# BODIPY-Based Nanomaterials--Sensing and Biomedical Applications
## 2 Metallic Nanoparticles@BODIPY
### Sensing Applications  
#### 2.1.1. Magnetite Nanoparticles  
There are many drugs with a very narrow \"therapeutic window\". This means that some drugs act in the desired way only in a narrow concentration range, which means that at a concentration below this range, there is no curing effect, and above it, a toxic one is observed. An example of these substances is tacrolimus--an immunosuppressive drug crucial in the transplantation field with therapeutic concentrations from 5 to 20 ng/mL. Tacrolimus is strongly bound to proteins; there is only 0.5% of the free fraction. Therefore, a fast and straightforward quantification method is needed to provide a safe therapy. [PERSON] and co-workers proposed the determination of this drug based on fluorescent magnetic nanobeads composed of BODIPY dyes as a fluorescent probe [59]. BODIPY dyes were deposited on polystyrene nanospheres antecedently decorated with ferrite nanograins and exposed to carboxylic functionalization (Figure 6). Later, the activated particles were conjugated to capture IgG anti-IgM antibodies through the amine groups. The procedure of tacrolimus determination relies on the addition of anti-FK506 (anti-tacrolimus) and anti-biotin antibodies to the sample with carboxylated drugs deposited on a glass surface where they competitively bind each other. After rinsing the sample with PBSTM buffer, nanoparticles were added to it and interacted with tied antibodies. The interaction was accelerated by a Nd magnet that kept the particles in the close neighborhood of tacrolimus-antibody glass. Finally, the fluorescence of fettered particles was measured. Thanks to the FRET phenomenon and significant Stokes shift, the brown color of ferrite did not disturb the measurement. The authors determined the tacrolimus detection limit to be 0.08 ng/mL [59]. Figure 5: Metallic nanoparticles/BODIPY in medicine [51; 52; 53; 54; 55; 56; 57; 58]. In another study, [PERSON] and co-workers designed magnetic silica nanoparticles based on BODIPY dye with nickel and applied them for selective detection and removal of lead ions both from the blood and water environment (Figure 7) [60]. Lead is well-known for causing dangerous side effects in humans. This element is responsible for muscle paralysis, neuropathy, and anemia. The authors prepared core/shell Ni@SiO\({}_{2}\) particles and attached BODIPY dye to them via a sol-gel reaction. Obtained particles bearing bounded Pb\({}^{2+}\) ions were spherical at a narrow size range of 30-40 nm. Nanoprobes without lead ions did not reveal fluorescence ability, which was expected as a result of efficient photoinduced electron transfer--PET. Continuous binding of lead ions turns on fluorescence, according to the chelation-enhanced fluorescence effect, which blocks the PET phenomenon. The addition of 15 ppb lead ions, which constitutes the acceptable level of lead in drinking water, caused over a 10% increase of fluorescence quantum yield, and this heavy metal was removed in 97%. Lead bounding by nanoparticles is reversible, and particles are active after a few detection/separation cycles. Moreover, the authors performed studies to determine the selectivity of lead ions in the presence of Li\({}^{+}\), Na\({}^{+}\), Mg\({}^{2+}\), K\({}^{+}\), Ca\({}^{2+}\), Ca\({}^{2+}\), Zn\({}^{2+}\), Ag\({}^{+}\), Cd\({}^{2+}\), and Hg\({}^{2+}\), and noticed that t two carbonyl groups forming coordination bonds play an important function in Pb\({}^{2+}\) binding. Finally, the authors performed experiments concerning the decontamination of a blood sample. In the blood, they placed 100 ppb of Pb\({}^{2+}\)--the amount believed as unsafe and noted that the designed nanoparticles efficiently removed 96% of the total lead content [60]. [PERSON] and co-workers proposed a similar nanoprobe for lead ions detection [61]. They used the same BODIPY molecule as [PERSON] and co-workers and core/shell Fe\({}_{3}\)O\({}_{4}\)@SiO\({}_{4}\) nanoparticles components (Figure 8). The detection limit was determined at 1.5 ppb, and the response time of 60 s was noted.