Operational condition of a molecular imprinting catalyst-based fructosyl-valine sensor

We have previously reported the development of an artificial enzyme catalysing hydrolytic oxidation reaction of fructosyl-valine (Fru-val). The enzyme was prepared by molecularly imprinting a catalytic polymer composed of vinyl imidazole to form a molecular imprinting catalyst (MIC). In this study, we have attempted to improve both the selectivity and sensitivity of the MIC-based Fru-val sensor by altering the operational conditions. Assuming that the hydrophobic interaction between the valine residue of Fru-val and the cross-linker in the polymer increases with increasing ionic strength of the buffer solution, and that the hydrophilic interaction between N-epsilon-substituted fructosyl-lysine (Fru-epsilon-lys) and the polymer decreases, we have used a higher concentration of the buffer solution for sensor operation. The sensitivity towards Fru-val increased, whereas the sensitivity towards Fru-epsilon-lys decreased when a 100 mM potassium phosphate buffer was used for sensor operation instead of a 10 mM buffer. The selectivity of the MIC towards Fru-val against Fru-epsilon-lys increased drastically from 1.9 to 5.7. In addition, the sensor was able to measure a glycated peptide, fructosyl valyl histidyl, which is a characteristic of the N-terminal structure of glycated hemoglobin.