Ternary Nanocomposite Materials Are Used For Photoelectrochemical DNA Methylation Biosensing Analysis

DNA methylation,as one of the important markers of epigenetic modification,plays a vital role in the growth and development of mammals.Abnormal DNA methylation,especially happened in the promoter region of tumor suppressor genes,can hinder the binding of transcription factors and related proteins,thereby inhibiting gene expression and causing gene silencing,which could cause various cancers,such as leukemia,breast cancer,lung cancer,and liver cancer.Up to now,the process of DNA methylation has been confirmed to be catalyzed by DNA Methyltransferase?DNA MTase?.With the help of enzyme and s-adenosylmethionine?SAM?,a methyl group is added to the fifth carbon atom of cytosine to form a 5-methyl-cytosine?5-mC?.Besides,it has also been found that changes in DNA MTase activity usually occur before the changes of dysfunction of this gene and also much earlier than the clinical diagnosis of methylation-related diseases,which renders DNA MTase to be a potential biomarker for clinical diagnosis of DNA methylation disorders diseases.Therefore,the detection of DNA MTase activity is an ideal mean for early clinical diagnosis of the DNA methylation disorders diseases,which has been the frontier of cross-sectional research between experimental diagnostics and epigenetics.Photoelectrochemical?PEC?method is a new technology,which developed on the basis of traditional electrochemical methods and added a light source as a signal excitation source.It not only retains the inherent advantages of electrochemical methods,such as easy operation,fast signal response,and good stability,but also combines the advantages of optics,such as low background interference,high detection sensitivity.Based on the above advantages,photoelectrochemical?PEC?biosensor is a newly developed method and has attracted increasing attention.In fabricating PEC biosensor,the selection of photoactive material is the most vital consideration.It has been found that nanocomposites have expanding light-harvesting ability and effective electron transmission by mixing or doping two or more photoactive materials with different forbidden band widths,which could lead to an enhanced photocurrent.Therefore,in this article,different types of DNA MTase had been chosen,different ternary nanocomposites photoactive material had been synthesized and different PEC response strategies had been performed for the detection of DNA MTase activity.The research contents and results are as follows:1.Dual signal amplified strategy for M.SssI MTase activity assay based on RGO-CdS:Mn nanoparticles and a CdTe@DNA networkIn this study,a novel PEC biosensor was fabricated for M.SssI MTase activity assay using a dual-signal amplified system of RGO-CdS:Mn NPs and a CdTe@DNA network.Firstly,RGO-CdS:Mn nanoparticles were modified on a gold electrode as substrate materials.Due to the large surface area of reduced graphene oxide?RGO?,more CdS:Mn NPs can be loaded,which can generate a certain photocurrent response.Next,probe DNA S1 and BSA were sequentially captured by the modified electrode.Then target DNA S2 with a recognition sequence for DNA methylation was hybridized to form dsDNA.After a process of methylation and digestion,the methylated dsDNA could be reserved and further hybridized with the CdTe@DNA network,which resulted in a higher photocurrent.Therefore,with the assistance of signal amplification,the photocurrent response had a good linear relationship with the logarithm of the M.SssI MTase concentration,with a linear range from 0.01 U/mL to 80 U/mL and a detection limit of 0.0071 U/mL.This approach is capable of detecting M.Sss I MTase activity sensitively and could provide new ideas for clinical diagnosis of DNA methylation.2.Co-sensitization amplification strategy for Dam MTase activity assay based on g-C₃N₄-CdS:Mn NPs and SiO₂@CdTeIn this study,a new PEC biosensor was fabricated for Dam MTase activity assay using g-C₃N₄-CdS:Mn NPs and SiO₂@CdTe co-sensitization amplification strategy.Firstly,g-C₃N₄-CdS:Mn NPs were modified on the electrode to provide a strong substrate photoelectrochemical response due to its expanding light-harvesting ability and effective electron transmission.Then,probe DNA S1,MCH and probe DNA S2assembled on the electrode.In the present of Dam MTase and Dpn I,the releasede target DNA S3 could hybridize with probe DNA for further digestion process of EXO III.After that,SiO₂@CdTe-DNA hybridized on the electrode which could be coupled with g-C₃N₄-CdS:Mn NPs to achieve a co-sensitization effect and produce a stronger photoelectrochemical response.With the co-sensitization amplification strategy,this developed PEC biosensor could detect as low as 0.0068 U/mL of Dam MTase with a linear range from 0.01 U/m L to 120 U/m L,which had promising application in clinical diagnosis and risk assessment of cancers and other related diseases.