Evanescent wave absorbance based label-free detection of microcystin in water and bodyfluids using polyaniline coated optical fiber

An increase in the eutrophication of water bodies globally is leading to a significant increase in harmful cyanobacterial blooms, causing contamination of water with cyanotoxins like microcystins. This poses a serious threat to human health and has far-reaching environmental consequences. Prolonged exposure to microcystin can result in oxidative stress, inflammation, liver damage, and potentially lead to liver cancer. The detection of microcystin typically requires sophisticated tests such as LC-MS, which are expensive, require high maintenance, and trained professionals to conduct. This poses a challenge when regular on-site assessment is necessary. In response, a simple and sensitive fiber optic immunosensor was developed by utilising the optical properties of polyaniline over the fiber surface. This evanescent wave absorbance-based sensor could successfully detect microcystin-LR in matrices such as lake water, urine, and serum with a limit of detection ranging from 0.001 µg/L to 0.004 µg/L. The sensor demonstrated a linear response from 0.1 to 1000 µg/L and excellent selectivity. The recovery results ranged from 88 % to 112 % indicating reasonable accuracy.