Biomineralization of BSA-Chalcogenide Bioconjugate Nano- and Microcrystals

Lead selenide (PbSe), cadmium selenide (CdSe), and selenium (Se) nano- and microcrystals were synthesized by using respective metal acetate salts along with sodium selenite as the Se Source in the presence of bovine serum albumen (BSA) as the cappintg/stabilizing agent. Aqueous phase hydrazine reduction at 85 degrees C produced fine crystalline morphologies within 48 h. Both PbSe and CdSe reactions produced Se microrods (MRs) as reaction byproduct. The concentrations of metal acetate and sodium selenite used were always 1:1 (i.e., 1.25 mM in each case) and that of hydrazine was fixed at 0.78 M. The amount of BSA was changed systematically from 1-10 x 10(-4) g/mL to determine its influence on the crystal growth of these chalcogenides. Their morphologies and chemical compositions were determined with FESEM, TEM, and EDX analysis. A selective and precise EDX analysis of a single particle helped us to elucidate its shape and chemical composition. Such analyses lead to the finding that both reactions produced Se rods, their sizes varied from the nano to micro scale with an increase of the amount of BSA. PbSe polyhedral nanocrystals were obtained at a low BSA amount, which ultimately attained the shape of thick MRs. However, no rod formation was observed for CdSe particles, which were always present in the form of groups of small nanoparticles along with Se MRs. Protein estimation indicated the presence of adsorbed BSA on the surface of chalcogenide particles. A potential reaction mechanism was proposed to explain the Se MRs formation as byproduct. Finally, the results were discussed on the basis of selective adsorption of denatured BSA on specific crystal planes of the rock salt (PbSe) geometry in order to produce rod like morphologies.