Rapid analysis of ketamine with in-house antibody conjugated boronic acid modified silver chip on MALDI-TOF MS measurement

Abstract

An antibody conjugated boronic acid modified silver chip (ABAS ship) is fabricated as a simple, rapid, accurate, sensitive and cost-effective sample preparation method for abused drug quantification in human urine. Ketamine, one common abused drug, was applied as proof of concept for ABAS chip with high resolution matrix-assisted laser desorption ionization time-of-flight mass spectrometer (MALDI-TOF MS) analysis. The overall testing process required 10 min at part per billion (ppb) sensitivity level, where current drug testing method necessitated several hours with similar sensitivity. The ABAS chip manufacture process started with slide glass by way of silver mirror reaction to form silver conductive glass for further chemical conjugation. Boronic acid functional group was decorated on silver conductive glass through the formation of silver-thiol (Ag–S) bond. Anti-ketamine antibody was covalently conjugated to boronic acid modified silver conductive glass through the formation of cyclic boronate ester between the boronic acid and the cis-diol groups on the glycans of antibody, which maintain the correct orientation to maximally capture its antigen. The resulting ABAS chip were designed to specifically capture ketamine in human urine samples, that could be directly analyzed by addition of MALDI α-Cyano-4-hydroxycinnamic acid (CHCA) matrix solution. The linear dynamic range of concentration in this method was 10–500 ng/mL with coefficient of determination 0.996. The limit of detection (LOD) and limit of quantification (LOQ) were 2.0 and 7.0 ng/mL, respectively. Importantly, the proposed method allows rapid and accurate quantification of ketamine from suspects’ urine samples in 10 min and small sample volume of 1 μL was required. The resulting data were consistent with traditional gas chromatography-mass spectrometry (GC-MS) analysis. Our homemade ABAS chip could thus provide a powerful tool not only for forensic science but also for most clinical diagnosis of disease as many expression antibodies for the occurrence of diverse diseases could be simply produced and purchased.