Aptameric photonic structure-based optical biosensor for the detection of microcystin.

An optical photonic biosensor for the detection of microcystin (MC) has been developed using an aptamer-immobilized interpenetrating polymeric network (IPN) intertwined with solid-state cholesteric liquid crystals (CLCs). The IPN was constructed with a polyacrylic acid hydrogel (PAA). Aptamer immobilization enhances polarity while blocking hydrogen bonding between the carboxylic groups of PAA-IPN hydrogel, thereby increasing the swelling ratio of the PAA-IPN hydrogel. This leads to an expansion in the helical pitch of the corresponding IPN-CLC biosensor chip and results in a red-shift in the reflected color. Upon exposure to an aqueous MC solution, the IPN-CLC biosensor chip exhibits aptamer-mediated engulfment of MC, resulting in reduced polarity of the IPN complex and a consequential blue-shift in the biosensor chip color occurred. The wavelength shift of the IPN-CLC biosensor chip demonstrates a linear change with an increase in MC concentration from 3.8 to 150 nM, with a limit of detection of 0.88 nM. This novel optical biosensor is characterized by its low cost, simplicity, selectivity, and sensitivity, offering a promising strategy for designing similar toxin biosensors through the modification of biological receptors.