Construction Of Electricity-fluorescence Dual-channel Graphene FET Biosensor System And Detection For DNA Molecules

The dynamic detection of DNA hybridization plays an increasingly important role in the diagnosis of diseases,the treatment of pathogenic infectious diseases,and the forensic identification.In this paper,we have constructed an electricity-fluorescence dual-channel biosensor and detection system based on Chemical Vapor Deposition(CVD)graphene which realizes the dynamic detection of DNA hybridization.CVD grown graphene films were transferred onto glass substrates to construct graphene field effect tubes(GFETs)as electrical detection channel.The FAM modified Aptamer was immobilized onto the GFETs via 1-Pyrenebutanoic acid succinimidyl ester(PBASE)as a probe chain.GO was used to combine with probe Aptamer and quenched the FAM to form the fluorescence channel.With existence of t DNA,the GO was separated from the probe Aptamer and the fluorescence of the probe was restored.Meanwhile,the tDNA replaced the GO and hybrided with probe chains to construct a new double conductive layer causing conductivity changes of graphene.The construction of the electricity-fluorescence dual-channel detection system mainly includes the optical path and the circuit.Among them,the composition of the light path portion mainly includes an LED lamp,a light collimator,convex lenses,a dichroic mirror,and a photomultiplier tube.the excitation light was emitted from a LED and converged by a collimator lens into a parallel beam.The parallel beam was then reflected by a dichroic mirror and focused by the converging lens to the reaction cell of GFETs.The emitted fluorescence in the reaction cell passed through a dichroic mirror and was focused by converging lens to the effective area of the PMT.The output of the PMT was recorded to reflect the fluorescence intensity in the reaction cell.The composition of the circuit part mainly includes power supply module,AD signal acquisition module,PMT gain control module,signal conditioning module,gate output module,and bridge circuit module.The system's power supply module performs voltage transformation on the power supply to provide a reliable and stable voltage for the entiresystem.When the biosensor detects the target molecule,the gate voltage outputted by the gate voltage output module is fixed,and the bridge circuit module is used to measure the voltage between the source and the drain of the field effect tube to reflect the change of the graphene conductivity.At the same time,the PMT gain control module is used to adjust the appropriate PMT amplification to perform data acquisition on the optical signals of the system.The AD signal acquisition module inputs the collected information of light path and circuit into the host computer for information processing.A home-made double channel data acquisition system was constructed to record the fluorescence intensity and conductivity of GFETs simultaneously.The hybridization kinetics between t DNA and probe Aptamer has been obtained in real-time by the double-checking biosensor with high reliability.In addition,this electricity-fluorescence double-checking biosensor has shown high sensitivity to DNA at a concentration as low as 50 nM which has increased by 2 orders of magnitude compared with the conventional method for real-time detection of DNA strand hybridization.This work also provide a new biosensor design method integrated multi-sensing technology.