DNA Regulation Of Optical Properties Of Metal Nanomaterials And Analysis Of Disease-related Biological Enzymes

Currently,accurate diagnosis and treatment of disease have become an urgent problem to be solved.Since biological enzymes were the biomarkers of many serious diseases,it has been needed to develop more new and practical biosensors to detect biological enzymes.In recent years,optical biosensors have attracted widespread interest because of their rapidity,sensitivity,and simplification.Due to the dual characteristics of both nanostructure and metal properties,metal nanomaterials exhibit some unique optical properties,among which local surface plasmon resonance,surface-enhanced Raman scattering(SERS)and fluorescence emission are the most prominent phenomena,which have been widely paid attention to the optical biosensors.Therefore,metal nanomaterials have potential advantages in improving the analytical performance of optical biosensors for biological enzymes.Although DNA,peptides and proteins can combine with metal nanomaterials,considering the diversity of DNA in length,sequence,skeleton,structure and modified group,which provides a prerequisite for the identification of biological enzymes and the precise regulation of metal nanomaterials.Compared with peptides and proteins,the combination of DNA with metal nanomaterials becomes a better choice result from excellent biological sensing advantages.The combination modes of DNA with metal nanomaterials including the formation of DNA-guided the morphology evolution of metal nanomaterials,the spatial assembly of DNA and metal nanomaterials,and DNA-templated metal nanomaterials.In this paper,using biological enzymes as the targets,we designed three biosensors based on the different combination modes between DNA with metal nanomaterials to regulate the optical properties of metal nanomaterials.The specific contents are listed as follows:1.Quantitative morphological evolution is of great importance in nanochemistry.In this work,morphology of silver nanotriangles(Ag NTs)is quantitatively evolved under the guidance of DNA.First,intact Ag NTs are prepared relying on the protection of horseradish peroxidase.Then different regions of Ag NTs are sequentially etched by C-rich DNA,leading to DNA-guided postshaping of Ag NTs.In combination with atomically resolved images and theoretical simulation,a model is established to track the postshaping process.Since real-time morphological evolution of Ag NTs is determined with spectra,a series of Ag NTs with specific corners can be obtained by controlling incubation time.The DNA-guided postshaping is sequence and structure dual-dependent,and a mechanism is proposed based on metal-base interaction,surface energy of faces,and freedom of DNA structure.In addition,the postshaping is further used to design DNA-mediated biosensors.This study provides a precise and quantitative method of controlling morphology of anisotropic metallic nanomaterials.2.Fabrication of high-performance SERS biosensors relies on the coordination of SERS substrates and sensing strategies.Herein,a SERS active Au Cu alloy with a starfish-like structure is prepared using a surfactant-free method.By covering the anisotropic Au Cu alloy with graphene oxide(GO),enhanced SERS activity is obtained owing to graphene-enhanced Raman scattering and assembly of Raman reporters.Besides,stability of SERS is promoted based on the protection of GO to the Au Cu alloy.Meanwhile,it is found that SERS activity of Au Cu/GO can be regulated by DNA.The regulation is sequence and length dual-dependent,and short poly(thymine)(poly T)reveals the strongest ability of enhancing the SERS activity.Relying on this phenomenon,a SERS biosensor is designed to quantify apurinic/apyrimidinic endonuclease 1(APE1).Because of the APE1-induced cycling amplification,the biosensor is able to detect APE1 sensitively and selectively.In addition,APE1 in human serum is analyzed by the SERS biosensor and enzyme-linked immunosorbent assay(ELISA).The data from the SERS method are superior to that from ELISA,indicating great potential of this biosensor in clinical applications.3.In this work,a method for quantifying the activity of formamidopyrimidine DNA glucosylase(Fpg)was designed based on phosphate group(P)-modulated multi-enzyme catalysis and fluorescent copper nanoclusters(Cu NCs).By eliminating 8-oxoguanine from double-stranded DNA,Fpg generates a nick with P at both 3' and 5' termini.Subsequently,part of the DNA is digested by 5'P-activated lambda exonuclease(? Exo),and the generated 3'P disables exonuclease I(Exo I),resulting in the generation of single-stranded DNA containing poly T.Using poly T as templates,Cu NCs were prepared to emit intense fluorescence as the readout of this method.However,in the absence of Fpg,the originally modified 5'P triggers the digestion of ? Exo.In this case,fluorescence emission is not obtained because Cu NCs cannot be formed without DNA templates.Therefore,the catalysis of ? Exo and Exo I can be tuned by 5'P and 3'P,which can be further used to determine the activity of Fpg.The fluorescent Fpg biosensor works in a “signal-on”manner with the feature of “zero” background noise,and thus shows desirable analytical features and good performance.Besides,Fpg in serum samples and cell lysate could be accurately detected with the biosensor,indicating the great value of the proposed system in practical and clinical analysis.