Synthesis of CdSe Quantum Dot Nanoparticles - VidInfo
Riboflavin is an essential vitamin for cellular metabolism, and the riboflavin carrier protein (RCP) is highly upregulated in metabolically active cells [,]. Thus, flavin mononucleotide (FMN), an endogenous RCP ligand, was used as a small molecule targeting ligand for metabolically active cancer or endothelial cells. Kiessling and co-workers synthesized FMN-coated ultrasmall superparamagnetic iron oxide nanoparticles (FLUSPIO) as MRI/optical dual probes for cancer detection . USPIO was coated with FMN through the phosphate groups of FMN, and guanosine monophosphate was added to stabilize the colloid. The hydrodynamic radius of FLUSPIO was 97 ± 3 nm, and an intense fluorescence emission band was observed at 530 nm due to FMN. cellular uptake of FLUSPIO was investigated by MRI (3T), TEM, and fluorescence microscopy of PC3 cells and HUVEC cells. Both PC3 cells and HUVEC cells showed a significantly higher R2 relaxation rate after 1 h incubation with FLUSPIO than with nontargeted USPIO. Such an uptake was considerably reduced by competitive blocking of RCP with free FMN. A strong green fluorescence in the cells was observed after FLUSPIO incubation. The perinuclear fluorescence signal suggested endosomal localization of the nanoparticles, consistent with TEM results, suggesting that FMN could serve as a versatile building block for generating tumor-targeted imaging and therapeutic modalities.
SYNTHESIS OF ULTRA-SMALL CdSe QUANTUM DOTS
FIG. 3: NARROW SCAN X-RAY PHOTOELECTRON SPECTRA OF AS-SYNTHESIZED CdSe NANOPARTICLES; CORE LEVEL SPECTRA OF A. Cd, and B. Se, IN AS-SYNTHESIZED CdSe QUANTUM DOTS
FIG. 4: TRANSMISSION ELECTRON MICROGRAPHS OF AS-SYNTHESIZED CdSe NANOPARTICLES, A. TEM IMAGES TAKEN AT DIFFERENT MAGNIFICATIONS, B. HISTOGRAM OF SIZE DISTRIBUTION OF PARTICLES CALCULATED FROM TEM IMAGES (THE SOLID LINE REPRESENTS THE GAUSSIAN FIT TO THE HISTOGRAM), C. HR-TEM IMAGE (REDUCED FFT IMAGES ARE PLACED BESIDE INDIVIDUAL NANOCRYSTAL. INDIVIDUAL CdSe NANOCRYSTALS ENCIRCLED), D. HR-TEM IMAGE OF AN INDIVIDUAL CdSe NANOPARTICLE.
BIOMIMETIC SYNTHESIS OF CdSe NANOPARTICLES …
In this review, different types of QD/drug nanoparticle formulations are described for their potential use in targeted delivery and therapy. Using the rich surface functionalization chemistry of QDs, targeting biomolecules and drug formulation can be integrated with QDs for traceable drug delivery and therapy and . Many studies have demonstrated that the incorporation of drug formulations with QDs did not compromise the drug efficacy. More importantly, the QD/drug nanoparticle formulations were able to serve as an excellent platform for development of a new generation of traceable drug delivery strategies for real time monitoring of the drug biodistribution and . Because of toxicity concerns, cadmium-based QDs might not be the best candidate for drug delivery and therapy. Thus, many research groups are currently synthesizing cadmium-free QDs for applications. For example, our group has demonstrated the synthesis of indium phosphide, silicon, and copper indium sulfide QDs for targeted tumor imaging and very low toxicity was observed from these formulations[-, ]. However, for -based drug studies, cadmium-based QDs will remain to be utilized, since toxicity is not a concern. Another potential concern for the use of QDs in delivery and therapy is the overall QD size. In general, it is preferable to minimize the overall size of QDs for applications to reduce their accumulation in the reticuloendothelial system. Recently, methods have been reported to reduce the size of the QDs by tailoring their surface coating. Finally, passivation of the QD surface with a long-lasting and robust polymer coating is essential to prevent the breakdown of QDs in the biological environment that gives rise to their toxicity. This is a definite concern for applications. Some reports have suggested that capping the QD core with a higher bandgap semiconductor or biomolecule can minimize the toxicity. But, it is worth noting that each additional step towards functionalizing the QDs will contribute to their final hydrodynamic size and could directly or indirectly affect their biodistribution. In the near future, we envision that the QD/drug nanoparticle formulations will gain wide interest in many healthcare-related research areas. For example, the developed formulations can be used for early cancer detection and therapy. Also, the formulations can be systematically tailored for personalized drug treatment. More importantly, additional modalities such as magnetic resonance imaging and positron emission tomography contrast agents can be integrated into the QD/drug formulations, thus allowing one to use two or more imaging modalities to verify the biodistribution and efficacy of the drug . We believe that in the next few years there will be a tremendous growth in developing QD/drug nanoparticle formulations for therapeutic and diagnostic applications.
Synthesis and characterization of CdSe nanoparticles …
In another interesting work, Louie and coworkers have reported the synthesis of a reversible T2 contrast agent that is capable of modulating the relaxation time in response to light irradiation . A spiropyran (SP) derivative that changes conformation between hydrophilic and hydrophobic isomers in response to light, has been covalently attached to dextran sulfate coated iron oxide nanoparticles (ADIO). The light induced reversible aggregation of MNPs has been found to modulate the T2 relaxation time (Figure ).