Activity Assay Of Botulinum Neurotoxin Type A By Capillary Electrophoresis And Laser Induced Fluorescence Detection

A method for detecting activity of Botulinum neurotoxin type A (BoNT A) in aqueous solution was studied by CE using a SDS separation buffer based on the toxin's endopeptidase reaction with its peptide substrate. The synthesized peptide substrate was biotin- and FITC-labeled, which enabled highly sensitive detection using laser induced fluorescence (LIF) detection as well as well quantitative determination of the cleaved product in presence of the large amount of the peptide substrate in the reaction buffer. It was found that the activity of BoNT A could be enhanced greatly by including 1 mg/ml Bovine serum albumin (BSA) into the reaction buffer. Using the current assay method, BoNT A with concentration as low as 0.1 ng/ml was detected with S/N ratio 3 and the linear range of the analysis was four orders magnitude. In addition, the SDS buffer could provide a safer way to work with BoNT A solutions because SDS can deactivate the toxicity of BoNT A. With CE's advantages of small sample volume needed and possible parallel analysis, this method could find particular applications in fast assay of BoNT A toxin for medical use and inhibitor screening.