Direct and label-free detection of cholic acid based on molecularly imprinted photonic hydrogels

Here we report the design and preparation of a novel self-reporting sensor for cholic acid, an important biological compound produced in hepatocytes. Traditional detection methods of cholic acid are mostly dependent on analytical equipment, and are either time-consuming or require a derivatization process. In this work, a new approach based on molecularly imprinted photonic hydrogels (IPHs) is described, by which direct, sensitive and label-free detection of cholic acid can be achieved without any derivatization treatment and expensive instruments. The unique 3D ordered porous hydrogels that reveal optical changes in responsive to cholic acid concentration were prepared by combining colloidal crystal templating with the molecular imprinting technique. Due to their special hierarchical porous structure, which consists of 3D-ordered interconnected macroporous arrays with nanocavities derived from molecular imprinting, the formed photonic hydrogels allow rapid and ultrasensitive detection of the target analyte. The interconnected macropores are favorable for the rapid transport of the analyte in the hydrogel, while the inherent high affinity of nanocavities distributed in thin hydrogel walls allows IPHs to recognize the analyte with high specificity.