Photoelectrochemical DNA Sensing Systems Based On Signal Amplification Strategies

With the rapid development of society,the development of sensors and detection models has aroused great enthusiasm.The general requirements for biosensors are high sensitivity,good selectivity,long-term stability and fast response.Photoelectrochemical(PEC)biosensing is a newly developed and promising technique in bioanalytical chemistry and photoelectrochemistry.PEC instrument is simple,inexpensive and easy to miniaturization and the total separation of excitation source(light)and detection signal(electricity)enables this method to have the advantages of low background signal and desirable sensitivity.These remarkable characteristics make photochemical sensors a promising candidate for rapid and accurate monitoring of various biomarkers.In this paper,based on the sensing strategy and novel photoelectric active materials,a photoelectric chemical sensor based on different signal amplification strategies is constructed to detect DNA.The research contents are as follows:(1)We report herein an ingenious and efficient cathodic photoelectrochemical(PEC)biosensing based on distance-triggered signaling on-off mechanism by plasmonic Au nanoparticles(AuNPs).In the proposal,type b3a2 of BCR/ABL fusion gene about chronic myelogenous leukemia(CML)was served as the model target DNA(tDNA).Specifically,three-dimensional(3D)NiO nanofilm was assembled with CdTe quantum dots(QDs)to prepare the CdTe/NiO photocathode.AuNPs as signaling labels were bound on the terminal of probe DNA(pDNA)to produce AuNPs-pDNA conjugates,which were immobilized on the CdTe/NiO photocathode for probing the tDNA.In the absence of tDNA,the pDNA was in the hairpin shape.In this case,the exciton-plasmon coupling between the CdTe QDs and the plasmonic AuNPs formed,resulting in an enhanced cathodic photocurrent(signal on).While in the existence of tDNA,the pDNA hybridized with the tDNA and open the pDNA hairpin structure,making that the AuNPs labels keep a certain distance with the CdTe/NiO photocathode.At this time,the exciton-plasmon coupling disappeared and meanwhile,the exciton energy transfer between the CdTe QDs and the plasmonic AuNPs happened,causing a significantly decreased cathodic photocurrent(signal off).By incorporating this superior signaling on-off mechanism into the cathodic PEC biosensing,ultrasensitive and specific detection of tDNA was realized.This work opens up a new horizon in the design of advanced cathodic PEC bioanalysis for various targets of interest.In the range of 1 fm-100 pM,the photocurrent signal decreases linearly with the increase of the logarithm of tDNA concentration,and the detection limit is 0.28 fM.(2)A nanochannels photochemical biosensor for amplification of silver-coated gold nanoparticles was designed.Fe:TiO2 nanosheets and ZnIn2S4 QDs were successively modified on the ITO electrode to prepare ZnIn2S4/Fe:TiO2/ITO electrode.The composite material greatly increased photoelectric conversion efficiency.cDNA,tDNA and AuNPs-pDNA was successively incubated in AAO nanopore template,and then Ag were grown in situ.Nanoparticles cause the AAO to be blocked.Due to the steric hindrance effect,the electron transfer is blocked and the photocurrent is reduced to detect tDNA sensitively.The linear range was 1fM～10 nM,with a detection limit of 0.28 fM.This work cleverly use AAO nanopore structures and nanoparticles to detect DNA.(3)CEA was detected by constructing an enhanced photochemical biosensor based on AgInS2 quantum dot sensitization.TiO2 nanoparticles and AuNPs were modified on ITO electrode to form AuNPs/TiO2 substrate electrode.Then the aptamer of CEA was incubated on the electrode,and the cDNA modified AgInS2 quantum dot was hybridized with the aptamer.Without CEA,after hybridization,the AgInS2 quantum dot is close to AuNPs/TiO2/ITO,which can produce sensitization effect,and the photocurrent is enhanced.In the presence of CEA,the adapter is specifically identified with CEA,and AgInS2 QD-cDNA is released from the electrode,and the sensitization effect of AuNPs/TiO2/ITO disappears,and the photocurrent decreases.The detection of CEA by the sensor in the concentration range of 1×10-12～1×10-8 g/mL showed a good linear range,and the detection limit was 0.34 pg/mL.