The platinum(IV) hydride complexes Tp(Me(2))PtR(2)H (Tp(Me(2)) = hydridotris(3,5-dimethylpyrazolyl)borate, R = Me (1a), Ph (1b)) react with molecular oxygen to form platinum(IV) hydroperoxide complexes Tp(Me(2))PtR(2)OOH (R = Me (2a) and Ph (2b), respectively) in high yield. The results of kinetic and mechanistic studies of these reactions are consistent with the net insertion of molecular oxygen into the Pt(IV)-H bonds occurring via radical chain mechanisms. The radical chain pathways resemble, in many respects, those documented for autoxidations of organic substrates, but significant differences are also evident. The autoxidations of 1a and 1b both autoaccelerate, but the nature of the rate accelerations and the dependence of the rates on the hydroperoxide products are not the same. The different rate laws observed for the reactions of Tp(Me(2))PtR(2)H complexes with molecular oxygen can be rationalized on the basis of similar initiation and propagation events with different chain termination steps.
The development of nonviral gene delivery systems is a great challenge to enable safe gene therapy. In this study, ligand-modified nanoparticles based on human serum albumin (HSA) were developed and optimized for an efficient gene therapy. Different glutaraldehyde cross-linking degrees were investigated to optimize the HSA nanoparticles for gene delivery. The peptide sequence arginine-glycine-aspartate (RGD) and the HIV-1 transactivator of transduction sequence (Tat) are well-known as promising targeting ligands. Plasmid DNA loaded HSA nanoparticles were covalently modified on their surface with these different ligands. The transfection potential of the obtained plasmid DNA loaded RGD- and Tat-modified nanoparticles was investigated in vitro, and optimal incubation conditions for these preparations were studied. It turned out that Tat-modified HSA nanoparticles with the lowest cross-linking degree of 20% showed the highest transfection potential. Taken together, ligand-functionalized HSA nanoparticles represent promising tools for efficient and safe gene therapy.
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