Laccase amperometric biosensors were developed to detect the catechol compound. The laccase enzyme (LAC) immobilization was performed on nanostructures of (a) titania (TiO2); (b) titania/Nafion (TiO2/NAF) (both immobilized by the sol-gel method) and a third nanostructure, which consisted of a single biosensor composite of Nafion and laccase enzyme denoted as NAF/LAC. The Nafion was deposited on a graphite electrode and used to avoid “cracking” on the matrix. The TiO2 particle size was an average of 66 nm. FTIR spectroscopy vibration modes of different composites were determined. The electrochemical behavior of the biosensor was studied using electrochemical spectroscopy (EIS) and cyclic voltammetry (CV). The biosensor based on TiO2/NAF/LAC presented the best electro-chemical properties with regard to sensitivity, stability and detection limit after a period of 22 days.

Nanoparticles of titanium dioxide (TiO 2 ) have unique properties in creating an appropriate microenvironment for immobilizing biomolecules without loss of biological activity, and facilitating electron transference between the enzyme and surface of the electrode. TiO 2 properties have led to its intensive use in building electrochemical biosensors. Another aspect is, the chemical process of sol-gel which offers new and interesting advantages in the encapsulation of biomolecules sensitive to heat and environmental conditions (enzymes, proteins, antibodies, and cells from plants, animals and micro-organisms), mainly due to a synthesized process at low temperatures. The nanomaterials produced by sol-gel have many advantages, including chemical inertia, physical rigidity, insignificant swelling in an aqueous medium, and porosity. For this reason, electrochemical biosensors consisting of nanomaterials have been extensively investigated and used in important industrial sectors, such as, those of pharmaceuticals, health, food, agriculture, and environment. They provide real-time data, which allows the control and traceability of each of the processes involved. Biosensors are devices that consist of one element of molecular recognition (biomolecules) and one transduction element. The objective of this work is to conduct a review of electrochemical biosensors using nanoparticles obtained from the sol-gel process and their potential application to measure phenol compounds.

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The derived materials obtained from the sol-gel process have been used in various technological applications, such as solar cells, intelligent coatings, catalysis, and, more recently, the fabrication of bioreceptors. The objective of this study was to develop a bioreceptor consisting of a titania-based nanostructure, which was synthesized using the sol-gel method. This nanostructure was immersed in a solution containing laccase and Nafion and integrated into a graphite-based electrode (TiO2/NAF/LAC). This device is called a bioreceptor and is used to detect gallic acid. The nanostructure was characterized by X-ray diffraction, Raman spectroscopy, and scanning electron microscopy (SEM). Particle size was measured using a nanosizer. Cyclic voltammetry (CV) tests were performed on a bioreceptor. In this study, the predominant phase of TiO2 was anatase, and the obtained nanoparticles had an average size of 66 nm. The CV tests of the bioreceptor showed an oxidation response that increased as the concentration of gallic acid in the solution increased, with a detection limit of 0.125 μM, as well as a wide linear range that varied from 0.125 to 175 μM and a factor correlation of 0.9968. As a result, it was possible to develop a bioreceptor capable of immobilizing laccase to detect gallic acid.

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