Encapsulation of a Ruthenium-Platinum Photosensitizer into Nanofibrous Membranes for Antibacterial Photodynamic Therapy

Abstract

The global rise of multidrug-resistant microorganisms necessitates antimicrobial technologies that avoid the resistance mechanisms associated with conventional antibiotics and chemical disinfectants. Light-activated antimicrobial systems represent a promising alternative because they generate reactive oxygen species in situ, producing rapid and broad-spectrum pathogen inactivation through non-specific oxidative damage to multiple cellular targets. Such multitarget activity significantly reduces the probability of resistance development. Herein, the chemical synthesis, photophysical and biological evaluation of the encapsulation of a binuclear ruthenium-platinum photosensitizer into electrospun nanofibrous membranes for antimicrobial photodynamic therapy is reported. The binuclear photosensitizer was found to produce singlet oxygen by energy transfer and superoxide through electron transfer, enabling a combined Type I and Type II photochemical mechanisms. The complex was incorporated into electrospun nanofibrous membranes based on polyacrylonitrile and polycaprolactone, yielding high-surface-area materials. Systematic optimization of the fabrication process produced bead-free fibers with controlled morphology, while comparative analysis revealed superior photosensitizer retention and structural stability in the hydrophilic polyacrylonitrile matrix. Under visible-light irradiation, both membrane systems exhibited strong antibacterial activity against Gram-positive and Gram-negative bacteria. The presence of sodium azide increased bacterial inactivation, suggesting that the antimicrobial activity shifted from primarily singlet-oxygen–based damage to a mechanism dominated by radical-mediated oxidative stress. Durability studies under prolonged bacterial exposure demonstrated that membrane performance is governed not only by molecular photochemistry but also by matrix-dependent antifouling resilience. The polyacrylonitrile-based membrane retained structural integrity and antibacterial efficacy after aging, whereas polycaprolactone-based systems showed pronounced fouling and reduced activity. These results establish a direct link between molecular photosensitizer engineering, nanofabrication strategy, and long-term functional performance, providing a blueprint for next-generation photodynamic antimicrobial materials.