Exploring specific peptide displayed phage probe for ultrasensitive label-free electrochemical immunosensor for glycated hemoglobin (HbA1c)

Diabetes mellitus is a global non-communicable disease. Glycated hemoglobin (HbA1c) is the gold standard for assessing long-term blood sugar levels, which is consistent with the average blood sugar concentration and can reflect the patient’s blood sugar control for 2–3 months. The detection of HbA1c is essential for the diagnosis of diabetes and the risk assessment of complications. Traditional HbA1c detection methods have limitations such as significant performance differences, complex technology and high cost. Herein we screened HbA1c-specific peptide by 3 rounds of negative biopanning against hemoglobin and four rounds of conventional panning against HbA1c, by which a specific peptide probe W10 (amino acid sequence: DLRKAGKKRTTS) with high affinity for HbA1c was explored. Then we constructed a label-free electrochemical impedance spectroscopy immunosensor using the W10-displayed phage as biorecognition probe. Under the optimized conditions, the sensor had a linear range of 1–1000 pg/mL and a detection limit of 0.32 pg/mL HbA1c (S/N = 3). The as-proposed sensor demonstrated selectivity against Hb and other blood components and good long-term stability. Clinical validation with 20 human blood samples showed < 7.1 % deviation from HPLC results, enabling direct HbA1c quantification without enzymatic pretreatment. Thus this work establishes a novel, cost-effective platform for diabetes monitoring, which have potential applications in resource-limited settings. This study shows that sensors based on peptide-displaying phages are expected to have potential applications in bioassay for diagnosis and therapy.