Using a Bacterial Protein to Selectively Target Bacterial Biofilms: Treatment of S. epidermidis Biofilms with Targeted Photothermal Gold Nanoparticles

Biofilm-related infections are associated with high mortality and morbidity, combined with increased treatment costs. Traditional antibiotics are becoming less effective due to the emergence of drug-resistant bacterial strains. The need to treat biofilms on medical implants is particularly acute, and one persistent challenge is selectively directing nanoparticles to the biofilm site. Here, we present a protein-based functionalization strategy that targets the extracellular matrix of biofilms. The protein, derived from the extracellular Staphylococcus epidermidis autolysin, directs nanoparticles to S. epidermidis cell wall components, which are not expected to be present in mammalian tissues. This functionalization is applied to a gold nanoparticle (AuNP) core, along with elastin-like polypeptides (ELPs), which generate a robust photothermal response. In addition to biofilm targeting, the particles exhibit low protein binding, and the photothermal conversion can be modulated by changing the ELP transition temperature. These functionalized AuNPs strongly interact with biofilms under static and flow conditions but exhibit weak interactions with serum-coated surfaces. Near-infrared laser irradiation resulted in a 10,000-fold improvement in killing efficiency compared to untreated controls (p < 0.0001). The targeting strategy utilized here represents a versatile approach to targeting drug-resistant infections and could be readily expanded to other anti-biofilm nanoparticle platforms.