Nanomedicine meets transplantation: Unlocking precision therapeutics for organ rejection

Transplant rejection remains a leading cause of graft failure after organ transplantation. Current immunosuppressive therapies can reduce acute rejection, but their lack of specificity often leads to systemic side effects and long-term complications. Therefore, novel strategies for localized and durable immune regulation are urgently needed. Nanomedicine offers a promising approach by enabling the precise delivery of therapeutic agents to specific cells or tissues involved in the rejection process. Through rational design, nanoparticles can be engineered to carry immunosuppressive molecules and selectively target transplanted organs, immune organs such as lymph nodes and spleen, or key immune cells, including dendritic cells, macrophages, and T lymphocytes. These delivery systems improve drug bioavailability, reduce off-target effects, and allow controlled or responsive drug release in complex immune environments. In this review, we summarize recent advances in nanoparticle-based interventions for transplant rejection. We discuss the design and classification of nanoparticles, delivery strategies tailored to different graft types, and therapeutic mechanisms targeting various stages and components of the immune response. Examples of both systemic and local administration routes are presented, demonstrating the versatility of nanomedicine in addressing diverse clinical scenarios. Despite encouraging progress in preclinical studies, several challenges continue to limit clinical translation. These include variability in nanoparticle behavior across species, difficulties in large-scale manufacturing, and the lack of standardized regulatory frameworks. Continued efforts in materials innovation, biological validation, and interdisciplinary collaboration are essential to fully realize the clinical potential of nanomedicine in transplantation.