Abstract
In this study, we have developed a label-free immunosensor with the variation of resonance frequency (Δf) of a quartz crystal microbalance (QCM) as readout signal for ultrasensitive detection of Ketamine (KT). An optimized strategy for immobilization of KT antibody on the surface of the QCM chip was implemented via the self-assembly modification of 3-mercaptopropionic acid, and then activated with 1-ethyl-3- (3-dimethylaminoprophl) carbodiimide and n-hydroxysuccinimide. The specific affinity between the antibody and the antigen ensured a selective response toward KT. The Δf linearly related to the concentration of KT in the range of 1 to 40 pg/mL, with a detection limit of 0.86 pg/mL (S/N = 3). The obtained immunosensor was applied to detect the KT in spiked human urine without any pretreatment but dilution with recoveries from 91.8% to 108%. The developed sensor is promising to perform the portable or on-spot KT detection in clinic or forensic cases.
Highlights
Ketamine ((RS)-2-(2-chlorophenyl)-2-(methylamino)cyclohexanone, KT), an NMDA receptor antagonist first developed in 1962, was once used as an anesthetic agent in veterinary and human surgery in 1970s because of its few side effects and short actuation duration [1,2,3]
By activation of the self-assembly monolayer (SAM) layer via the reaction involving 3-(3-dimethylaminopropl)-1-ethylcarbodiimide hydrochloride (EDC) and n-hydroxysuccinimide (NHS), an amide bond was formed between the carboxylic acid group of 3-mercaptopropionic acid (3-MPA) and the amine group of KT antibody
During the EDC/NHS activation step [17], the carboxylic group of the SAM were replaced by amino group from EDC and resulted in an electrostatic interaction with the negatively charged hydroxyl terminal of NHS with a resistance of 3652 Ω, as shown in curve “c”
Summary
Ketamine ((RS)-2-(2-chlorophenyl)-2-(methylamino)cyclohexanone, KT), an NMDA receptor antagonist first developed in 1962, was once used as an anesthetic agent in veterinary and human surgery in 1970s because of its few side effects and short actuation duration [1,2,3]. The high-dose intake of KT will result in similar effects to that of phencyclidine or lysergide including harming the central nervous system [5] Because of this serious situation, its detection is very important in clinic or forensic field. Sensitive response can be obtained because of the high quality factor of quartz crystal (105–106) In recent years, it has been intensively reported for a lot of applications, such as monitoring of environmental contaminants, biosensor developing and drug analysis etc. By activation of the SAM layer via the reaction involving 3-(3-dimethylaminopropl)-1-ethylcarbodiimide hydrochloride (EDC) and n-hydroxysuccinimide (NHS), an amide bond was formed between the carboxylic acid group of 3-MPA and the amine group of KT antibody In this way, the KT antibody was immobilized on the QCM chip [32]. The quantifying character of developed sensor was verified by detecting the KT in spiked human urine
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