Surgical site infections (SSI) often occur after invasive surgery due to microbial contamination, representing a serious health problem. The recurrent use of antibiotics to treat such infections has led to an increase in microbial strain resistance and a decrease of its efficiency. Thus, it is important to develop new biomaterials with antimicrobial properties, aimed at reducing the risk of such infections and the use of antibiotics. Spider silk is an outstanding biomaterial due to the combination of high strength, toughness and excellent elasticity. Through recombinant DNA technology, spider silk-based materials can be bioengineered and functionalized with antimicrobial peptides (AMP). The aim of this study was to explore the use of bioengineered spider silk proteins functionalized with AMP as new coatings for commercial silk sutures (Perma-Hand®) to prevent infections. To achieve this purpose, Perma-Hand® sutures were coated with spider silk protein functionalized with AMP (6mer-HNP1) and with spider silk protein without AMP (6mer). The biological and antibacterial potential of the new Perma-Hand® coated sutures were assessed. Perma-Hand® suture without coating and a suture with antibacterial properties (VicrylPlus®) were used as controls.

In vitro cell studies using human lung fibroblasts cell line (MRC5) showed a nontoxic and cytocompatible behavior of the Perma-Hand® sutures coated with 6mer-HNP1 or 6mer. Like VicrylPlus® sutures, Perma-Hand® sutures coated with 6mer-HNP1 exhibited a lower adherence of Methicillin resistant Staphylococcus aureus (MRSA) when compared to Perma-Hand® sutures coated with 6mer or uncoated ones. Also, biofilm formation was only visible in the Perma-Hand® sutures coated with 6mer and uncoated ones, demonstrating the antibacterial potential of these sutures coated with 6mer-HNP1. The hemolytic activity of the Perma-Hand® sutures coated with 6mer-HNP1 and 6mer was also evaluated and no negative effect was observed, further evidencing to the biocompatibility of the bioengineered spider silk proteins. The outcomes of this study suggest that bioengineered spider silk protein functionalized with AMP as coating of surgical sutures inhibit the formation of biofilm and also, demonstrated a positive cellular response. The functionalization of spider silk proteins with AMP could pose as a new strategy to develop coatings capable of preventing microbial proliferation associated to infections problems on biomaterials.

 AcknowledgementsThe authors thank Portuguese funds through FCT–Fundação para a Ciência e a Tecnologia in the framework of POCI-01-0145-FEDER-007038. ARF would like to thank the Post-Doctoral grant SFRH/BPD/100760/2014.