Probiotic-Based Materials as Living Therapeutics.

The growing demand for safer, more targeted therapeutics requires the development of advanced biomaterials. Among these, Engineered Living Materials (ELMs)-which integrate synthetic biology with material science-are emerging as promising platforms for biomedical applications. This review focuses on a subclass of ELMs based on genetically engineered probiotics combined with matrices, that are termed Probiotic Living Materials (PLMs) to differentiate them from Living Biotherapeutic Products (LBPs). Recent studies highlight PLM's potential in addressing different health conditions, offering targeted and dynamic therapies. However, PLMs face multiple challenges to be implemented in clinics, including a lack of robust genetic toolkits for probiotic engineering, concerns about biosafety (e.g., horizontal gene transfer or non-desirable biological activity), difficulties in translating preclinical results to humans, and the absence of clear regulatory guidance for clinical use. This review first explores the fundamental features of ELMs, then provides an overview of probiotics, followed by recent advances in the design of engineered PLMs for biomedical applications, particularly in biosensing development, infection treatment, bone repair, wound healing, vaginal imbalances, gut-related conditions, and cancer therapy. Finally, biosafety issues and current gaps in regulatory frameworks to ensure safe and effective use of PLMs, with a particular focus on vulnerable populations, are discussed.