On-resonance islands of Ag-nanowires sense the level of glycated hemoglobin for diabetes diagnosis

Glycated hemoglobin (HbA1c) is one of the most important indicators for the diabetes diagnosis. In this study, we designed and characterized a disordered silver nanowire-based chip for the detection of HbA1c level in human blood samples upon localized surface plasmon resonance (LSPR). The architecture of the chip intended to enhance the LSPR shift by the combination of two mechanisms: (1) an overall variation in refractive index change upon the protein binding due to the presence of the nanowires, and (2) a plasmonic coupling between the Ag nanowires. The hydrophobic surface made by the disordered nanowires retained the sample during the testing. Samples with different HbA1c levels, including the ones recommended by the American Diabetes Association for diabetes diagnosis, displayed a blueshift and bandwidth narrowing of the absorbance spectra, signifying the sensitivity of the chip. Besides, the sensorgrams demonstrated peaks with intensities varying according to the characteristics of the samples. The analysis of the HbA1c-specific-peak displayed that the values similar to HbA1c levels in calibrated blood samples with an error of less than 1%. This technique helps to open up a new avenue toward highly sensitive trace protein detection via the plasmonic method.