Polydopamine-based multifunctional biomaterials: Strategies for controlling redox and photothermal properties for...

Bioinspired polydopamine (PDA) has emerged as a versatile platform for advanced biomedical applications due to its unique redox activity, photothermal properties, and strong adhesion capabilities. This review systematically explores PDA's multifunctional potential, focusing on strategies to control its antioxidant and prooxidant behaviours, photothermal efficiency, and stimuli-responsive performance. By modulating structural, morphological, and compositional parameters - such as nanoparticle size, porosity, metal-ion coordination, and surface charge - PDA-based materials can be tailored for specific therapeutic needs, including reactive oxygen species scavenging, antibacterial action, and targeted drug delivery. A key emphasis is placed on integrating PDA into complex biomedical systems, where it enables synergistic combinations of photothermal therapy, chemodynamic therapy, stimuli-responsive drug release, and electrical stimulation. Besides, special attention is given to stimuli-responsive systems that leverage near-infrared light, pH, and enzymatic triggers for spatiotemporal control over drug release and therapeutic activation. Furthermore, PDA's role in electroactive scaffolds and shape-memory materials is also highlighted, such as piezoelectric scaffolds for neural repair and self-healing wound dressings, underscoring PDA's transformative potential in personalised medicine. Unlike previous reviews, this work provides a comprehensive analysis of PDA's multifunctionality within integrated therapeutic platforms, addressing the critical challenge of precisely controlling its diverse properties. Challenges remain in optimising long-term stability, scalability, and biocompatibility. Future research should focus on elucidating degradation mechanisms, refining multi-stimuli responsiveness, and advancing clinical translation. By bridging fundamental insights with practical applications, this review aims to guide the development of next-generation PDA-based biomaterials for regenerative medicine, targeted therapy, and smart implants.