**6.2 Glycated hemoglobin (HbA1c) biosensor**

In 1976, HbA1c was identified as a helpful tool for assessing diabetic patients' glycemic management. In the 1980s, the HbA1c test became widely used in clinical settings [23]. The system relies on electrochemistry, with glycated hemoglobin (HbA1c) indicating blood glucose levels during 2 to 3 months, similar to erythrocyte lifespans of 100–120 days [19]. Hemoglobin glycosylation involves a two-step, sequential, nonenzymatic process, creating reversible Schiff base intermediates when neutral amino groups from Hb N-terminal or Lys residues interact with sugar molecules' aldehyde or ketone groups [24]. Recognition elements in electrochemical

HbA1c biosensors include boronic acid derivatives, antibodies, and enzymes [25]. Clinicians may monitor a patient's long-term glucose management and determine a patient's prospective risk for developing diabetes issues using the HbA1c level in a method that is unaffected by changes in blood glucose levels [19].
