Immunosuppressive enzyme-responsive nanoparticles for enhanced accumulation in liver allograft to overcome acute rejection

Acute rejection is a life-threatening complication after liver transplantation. Immunosuppressants such as tacrolimus are used to inhibit acute rejection of liver grafts in clinic. However, inefficient intragraft accumulation may reduce the therapeutic outcomes of tacrolimus. Here, an enzyme-responsive nanoparticle is developed to selectively enhance the accumulation of tacrolimus in liver allograft through enzyme-induced aggregation to refine immunotherapeutic efficacy of tacrolimus. The nanoparticles are composed of amphiphilic tacrolimus prodrugs synthesized by covalently conjugating tacrolimus and matrix metalloproteinase 9 (MMP9)-cleavable peptide-containing methoxy poly (ethylene glycol) to poly (l-glutamic acid). Upon exposure to MMP9, which is overexpressed in rejected liver allografts, the nanoparticles undergo a morphological transition from spherical micellar nanoparticles to microscale aggregate-like scaffolds. Intravenous administration of MMP9-responsive nanoparticles into a rat model of acute liver graft rejection results in enhanced nanoparticle accumulation in allograft as compared to nonresponsive nanoparticles. Consequently, the MMP9-responsive nanoparticles significantly inhibit intragraft inflammatory cell infiltration and proliferation, maintain intragraft immunosuppressive environment, alleviate graft damage, improve liver allograft function, abate weight loss and prolong recipient survival. This work proves that morphology-switchable enzyme-responsive nanoparticles represent an innovative strategy for selectively enhancing intragraft accumulation of immunosuppressive agents to improve treatment of liver allograft rejection.