Fullerene-Functionalized Cellulosic Hydrogel Biosensor with Bacterial Turn-on Fluorescence Response Derived from Carboxymethyl Cellulose for Intelligent Food Packaging with DFT Calculations and Molecular Docking.

This study reports the synthesis and characterization of a novel carboxymethyl cellulose-N-fullerene-g-poly(co-acrylamido-2-methyl-1-propane sulfonic acid) (CMC-N-fullerene-AMPS) hydrogel for potential application in biosensing within food packaging. The hydrogel was synthesized via free radical polymerization and characterized using FTIR, SEM, and fluorescence microscopy. FTIR analysis confirmed the successful grafting of AMPS and incorporation of N-fullerenes, indicated by characteristic peaks and a shift in the N-H/O-H stretching frequency. Density Functional Theory (DFT) calculations revealed that the CMC-N-fullerene-AMPS hydrogel exhibited higher stability and a lower band gap energy (0.0871 eV) compared to the CMC-AMPS hydrogel, which means a high reactivity of CMC-N-fullerene-AMPS. The incorporation of N-fullerenes significantly enhanced the hydrogel's antibacterial activity, demonstrating a 22 mm inhibition zone against E. coli and a 24 mm zone against S. aureus, suggesting potential for active food packaging applications. Critically, the hydrogel displayed a unique "turn-on" fluorescence response in the presence of bacteria, with distinct color changes observed upon interaction with E. coli (orange-red) and S. aureus (bright green). This fluorescence enhancement, coupled with the porous morphology observed via SEM (pore size 377-931 µm), suggests the potential of this hydrogel as a sensing platform for bacterial contamination within food packaging. These combined properties of enhanced antibacterial activity and a distinct, bacteria-induced fluorescence signal make the CMC-N-fullerene-AMPS hydrogel a promising candidate for developing intelligent food packaging materials capable of detecting bacterial spoilage.