Selective detection of HbA1c using surface enhanced resonance Raman spectroscopy.

In the current work, we report on selective detection of HbA1c, a marker for glycemic control in diabetic patients, using surface enhanced resonance raman spectroscopy (SERRS). We found a characteristic band around 770-830 cm(-1) in the SERRS spectrum of HbA1c which was not present in the SERRS spectrum of HbA. To examine the contribution of glucosyl moiety to the characteristic SERRS band of HbA1c, we investigated SERRS spectra for nonenzymatically glycosylated HbA. We found that the SERRS spectral features are essentially identical for both HbA1c and nonenzymatically glycosylated HbA. Furthermore, addition of HbA into colloidal solution of silver nanoparticles (Ag NPs) resulted in the formation of large aggregates of Ag NPs and subsequent sedimentation. On the other hand, aggregation of Ag NPs was considerably low in the case of HbA1c. The differential effect of HbA and HbA1c on colloidal solution of Ag NPs, probably due to their difference in hydrophilicity, enabled us to separate them in a mixture. The separation was characterized by electrophoresis and SERRS analysis. Thus, colloidal solution of Ag NPs and SERRS would be a promising tool for the selective detection of HbA1c.