Nanoparticle injection

In vivo imaging of rat quantum dots (QDs) injected into translucent skin of foot (a) show fluorescence, but not through thicker skin of back (b) or abdomen (c) PEI/NaYF4 Yb, Er nanoparticles injected below abdominal skin (d), thigh muscles (e) or below skin of back (f) show luminescence. QDs on a black disk in (a) and (b) are used as the control. 

Various DDSs based on PLGA have been developed in recent times. The developed DDS includes microparticles, nanoparticles, injectables, dry powder for inhalation,... 

Hyun BR, Zhong YW, Bartmk AC, Sun L, Abruna AD, Wise PW, Goodreau JD, Matthews JR, Leshe TM, BorreUi NP (2008) Electron injection from colloidal PbS quantum dots into titanium dioxide nanoparticles. ACS Nano 2 2206-2212... 

The reaction was studied for all coinage metal nanoparticles. In the case of GMEs the rate follows zero-order kinetics with IT for all the coinage metal cases. The observed IT for the Cu catalyzed reaction was maximum but its rate of reduction was found to be minimum. Just the reverse was the case for Au and an intermediate value was obtained for the Ag catalyzed reaction (Figure 7). The adsorption of substrates is driven by chemical interaction between the particle surface and the substrates. Here phe-nolate ions get adsorbed onto the particle surface when present in the aqueous medium. This caused a blue shift of the plasmon band. A strong nucleophile such as NaBH4, because of its diffusive nature and high electron injection capability, transfers electrons to the substrate via metal particles. This helps to overcome the kinetic barrier of the reaction. 

A similar technique, the so-called spontaneous emulsification solvent diffusion method, is derived from the solvent injection method to prepare liposomes [161]. Kawashima et al. [162] used a mixed-solvent system of methylene chloride and acetone to prepare PLGA nanoparticles. The addition of the water-miscible solvent acetone results in nanoparticles in the submicrometer range this is not possible with only the water-immiscible organic solvent. The addition of acetone decreases the interfacial tension between the organic and the aqueous phase and, in addition, results in the perturbation of the droplet interface because of the rapid diffusion of acetone into the aqueous phase. 

E Allemann, E Doelker, R Gurny. Drug loaded poly (lactic acid) nanoparticles produced by a reversible, salting-out process purification of an injectable dosage form. Eur J Pharm Biopharm 39 13-18, 1992. 

Xiang, J., F. S. Rondonuwu, Y. Kakitani, R. Fujii, Y. Watanabe, Y. Koyama, H. Nagae, Y. Yamano, and M. Ito. 2005. Mechanisms of electron injection from retinoic acid and carotenoic acids to Ti02 nanoparticles and charge recombination via the T, state as determined by subpicosecond to microsecond time-resolved absorption spectroscopy Dependence on the conjugation length. J. Phys. Chem. B 109 17066-17077. 

Apart from recapture of the injected electrons by the oxidized dye, there are additional loss channels in dye-sensitized solar cells, which involve reduction of triiodide ions in the electrolyte, resulting in dark currents. The Ti02 layer is an interconnected network of nanoparticles with a porous structure. The functionalized dyes penetrate through the porous network and adsorb over Ti02 the surface. However, if the pore size is too small for the dye to penetrate, that part of the surface may still be exposed to the redox mediator whose size is smaller than the dye. Under these circumstances, the redox mediator can collect the injected electron from the Ti02 conduction band, resulting in a dark current (Equation (6)), which can be measured from intensity-modulated experiments and the dark current of the photovoltaic cell. Such dark currents reduce the maximum cell voltage obtainable, and thereby the total efficiency. 

Nanoparticle surface modification is of tremendous importance to prevent nanoparticle aggregation prior to injection, decrease the toxicity, and increase the solubility and the biocompatibility in a living system [20]. Imaging studies in mice clearly show that QD surface coatings alter the disposition and pharmacokinetic properties of the nanoparticles. The key factors in surface modifications include the use of proper solvents and chemicals or biomolecules used for the attachment of the drug, targeting ligands, proteins, peptides, nucleic acids etc. for their site-specific biomedical applications. The functionalized or capped nanoparticles should be preferably dispersible in aqueous media. 

MacKay JA, Chen M, McDaniel JR, Liu W, Simnick AJ, Chilkoti A (2009) Self-assembling chimeric polypeptide-doxorubicin conjugate nanoparticles that abolish tumours after a single injection. Nat Mater 8 993-999... 

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