Engineering Quercetin-Loaded Nanostructured Lipid Carriers for Enhanced Oral Delivery: Physicochemical Characterization and In Vitro Antioxidant Evaluation

Depression is a relatively common mental disorder characterized by a severe imbalance of neurotransmitters. Numerous current therapies are available, but they have drawbacks such as limited bioavailability restricted by the blood–brain barrier (BBB). To address the poor aqueous solubility and limited bioavailability of quercetin (Que), Que-loaded nanostructured lipid carriers (Que-NLCs) were developed and evaluated for their physicochemical characteristics, stability, in vitro drug release behavior, and antioxidant activity. Que-loaded NLCs were prepared by probe-sonicator homogenizer and characterized for particle size (167 ± 0.57 nm) and zeta potential (−9.90 ± 0.05 mV). Total drug content and entrapment efficiency were 86.2% ± 2.15% and 98.35% ± 1.35%, respectively. Fourier transform infrared spectroscopy and differential scanning calorimetry studies confirmed drug encapsulation. High-resolution transmission electron microscopy and field emission scanning electron microscopy revealed spherical particle morphology. pH determination and stability studies showed no significant degradative changes. In vitro drug release followed the Korsmeyer–Peppas model, indicating a non-Fickian mechanism. DPPH analysis demonstrated concentration-dependent antioxidant activity of Que-NLCs. These findings demonstrate favorable physicochemical, release, stability, and antioxidant characteristics of Que-NLCs; however, further studies are required to establish their BBB permeability and therapeutic potential for neurological applications.