Boronate-Modified Interdigitated Electrode Array for Selective Impedance-Based Sensing of Glycated Hemoglobin

An impedance-based label-free affinity sensor was developed for the recognition of glycated hemoglobin (HbAlc). Interdigitated gold microelectrode arrays (IDAs) were first modified with a self-assembled monolayer of cysteamine followed by cross-linking with glutaraldehyde and subsequent binding of 3-aminophenylboronic acid (APBA), which selectively binds HbAlc via cis diol interactions. Impedance sensing was demonstrated to be highly responsive to the clinically relevant HbAlc levels (0.1%-8.36%) with a detection and quantitation limit of 0.024% (3 sigma/slope) and 0.08% (10 sigma/slope), respectively. The specificity of the assay was evaluated with nonglycated hemoglobin (HbAo), showing that the impedance response remained unchanged over the concentration range of 10 to 20 g dL(-1)HbAo. This demonstrated that the sensor system could be used to specifically distinguish HbAlc from HbAo. Moreover, the binding of HbAlc to the APBA-modified electrodes was reversible, providing a reusable sensing interface as well as showing a stable response after 4 weeks (96% of the initial response). When assaying normal (4.10%) and diabetic (8.36%) HbAlc levels (10 assays per day during a three-day period including a regeneration step after each assay), the overall assay reproducibility, expressed as relative standard error of the mean (n = 30), was 1.1%. The performance of the sensor system was also compared with a commercial method (n = IS) using patient-derived blood samples. A good agreement (Bland-Altman bias plot) and correlation (Passing-Bablok regression analysis) was demonstrated between the boronate-based affinity sensor and the standard method.