Physical characterization and bioavailability assessment of 5-fluorouracil-based nanostructured lipid carrier (NLC): In vitro drug release, Hemolysis, and permeability modulation.

5-Fluorouracil (5-FU) is an anticancer agent belonging to BCS Class III that exhibits poor release characteristics and low retention in the biological system. The main objective of this investigation was to develop a drug delivery system, i.e., Nanostructure Lipid Carriers (NLCs) loaded with 5-FU to prolong its biological retention through 5-FU-loaded NLCs (5-FUNLC) were designed to manipulate physicochemical characteristics and assessment of in vitro and in vivo performance. The developed NLCs underwent comprehensive characterization, including assessments for particle size, zeta potential, morphological evaluation, and FT-IR spectroscopy. Additionally, specific evaluations were conducted for 5-FUNLCs, encompassing analyses for encapsulation efficiency of the drug, release characteristics in PBS at pH 6.8, and stability study. The lipophilic character of 5-FUNLC was confirmed through the measurement of the partition coefficient (log P). 5-FUNLCs were observed as spherical-shaped particles with a mean size of 300 ± 25 nm. The encapsulation efficiency was determined to be 89%, indicating effective drug loading within the NLCs. Furthermore, these NLCs exhibited a sustained release nature lasting up to 3-4 h, indicating their potential for controlled drug release over time. Lipid components were biocompatible with the 5-FU to determine thermal transition temperature and show good stability for 30 days. Additionally, an in vitro hemolysis study that confirmed the system did not cause any destruction to the RBCs during intravenous administration. The drug's gut permeability was assessed utilizing the optimized 5-FUNLC (F2) in comparison to 5-FU through the intestine or gut sac model (in the apical to basolateral direction, A → B). The permeability coefficient was measured as 4.91 × 10