Erythropoietin-loaded solid lipid nanoparticles: Preparation, optimization, and in vivo evaluation.

Solid lipid nanoparticle (SLN) is a promising approach for delivery of various drugs including proteins and peptides. However, the loading of hydrophilic drugs into the lipoid matrix of SLNs is challenging. The statistical design is a potential method facilitating the optimization of nanoparticles characteristics. In this study, the Box-Behnken design was conducted to optimize the preparation of Erythropoietin (EPO) loaded SLNs. Circular dichroism, size exclusion chromatography, SDS-PAGE, and ELISA tests were used to prove the compatibility of the process with the stability of EPO. In the controlled situation, EPO preserved its conformation and activity during the SLN preparation. Regarding the particle size, entrapment efficiency, and polydispersity index, an optimum formulation was obtained with 130 mg Span®80, 152.5 μl EPO, and 1.9 min high-shear homogenization. Using the optimum condition, 280 nm sized SLNs with the narrow size distribution of 0.282 and entrapment efficiency of 43.4% were acquired. The in vitro cytotoxicity of optimum SLN formulation was conducted using MTT assay to show its safety on the evaluated cell line. The in vivo studies demonstrated that 2500 U EPO loaded SLN has similar or even better effects on elevating the RBC, hemoglobin, and hematocrit level compared to the 5000 U EPO solution. Generally, this study proposed a suitable EPO-loaded SLN preparation method as a potential drug delivery system for proteins.