Initial doxycycline hyclate diffusion and solvent exchange from borneol-based in situ forming matrices using UV–Vis imaging

Abstract

UV–Visible (UV–Vis) imaging provides real-time and spatially resolved insights into drug transport, solvent diffusion, and matrix formation, making it a useful tool for evaluating in situ forming matrices (ISMs). ISMs are injectable liquids that solidify upon contact with aqueous environments to sustain drug release. Borneol, a poorly water-soluble and biocompatible monoterpene alcohol, was selected as the matrix former, with triacetin as a hydrophobic co-solvent to modulate drug release in a concentration-dependent manner. This study investigated the effects of borneol matrix and triacetin concentration on solvent exchange, matrix structure, and drug transport in borneol-based ISMs. Formulations containing borneol (40 % w/w), doxycycline hyclate (0.5 % w/w), and triacetin (0–25 % w/w) in N-methyl-2-pyrrolidone (NMP) were characterized by microscopy and UV–Vis imaging to evaluate morphology, solvent diffusion, and drug release. The results showed that borneol matrices effectively restricted solvent and drug transport. Incorporation of 5 % w/w triacetin had a negligible effect on initial solvent exchange and drug release, whereas 25 % w/w triacetin disrupted matrix integrity, resulting in accelerated solvent exchange and unrestricted Dox diffusion. A strong linear correlation between drug and solvent diffusion was observed, with the borneol matrix promoting more efficient drug transport under equivalent solvent diffusion conditions compared to the non-matrix system. Overall, UV–Vis imaging provided real-time insights into solvent exchange mechanisms, matrix formation, and drug release behavior in ISM, confirming that borneol matrices with 5 % w/w triacetin loading can prolong drug release.