MicroRNAs(miRNAs),as the small,non-coding,evolutionary conserved,and post-transcriptional gene regulators of the genome,have been highly associated with various diseases such as cancers,viral infections,and cardiovasc...MicroRNAs(miRNAs),as the small,non-coding,evolutionary conserved,and post-transcriptional gene regulators of the genome,have been highly associated with various diseases such as cancers,viral infections,and cardiovascular diseases.Several techniques have been established to detect miRNAs,including northern blotting,real-time polymerase chain reaction(RT-PCR),and fluorescent microarray platform.However,it remains a significant challenge to develop sensitive,accurate,rapid,and cost-effective methods to detect miRNAs due to their short size,high similarity,and low abundance.The electro-chemical biosensors exhibit tremendous potential in miRNA detection because they satisfy feature integration,portability,mass production,short response time,and minimal sample consumption.This article reviewed the working principles and signal amplification strategies of electrochemical DNA biosensors summarized the recent improvements.With the develop-ment of DNA nanotechnology,nanomaterials and biotechnology,electrochemical DNA biosensors of high sensitivity and specificity for microRNA detection will shortly be commercially accessible.展开更多
Objective: To establish a DNA detection platform based on a tapered optical fiber to detect Leptospira DNA by targeting the leptospiral secY gene.Methods: The biosensor works on the principle of light propagating in t...Objective: To establish a DNA detection platform based on a tapered optical fiber to detect Leptospira DNA by targeting the leptospiral secY gene.Methods: The biosensor works on the principle of light propagating in the special geometry of the optical fiber tapered from a waist diameter of 125 to 12 μm. The fiber surface was functionalized through a cascade of chemical treatments and the immobilization of a DNA capture probe targeting the secY gene. The presence of the target DNA was determined from the wavelength shift in the optical transmission spectrum.Results: The biosensor demonstrated good sensitivity, detecting Leptospira DNA at 0.001 ng/μL, and was selective for Leptospira DNA without cross-reactivity with non-leptospiral microorganisms. The biosensor specifically detected DNA that was specifically amplified through the loop-mediated isothermal amplification approach.Conclusions: These findings warrant the potential of this platform to be developed as a novel alternative approach to diagnose leptospirosis.展开更多
A DNA biosensor with [Ru(DA-bpy)3]Cl2(DA-bpy:4,4'-diamino-2,2'-bipyridine) (RuL) as the electrochemical probe was prepared on pyrolytic graphite electrode (PGE) through the supramolecular interaction betwee...A DNA biosensor with [Ru(DA-bpy)3]Cl2(DA-bpy:4,4'-diamino-2,2'-bipyridine) (RuL) as the electrochemical probe was prepared on pyrolytic graphite electrode (PGE) through the supramolecular interaction between RuL complex and DNA template. Cyclic voltammetry of RuL-DNA film showed a pair of stable and reversible peaks corresponding to the Ru(Ⅲ)/Ru(Ⅲ) redox potential of-0.165 V versus AglAgCl in pa 7.4 0.1 mol·L^-1Tris-HCl. The electron transfer was expected across the double-strand DNA by an "electron tunneling" mechanism. When the DNA biosensor was immerged in gold (Ⅲ) buffer solution, the current peak signal (I) of the RuL-DNA supramolecular depressed and △I was linear in the concentration range of Au ion from 1×10^-7 to 2×10^-5 mol·L^-1 with a regression coefficient of 0.9879. The detection limit was 5×10^-8 mol·L^-1. The developed procedures were applied to the analysis of synthetic samples of real materials with good sensitivity and selectivity.展开更多
Herein we report an electrochemical DNA biosensor for the rapid detection of sequence (5’ AAT GGA TTT ATC TGC TCT TCG 3’) specific for the breast cancer 1 (BRCA1) gene. The proposed electrochemical genosensor is bas...Herein we report an electrochemical DNA biosensor for the rapid detection of sequence (5’ AAT GGA TTT ATC TGC TCT TCG 3’) specific for the breast cancer 1 (BRCA1) gene. The proposed electrochemical genosensor is based on short oligonucleotide DNA probe immobilized onto zinc oxide nanowires (ZnONWs) chemically synthesized onto gold electrode via hydrothermal technique. The morphology studies of the ZnONWs, performed by field emission scanning electron microscopy (FESEM), showed that the ZnO nanowires are uniform, highly dense and oriented perpendicularly to the substrate. Recognition event between the DNA probe and the target was investigated by differential pulse voltammetry (DPV) in 0.1 M acetate buffer solution (ABS), pH 7.00;as a result of the hybridization, an oxidation signal was observed at +0.8 V. The influences of pH, target concentration, and non-complimentary DNA on biosensor performance were examined. The proposed DNA biosensor has the ability to detect the target sequence in the range of concentration between 10.0 and 100.0 μM with a detection limit of 3.32 μM. The experimental results demonstrated that the prepared ZnONWs/Au electrodes are suitable platform for the immobilization of DNA.展开更多
An effective procedure for constructing a DNA biosensor is developed based on covalent immobilization of NH2 labeled,single strand DNA(NH2-ssDNA) onto a self-assembled diazo-thiourea and gold nanoparticles modified ...An effective procedure for constructing a DNA biosensor is developed based on covalent immobilization of NH2 labeled,single strand DNA(NH2-ssDNA) onto a self-assembled diazo-thiourea and gold nanoparticles modified Au electrode(diazo-thiourea/GNM/Au).Gold nano-particles expand the electrode surface area and increase the amount of immobilized thiourea and single stranded DNA(ssDNA) onto the electrode surface.Diazo-thiourea film provides a surface with high conductibility for electron transfer and a bed for the covalent coupling of NH2-ssDNA onto the electrode surface.The immobilization and hybridization of the probe DNA on the modified electrode is studied by differential pulse voltammetry(DPV) using methylene blue(MB) as a well-known electrochemical hybridization indicator.The linear range for the determination of complementary target ssDNA is from 9.5(±0.1) × 10^-13 mol/L to1.2(±0.2) x 10^-9 mol/L with a detection limit of 1.2(±0.1) 〉 10^-13 mol/L.展开更多
The core-shell structured Au@Bi2S3 nanorods have been prepared through direct in-situ growth of Bi2S3 at the surface of pre-synthesized gold nanorods.The product was characterized by X-ray diffraction,transmission ele...The core-shell structured Au@Bi2S3 nanorods have been prepared through direct in-situ growth of Bi2S3 at the surface of pre-synthesized gold nanorods.The product was characterized by X-ray diffraction,transmission electron microscopy and energy-dispersive X-ray spectroscopy.Then the obtained Au@Bi2S3 nanorods were coated onto glassy carbon electrode to act as a scaffold for fabrication of electrochemical DNA biosensor on the basis of the coordination of-NH2 modified on 5’-end of probe DNA and Au@Bi2S3.Electrochemical characterization assays demonstrate that the Au@Bi2S3 nanorods behave as an excellent electronic transport channel to promote the electron transfer kinetics and increase the effective surface area by their nanosize effect.The hybridization experiments reveal that the Au@Bi2S3 matrix-based DNA biosensor is capable of recognizing complementary DNA over a wide concentration ranging from 10 fmol/L to 1 nmol/L.The limit of detection was estimated to be 2 fmol/L(S/N=3).The biosensor also presents remarkable selectivity to distinguish fully complementa ry sequences from basemismatched and non-complementary ones,showing great promising in practical application.展开更多
In the present study, a disposable electrochemical DNA nano-biosensor is proposed for the rapid detection of genotoxic compounds and bio-analysis of water pollution. The DNA nano-biosensor is prepared by immobilizing ...In the present study, a disposable electrochemical DNA nano-biosensor is proposed for the rapid detection of genotoxic compounds and bio-analysis of water pollution. The DNA nano-biosensor is prepared by immobilizing DNA on Au nanoparticles and a self-assembled monolayer of cysteamine modified Au electrode. The assembly processes of cysteamine, Au nanoparticles and DNA were characterized by cyclic voltammetry (CV). The Au nanoparticles enhanced DNA immobilization resulting in an increased guanine signal. The interaction of the analyte with the immobilized DNA was measured through the variation of the electrochemical signal of guanine by square wave voltammetry (SWV). The biosensor was able to detect the known genotoxic compounds: 2-anthramine, acridine orange and 2- naphthylamine with detection limits of 2, 3 and 50 nmol/L, respectively. The biosensor was also used to test actual water samples to evaluate the contamination level. Additionally, the comparison of results from the classical genotoxiciw bioassay has confirmed the applicability of the method for real samoles.展开更多
The ultrafast monitoring of deoxyribonucleic acid(DNA)dynamic structural changes is an emerging and rapidly growing research topic in biotechnology.The existing optical spectroscopy used to identify different dynamica...The ultrafast monitoring of deoxyribonucleic acid(DNA)dynamic structural changes is an emerging and rapidly growing research topic in biotechnology.The existing optical spectroscopy used to identify different dynamical DNA structures lacks quick response while requiring large consumption of samples and bulky instrumental facilities.It is highly demanded to develop an ultrafast technique that monitors DNA structural changes with the external stimulus or cancer-related disease scenarios.Here,we demonstrate a novel photonic integrated graphene-optofluidic device to monitor DNA structural changes with the ultrafast response time.Our approach is featured with an effective and straightforward design of decoding the electronic structure change of graphene induced by its interactions with DNAs in different conformations using ultrafast nanosecond pulse laser and achieving refractive index sensitivity of~3×10^(−5) RIU.This innovative technique for the first time allows us to perform ultrafast monitoring of the conformational changes of special DNA molecules structures,including G-quadruplex formation by K+ions and i-motif formation by the low pH stimulus.The graphene-optofluidic device as presented here provides a new class of label-free,ultrafast,ultrasensitive,compact,and cost-effective optical biosensors for medical and healthcare applications.展开更多
An E. coli SOS-EGFP biosensor which expresses enhanced green fluorescent protein as a reporter protein under the control of recA gene promoter in SOS response was constructed for detection of DNA damage and evaluation...An E. coli SOS-EGFP biosensor which expresses enhanced green fluorescent protein as a reporter protein under the control of recA gene promoter in SOS response was constructed for detection of DNA damage and evaluation of DNA damaging chemicals. The chemicals that may cause substantial DNA damage will trigger SOS response in the constructed bacterial biosensor, and then the reporter egfp gene under the control of recA promoter is stimulated to express as a fluorescent protein, allowing fast and sensitive fluorescence detection. Interestingly, this biosensor can be simultaneously applied for evaluation of genotoxicity and cytotoxicity. The SOS-EGFP bacterial biosensor provides a sensitive, specific and simple method for detecting known and potential DNA damaging chemicals.展开更多
A new method of preparing fiber-optic DNA biosensor and its arrayfor the simultaneous detection of multiple genes is described. The optical fibers were first treated with poly-l-lysine, and then were made into fiber-o...A new method of preparing fiber-optic DNA biosensor and its arrayfor the simultaneous detection of multiple genes is described. The optical fibers were first treated with poly-l-lysine, and then were made into fiber-optic DNA biosensors by adsorbing and immobilizing the oligonucleotide probe on its end. By assembling the fiber-optic DNA biosensors in a bundle in which each fiber carried a different DNA probe, the fiber-optic DNA biosensor array was well prepared. Hybridization of fluorescent- labeled cDNA of p53 gene, N-ras gene and Rb1 gene to the DNA array was monitored by CCD camera. A good result was achieved.展开更多
Due to the fact that most microRNAs are small in size,low abundance in biological samples,homologous sequence among family members,and protein enzymes-based strategies display limited practical applications,therefore,...Due to the fact that most microRNAs are small in size,low abundance in biological samples,homologous sequence among family members,and protein enzymes-based strategies display limited practical applications,therefore,we reported a simple enzyme-free DNA sensor for microRNA detection utilizing a multiple signal amplification strategy.The sensing system termed as C-CHA-HCR includes six hairpin DNA reactants that are metastable on account of intramolecular hybridization.The DNA hairpin reactants are opened and hybridized with the corresponding complementary DNA strand in the presence of miR-21 via toehold-mediated CHA,HCR reaction,and circulation between CHA and HCR,resulting in a hugely amplifying signal output.Without introducing external protein enzymes,this sensing system showed highly sensitive and selective on the detection of miR-21.A linear response range of miR-21 from 25 pmol/L to 1 nmol/L with a limit of detection(LOD)of 1.8 pmol/L was obtained.This promising biosensor was successfully applied to the detection of microRNA in human serum samples with acceptable recovery rates,suggesting the potential applications in disease diagnosis,treatment,and prognosis.展开更多
基金We gratefully thank the financial support from Shanghai Municipal Science and Technology Project(18430760500 and 2017SHZDZX01)Shanghai Municipal Education Commission Project(ZXWF082101)+1 种基金Shanghai Jiao Tong University Projects(YG2021ZD19,Agri-X20200101,SL2020MS026,19X190020154,ZH2018ZDA01,YG2016QN24,YG2016MS60,2020 SJTU-HUJI,2019 SJTU-Usyd,SD0820016)Shanghai Municipal Health Commission Project(2019CXJQ03),Shanghai Clinical Medical Research Center Project(19MC1910800).
文摘MicroRNAs(miRNAs),as the small,non-coding,evolutionary conserved,and post-transcriptional gene regulators of the genome,have been highly associated with various diseases such as cancers,viral infections,and cardiovascular diseases.Several techniques have been established to detect miRNAs,including northern blotting,real-time polymerase chain reaction(RT-PCR),and fluorescent microarray platform.However,it remains a significant challenge to develop sensitive,accurate,rapid,and cost-effective methods to detect miRNAs due to their short size,high similarity,and low abundance.The electro-chemical biosensors exhibit tremendous potential in miRNA detection because they satisfy feature integration,portability,mass production,short response time,and minimal sample consumption.This article reviewed the working principles and signal amplification strategies of electrochemical DNA biosensors summarized the recent improvements.With the develop-ment of DNA nanotechnology,nanomaterials and biotechnology,electrochemical DNA biosensors of high sensitivity and specificity for microRNA detection will shortly be commercially accessible.
基金funded by Universiti Putra Malaysia through the Geran Inisiatif Putra Siswazah (GP-IPS/2019/9678200)。
文摘Objective: To establish a DNA detection platform based on a tapered optical fiber to detect Leptospira DNA by targeting the leptospiral secY gene.Methods: The biosensor works on the principle of light propagating in the special geometry of the optical fiber tapered from a waist diameter of 125 to 12 μm. The fiber surface was functionalized through a cascade of chemical treatments and the immobilization of a DNA capture probe targeting the secY gene. The presence of the target DNA was determined from the wavelength shift in the optical transmission spectrum.Results: The biosensor demonstrated good sensitivity, detecting Leptospira DNA at 0.001 ng/μL, and was selective for Leptospira DNA without cross-reactivity with non-leptospiral microorganisms. The biosensor specifically detected DNA that was specifically amplified through the loop-mediated isothermal amplification approach.Conclusions: These findings warrant the potential of this platform to be developed as a novel alternative approach to diagnose leptospirosis.
基金This study is financially supported by the National Natural Science Foundation of China (No. 60508012)the Natural Sci-ence Foundation of Zhejiang Province (No. Y106725)+1 种基金the Natural Science Foundation of Ningbo (No. 2006A610048)the Scientific and Technological Project Funding of Zhejiang Province (No. 2006C31040).
文摘A DNA biosensor with [Ru(DA-bpy)3]Cl2(DA-bpy:4,4'-diamino-2,2'-bipyridine) (RuL) as the electrochemical probe was prepared on pyrolytic graphite electrode (PGE) through the supramolecular interaction between RuL complex and DNA template. Cyclic voltammetry of RuL-DNA film showed a pair of stable and reversible peaks corresponding to the Ru(Ⅲ)/Ru(Ⅲ) redox potential of-0.165 V versus AglAgCl in pa 7.4 0.1 mol·L^-1Tris-HCl. The electron transfer was expected across the double-strand DNA by an "electron tunneling" mechanism. When the DNA biosensor was immerged in gold (Ⅲ) buffer solution, the current peak signal (I) of the RuL-DNA supramolecular depressed and △I was linear in the concentration range of Au ion from 1×10^-7 to 2×10^-5 mol·L^-1 with a regression coefficient of 0.9879. The detection limit was 5×10^-8 mol·L^-1. The developed procedures were applied to the analysis of synthetic samples of real materials with good sensitivity and selectivity.
基金the Ministry of Higher Education Malaysia for the ERGS grant(600/RMI/st/ERGS/5/3/fst12/2011)Universiti Teknologi MARA for financial support via postgraduate teaching assistant scheme(UPTA)to Nur Azimah Mansor for conducting this research.
文摘Herein we report an electrochemical DNA biosensor for the rapid detection of sequence (5’ AAT GGA TTT ATC TGC TCT TCG 3’) specific for the breast cancer 1 (BRCA1) gene. The proposed electrochemical genosensor is based on short oligonucleotide DNA probe immobilized onto zinc oxide nanowires (ZnONWs) chemically synthesized onto gold electrode via hydrothermal technique. The morphology studies of the ZnONWs, performed by field emission scanning electron microscopy (FESEM), showed that the ZnO nanowires are uniform, highly dense and oriented perpendicularly to the substrate. Recognition event between the DNA probe and the target was investigated by differential pulse voltammetry (DPV) in 0.1 M acetate buffer solution (ABS), pH 7.00;as a result of the hybridization, an oxidation signal was observed at +0.8 V. The influences of pH, target concentration, and non-complimentary DNA on biosensor performance were examined. The proposed DNA biosensor has the ability to detect the target sequence in the range of concentration between 10.0 and 100.0 μM with a detection limit of 3.32 μM. The experimental results demonstrated that the prepared ZnONWs/Au electrodes are suitable platform for the immobilization of DNA.
文摘An effective procedure for constructing a DNA biosensor is developed based on covalent immobilization of NH2 labeled,single strand DNA(NH2-ssDNA) onto a self-assembled diazo-thiourea and gold nanoparticles modified Au electrode(diazo-thiourea/GNM/Au).Gold nano-particles expand the electrode surface area and increase the amount of immobilized thiourea and single stranded DNA(ssDNA) onto the electrode surface.Diazo-thiourea film provides a surface with high conductibility for electron transfer and a bed for the covalent coupling of NH2-ssDNA onto the electrode surface.The immobilization and hybridization of the probe DNA on the modified electrode is studied by differential pulse voltammetry(DPV) using methylene blue(MB) as a well-known electrochemical hybridization indicator.The linear range for the determination of complementary target ssDNA is from 9.5(±0.1) × 10^-13 mol/L to1.2(±0.2) x 10^-9 mol/L with a detection limit of 1.2(±0.1) 〉 10^-13 mol/L.
基金supported by the National Natural Science Foundation of China (Nos.21802064,21275127)Natural Science Foundation of Fujian Province,China (Nos.2018J01435,2017J01419)Foundation of Key Laboratory of Sensor Analysis of Tumor Marker,Ministry of Education,Qingdao University of Science and Technology
文摘The core-shell structured Au@Bi2S3 nanorods have been prepared through direct in-situ growth of Bi2S3 at the surface of pre-synthesized gold nanorods.The product was characterized by X-ray diffraction,transmission electron microscopy and energy-dispersive X-ray spectroscopy.Then the obtained Au@Bi2S3 nanorods were coated onto glassy carbon electrode to act as a scaffold for fabrication of electrochemical DNA biosensor on the basis of the coordination of-NH2 modified on 5’-end of probe DNA and Au@Bi2S3.Electrochemical characterization assays demonstrate that the Au@Bi2S3 nanorods behave as an excellent electronic transport channel to promote the electron transfer kinetics and increase the effective surface area by their nanosize effect.The hybridization experiments reveal that the Au@Bi2S3 matrix-based DNA biosensor is capable of recognizing complementary DNA over a wide concentration ranging from 10 fmol/L to 1 nmol/L.The limit of detection was estimated to be 2 fmol/L(S/N=3).The biosensor also presents remarkable selectivity to distinguish fully complementa ry sequences from basemismatched and non-complementary ones,showing great promising in practical application.
基金funded by the National Natural Science Foundation of China(Nos.21103059,51136002 and 51076079)the China Key Technologies R&D Program(No.2012BAJ02B03)
文摘In the present study, a disposable electrochemical DNA nano-biosensor is proposed for the rapid detection of genotoxic compounds and bio-analysis of water pollution. The DNA nano-biosensor is prepared by immobilizing DNA on Au nanoparticles and a self-assembled monolayer of cysteamine modified Au electrode. The assembly processes of cysteamine, Au nanoparticles and DNA were characterized by cyclic voltammetry (CV). The Au nanoparticles enhanced DNA immobilization resulting in an increased guanine signal. The interaction of the analyte with the immobilized DNA was measured through the variation of the electrochemical signal of guanine by square wave voltammetry (SWV). The biosensor was able to detect the known genotoxic compounds: 2-anthramine, acridine orange and 2- naphthylamine with detection limits of 2, 3 and 50 nmol/L, respectively. The biosensor was also used to test actual water samples to evaluate the contamination level. Additionally, the comparison of results from the classical genotoxiciw bioassay has confirmed the applicability of the method for real samoles.
基金from the National Natural Science Foundation of China(21874096,21575095,51602305,61604102 and 61875139)the 111 Project,and the Priority Academic Program Development of Jiangsu Higher Education Institutions(PAPD)+2 种基金the China Postdoctoral Science Foundation(2018M633118)Shenzhen Nanshan District Pilotage Team Program(LHTD20170006)Australian Research Council(ARC,FT150100450,IH150100006 and CE170100039).Q.Bao acknowledges support from the Australian Research Council(ARC)Centre of Excellence in Future Low-Energy Electronics Technologies(FLEET).
文摘The ultrafast monitoring of deoxyribonucleic acid(DNA)dynamic structural changes is an emerging and rapidly growing research topic in biotechnology.The existing optical spectroscopy used to identify different dynamical DNA structures lacks quick response while requiring large consumption of samples and bulky instrumental facilities.It is highly demanded to develop an ultrafast technique that monitors DNA structural changes with the external stimulus or cancer-related disease scenarios.Here,we demonstrate a novel photonic integrated graphene-optofluidic device to monitor DNA structural changes with the ultrafast response time.Our approach is featured with an effective and straightforward design of decoding the electronic structure change of graphene induced by its interactions with DNAs in different conformations using ultrafast nanosecond pulse laser and achieving refractive index sensitivity of~3×10^(−5) RIU.This innovative technique for the first time allows us to perform ultrafast monitoring of the conformational changes of special DNA molecules structures,including G-quadruplex formation by K+ions and i-motif formation by the low pH stimulus.The graphene-optofluidic device as presented here provides a new class of label-free,ultrafast,ultrasensitive,compact,and cost-effective optical biosensors for medical and healthcare applications.
基金supported by the National Natural Science Foundation of China (No. 20707034, 20877091,20890112, 20921063)the National Basic Research Program (973) of China (No. 09CB421605,2010CB933500, 2011CB936001)
文摘An E. coli SOS-EGFP biosensor which expresses enhanced green fluorescent protein as a reporter protein under the control of recA gene promoter in SOS response was constructed for detection of DNA damage and evaluation of DNA damaging chemicals. The chemicals that may cause substantial DNA damage will trigger SOS response in the constructed bacterial biosensor, and then the reporter egfp gene under the control of recA promoter is stimulated to express as a fluorescent protein, allowing fast and sensitive fluorescence detection. Interestingly, this biosensor can be simultaneously applied for evaluation of genotoxicity and cytotoxicity. The SOS-EGFP bacterial biosensor provides a sensitive, specific and simple method for detecting known and potential DNA damaging chemicals.
文摘A new method of preparing fiber-optic DNA biosensor and its arrayfor the simultaneous detection of multiple genes is described. The optical fibers were first treated with poly-l-lysine, and then were made into fiber-optic DNA biosensors by adsorbing and immobilizing the oligonucleotide probe on its end. By assembling the fiber-optic DNA biosensors in a bundle in which each fiber carried a different DNA probe, the fiber-optic DNA biosensor array was well prepared. Hybridization of fluorescent- labeled cDNA of p53 gene, N-ras gene and Rb1 gene to the DNA array was monitored by CCD camera. A good result was achieved.
基金supported by the National Natural Science Foundation of China(21874042,21974042).
文摘Due to the fact that most microRNAs are small in size,low abundance in biological samples,homologous sequence among family members,and protein enzymes-based strategies display limited practical applications,therefore,we reported a simple enzyme-free DNA sensor for microRNA detection utilizing a multiple signal amplification strategy.The sensing system termed as C-CHA-HCR includes six hairpin DNA reactants that are metastable on account of intramolecular hybridization.The DNA hairpin reactants are opened and hybridized with the corresponding complementary DNA strand in the presence of miR-21 via toehold-mediated CHA,HCR reaction,and circulation between CHA and HCR,resulting in a hugely amplifying signal output.Without introducing external protein enzymes,this sensing system showed highly sensitive and selective on the detection of miR-21.A linear response range of miR-21 from 25 pmol/L to 1 nmol/L with a limit of detection(LOD)of 1.8 pmol/L was obtained.This promising biosensor was successfully applied to the detection of microRNA in human serum samples with acceptable recovery rates,suggesting the potential applications in disease diagnosis,treatment,and prognosis.