In situ plasma-assisted synthesis of polydopamine-functionalized gold nanoparticles for biomedical applications

Despite possessing versatile properties and great potential for biomedical research, the number of studies on the application of polydopamine-functionalized gold nanoparticles (Au@PDA NPs) remains infrequent due to their preparation procedure, which consists of multiple-steps employing hazardous redox agents. We herein present an unprecedented single-step synthesis protocol using a non-equilibrium atmospheric pressure plasma jet to trigger the redox reaction between dopamine (DA) and gold ions in distilled water to simplify the fabrication process, eliminating the use of additional chemicals. Under the plasma treatment, the solvated electrons and reactive oxygen species generated from the plasma–liquid interaction can simultaneously reduce Au ions to metallic Au and oxidize DA to polydopamine (PDA), respectively, thus leading to the formation of Au@PDA NPs. The simultaneous reactions between plasma, DA and ionic Au create a synergistic effect shortening the reaction time compared to conventional chemical synthesis. The morphology of Au@PDA NPs can be tailored by plasma reaction time and DA concentrations. Owing to the unique properties of the quickly fabricated Au NPs, these NPs were used for the in vitro treatment of cancer cells. Interestingly, the plasma-synthesized Au@PDA NPs demonstrate high cellular uptake and cytotoxicity in breast cancer cells. Our data emphasize the importance of plasma–liquid interaction in synthesizing Au@PDA NPs for suppressing cancer cell growth and level of their intracellular delivery to improve cancer therapy. Hence, the Au@PDA NPs prepared by the one-pot plasma-assisted synthesis may have future biomedical applications as an anticancer agent.