New Smart Polymeric Materials with Optical Sensing Properties: Determination of Antimicrobial Properties Using Photodynamic Therapy

Antimicrobial resistance has intensified the search for non-antibiotic strategies activated by external stimuli, including antimicrobial photodynamic therapy. In this work, a hybrid system based on spiropyran-functionalized poly(maleic anhydride-alt-acrylic acid), P(MAn-alt-AA)-SP, and CdTe@ZnS quantum dots incorporated at 5 wt.% was prepared and characterized. Structural, thermal, morphological, and optical properties were evaluated by ¹H NMR, FTIR, TGA, UV–Vis spectroscopy, fluorescence spectroscopy, TEM, and XRD. Irradiation at 365 nm induced the conversion of spiropyran (SP) to merocyanine (MC), evidenced by the appearance of an absorption band near 559 nm and a visible color change. CdTe@ZnS quantum dots exhibited an average diameter of 3.29 ± 0.94 nm, while the hybrid system displayed a broad emission band centered at approximately 635 nm, whose intensity depended on molecular oxygen. Antibacterial assays against methicillin-sensitive Staphylococcus aureus showed increased activity after irradiation, with the hybrid formulation exhibiting the highest mean inhibition among the evaluated systems. Overall, the results support a coordination-mediated cooperative response between the photoactive polymer and quantum dots and are consistent with the participation of reactive oxygen species (ROS) in photodynamic processes, highlighting the potential of this hybrid material for the development of light-responsive antimicrobial platforms. These findings support future antimicrobial coatings and surface applications.