the aim of this study was to assess the ability of pLGA nanoparticles (nps) to reduce the tacrolimus (tAc)-associated nephrotoxicity following multiple dose administration. the mean diameter of prepared NPs was in the range of 227 to 263 nm with an 8.32% drug loading (w/w). Moreover, in vitro release profile of TAC-loaded NPs showed a sustained release of the drug with only less than 30% release within 12 days. Flow cytometry as well as fluorescence microscopy results confirmed the uptake of FITClabelled pLGA nps by dendritic cells. the ex vivo study showed that TAC-loaded NPs caused a significant suppression of the proliferation of CD4 + and CD8 + cells, which was comparable to the control formulation (prograf). In vivo immunosuppressive activity as well as the kidney function were assessed following drug administration to mice. The animals received TAC subcutaneously at a daily dose of 1 mg/kg for 30 days delivered as the control formulation (Prograf) or TAC-loaded NPs. The results revealed significantly lower drug-associated toxicity with an activity comparable to prograf for tAc-loaded pLGA nps. these findings show a potential for PLGA NPs in reducing the nephrotoxicity of TAC while preserving the immunosuppressive activity.Tacrolimus is a potent immunosuppressive agent used clinically to reduce the risk of graft rejection in post-operative transplants patients 1-3 . It acts by suppressing interleukin-2 (IL-2) production in T-cells 4 , and also by inhibiting phosphatase activity of calcineurin through binding to the intracellular immunophilin FKBP-12 5 . The currently available intravenous formulation of TAC (Prograf) contains HCO-60 (PEGylated castor oil) as a surfactant, which is reported to cause several side effects including hypersensitivity reactions 6-8 . TAC is available in oral dosage forms including immediate release capsules (Prograf), extended release capsules (Astagraf XL and Advagraf), and extended release tablets (Envarsus XR). Several adverse effects have been reported with the use of TAC including hypertension, pruritus, leucocytosis, neurotoxicity, nephrotoxicity, cardiotoxicity and hepatotoxicity [9][10][11][12][13] . open Scientific RepoRtS | (2020) 10:6675 | https://doi.org/10.1038/s41598-020-63767-1 www.nature.com/scientificreports www.nature.com/scientificreports/ Drug-induced nephrotoxicity is the major dose-limiting side effect of TAC with a reported overall incidence as high as 44% 14 . Unfortunately, nephrotoxicity can lead to severe complications such as negative impact on graft survival and life expectancy of the patients. Indeed, nephrotoxic effects present challenges during therapeutic regimen with these drugs 15,16 . Several strategies have been proposed to address this problem. Dose reduction is one of the strategies that has been evaluated by clinicians along with using other agents such as sirolomus or everolimus, which are found to be effective in improving long-term effects in renal transplant cases 17,18 .Several formulations have been investigated to improve the aqueous ...