Evolution of high-affinity aptamer probe for label-free and probe conformation switch-based fluorescent biosensing of β-carotene in seaweeds

β-Carotene is an important bioactive component showing great activities and receiving great attention in recent years. The traditional methods for the accurate detection of β-carotene in food are time-consuming. There is an urgent need to establish rapid quantification methods for β-Carotene. Herein, a label-free fluorescent aptasensor which was based on the conformation-switch of the aptamer probe was developed to detect β-carotene in seaweeds. Firstly, a post-SELEX strategy based on extraction and terminal-fixation was established to evolve the anti-β-carotene aptamer to achieve high affinity. An aptamer probe (β-2-TF) with a 177.5-fold affinity increment was obtained and then applied to develop a probe conformation-switch-based fluorescent aptasensor with the assistance of SYBR Green I (SGI). Under the optimal conditions, the aptasensor exhibited good accuracy and selectivity, with a linear detection range of 62.5–4000 nM and a limit of detection (LOD) as low as 39.64 nM. The developed strategies can act as robust references for the analytical method development in the food field.