Enhanced circulation longevity and pharmacodynamics of metformin from surface-modified nanostructured lipid carriers based on solidified reverse micellar solutions.

Metformin hydrochloride (MTH) has been associated with poor/incomplete absorption (50-60%), low bioavailability, short half-life (0.4-0.5 h), high dosage and dose-related side effects. To overcome these barriers and improve oral bioavailability and efficacy of MTH, surface-modified nanostructured lipid carriers (NLCs) were developed. Lipid matrices composed of rational blends of beeswax and Phospholipon® 90H (as solid lipids) and Capryol-PGE 860 (as liquid lipid) were prepared by fusion, and the resultant lipid matrices were PEGylated to give 10, 20 and 40% PEGylated lipid matrices. MTH-loaded non-PEGylated and PEGylated NLCs were prepared via high-shear hot homogenization and characterized regarding particle properties and physicochemical performance. The encapsulation efficiencies (EE%) and loading capacities (LC) of the MTH-loaded NLCs were determined while the drug release was evaluated in phosphate buffered saline (PBS, pH 7.4). Antidiabetic and pharmacokinetics properties of the NLCs were ascertained in an alloxan-induced diabetic rats model after oral administration. The MTH-loaded NLCs were nanomeric (particle size: 184.8-882.50 nm) with low polydispersity index (0.368-0.687) and zeta potential (26.5-34.2 mV), irregular shape, amorphous nature with reduced crystallinity. The EE% and LC were >90 % and 16%, respectively. The formulations showed >65 % release over 12 h in a greater sustained manner than marketed MTH formulation (Glucophage®) as well as enhanced pharmacokinetics properties and sustained blood glucose lowering effect, even at reduced doses with PEGylated NLCs than Glucophage®. Thus, PEGylated NLC is a promising approach for improved delivery and oral bioavailability of MTH thus encouraging further development of the formulation.