Electrochemical Aptamer-Based Sensor for Real-Time Monitoring of Insulin

In this paper, we developed an electrochemical, aptamer-based (E-AB) for the real-time monitoring of insulin. The sensor utilizes a redox label-modified guanine-rich aptamer which folds into a G-quadruplex for specific recognition of insulin. To develop a reproducible E-AB sensor employing insulin aptamer probes for the detection of insulin, 10% sodium dodecyl sulfate (SDS) pretreatment is crucial as it disrupts interstrand G-quartets. After sensor pretreatment with 10% SDS, a more uniform sensor response is obtained. Upon introduction of the insulin target, binding-induced steric hindrance quantitatively reduces the efficiency of electron transfer of a distal-end redox label leading to the rapid signal change within ∼60 s. Testing demonstrates that the E-AB insulin exhibits a limit of detection of 20 nM and can be used to discriminate against both glucagon and somatostatin in Krebs–Ringer bicarbonate buffer, typically used in perfusion experiments. These results demonstrate that this assay has potential for rapid, specific, and quantitative analysis of insulin.