In vitro determination of the immunosuppressive effect, internalization, and release mechanism of squalene-gusperimus nanoparticles for managing inflammatory responses

Gusperimus is an anti-inflammatory drug that has shown to be effective in managing autoimmunity and preventing graft rejection. This is unstable and easily broken down into cytotoxic components. We encapsulated gusperimus binding it covalently to squalene obtaining squalene-gusperimus nanoparticles (Sq-GusNPs). These nanoparticles enhanced the immunosuppressive effect of gusperimus in both mouse macrophages and T cells. The half-maximal inhibitory concentration in macrophages was 9-fold lower for Sq-GusNPs compared with the free drug. The anti-inflammatory effect of the Sq-GusNPs was maintained over time without cytotoxicity. By studying nanoparticles uptake by cells with flow cytometry, we demonstrated that Sq-GusNPs are endocytosed by macrophages after binding to low-density lipoprotein receptors (LDLR). In presence of cathepsin B or D release of gusperimus is increased demonstrating the participation of proteases in the release process. Our approach may allow the application of Sq-GusNPs for effective management of inflammatory disorders including autoimmunity and graft rejection.