RESUMO
Biocompatible hydrogels that serve as the hosting membrane for various bioreceptors contribute to the response of impedimetric biosensors. The temperature response of poly(2-hydroxymethacrylate) [p(HEMA)]-based hydrogel networks prepared with poly(ethylene glycol) methacrylate (PEGMA) for enhanced biocompatibility and with N-[tris(hydroxymethyl)methyl] acrylamide (HMMA) was studied. Hydrogels were cross-linked with tetraethyleneglycol diacrylate (TEGDA) and synthesized by UV initiation (2M% DMPA photoinitiator). The p(HEMA-co-PEGMA-co-HMMA) based hydrogels were fabricated as discrete gel pads (D=2.5 mm, H=2 mm and V=9.82 µL) on top of 250 µm diameter cysteamine modified and acryloyl (polyethylene glycol)(110) N-hydroxy succinamide ester (acryloyl-PEG-NHS) derivatized gold microelectrodes set within 8-well (8W1E) cell culture biochips. Gel pads were fabricated with cross-link densities corresponding to 1, 3, 5, 7, 9 and 12 M% TEGDA and were studied by frequency dependent 3-electrode electrochemical impedance spectroscopy (1 mHz to 100 kHz; 50 mV p-t-p) and by temporal 2-electrode impedimetry (64 kHz; 50 mV p-t-p) over the temperature range 30-45°C at 90% RH or in aqueous 0.1 M Tris/KCl at pH 7.2 buffer. The p(HEMA-co-PEGMA-co-HMMA) hydrogels showed an increase in the real component of impedance with increasing cross-link density and demonstrated activation energies for impedimetric transport that ranged from 15 kJ/mol (3 M%) to 20 kJ/mol (12 M%) confirming the dominance of proton migration in the impedance of the hydrogels.