Electrochemical epinephrine sensor using artificial receptor synthesized by sol–gel process

An artificial adrenergic receptor was fabricated with molecular imprinting silica. Epinephrine (EP) was imprinted in the organic–inorganic hybrid silica film through π–π interaction from phenyltrimethoxysilane (PTMOS). The epinephrine-imprinted film was spin coated on an indium tin oxide (ITO) glass. The affinity of epinephrine to the imprinted film was determined by the oxidation current of epinephrine. The epinephrine-imprinted film showed a good selectivity toward epinephrine. Epinephrine and isoproterenol (IPT) which have two more methyl group on amino-N had comparable current responses, 79.9% and 75.3%, respectively. Negatively charged analytes including 3,4-dihydroxy-l-phenylalanine, 3,4-dihydroxyhydrocinnamic acid, and ascorbic acid had current responses lower than 47%. The mechanism of facilitated transport by fixed-site carriers was suitable to explain the current enhancement by the imprinted film. Binding sites of epinephrine-imprinted film were believed to function as the fixed site carriers for the facilitated transport. The occupation of binding sites by 2-phenethylamine which structurally resembles epinephrine decreased the current at high epinephrine concentration.