Gold coated dual-resonance long-period fiber gratings (DR-LPFG) based aptasensor for cyanobacterial toxin detection

Here, we present the development of aptasensor for the label-free, stable, and sensitive detection of environmental toxin microcystin-LR (MC-LR). A thiolated aptamer used as a bio-receptor was covalently immobilized on dual-resonance long-period fiber gratings (DR-LPFG) to detect MC-LR toxin. We monitored the DR-LPFG spectral response for various concentrations of MC-LR toxin. The DR-LPFG sensor sensitivity was augmented by coating an appropriate thickness of a gold layer, which served two purposes: first it locally supports a Surface-Plasmon mode associated with the modified cladding modes, and second, it helps covalently immobilize the MC-LR targeting aptamer on the sensor surface. The MC-LR binding to the sensor surface coated with aptamer as a recognition element was measured by observing a change in the resonance wavelengths of ultra-sensitive DR-LPFGs (3891.5 nm/RIU). Real-time, dynamic, and molecular binding of MC-LR to the sensor surface is also confirmed using atomic force microscopy. Keywords: Aptamer, Aptasensor, Cyanobacteria, DR-LPFG, Hepatotoxins, Microcystin-LR