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Background: Smaller nanoparticles facilitate the delivery of DNA into cells through endocytosis and improve transfection efficiency. The aim of this study was to determine whether protamine sulfate-coated calcium phosphate (PS-CaP) could stabilize particle size and enhance transfection efficiency. Methods: pEGFP-C1 green fluorescence protein was employed as an indicator of transfection efficiency. Atomic force microscopy was used to evaluate the morphology and the size of the particles, and an MTT assay was introduced to detect cell viability and inhibition. The classical calcium phosphate method was used as the control. Results: Atomic force microscopy images showed that the PS-CaP were much smaller than classical calcium phosphate particles. In 293 FT, HEK 293, and NIH 3T3 cells, the transfection efficiency of PS-CaP was higher than for the classical calcium phosphate particles. The difference in efficiencies implies that the smaller nanoparticles may promote the delivery of DNA into cells through endocytosis and could improve transfection efficiency. In addition, PS-CaP could be used to transfect HEK 293 cells after one week of storage at 4°C with a lesser extent of efficiency loss compared with classical calcium phosphate, indicating that protamine sulfate may increase the stability of calcium phosphate nanoparticles. The cell viability inhibition assay indicated that both nanoparticles show similar low cell toxicity. Conclusion: PS-CaP can be used as a better nonviral transfection vector compared with classical calcium phosphate.

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This paper discloses that the oxygenation of cyclohexane by dioxygen (O2) to cyclohexanol and cyclohexanone over three vanadium‐substituted tungstophosphoric acids (PW11V1, PW10V2, PW9V3) can occur in MeCN under visible‐light irradiation, but provides very low cyclohexane conversion (0.8–2.4 %) with modest cyclohexanone selectivity (51–58.3 %). Importantly, an HCl aqueous solution was found to drastically promote this photooxygenation catalyzed by PW10V2 and especially PW9V3 acids, respectively providing approximately 20.4 and 23.4 % cyclohexane conversion and approximately 82.5 and 87.1 % cyclohexanone selectivity, with a concomitant formation of a small amount of chlorocyclohexane. However, such promoting effect was negligible in the PW11V1‐ photocatalyzed oxygenation and the other acids and the chlorine‐containing salts did not show any promotion effect on the present photocatalysis reaction. Notably, the HCl‐promoted photocatalytic oxygenation was significantly influenced by the amount of water. The cyclohexanone selectivity continuously and significantly increased with water amount, but photooxygenation efficiency drastically decreased if a slight excess amount of water was added. Based on these findings and the UV/Vis spectral and cyclic voltammetric measurements, a free‐radical mechanism initiated by the Cl atoms generated in the present photocatalysis system was proposed.

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