Influence of the host matrix of the enzyme in the performance of amperometric biosensors

In this work we present a comparative study of four amperometric biosensors of phenol prepared by means of immobilization of tyrosinase in organic and inorganic matrices. The immobilization within organic matrices consisted on enzyme entrapped in both polyacrylamide microgels, and polyvinylimidazole microparticles. On the other hand, two inorganic matrices were investigated: a laponite clay and the calcium phosphate cement, brushite. The enzyme was absorbed on these inorganic matrices and subsequently was cross-linked by glutaraldehyde. The detection of phenolic compounds was performed in aqueous and organic media by direct electrochemical reduction of the enzymatic product, o-quinone, at −0.1 V versus SCE. The large differences found in biosensors performance are attributed to the environment surrounding the enzyme, or the biomaterial layers used in the fabrication of the biosensor. Sensors based on inorganic matrices provided the best results in detection of monophenols and catechol in aqueous solution, being the biosensor of brushite the most sensitive device (S = 46 A M−1 cm−2) with the lowest detection limit (DL = 3 nM). On organic media (acetonitrile, dioxane, and ethanol), the optimum catechol detection was achieved with both, biosensors based on brushite (S = 3.3 A M−1 cm−2, DL = 40 nM) and also with biosensors prepared with polyvinylimidazole microparticles (S = 12.5 mA M−1 cm−2, DL = 8 μM).