Nanobiosensor Design to Detect Cholic Acid Using Multiwalled Carbon Nanotube /TiO2 Nanoparticle for 3α-Hydroxysteroid Dehydrogenase Immobilization

Determination of cholic acid concentration is a useful method to monitor liver diseases. We propose a rapid and simple method for measuring cholic acid. The development of a cholic acid electrochemical biosensor is described that is based on the modification of glassy carbon electrode surface using a mixture of carboxylated multiwalled carbon nanotube and titanium dioxide nanoparticles in chitosan solution and immobilization of 3α-hydroxysteroid dehydrogenase. The modification process of the sensing surface was characterized by Fourier transform infrared spectroscopy, Energy Diverse X-ray Spectrometry, Field Emission Scanning Electron Microscopy, and voltammetry techniques. A good correlation was demonstrated between cholic acid concentration and the peak currents in the presence of nicotinamide adenine dinucleotide. Using a carboxylated multiwalled carbon nanotube and titanium dioxide nanoparticles for electrode modification showed more effective area than an unmodified electrode at optimum pH of 6. Two linear ranges were obtained at 7.1 - 42.7, and 70.9-476.2 nM of cholic acid. Also, the detection limit was 6 nM and the sensitivities of the two ranges were obtained 956.9 and 28.7 µA/µM.