Norfloxacin-Loaded Chitosan–Zinc Phthalocyanine Hydrogels for Photodynamic Antibacterial Therapy

Antimicrobial resistance and infected wounds require localized systems capable of combining controlled antibiotic delivery with light-activated antibacterial action. Here, norfloxacin-loaded chitosan hydrogels containing an aldehyde-functionalized zinc phthalocyanine (ZnPc) were developed as dual chemo-photodynamic platforms. ZnPc was covalently incorporated through Schiff-base formation, acting simultaneously as a photosensitizer and secondary crosslinker. Formulations containing 1–10 mg ZnPc and 10 mg norfloxacin were evaluated structurally, morphologically, thermally, mechanically, rheologically, and biologically. FTIR and XRD supported covalent ZnPc incorporation and homogeneous, predominantly amorphous component distribution. ZnPc strengthened the hydrogel network, reduced swelling, and enabled composition-dependent tuning of mechanical and release properties. Norfloxacin loading efficiencies remained above 94%, while 24-h release was greater at pH 5.8 (up to 96%) than at pH 7.7 (25–56%). All ZnPc-containing systems generated singlet oxygen under 660-nm irradiation, with relative efficiencies increasing with ZnPc content. Cs-ZnPc-3-Norf showed the strongest antibacterial response, producing 1.09-log and 0.52-log reductions in Escherichia coli and Staphylococcus aureus , respectively. However, its extract reduced L929 fibroblast metabolic activity even after dilution, indicating that formulation optimization is required before further biomedical evaluation.