Ultracompact high-sensitivity biosensing based on regenerable laminated bio-conjugation in integrated photonic circuits

Abstract

Biosensor based on micro-ring resonator platform has attracted much attention owing to its high sensitivity for identifying various toxins in the environment. Among various bio-toxins, Botulinum neurotoxin (BoNT) are one type of poisonous substances causing the life-threatening neuroparalytic disease and probably used as biological weapon. In our study, a silicon based micro-ring resonator is designed, fabricated and demonstrated to detect BoNT in water sources. First, the capture antibody is labelled on the surface of silicon waveguide for capturing BoNT. The amount of BoNT bound on the surface results in the change of the effective refractive index. As a result, the concentration of toxins can be sensed based on the resonant shift response. Before involving the detection antibody in the assay, the BoNT concentration can be detected in the range from 200 ng/mL to 1 μg/mL. For further improving LOD, a signal enhancement strategy is to use biotin conjugated detection antibody to form a sandwich structure, and then to bind streptavidin-HRP and biotin conjugated anti-HRP antibody. LOD can be improved to 30 ng/mL after linking the detection antibody. After associating with the layer-by-layer structure composed by HRP and anti-HRP antibody on the sandwich assay, LOD can be improved to several pg/mL. Based on this strategy, the process of signal enhancement is flexible to achieve target LOD. And it also can be regenerated and reused after a cycle of detection. Therefore, this platform shows a high potential to apply for robust, realtime and high sensitive detection for various bio-toxins in water sources.