Sol-gel immobilization of lipase enzyme on FTO modified with silica-zirconia and gold nanoparticles films for design of triglyceride impedimetric biosensor

A novel electrochemical sensing platform was created using the formation of a sequence of films, over a conductive fluorine-doped tin oxide glass (FTO), obtained using the sol-gel method and the dip coating technique. Firstly, thin films of silica-zirconia mixed oxides were deposited, in sequence an ionic silsesquioxane film stabilizing and controlling the size of gold nanoparticles (6.5 ± 2.4 nm) was settled, and after the lipase enzyme, obtained from Candida rugosa, was entrapped into a silica film maintaining its operational stability. The films were characterized by scanning electron microscopy (SEM) with EDX, UV–Vis spectroscopy and X-ray photoelectron spectroscopy (XPS). The thickness of each film on the FTO glass was evaluated by optical profilometry. The presence of the enzyme on the platform was confirmed by cyclic voltammetry with the ρ-nitrophenyl palmitate method. This platform was applied successfully as a biosensor for tributyrin (TB) determination by electrochemical impedance spectroscopy EIS, showing low limit of detection (LD) of 1.86 μmol L−1 and high sensitivity of 5.37 μΩ μmol−1 L. The biosensor presented a low KMapp value of 22.69 μmol L − 1 and the Vmaxapp value of 85.57 μmol L−1 min−1 suggesting that the enzyme, immobilized with this method retained activity promoting a fast enzymatic reaction with the TB.