Insulin quantification towards early diagnosis of prediabetes/diabetes

Insulin is an essential and versatile hormone taking part in the control of blood glucose levels and protein anabolism. Abnormal levels of circulating insulin in the body can be problematic. Insulin resistance means the body fails to react with high or normal level insulin, causing our body to produce more insulin through feedback, and is the main cause of many chronic diseases such as type 2 diabetes and obesity. Pre-diabetes or obesity often occurs in people with high insulin resistance. Thus, quantification of insulin levels is essential for the early diagnosis and treatment of diabetes mellitus and obesity. Immunoassays and chromatography assays are currently reliable methods for insulin detection, although they are time-consuming, expensive, and require complex procedures, centralized instruments as well as trained personnel. Modern biosensing technologies have demonstrated success and huge potential for the quantification of insulin. This review provides a summary of the biological significance of insulin with a focus on the role of insulin resistance and its consequences in pre-diabetes/diabetes and obesity. The current practice for insulin detection followed by recent advances in developing biosensors for detection of insulin are reviewed, compared, and discussed from the aspects of detection principle, analytical performances, and challenges. Finally, future perspectives in the quantification of insulin in clinical settings are proposed.