Photo-Controlled Reversible Uptake and Release of a Modified Sulfamethoxazole Antibiotic Drug from a Pillar[5]arene Cross-Linked Gelatin Hydrogel

Pillararene cross-linked gelatin hydrogels were designed and synthesized to control the uptake and release of antibiotics using light. A suite of characterization techniques ranging from spectroscopy (FT-IR, 1 H and 13 C NMR, and MAS NMR), X-ray crystallographic analysis, scanning electron microscopy (SEM), and thermogravimetric analysis (TGA) was employed to investigate the physicochemical properties of hydrogels. The azobenzene-modified sulfamethoxazole ( Azo - SMX ) antibiotic was noncovalently incorporated into the hydrogel via supramolecular host–guest interactions to afford the A - hydrogel . While in its ground state, the Azo-SMX guest has a trans configuration structure and forms a thermodynamically stable inclusion complex with the pillar[5]arene motif in the hydrogel matrix. When the A - hydrogel was exposed to 365 nm UV light, Azo - SMX underwent a photoisomerization reaction. This changed the structure of Azo-SMX from trans to cis, and the material was released into the environment. The Azo - SMX released from the hydrogel was effective against both Gram-positive and Gram-negative bacteria. Importantly, the A - hydrogel exhibited a striking difference in antibacterial activity when applied to bacterial colonies in the presence and absence of UV light, highlighting the switchable antibacterial activity of A - hydrogel aided by light. In addition, all hydrogels containing pillar[5]arenes have demonstrated biocompatibility and effectiveness as scaffolds for biological and medical purposes.