Screening Study for Formulation Variables in Preparation and Characterization of Repaglinide-Loaded Nanostructured Lipid Carriers

Abstract

Objective: To formulate and comprehensively characterize Repaglinide-loaded nanostructured lipid carriers (REP-NLCs) as a strategy to enhance its aqueous solubility, physicochemical stability, and oral bioavailability, thereby improving its therapeutic efficacy. Methods: Repaglinide (REP) solubility was screened in various solid and liquid lipids. Precirol®ATO5 and Labrasol®ALF (70:30) were selected based on solubility and melting behavior. Surfactants were chosen by emulsification efficiency. REP-NLCs were prepared via high-speed homogenization and probe sonication. Particle size, polydispersity index (PDI), zeta potential (ZP), and entrapment efficiency (EE) were evaluated. Lyophilization was performed with different cryoprotectants. In vitro release was assessed using the dialysis bag method, and morphology was examined by TEM. Results: REP showed highest solubility in Compritol®888 ATO (1600±225 mg/g) and Precirol®ATO5 (800±100 mg/g), while peppermint oil (33.36±2.01 mg/ml) exhibited the highest solubility among liquid lipids. The optimized lipid blend (Precirol®ATO5: Labrasol®ALF, 70:30) showed suitable thermal properties (55–59 °C). The prepared nanoparticles exhibited particle sizes ranging from 59.1±3.2 nm to 898.4±40.3 nm, with entrapment efficiency between 70.11±5.3% and 85.32±4.6%. Zeta potential values were negative (−32.27±1.01 mV to −26.13±7.37 mV). In vitro release studies demonstrated a biphasic, controlled drug release profile. Conclusion: REP-NLCs effectively enhanced Repaglinide solubility and controlled release, supporting their potential as an oral delivery system for poorly water-soluble antidiabetic drugs.