A Photonic Crystal Protein Hydrogel Sensor for Candida albicans.

We report two-dimensional (2D) photonic crystal (PC) sensing materials that selectively detect Candida albicans (C.albicans). These sensors utilize ConcanavalinA (ConA) protein hydrogels with a 2D PC embedded on the ConA protein hydrogel surface, that multivalently and selectively bind to mannan on the C.albicans cell surface to form crosslinks. The resulting crosslinks shrink the ConA protein hydrogel, reduce the 2D PC particle spacing, and blue-shift the light diffracted from the PC. The diffraction shifts can be visually monitored, measured with a spectrometer, or determined from the Debye diffraction ring diameter. Our unoptimized hydrogel sensor has a detection limit of around 32CFU/mL for C.albicans. This sensor distinguishes between C.albicans and those microbes devoid of cell-surface mannan such as the gram-negative bacterium E.coli. This sensor provides a proof-of-concept for utilizing recognition between lectins and microbial cell surface carbohydrates to detect microorganisms in aqueous environments.