Molecularly imprinted photonic hydrogel sensor for optical detection of L-histidine

A molecularly imprinted photonic hydrogel (MIPH) is described for the optical determination of L-histidine (L-His). The inverse opal structure of MIPH was obtained by placing silica particles (230 nm) in molecularly imprinted polymer on a glass slide. After being fully etched by hydrofluoric acid, this inverse opal structure brings about a high specific surface and plentiful binding sites for L-His. If L-His is absorbed by the modified MIPH, its average effective refraction coefficient is increased. This causes the Bragg diffraction peak to be red-shifted by about 34 nm as the concentration of L-His increases from 0 to 100 nM. Much smaller diffraction peak shifts are obtained for other amino acids. The detection limit of this method is 10 pM. The response time towards L-His is as short as 60 s. In addition, the sensor can be recovered by treatment with 0.1 M acetic acid/methanol. It was applied to the determination of L-His in drinks sample. Graphical abstract After absorbing L-histidine, the average effective refractive index of this molecularly imprinted photonic hydrogel (MIPH) is increased, and the Bragg diffraction peak is shifted. The shift of the diffraction peak can be used for the detection of L-His.