As of 2014, roughly 29 million Americans had been diagnosed with Type II diabetes. The condition affects approximately 1 out of every 10 individuals over the age of twenty. Frequent insulin testing, either at home or in a clinical setting, is an essential part of every treatment plan. Surface plasmon resonance (SPR) instruments have been used for over a decade to detect the presence of insulin and insulin analogs.

Since the late 1990s, SPR has been used in insulin-related studies. Early experiments involved the development of biosensor ligands for human insulin analogue (MI3) to better understand the effect of synthetic insulin in human insulin production. These ligands are aromatic molecules that were chemically coupled to the gold-coated SPR chip. The resulting sensor offered several useful utilities such as sterilization and a testing surface capable of being regenerated for 60 cycles over 6 months with 1100 ppm sensitivity; which was a competitive threshold when compared with commercially available methods at the time.

More recently, SPR applications for insulin detection have been more varied as both the instrumentation and the associated chemistry have become more sophisticated. A recent study involved the development of a method with polyethylene glycol-based (PEG-based) detection of insulin, which touted a fully-automatic and label-free detection of natural insulin in a wait-time less with less than 5 minutes. Similarly, advances have been made in polymer chemistry that have allowed for the development of dendrimers that have a similar capacity for measuring insulin. Such SPR sensors have application in measuring insulin levels in healthy and diabetic patients with accurate readings up to 0.5 picomolar concentrations, which compare favorably to other commercial methods.

The use of surface plasmon resonance has undergone a dramatic shift over the past decade. Earlier SPR studies using SPR detection often involved chemical labels and offered sensitivity only on the order of 1000 ppm. However, developments in technology have also brought developments in insulin-detecting biosensors, which are now able to detect insulin quickly, efficiently, and with unprecedented picomolar sensitivity.

http://www.healthline.com/health/type-2-diabetes/statistics

http://www.sciencedirect.com/science/article/pii/S0956566399000214