Dissolving\nPEGDA-Based Microneedles to Transdermally\nDeliver PDA@Cu with Photothermal Properties for Potential Antibacterial\nApplications

The\nstratum corneum of the skin functions as a barrier, obstructing\ndrug absorption and complicating the treatment of skin infections\ncaused by pathogens such as bacteria, fungi, and viruses through topical\nmethods. In this research, a microneedle patch was developed, which\nconsists of gelatin-sucrose (SG) that encapsulates polydopamine-copper\nnanoparticles (PDA@Cu) at the tip for antibacterial purposes. Poly(ethylene\nglycol) diacrylate (PEGDA) served as the primary substrate for the\nmicroneedle shaft (PDA@Cu-SG/PEGDA). This patch was engineered to\nenhance skin permeability and facilitate the efficient delivery of\ndrugs through the rapid dissolution of the tips. Coordinate bonds\ncan be formed between PDA and Cu ions, resulting in the immobilization\nof Cu particles on the PDA surface, which aids in the green synthesis\nof PDA@Cu photothermal antibacterial particles. The SG polymer, which\ncontained PDA@Cu, was employed to fill the tip cavities through a\nseries of centrifugation steps. Subsequently, UV-induced polymerization\nwas carried out to produce PEGDA microneedles with hydrophilic tips\n(PDA@Cu-SG/PEGDA). Furthermore, the physicochemical characteristics\nof the polymer microneedles, including morphology, composition, and\nmechanical strength, were thoroughly characterized. These microneedles\nwith hydrophilic tips demonstrated sufficient mechanical strength.\nOwing to the ability of PDA@Cu to disrupt bacterial membranes, the\nmicroneedle patch demonstrated excellent in vitro antibacterial efficacy.\nWe validated the antibacterial activity of the microneedle patch against <i>Escherichia coli</i> and <i>Staphylococcus aureus</i> by conducting in vitro bacterial plate coating assays. The results\nof the assays indicated that this minimally invasive strategy achieved\nbroad-spectrum antibacterial effects; thus, this may be a suitable\napproach for managing polymicrobial skin infections during clinical\ntrials.