Surface acoustic waves (SAW) sensor for the active detection of Microcystin-LR (Cyanobacteria)

Abstract

Cyanobacteria are a family of prokaryotic bacteria whose death causes the release of harmful toxins. Upon ingestion, these toxins produce symptoms similar to food poisoning and are dangerous to humans, as well as livestock. As there is no easily accessible way to remove cyanotoxins from water sources, thus detection before consumption is vitally important. In this article, we report a shear horizontal surface acoustic wave (SH-SAW) based sensor for the active detection of the microcystin congener, microcystin-LR (MC-LR). The sensing platform was devised on 36° YX cut-LiTaO₃ which is a piezoelectric substrate. The sensor system was designed based on delay line configuration and was actively coated with silicon dioxide as a waveguide layer for better mass-load sensitivity. Unlike conventional SAW, the sensing platform utilizes a 5-count tone burst signal, enhancing sensitivity due to its sensitive coda waves. Signal transformation and analysis were made for distinct detection in the frequency domain. The sensor also incorporates the functionalization of gold nanospheres for a high surface-to-volume ratio and enhanced degree of orientation leading to better sensitivity. The sensor detection limit was down to 5.13 nM. Further evidence was provided by selectivity analysis and the sensor could identify MC-LR from the other biomarkers.