Synaptotagmin II peptide-bead conjugate for botulinum toxin enrichment and detection in microchannels

This paper reports an enrichment platform for botulinum neurotoxin type B (BoNT/B) that has been realized through the fusion of bioconjugation chemistry and microfluidics. Micrometer-sized magnetic beads were conjugated to a 22mer synthetic peptide derived from the synaptotagmin II (Syt II) neuronal protein that is specific for BoNT/B binding. Exposure to BoNT/B in buffer, whole milk and fruit juices resulted in toxin capture, which was confirmed using immunofluorescence. Peptide-modified beads were integrated into arrayed, polymeric microfluidic channels, and all assay steps, from capture to detection, were performed directly in the microchannels, thereby simplifying assay utility and increasing throughput relative to existing detection methodologies. Our sensitive microscale approach required only 7 μL of intentionally adulterated sample without any pre-processing (i.e. dilution, centrifugation, filtering), and with a "hands-on" time of only 1 h to detect 16.6 pg of BoNT/B in whole milk.