Silver nanoparticles (AgNPs) are extensively applied for their broad-spectrum and excellent antibacterial ability in recent years. Polydopamine (PDA) has great advantages for synthesizing large amounts of AgNPs, as it has multiple sites for silver ion binding and phenolic hydroxyl structure to reduce silver ions to AgNPs. Here, we mixed sericin and agar solution and dried at 65 °C to prepare a sericin (SS)/Agar composite film, and then coated polydopamine (PDA) on the surface of SS/Agar film by soaking SS/Agar film into polydopamine solution, subsequently synthesizing high-density AgNPs with the assistance of PDA to yield antibacterial AgNPs-PDA- SS/Agar film. Scanning electron microscope (SEM), Fourier transform infrared spectroscopy (FT-IR) and X-ray diffraction (XRD) spectra indicated the successful synthesis of high-density AgNPs on the surface of PDA-SS/Agar film. PDA coating and AgNPs modification did not affect the structure of sericin and agar. Furthermore, water contact angle, water absorption and mechanical property analysis showed that AgNPs-PDA-SS/Agar film had excellent hydrophilicity and proper mechanical properties. Inhibition zone and growth curve assays suggested the prepared film had excellent and long-lasting antibacterial ability. In addition, it had excellent cytocompatibility on the fibroblast NIH/3T3 cells. The film shows great potential as a novel kind of wound dressing.

Silk sericin has great potential as a biomaterial for biomedical applications due to its good hydrophilicity, reactivity, and biodegradability. To develop multifunctional sericin materials for potential antibacterial application, a one-step synthesis method for preparing silver nanoparticles (AgNPs) modified on polydopamine-coated sericin/polyvinyl alcohol (PVA) composite films was developed. Polydopamine (PDA) acted as both metal ion chelating and reducing agent to synthesize AgNPs in situ on the sericin/PVA composite film. Scanning electron microscopy and energy dispersive spectroscopy analysis revealed that polydopamine could effectively facilitate the high-density growth of AgNPs as a 3-D matrix. X-ray diffractometry studies suggested the synthesized AgNPs formed good face-centered cubic crystalline structures. Contact angle measurement and mechanical test indicated AgNPs modified PDA-sericin/PVA composite film had good hydrophilicity and mechanical property. The bacterial growth curve and inhibition zone assays showed the AgNPs modified PDA-sericin/PVA composite film had long-term antibacterial activities. This work develops a new method for the preparation of AgNPs modified PDA-sericin/PVA film with good hydrophilicity, mechanical performance and antibacterial activities for the potential antimicrobial application in biomedicine.