Chemically amplified kojic acid responses of tyrosinase-based biosensor, based on inhibitory effect to substrate recycling driven by tyrosinase and L-ascorbic acid

A tyrosinase-based chemically amplified biosensor, based on the substrate recycling of polyphenols driven by tyrosinase-catalyzed oxidation and chemical reduction by L-ascorbic acid (AsA), has been utilized for the highly sensitive detection of inhibitors of tyrosinase such as kojic acid, benzoic and SCN- ion. The amplified current response of immobilized tyrosinase-coupling oxygen electrode due to the recycling was suppressed by the addition of inhibitors, and a highly amplified response to kojic acid over other inhibitors was observed in the presence of 5 mM AsA. The amplification factor (AF) of kojic acid is substantially proportional to the AF of substrates, and the AF for 1 x 10(-7) M kojic acid was increased by up to a factor of 143 when 1 x 10(-5) M dopamine was used as a competitive substrate in the presence of 5 mM AsA. The amplified calibration curve of kojic acid obtained with 5 mM AsA was shifted towards more than a two decades lower concentration range compared with that of the non-amplified response, and the detection limit of kojic acid was lowered to 7 x 10(-8) M.