Low-voltage/temperature double responsive N-isopropylacrylamide based shape-changing double network hydrogel with enhanced mechanical properties for controlled drug release and its mechanism

• A low-voltage/temperature double responsive NIPAAm/CNTs/Fe(phen) 3 hydrogel was synthesized by double network. • NIPAAm/CNTs/Fe(phen) 3 hydrogel could release drug at 10 V/35℃. • Tunable release kinetics achieved by adjusting voltage/temperature. • Hydrogel controlled drug release system with enhanced mechanical properties. • Impact of crosslinking agent and carbon nanotubes on drug loading capacity and releasing was studied. A low-voltage/temperature double responsive shape-changing double network hydrogel with enhanced mechanical properties based on N-isopropylacrylamide (NIPAAm) and 5-acrylamido-1,10-phenanthroline bis (1,10-phenanthroline) iron (Ⅱ) (Fe(phen) 3 ) was synthesized. The synthesized hydrogel was systematically characterized through Fourier-transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), differential scanning calorimetry (DSC), and thermogravimetric analysis (TGA). Its functional performance was further evaluated in terms of swelling properties, thermoresponsive behavior, electroresponsive behavior, and electrochemical characteristics. Bovine Serum Albumin (BSA) was served as the drug model to evaluate the drug loading/releasing performance and potential of hydrogel. It was observed that loading time, crosslinking agent (MBA) content, CNTs content and initial BSA solution concentration significantly influenced the drug loading capacity of the hydrogel. The drug loading mechanism was discussed. Under stimulation for 40 min at 10 V/35 °C, a hydrogel with 0.5 wt% CNTs and 2.00 % MBA released 43.46 % and 55.56 % of BSA, whereas at 20 V/45 °C, release increased to 66.03 % and 64.94 %. Additionally, this hydrogel system featured an “ON-OFF” drug release mechanism during electrical stimulation. Fitting the Korsmeyer-Peppas model demonstrated that drug release adhered to Fickian diffusion without being influenced by cavity collapse or skeleton dissolution.