Multifunctional Antimicrobial Thin Films Based on Biopolymer–Nanomaterial Hybrids: Surface Design, Antibiofilm Activity and Photothermal Approaches

Bacterial adhesion and biofilm formation on material surfaces contribute to persistent and device-associated infections, particularly in the context of antimicrobial resistance. This review examines biopolymer–nanomaterial hybrid thin films through a structure-surface-function framework, linking film composition and architecture to interfacial properties, bacterial attachment, and antimicrobial outcomes. It compares how surface chemistry, hydration, charge, and micro/nanotopography influence initial colonization, and how incorporated nanomaterials provide contact-active, ion-mediated, oxidative, or stimulus-responsive activity. Particular emphasis is placed on a hierarchical antibacterial design strategy: first reducing attachment, then inactivating cells that reach the interface, and finally targeting persistent or established biofilms through complementary mechanisms, including near-infrared activated photothermal treatment. Quantitative examples are interpreted in light of the experimental conditions reported, because wavelength, irradiance, exposure time, substrate, assay, and endpoint differ substantially across studies. The review also identifies limitations in cross-study comparability and highlights the need for standardized reporting, direct controls, repeated-cycle durability testing, and application-relevant biosafety assessment. The central conclusion is that performance depends not on maximizing a single material property, but on coordinating composition, surface architecture, and activation conditions to deliver reproducible antibacterial function.