Disposable multichannel immunosensors for 2,4‐dichlorophenoxyacetic acid using acetylcholinesterase as an enzyme label

Abstract

An improved version of the disposable multichannel immunochemical biosensor for the herbicide 2,4-dichlorophenoxyacetic acid (2,4-D) based on a screen-printed amperometric transducer and monoclonal antibodies (MAb) against 2,4-D is reported. Entrapment within a thin Nafion film was used for the direct immobilization of MAb at the electrode surface. The amount of the tracer (2,4-D conjugated to acetylcholinesterase) bound in a competitive immunochemical reaction was determined amperometrically using acetylthiocholine iodide as substrate. The measuring procedure (times of incubation with tracer and substrate, pH, tracer concentration) was optimized. The sensor was able to detect less than 0.01 pgL of free 2,4-D in water. One analysis (8 samples) was completed in 30 min (20min for immunochemical reaction, 5 min incubation with substrate, 5 min measurement). The performance of the immunosensor (two configurations) was evaluated on real samples (tap water) with added 2,4-D. The determined amounts (mean values 0.097 to 0.105 and 0.89 to 1.13) corresponded well with the added contents of 2,4-D (0.100 and 1.00 pgL, respectively).

Hybridization Assay at a Disposable Electrochemical Biosensor for the Attomole Detection of Amplified Human Cytomegalovirus DNA

“…Further improvement is desired such as the development of compact, user-friendly, hand-held multichannel device (35), or the miniaturization of the sensor (i.e., microelectrodes) with the aim of working in smaller assay volumes for increasing the sensitivity. We have recently shown that a monolayer of biotin can be electrochemically grafted on the surface of carbonbased SPE, thus offering new opportunity for the immobilization of oligonucleotides on small electrode surfaces (36).…”

Breve revisão de métodos de determinação de resíduos do herbicida ácido 2,4-diclorofenoxiacético (2,4-D)

“…Faixas de detecção na ordem de 10 -7 a 10 -11 mol L -1 foram obtidas. Essa mesma classe de enzimas foi explorada na construção de um imunossensor descartável 55 , do tipo multicanal, usando um anticorpo monoclonal e um conjugado 2,4-DAChE. O método mostrou-se sensível na ordem de partes por milhão, e foi aplicado à análise de amostras de água.…”

Imunossensor amperométrico

“…Acetilcolinesterase (AchE): emprega a acetiltiocolina como substrato e a determinação do analito ocorre monitorando a tiocolina 37 ; tem sido usada como enzima marcadora de reação imunoenzimática, uma vez que exibe uma alta constante catalítica 38 ; a presença de grupos amino primário permite o uso da AchE no acoplamento de haptenos sem alterar as propriedades catalíticas da enzima 39 .…”