pH and polyphenol-controlled release dual-responsive intelligent hydrogel absorbent pad strategy:...

We developed a pH/polyphenol-controlled dual-response intelligent hydrogel absorbent pad based on methylcellulose and sodium alginate (MC-SA). The hydrogel was incorporated with composite particles consisting of anthocyanins encapsulated in metal-organic frameworks (MOFs). Synergistic interactions between anthocyanins and MOFs enhanced the pad's water absorption (511.4%) and retention capacity (88.9%), swelling properties, and thermal stability. The pad possessed antimicrobial (TVC < 6 log(CFU)) and antioxidant activity and thereby could suppress microbial growth and lipid/protein oxidation (TBARS: 0.76 mg MDA/kg; total sulfhydryl content: 46.25 μmol/g) in fresh pork during 9 days of storage at 4 °C. Furthermore, with their pH-responsive color change and controlled release properties, the incorporated anthocyanins enabled real-time visual monitoring of pork freshness and preservation efficacy. Among all hydrogel pads, the MC-SA-Ant@Fe-MOFs pad showed the most optimal preservation performance and was able to extend pork shelf life by 2-4 days. This pad also exhibited excellent biocompatibility and soil degradability. Overall, this study presents a pH/polyphenol-controlled dual-responsive smart hydrogel absorbent pad that can serve as both a preservative material and a freshness indicator.