Advanced polymers for kidney and urinary tract tissue engineering.

Kidney tissue engineering has emerged as a promising strategy to address the growing clinical burden of end-stage renal disease (ESRD), for which current treatments such as hemodialysis and kidney transplantation remain limited by donor shortage, cost, and long-term complications. Central to these approaches is the development of advanced biomaterials capable of recapitulating the complex structural, mechanical, and biochemical microenvironment of native renal tissue. Among available material platforms, polymers and hydrogels have received significant attention due to their tunable properties, processability, and compatibility with renal cell types. This review provides a comprehensive overview of synthetic and natural polymeric biomaterials, as well as bio-based hydrogels, that have been investigated for kidney and urinary tract tissue engineering applications. Key design principles required to support renal cell adhesion, proliferation, differentiation, and function are discussed, with particular emphasis on material chemistry, mechanical properties, degradation behavior, and microarchitectural features. The impact of fabrication and modification strategies, including scaffold processing, surface functionalization, and composite material design, on renal cell behavior and tissue formation is also highlighted. In addition, emerging strategies such as decellularized kidney matrices, glomerular tissue engineering, and hydrogel-based systems aimed at recreating essential functional units of the kidney are reviewed. Despite notable progress, major challenges remain, including the replication of hierarchical renal architecture, the establishment of functional vascular networks, and long-term tissue integration. By critically assessing recent advances and current limitations, this review outlines material-driven strategies and future directions toward the development of functional renal constructs with potential therapeutic relevance.