Development and Application of Visible-Light-Responsive Perylene Diimide Functionalized Silk Fibroin/Polylactic Acid Antibacterial Nanofibrous Membranes

The issue of antibiotic resistance is becoming increasingly severe, urgently requiring the development of new antibacterial strategies. Photodynamic therapy (PDT) has gradually emerged as a promising alternative due to its spatiotemporal controllability, low risk of drug resistance, and broad-spectrum antibacterial properties. However, most existing photosensitizers (PSs) are hydrophobic, which limits their application efficiency in PDT. To address this problem, we designed and synthesized a water-soluble perylene diimide derivative (PDICN-CBn) as a photosensitizer. By introducing quaternary ammonium salt groups, its water solubility was improved, and antibacterial activity was enhanced. Subsequently, PDICN-CBn was assembled into silk fibroin/polylactic acid (SF/PLA) nanofibrous membranes via electrospinning technology, successfully constructing a visible-light-responsive ternary composite nanofibrous membrane (SF/PLA@PDICN-CBn). Using various characterization methods such as nuclear magnetic resonance (¹H-NMR), Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and scanning electron microscopy (SEM), the microstructure, chemical composition, and structural characteristics of the nanofibrous membranes were systematically analyzed, verifying the successful synthesis of the photosensitizer and its assembly into the nanofibrous membranes. In the reactive oxygen species (ROS) experiment, electron spin resonance (ESR) spectra showed that PDICN-CBn efficiently generated singlet oxygen (¹O₂), superoxide anion (·O₂^-), and hydroxyl radical (·OH) under visible light irradiation, confirming its ability to produce different types of ROS through both type I and type II photodynamic reactions. In the antibacterial experiments, <i>Escherichia coli</i> (<i>E. coli</i>), <i>Staphylococcus aureus</i> (<i>S. aureus</i>), and methicillin-resistant <i>Staphylococcus aureus</i> (MRSA) were selected for a series of tests, including plate-counting antibacterial assays, bacterial live/dead staining, and SEM observation of morphology. The results showed that 8 μg/mL of PDICN-CBn effectively destroyed the bacterial cell membrane structure and killed bacteria (bactericidal rate > 95%) after 2 h of visible light irradiation. This work successfully developed a novel visible-light-responsive SF/PLA@PDICN-CBn nanofibrous membrane with a dual antibacterial system combining photodynamic and electrostatic adsorption antibacterial properties, providing new ideas and methods for the design and development of photodynamic antibacterial materials. The prepared nanofibrous membrane has potential application values in fields such as wound dressings and medical protective materials and is expected to provide strong support for solving clinical infection problems.