Tannic acid-modified FK506-loaded nanoparticles targeting lymph nodes for acute heart transplant rejection treatment

Significant efforts have been made to deliver immunosuppressants-loaded nanoparticles (NPs) to lymph nodes (LNs) to mitigate transplant rejection. However, conventional administration techniques encounter challenges in enhancing the retention of NPs in the LNs. Attributing the strong affinity of tannic acid (TA) molecules to the elastin of LN conduits, we developed a novel formulation of NPs encapsulating Tacrolimus (FK506), and subsequently modified with TA to produce TA-FNP with a final diameter of approximately 86.07 +/- 2.78 nm. These particles could traverse the the intercellular gaps in the lymphatic endothelial cells layers, enter the paracortex through LN capsule-associated conduits, and releases FK506 to inhibit the activation and proliferation of allogeneic T cells. Our finding demonstrated that TA-FNP could accumulate in LNs, significantly increasing the local concentration of FK506 from 69.06 +/- 21.96 ng/g to 1041.28 +/- 343.59 ng/g compared to the free FK506 treatment group. Subsequently, the therapeutic efficacy of TA-FNP was assessed in heart transplantation model, where treatment with TA-FNP resulted in decreased T cells infiltration within the grafts, reduced rejection grades, and a significant extension of graft survival time. In contrast, FNP without TA showed relatively poor therapeutic outcomes. Consequently, this study reveals a promising strategy utilizing TA to enhance the prolonged retention of FK506 within LNs, underscoring its potential therapeutic application in preventing heart transplant rejection.