The employment of a conformal polydopamine thin layer reduces the cytotoxicity of silver nanoparticles

Silver nanoparticles (AgNPs) with their unique properties represent great promise in biological applications. However, the high toxicity of AgNPs still remains a major bottleneck and hinders their basic usage. In the present study, to improve the cytotoxicity of AgNPs, a thin layer of polydopamine (PDOP) was proposed as shell material. For this, the as-prepared citrate-stabilized AgNPs were dispersed in dopamine solution under alkaline conditions. The thickness of the PDOP layer could be manipulated simply by tuning the polymerization time. It was indicated that all NP systems (PDOP, AgNP, and AgNP@PDOP) were efficiently synthesized in the desired size and morphology. Gytotoxicity tests of all NP systems were performed in the Caco2 cell line and the results were evaluated through sulforhodamine B (SRB) assay. Due to their natural characteristics, even at low concentrations (12.5 ppm) AgNPs exhibited high cytotoxicity. In contrast, PDOP had almost no toxic effect on cells at high concentrations (200 ppm). The employment of a thin layer of PDOP (5 +/- 1 nm) distinctively improved the cytotoxicity of the AgNP@PDOP NP system without any change of optoelectronic properties of AgNPs. A dose of 200 ppm of AgNP@PDOP NPs did not create any toxicity and the cells preserved their interaction, morphology, and cellular integrity.