Patent Publication Number: US-2011064674-A1

Title: Luminescent multimodal nanoparticle probe system and method of manufacture thereof

Description:
CROSS-REFERENCE TO RELATED APPLICATION(S) 
     This application claims the benefit of U.S. Provisional Patent Application Ser. No. 61/128,332 filed May 21, 2008, and the subject matter thereof is incorporated herein by reference thereto. 
    
    
     GOVERNMENT RIGHTS 
     This invention was made with Government support under grant No. NiH-R01-EB000364 awarded by the National Institutes of Health. The government has certain rights in the invention. 
    
    
     TECHNICAL FIELD 
     The present invention relates generally to a nanoparticle probe, and more particularly to a luminescent multi-modality nanoparticle probe system. 
     BACKGROUND ART 
     Luminescent nanoparticles show tremendous promise for in vitro and in vivo biochemical detection and imaging, such as imaging of biochemical markers for cancer and infectious diseases. Their unique optical properties have prompted a rapid expansion of their applications, especially in living animals, with potential utility for clinical use. However, most luminescent nanoparticles contain toxic elements such as cadmium, arsenic, indium and mercury, thus raising growing concerns regarding environmental and safety issues. Detailed safety data are largely unavailable for these particles, thus restricting their use to preclinical/non-human applications. 
     One important requirement for nanoparticles for use in living organisms is efficient luminescent emission in the near infrared range (NIR), in the optical window between hemoglobin absorption and water absorption. Further, operation at long NIR wavelengths reduces Rayleigh scattering in tissues. Operation in the NIR thus increases the tissue depth for imaging and reduces autofluorescence background from native proteins such as collagens, porphyrins, and flavins. 
     Additionally there is a need for multi-modality nanoparticles: particles that exhibit properties that enable detection by different means of detection such as optical, x-ray, and nuclear magnetic resonance detection. 
     Thus, a need still remains for non-toxic multi-modality nanoparticles for biochemical detection in vitro and in vivo. In view of the need for quantitative biochemical detection in biochemical specimens and living organisms, it is increasingly critical that answers be found to these problems. In view of the ever-increasing commercial competitive pressures, along with growing consumer expectations and the diminishing opportunities for meaningful product differentiation in the marketplace, it is critical that answers be found for these problems. Additionally, the need to reduce costs, improve efficiencies and performance, and meet competitive pressures adds an even greater urgency to the critical necessity for finding answers to these problems. 
     Solutions to these problems have been long sought but prior developments have not taught or suggested any solutions and, thus, solutions to these problems have long eluded those skilled in the art. 
     DISCLOSURE OF THE INVENTION 
     The present invention provides a method of manufacture of a luminescent nanoparticle probe system including forming a bismuth sulfide core; and coating the bismuth sulfide core with a shell. 
     In addition, the present invention provides a luminescent nanoparticle probe system, including: a bismuth sulfide core; and a shell coating the bismuth sulfide core. 
     Certain embodiments of the invention have other steps or elements in addition to or in place of those mentioned above. The steps or element will become apparent to those skilled in the art from a reading of the following detailed description when taken with reference to the accompanying drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a plot of luminescence emission wavelength for a luminescent nanoparticle probe system  102  in one embodiment of the present invention compared to the emission of nanoparticles of different composition. 
         FIG. 2  is a synthesis scheme for manufacturing the luminescent nanoparticle probe system in one embodiment of the present invention. 
         FIG. 3  is a high-resolution Transmission Electron Microscope (TEM) image showing the bismuth sulfide core in the luminescent nanoparticle probe system of the present invention. 
         FIG. 4  is a size distribution plot of the bismuth sulfide core. 
         FIG. 5  is X-ray diffraction data for the bismuth sulfide core of the luminescent nanoparticle probe system of the present invention. 
         FIG. 6  is fluorescence emission spectra of the bismuth sulfide core in the luminescent nanoparticle probe system of the present invention. 
         FIG. 7  is X-ray (CT) contrast data for the bismuth sulfide core compared to that of a cadmium telluride nanoparticle. 
         FIG. 8  is an image showing fluorescence of the bismuth sulfide core in the luminescent nanoparticle probe system. 
         FIG. 9  is an image of a nude mouse that has been administered intradermally a saline solution containing the bismuth sulfide core (i.e., a suspension of these nanoparticles). 
         FIG. 10  is a schematic diagram of the luminescent nanoparticle probe system in one embodiment of the present invention. 
         FIG. 11  is a luminescent nanoparticle probe system incorporating the luminescent nanoparticle probe system of  FIG. 10  and an external molecule. 
         FIG. 12  a flow chart of a method of manufacture of a luminescent nanoparticle probe system in a further embodiment of the present invention. 
     
    
    
     BEST MODE FOR CARRYING OUT THE INVENTION 
     The following embodiments are described in sufficient detail to enable those skilled in the art to make and use the invention. It is to be understood that other embodiments would be evident based on the present disclosure, and that system, process, or mechanical changes may be made without departing from the scope of the present invention. 
     In the following description, numerous specific details are given to provide a thorough understanding of the invention. However, it will be apparent that the invention may be practiced without these specific details. In order to avoid obscuring the present invention, some well-known chemistries and manufacturing processes are not disclosed in detail. 
     The drawings showing embodiments of the system are semi-diagrammatic and not to scale and, particularly, some of the dimensions are for the clarity of presentation and are shown exaggerated in the drawing FIGs. Similarly, although the views in the drawings for ease of description generally show similar orientations, this depiction in the FIGs. is arbitrary for the most part. Generally, the invention can be operated in any orientation. 
     Where multiple embodiments are disclosed and described having some features in common, for clarity and ease of illustration, description, and comprehension thereof, the same numbers are used in all the drawing FIGs. to relate to the same elements. The embodiments have been numbered first embodiment, second embodiment, etc. as a matter of descriptive convenience and are not intended to have any other significance or provide limitations for the present invention. 
     Referring now to  FIG. 1 , therein is shown a plot of luminescence emission wavelength  100  for a luminescent nanoparticle probe system  102  in one embodiment of the present invention compared to the emission of nanoparticles of different composition. The luminescent nanoparticle probe system  102  of  FIG. 1  is a nanoparticle that includes bismuth sulfide (Bi 2 S 3 ). Dotted lines  104  show the bounds of the optimal imaging range for in vivo applications. 
     As shown in  FIG. 1 , luminescent nanoparticle emissions span across a broad spectral range from ultra-violet (UV) to the infrared (IR). All visible and infrared colors shown can be excited with a single excitation wavelength. Only a limited number of materials can form near infra-red (NIR) nanoparticles with optimal wavelengths for in vivo detection, primarily indium phosphide (InP), gallium antimonide (GaSb), gallium arsenide (GaAs), mercury telluride (HgTe), mercury selenide (HgSe), cadmium telluride (CdTe) and the luminescent nanoparticle probe system  102  of the present invention. These compounds tend to oxidize readily in air and in aqueous environments, and therefore must be protected by an inert shell or coating. These coatings must be compatible with in biological environments. 
     Bismuth sulfide (Bi 2 S 3 ) and other bismuth compounds are attractive materials for bioimaging. The optical band gap of bismuth sulfide is positioned in an ideal spectral range, as quantum confinement should shift the emission into the 700-850 nm range—the perfect near-infra-red range for deep in vivo imaging in tissues. This material is characterized by high stability and very low solubility in either aqueous or organic media. Furthermore, it stands out as a potentially non-toxic compound. Bismuth compounds have been used in pharmaceutical formulations for more than a century, to treat maladies such as diarrhea, syphilis, or peptic ulcers, as well as in cosmetics. 
     Synthesis of nanosized bismuth sulfide has been investigated mostly for potential applications in electronic and optoelectronic devices, with most reported syntheses focusing on nanorod, nanowire, and nanotube morphologies; however, there are no reports of the synthesis of bismuth sulfide nanoparticles that are consistent in mass, shape, and mass distribution (referred to as “monodisperse” bismuth sulfide nanoparticles). 
     Referring now to  FIG. 2 , therein is shown a synthesis scheme  200  for manufacturing the luminescent nanoparticle probe system  102  in one embodiment of the present invention. A first reaction  202  in the synthesis scheme  200  produces a bismuth sulfide core  204 . A second reaction  206  coats the bismuth sulfide core  204  with a shell  208  preferably using an X-ray contrast material  210  such as bismuth oxide (Bi 2 O 3 ). A third reaction introduces a shell dopant  214  on the surface of the shell  208 , which is preferably a contrast material for magnetic resonance imaging such as galodinium (Gd 3+ ). 
     In the first reaction  202 , bismuth tri-mercaptoundecanoate, Bi(SR) 3  intermediate is prepared from bismuth citrate (2.5 mmol) and mercaptoundecanoic acid (7.5 mmol) by stirring in basic aqueous solution (600 mL). A number of bismuth salts can be used for the reaction including a number of anions that are generally regarded as safe (GRAS) such as citrate salts, cysteine salts, and acetate salts. Other marcaptoalkylcarboxilic acids may also be used. Dropwise addition of sodium sulfide (1.25 mmol in 100 mL) over 1.5 hours with vigorous overhead stirring results in a yellow to dark brown color change without a corresponding change in turbidity, signaling the formation of the bismuth sulfide core  204  rather than bulk bismuthinite. After stirring for 3 hours, the particles are purified by repeated ultrafiltration (30 kDa membrane) to yield a homogeneous solution of containing the bismuth sulfide core  204 . 
     In the second reaction  206 , the bismuth sulfide core  204  (10-100 mg of bismuth sulfide core nanoparticles) is added to an overhead stirred reactor at room temperature in 500 mL of water, and mixed with a solution of bismuth citrate (or other salt) at neutral pH. The molar ratio of bismuth citrate:core particles is determined based on the targeted shell thickness. Under vigorous stirring, the pH is slowly adjusted by addition of sodium hydroxide (NaOH) with a syringe pump until the pH reaches a level where precipitation of bismuth hydroxide/bismuth oxyhydroxide is known to occur at the concentrations used (established with previous range-finding experiments). Slow addition of further base at this point results in preferential shell growth on the existing core-particle surface. 
     Bismuth (Bi 3+ ) is similar in size (1.03 Å) to galodinium (Gd 3+ ) (0.938 Å), making it possible to dope the shell  208  with the shell dopant  214 , which is preferably galodinum for enhanced MRI contrast. As part of the third reaction  212 , the bismuth sulfide core  204  coated with the shell  208  (10-100 mg) is added to an overhead stirred reactor at room temperature in 500 mL of water, and mixed with a solution of bismuth citrate (or other salt) and galodinium citrate (or other salt) at neutral pH. 
     The stoichiometry of bismuth- and galodinium-salts can be altered as needed. Under vigorous stirring, the pH is slowly adjusted by addition of sodium hydroxide as done in the formation of the shell  208 . The resulting luminescent nanoparticle probe system  102  is purified as before. In the luminescent nanoparticle probe system  102 , the shell dopant  214  is preferably present at the exposed surface of the shell  208 , where it can participate in water relaxation. 
     It has been discovered that the luminescent nanoparticle probe system  102  shown in  FIG. 2  provides multimodality detection including luminescence X-ray contrast, and Magnetic Resonance Imaging contrast. Thus the luminescent nanoparticle probe system  102  of the present invention may be used in conjunction with optical imaging, X-ray imaging (including computed tomography), and magnetic resonance equipment or multi-modality equipment incorporating two or more of these means of detection. 
     Referring now to  FIG. 3 , therein is shown a high-resolution Transmission Electron Microscope (TEM) image  300  showing the bismuth sulfide core  204  in the luminescent nanoparticle probe system  102  of the present invention. A scale bar  302  shows a relative scale of 5 nm. An insert  304  shows a Fourier Transformation of a corresponding part of the high-resolution Transmission Electron Microscope (TEM) image  300  with the bismuth sulfide core  204 . The high-resolution Transmission Electron Microscope (TEM) image  300  exhibits clear lattice fringes revealing the high crystallinity of the bismuth sulfide core  204 . 
     Referring now to  FIG. 4 , therein is a size distribution plot  400  of the bismuth sulfide core  204 . The synthesis scheme  200  of  FIG. 2  produces a nearly spherical and nearly size-uniform-bismuth sulfide core  204  in the size range of 3-5 nm. Particle size may be controlled by adjusting the relative amounts of reactants in the first reaction  202  of the synthesis scheme  200 . 
     Referring now to  FIG. 5 , therein is shown X-ray diffraction data  500  for the bismuth sulfide core  204  of the luminescent nanoparticle probe system  102  of the present invention. Diffraction peaks  502  in the X-ray diffraction data  500  indicate an orthorhombic bismuth sulfide structure. The broadening of the diffraction peaks  502  is ascribed to the small particle size effect, since the width of the diffraction peak exhibits inverse dependence to crystallite size. 
     Referring now to  FIG. 6 , therein is shown fluorescence emission spectra  600  of the bismuth sulfide core  204  in the luminescent nanoparticle probe system  102  of the present invention. Aqueous emission  602  of the bismuth sulfide core  204  displays a broad peak at 1050 nm and is relatively dim presumably due to “deep-trap” emission. In contrast, ethanol emission  604  has a narrow, bright-band edge emission with a peak at approximately 750 nm, due to surface exchange and ethanolic dispersion. 
     Referring now to  FIG. 7 , therein is shown X-ray (CT) contrast data  700  for the bismuth sulfide core  204  compared to that of a cadmium telluride nanoparticle. The X-ray (CT) contrast data  700  includes bismuth sulfide contrast  702  and cadmium telluride nanoparticle contrast  704 . The bismuth sulfide contrast  702  provided by the bismuth sulfide core is comparable to the cadmium telluride nanoparticle contrast  704 . 
     Referring now to  FIG. 8 , therein is shown an image  800  showing fluorescence of the bismuth sulfide core  204  in the luminescent nanoparticle probe system  102 . The bismuth sulfide core fluorescence  802  is easily detectable compared to a water-filled cuvette signal  804 . 
     Referring now to  FIG. 9 , therein is shown an image  900  of a nude mouse  902  that has been administered intradermally a saline solution containing the bismuth sulfide core  204  (i.e., a suspension of these nanoparticles). A fluorescence signal  904  from the bismuth sulfide core  204  is clearly seen at the injection site for the saline solution containing the bismuth sulfide core  204 . 
     Referring now to  FIG. 10 , therein is shown a schematic diagram of a luminescent nanoparticle probe system  1000  in one embodiment of the present invention. The luminescent nanoparticle probe system  1000  includes the bismuth sulfide core  204 , the shell  208 , and the shell dopant  214  on the surface of the shell  208 . In addition, in this embodiment of the invention the luminescent nanoparticle probe system  1000  includes a stabilization layer  1002  with a functional molecule  1004  on the surface of the stabilization layer  1002 . The stabilization layer  1002  may be implemented using mercaptoalkylacetic acid ligands or modified mercaptoalkylacetic acid, in both cases with alkyl group number ranging from 1 to 16. 
     The stabilization layer  1002  provides passivation, compatibility with external biological environments, and long-term stability for luminescent nanoparticle probe system  1000 . The functional molecule  1004  is an attachment point for conjugations or complexing to elements external to the luminescent nanoparticle probe system  1000 . 
     Referring now to  FIG. 11 , therein is shown a luminescent nanoparticle probe system  1100  incorporating the luminescent nanoparticle probe system  1000  of  FIG. 10  and an external molecule  1102 . In this embodiment of the present invention, the external molecule  1102  may be a biomolecule  1104  or an energy donor  1106 . 
     The biomolecule  1104  is any organic or biological molecule without limitation including peptides, proteins such as enzymes, fusion proteins, and antibodies, poly-nucleotides such as DNA and RNA, biotin, and sugars. The energy donor  1106  is any nanoparticle, biomolecule, dye, polymer, or chemical entity capable of acting as an energy donor in an energy transfer process between the energy donor  1106  and the luminescent nanoparticle probe system  1000 . Examples of energy transfer processes include Fluorescence Resonance Energy Transfer (FRET, where the energy donor is a fluorescent entity), Bioluminescence Resonance Energy Transfer (BRET, with a bioluminescent protein acting as the energy donor), or Chemiluminescence Resonance Energy Transfer (CRET, with a chemiluminescent entity acting as the energy donor). 
     Referring now to  FIG. 12 , therein is shown a flow chart of a method  1200  of manufacture of a luminescent nanoparticle probe system  102  in a further embodiment of the present invention. The method  1200  includes: forming a bismuth sulfide core in a block  1202 ; and coating the bismuth sulfide core with a shell in a block  1204 . 
     The resulting method, process, apparatus, device, product, and/or system is straightforward, cost-effective, uncomplicated, highly versatile, accurate, sensitive, and effective, and can be implemented by adapting known components for ready, efficient, and economical manufacturing, application, and utilization. 
     Another important aspect of the present invention is that it valuably supports and services the historical trend of reducing costs, simplifying systems, and increasing performance. 
     These and other valuable aspects of the present invention consequently further the state of the technology to at least the next level. 
     While the invention has been described in conjunction with a specific best mode, it is to be understood that many alternatives, modifications, and variations will be apparent to those skilled in the art in light of the aforegoing description. Accordingly, it is intended to embrace all such alternatives, modifications, and variations that fall within the scope of the included claims. All matters hithertofore set forth herein or shown in the accompanying drawings are to be interpreted in an illustrative and non-limiting sense.