A continuous fluidic bioreactor utilising electrodeposited silica for lipase immobilisation onto nanoporous gold

An electrochemically triggered sol-gel process was used to generate a thin silica layer for the immobilisation of lipase from Thermomyces lanuginosus onto dealloyed nanoporous gold (NPG). The catalytic response of the entrapped lipase was examined using the hydrolysis of 4-nitrophenyl butyrate (4-NPB) as a model reaction. For the electrodeposition process, parameters including the deposition time and the concentration of lipase affected the observed catalytic activity. A deposition time of 180 s and a lipase concentration of 3 mg mL^{− 1} were used to prepare the optimised electrode. The operational stability of the silica immobilised enzyme was enhanced on NPG in comparison to that on planar gold, which may arise from confinement of the enzyme in the porous structure. The modified electrodes were incorporated into a 3D printed flow cell with conversion efficiencies of up to 100% after 8 cycles.