Highly-sensitive and selective colorimetric sensor for amino acids chiral recognition based on molecularly imprinted photonic polymers

The incorporation of molecularly imprinted materials into photonic crystals presents an ideal sensing platform on which analyte recognition and analyte-dependent transduction methodology could be realized simultaneously. Here, a colorimetric molecularly imprinted photonic polymer (MIPP) sensor has been developed for the sensitive and selective chiral recognition of amino acids. The sensor was fabricated by infiltrating a polystyrene photonic crystal template with precursor and imprinting molecules, followed by a thermal polymerization. After removal of templates, the resulted MIPP consists of a three-dimensional, highly-ordered and interconnected macroporous array. The amino acids recognition events thus could be directly transferred into visible color changes and readable optical signals through the diffraction peak shifts of MIPP. A function relationship was found between the diffraction peak shift and the concentration of l-pyroglutamic acid (l-Pga) in the range of 0.01–0.50 mM at pH 4, and a linear relationship with a slope of 278 nm/mM was found when the concentration of l-Pga was lower than 0.20 mM. The chiral recognition process accompanying with a gradual color change of MIPP can be easily visualized by the naked eye. The developed method has been applied to detect l-Pga in monosodium glutamate samples.