A Label-free Genetic Biosensor For Diabetes Based On AuNPs Decorated ITO With Electrochemiluminescent Signaling

Diabetes,a common disease,is caused by a complex interplay between genetic and environmental factors.Studies have shown that the I27L gene variant was associated with increased risk of type 2 diabetes.Thus,the studies focusing on the DNA sensing for I27L are significant since the DNA identifying might aid the early prediction of disease to prevent the possible complications;and also helpful for understanding the disease pathogenesis or for evaluating the pharmacological efficiency of therapeutic drugs.Recently,there has been a great interest in developing various DNA biosensors to monitor the DNA hybridization,based on the signaling of radiochemical,enzymatic,fluorescent,optical or acoustic techniques etc.They have achieved high sensitivity and selectivity,but still face some imperfect issues as the requirement of tedious labels,costly polymerase,time consuming/complex operation,and expensive instrumentation.The electrochemiluminescence（ECL）,a promising approach with admirable versatility,high sensitivity,good controllability,simple operation and installation,has attracted considerable attention.Up to now,the ECL sensing has been attempted in DNA analysis owing to these merits.This paper reports a novel label-free electrochemiluminescent DNA（ECL-DNA）biosensor for simple,effective and convenient determination of I27L gene.In this work,with indium tin oxide（ITO）glass as the conductive substrate,the AuNPs have been assembled on its surface via the adhesion of hydrolyzed polymer of（3-aminopropyl）trimethoxysilane（APTMS）to prepare the Au plate electrode with nano-characteristic.The fabricated electrodes were characterized by scanning electron microscopy（SEM）,cyclic voltammetry（CV）,and electrochemical impedance spectroscopy（EIS）.Electrochemiluminescence（ECL）technique was employed to monitor the hybridization of DNA by measuring the changes of the intensity in the process of ECL.Here,ECL signals was quenched,which due to the electrostatic repulsion and space resistance between negatively charged DNA sensor surface and Lum^-probe,and blocking Lum^-access to the electrode surface.The quantification of target strand（TS）was directly accomplished by calibrating the quenched ECL signals.Under the optimal conditions,the decreased ECL intensity had a good linear relationship with the logarithm of the concentration of target DNA in the range of 1.0×10^-11–1.0×10^-7 M with a detection limit of 8.06×10^-12 M,In addition,the biosensor exhibited acceptable stability,excellent reproducibility and outstanding selectivity against one-base mismatched DNA.What’s more,the simple,low-cost,sensitive device could be easily miniaturized,which make it an attractive candidate for integration into portable platforms for Point-of-Care（POC）molecular diagnostics.