Biodistribution and pharmacokinetic studies on topically delivered technetium-99m-labeled 5-FU nanogel formulation for management of pre-cancerous skin lesions

Purpose: To prepare technetium-99m (99mTc)-labelled nanogel loaded with 5-fluorouracil (5-FU) containing synthesized gallic acid-stearylamine (GA-SA) conjugate in order to reduce its systemic toxicity and provide site-specific delivery to skin lesions. Methods: Lipid nanocarrier-based 1 % (w/w) 5-FU nanogel containing GA-SA conjugate was successfully formulated. Parameters that included pH, viscosity and entrapment efficiency were measured. Furthermore, 1 % (w/w) 5-FU nanogel and 1 % (w/w) 5-FU commercial formulations were radiolabelled with 99mTc. The radiolabelled 99mTc-5-FU nanogel and commercial formulations were subjected to successive preclinical assessments with respect to radiochemical stability, biodistribution, and gamma scintigraphy in BALB/c mice, and pharmacokinetic studies in New Zealand albino rabbits. Results: The entrapment efficiency of 5-FU in the nanogel preparation was 82.12 ± 1.2 %. The 5-FU nanogel formulation exhibited excellent radiolabelling efficiency (> 93 %) and high stability. Skin/blood localization ratios of 274.93 and 167.89 were obtained for topical radiolabelled drug-loaded 5-FU nanogel formulation and 5-FU commercial formulation, respectively, after 1 h of administration. Gamma scintigraphy and biodistribution studies showed that topically administered 99mTc-5-FU nanogel was distributed mostly in skin, when compared to marketed 5-FU formulation. Pharmacokinetic studies revealed low maximum activity in the blood (Cmax = 34.20 µg/mL), with low intensity (AUC) for topically administered 99mTc-5-FU nanogel formulation. Conclusion: 5-FU nanogel enhances specific delivery of 5-FU at targeted sites and decreases its toxicity in tissues distant from the site of application. The results suggest that nanogel loaded with 5-FU containing synthesized GA-SA conjugate is a novel effective approach for the treatment of skin lesions.