Spectrophotometric detection of cholinesterase inhibitors with an integrated acetyl-/butyrylcholinesterase surface

Discrimination between inhibitors of acetylcholinesterase (AChE), butyrylcholinesterase (BChE), and both AChE and BChE can be accomplished through the use of a surface containing two immobilized enzymes. The interaction of tetraphenyl porphyrin (TPPS1) with immobilized AChE and BChE yields characteristic absorbance peaks at 446 and 421 nm, respectively. Exposure of the immobilized TPPS1–enzyme surface to competitive inhibitors of either enzyme results in a loss in absorbance of the characteristic peak of the inhibited of the porphyrin bound to the inhibited enzyme while non-competitive inhibitors do not result in a change in absorbance. Exposure to inhibitors of both enzymes results in loss of absorbance intensity at both porphyrin–enzyme peaks. Inhibitor concentrations less than 100 ppt can be detected.