. 13A-13B. 
               
            
           
         
       
     
     DISCUSSION 
     To further confirm the reputation of the primary cilia-specific in vitro subcellular localization of HGEu001, in vitro imaging of HGEu001 was performed on a multi-photon confocal microscope ( FIGS. 3A-3H ). With 3 hours of incubation in HeLa cells, red europium emission of HGEu001 was found in a particularly focused area in the primary cilium under two photon excitation (λ ex =700 nm,  FIGS. 3A-3H ) and optimum emission intensity lasted for 24 hours. However, the red emission of HGEu002 was found dispersed in the cytoplasm ( FIGS. 14A-14H and 15A-15F ). The in vitro subcellular localization of HGEu001 and HGEu002 are the same in number of cell lines, such as HeLa, SK-N-SH and MRC-5 ( FIGS. 13A-13B ). 
     Aiming to confirm this subcellular localization of HGEu001, a positive control has been done. The co-localization experiments have been done by Green Fluorescent Protein-fused with primary cilia marker ARL13B (GFP-ARL13B). The advantages of using Green Fluorescent Protein “GFP” are its bright luminescence and availability to trace the localization of cellular proteins, such as antibody, at the targets in vitro. However, GFP also gives scientists a lot of hassle in molecular imaging, such as its complicated process in cloning, transfection and their broad emission profile and short emission lifetime presents a low signal to noise ratio problem. There are no commercially available simple primary cilia markers, therefore, the present invention could only compare the subcellular localization between HGEu001 and GFP-ARL13B (ARL13B is the cilium-specific protein required for culinary axoneme structure) and with HGEu002 as a negative control ( FIGS. 2A-2I ). 
     The perfect overlapping of the in vitro red emission from HGEu001 (dosage concentration=10 μM, incubated for 6 hour after GFP was transfected and expressed) with the green emission from GFP-ARL13B (transfection procedure see ESI) is shown in  FIGS. 4A-4H . The yellow emission of the merged images is shown as well (HGEu001, λ ex  700 nm, BP 550-665 nm, and GFP-ARL13B λ ex =488 nm, BP 505-555 nm). On the other hand, the red emission of HGEu002 and green emission of GFP-ARL13B are localized in different parts in the cytoplasm and only slight yellow emission can be found in their merged images ( FIG. 4G ). This can confirm the selectivity of HGEu001 in primary cilia, but not HGEu002. As primary cilium is a rod-like organelle, two dimensional florescence images or confocal images are not good enough to show the specificity of the HGEu001 localization. With their two photon induced emission properties, three dimensional confocal images of HGEu001 and HGEu002 were obtained in HeLa cells by two photon confocal microscope (z stack) with excitation at 700 nm ( FIGS. 5A-5H and 6A-6D ). Red emission can be found in the HeLa cells and is shown as the red column ( FIG. 5A ). In control experiments, HGEu002 did not show any europium emission in the rod-like organelles ( FIG. 5B ). However, HGEu002 appears to localize in certain part of the cytoplasm instead of primary cilia. 
     To further confirm the selective primary cilia subcellular localization of HGEu001, three dimensional red in vitro imaging of HGEu001 and its motif control HGEu002 were compared with the primary cilia-specific green GFP-ARL13B and also with another primary cilia marker GFP-IFT88 (IFT88 is the component of IFT complex B involved in cilium biogenesis) ( FIGS. 6A-6D ). Only HGEu001 showed the yellow merged in vitro emission with the co-staining with GFP-ARL13B or GFP-139IFT88. Besides, HGEu001 did not show merged yellow in vitro emission with green mito-tracker. HGEu002 also did not show merged yellow in vitro emission with neither GFP-ARL13B, GFP-IFT88 nor green mito-tracker. The 3D video of in vitro imaging in  FIGS. 5A-5F and 6A-6D  are shown in the supporting information. 
     In general, with comprehensive co-staining subcellular localization in vitro imaging studies, the selectivity of HGEu001 in primary cilia in vitro can be confirmed with good confidence. HGEu001 and HGEu002 have very similar structures, however, only HGEu001 preferentially localizes in primary cilium. Since HGEu001 did not show any non-specific staining on other organelles such as lysosome, mitochondria, or Golgi apparatus ( FIGS. 2A-2I ), binding to the structural components of primary cilium (e.g. cilium membrane, microtubules and associated proteins) or its associated factors, shall be a possible explanation for the specifically localization on the primary cilium of HGEu001. 
     The binding mechanism of the present molecules could be studied by analytical means such as proteomics mass spectrometry. Hence the present invention provides a blueprint or strategy for developing a set of primary cilia targeting probes with special functions or delivering purposes towards primary cilia by simple conjugation with the HGEu001 motif structure. In fact, the imaging protocol established in the present invention can also be used to validate the specific binding of any future probes to primary cilium, with emphasis on visualizing the rod-like structure by 3D imaging. 
     There is provided in the present invention a direct imaging tool for primary cilia which is specific, and can be excited by light in the near infrared (NIR) region. Comprehensive in vitro studies and several control experiments were done to confirm the specific primary cilium localization of HGEu001, showing a great degree of agreement with GFP-conjugated primary cilia markers ARL13B and IFT88 in co-localization experiments. These novel primary cilium marker could help to understand the functions and roles of primary cilium in life science, such as tumorigenesis. 
     There is also provided in the present invention a possible template for designing primary cilium-specific molecules with potential modification to become target-specific drug delivery vehicles to help understand the functions of primary cilium and evolve into cancer or diseases treatment applications. A molecular library, HGEu003-HGEu016 (structures shown in  FIG. 28 ) based on the complex HGEu001 has been developed and primary cilium imaging screening has been undertaken. Proteomic mass spectroscopy studies could also be carried out to evaluate the specific binding of HGEu001 with particular proteins in primary cilium. 
     Primary Cilium Imaging Marker with Expanded Excitation and Emission Wavelength. 
     The excitation of the primary cilium imaging marker HGEu001 can be accomplished by UV light or NIR light (e.g., using a femtosecond laser). Consequently, its application may be limited by the configuration and/or availability of the imaging microscopy instrument(s) on hand. Moreover, the fluorescent filter of some fluorescence microscopy instruments is not turntable, which means that if UV excitation is applied, red emission cannot be collected due to the configuration of the microscopy instrument. For NIR femtosecond laser excitation, the cost of femtosecond laser instruments is still prohibitively high, which has limited the availability of these instruments in research laborites. To extend the range of microscopy instruments that the primary cilium imaging markers described herein can be used in connection with and thus their accessibility, additional excitation and emission wavelengths can be achieved using certain embodiments of the compound of Formula (IV) (e.g., HGEu001-Coumarin and HGEu001-Por). Using such cilium imaging markers removes the need to change the configuration of commonly used and widely available fluorescent/confocal microscopy instruments. The absorption and emission spectra of HGEu001-Coumarin and HGEu001-Por were examined in aqueous solution. ( FIGS. 31 a,b , and  c    and  FIGS. 32 a,b , and  c   ) HGEu001-Coumarin shows an additional absorption band located at 430 nm compared to HGEu001, which belongs to the π→π* of coumarin moiety. In the emission spectra, with 330 nm excitation, both characteristic emission bands from europium (III) ion and coumarin moiety can be observed. With 430 nm excitation, only the coumarin emission band can be observed since light having a wavelength of 430 nm cannot excite HGEu001. Similar results can be observed from HGEu001-Por. HGEu001-Coumain and HGEu001-Por provide new excitation and emission channels for optical imaging, which can expand the application of the chemically synthesized primary cilium imaging markers described herein to all type of microscopy. 
     Primary Cilium Related Protein Enrichment and Analysis 
     Two new exemplary probes HGEu001-EDECRIN and HGEu001-Biotin were synthesized for primary cilium related protein enrichment. The hypothesis was that HGEu001 allows for specific imaging of primary cilia due to the specific binding of HGEu001 with primary cilium related proteins. From SIDS-PAGE gel analysis of HGEu001-EDECRIN labeling assay, a number of protein bands can be seen from the image of the gel stained by Coomassie blue since the cell lysate contains all the proteins of the cells. However, in the fluorescent imaging using UV excitation only one emission band can be clearly observed. Fluorescent imaging of HGEu001-Biotin was not performed, because the interaction between HGEu001-Biotin and its binding protein target is noncovalent binding, and the HGEu001-Biotin-protein binding partner were destroyed by the SDS-PAGE treating conditions. ( FIG. 34 ) The protein detection limitation of Coomassie blue staining method is too pool that there is no clear band can be seen of gel of HGEu001-Biotin enriched protein. However, the LC-MS/MS analysis identified 93 and 391 proteins by HGEu001-Biotin and HGEu001-EDECRIN respectively. Comparing the proteins identified, there were 72 proteins that overlapped using the two different methods. ( FIG. 35 ) Primary cilium related tubulin and actin proteins could be found in these 72 overlapping proteins. In addition, one HGEu001-EDECRIN labeled peptide was found by the primary data analysis. The peptide sequence identified belonged to amino acids 71-103 of human beta-actin protein (GenBank: ABD66582.1), which is a known primary cilium related protein. 
     INDUSTRIAL APPLICABILITY 
     The presently claimed invention provides a water-soluble, simple, stable tris(N-(tert-butyl)acetamide) cyclen-based europium complex HGEu001 which exhibits the specific subcellular localization in the primary cilium with a quantum yield as high as 10% in water and a lifetime of 0.56 ms lifetime. In particular, the present invention provides simplicity of the design and synthesis of a complex HGEu001. The present molecules or complexes are useful in imaging primary cilium in biological cells which serve as an organelle-specific probe for primary cilium in order to identify any disorder, disease or cancer that is associated with this particular organelle. Currently there is no such organelle-specific probe in place, which the present invention can meet this need.