Phytic Acid-Polypeptide Network-Promoted Deposition of Photoactive Agents for the Construction of Synergistic Bactericidal Coatings

Constructing antimicrobial surface coatings is essential to protect biomedical implants and devices from biological contamination or microbial infections. In this study, a simple technique was developed to prepare phytic acid (PA) and <i>ε</i>-polylysine (Ply)/hyperbranched polylysine (HPL) network coatings on implant surfaces due to the intrinsic surface affinity of PA and electrostatic attraction between Ply/HPL and PA. The PA-Ply (or PA-HPL) coating facilitates the encapsulation of diverse photoactive agents, including gold nanoparticles (Au NPs), multiwalled carbon nanotubes (MWNTs), graphene oxide (GO), indocyanine green (ICG), and chlorophyll copper sodium salt (SCC) onto substrate surfaces in a matrix-independent manner. The physicochemical characterization confirms that PA-Ply network coatings accommodate high quantities of photoactive components. Although multiple substrates and photoactive agents are initially explored to compare coating formation and loading capacity, the primary focus of this study is the <i>in vitro</i> and <i>in vivo</i> antibacterial performance of SCC- and ICG-functionalized coatings. <i>In vitro</i> studies demonstrate that PA-Ply exerts more detrimental effects on bacterial pathogens compared to PA-HPL network coatings. Additionally, PA-Ply (or HPL)-SCC generates singlet oxygen (¹O₂) under xenon lamp irradiation, while the PA-Ply-SSC-modified titanium (Ti) surface achieves enhanced bacterial inactivation through a synergistic mechanism of contact killing and photodynamic action. Similarly, the PA-Ply (or HPL)-ICG-modified implants exhibit favorable biocompatibility and synergistic antibacterial effects <i>in vivo</i> under near-infrared (NIR) irradiation. The findings present a feasible strategy for surface modification, endowing medical implants with enhanced antibacterial protection.