A β-cyclodextrin-based supramolecular photonic crystal hydrogel biosensor with macroporous structures for naked-eye visual detection of cholesterol.

Cholesterol (CHO) is an essential lipid in cell membranes and a precursor for vital living substances. Abnormal CHO levels can cause cardiovascular diseases. Therefore, simple and accurate monitoring of CHO levels is crucial for early diagnosis and effective management of cardiovascular diseases. Herein, we report a β-cyclodextrin-based supramolecular photonic crystal hydrogel (PCH) biosensor for naked-eye visual CHO detection. This sensor is composed of a poly(acrylamide-co-N-isopropylacrylamide-co-maleic anhydride-β-cyclodextrin) smart hydrogel with embedding Fe3O4 colloidal chains, which can translate CHO concentration signals into visually detectable color changes of the hydrogel. By carefully selecting a macromolecular crosslinker, a macroporous structure of the hydrogel was achieved, significantly enhancing CHO responsiveness. Molecular docking provides detailed information about the binding mode between MAH-β-CD and CHO. The cyclohexanol portion and alkyl chain of CHO molecule are inserted into MAH-β-CD cavity, driven primarily by hydrophobic interactions. Moreover, this sensor demonstrates excellent regenerability and could be facilely regenerated by washing using hot/cold water or acid solution. Furthermore, it is highly selective for CHO and is suitable for detecting actual human serums. Such a β-CD-based supramolecular PCH biosensor with visualization, excellent regenerability, and high sensitivity and selectivity toward CHO, provides a basis for clinical diagnosis of diseases relative to CHO abnormalities.