| Tumor markers are kinds of substance that indicate the existence of tumours.With the development of medicine,different tumour markers have been discovered gradually.Among these substance,telomerase and 8-hydroxy-2?-deoxyguanosine?8-OHdG?were deeply investigated.The establishment of low cost,highly sensitive,specific,simple and fast determination methods is important content of clinical examination and study of diagnostic discipline.The vital importance of qualitative and quantitative analysis of these markers in disease early diagnoses,treatment,and prognosis estimation will facilitate the development of construction of these methods.Fluorescence biosensors play an important role by converting intermolecular forces into fluorescent signals in bioanalysis.The results of the interactions caused by these molecules are usually manifest as fluorescence enhancement,fluorescence quenching or emission wavelengths.The simple,fast and sensitive detection of target material can be achieved through the fluorescence spectroscopy.Due to the specific optical properties,new fluorescent sensing materials and nano-materials have become a hot research area in recent years.The applications of these materials become more and more extensive and in-depth in fluorescence biosensors.The combinations of these materials and fluorescence biosensors contain the knowledge in biotechnology,nanoscience and other disciplines.Consequently,the researchs of these new materials in biosensors will provide lots of innovative research ideas for the detection of tumor markers.In this paper,nucleic acid fluorescent biosensors were constructed by using nucleic acids and novel fluorescence sensing materials and gold nanoparticles.These biosensors can achieve the sensitive detection of tumor markers such as telomerase and 8-hydroxy-2?-deoxyguanosine and provide the new methods for the detections of tumor markers.The main contents of this paper are as follows:?1?Visual and fluorometric determination of telomerase activity by using a cationic conjugated polymer?CCP?and fluorescence resonance energy transfer?FRET?.Herein,we proposed a sensitive and visual fluorescence method for telomerase activity detection by using CCP-based FRET strategy.Telomerase substrate primers were labelled with carboxyfluorescein?FAM-TS?,which had weak electrostatic interactions with CCP and prevented the FRET from CCP to FAM.In the presence of telomerase,telomeric repeats?TTAGGG?x were elongated to the 3'end of FAM-TS,which formed multiple G-quadruplexes in the presence of potassium ion?K+?.These G-quadruplexes led to strong electric interaction between more condensed G-quadruplex and CCP,which made them close together and efficient FRET process occurred.As a result,strong fluorescence of FAM at 527nm emitted in the presence of telomerase.Under an UV lamp,the solutions showed obviously different colors in the presence of different concentrations of telomerase,which could be used to detect the activity of telomerase.Telomerase activity also could be quantitatively detected in the range of 30-1 000 HeLa cells,with the detection limit as low as 5 cellsˇmL-1?S/N=3?by using fluorescence spectrometer.The proposed noninvasive method was used for detection of various cancer cell lines and had been applied in various human urine samples.The results were in good agreement with the clinical diagnosis,which confirmed the feasibility,accuracy,and practicality of the method.?2?Skilfully engineering of an enzyme-powered three-dimensional DNA nanomachine and its application in detection of 8-OHdG.Nicking endonuclease?NEase?-powered three-dimensional?3-D?DNA nanomachine was constructed as the novel biosensor for the detection of 8-OHdG.This nanomachine was assembled by modifying hundreds of carboxyl fluorescein?FAM?labeled single-strand oligonucleotides?signal reporter,SR?and tens of swing arms?single-foot DNA walkers,DW?on one gold nanoparticle?AuNP?.The activity of this DNA nanomachine was controlled by introducing the protecting oligonucleotides.Protecting DNA can hybridize to or dehybridize from the DNA walker,which was strongly dependent on the present of 8-OHdG aptamer or not.In the presence of aptamer,the toehold-mediated strand displacement removed the protecting DNA from the swing arms.Then,detached DNA walker hybridized to FAM-labelled DNA,which was recognized and cleaved by NEase.The DNA walker autonomously and progressively moved along the surface of AuNP,releasing hundreds of signal reporters and resulting in a rapid fluorescence increase.Upon addition of 8-OHdG,its aptamer formed G-quadruplexes,deactivating the DNA nanomachine because the free protecting DNA prevented the hybridization of swing arms and the FAM-labelled DNA.As a result,signal reporters cannot be cleaved and released.So,8-OHdG can be sensitively detected by comparing the fluorescences of the engineered3-D DNA nanomachine.This 3-D DNA nanomachine is highly efficient due to the high local concentrations of the DNA and the autonomous and progressive movements of the swing arm on the AuNP,which released hundreds of signal reporters when one aptamer was present.These unique properties allowed us to construct a DNA nanomachine-based biosensor to sensitively detect 8-OHdG as low as 4 pM,which was more sensitive than most previously reported methods. |
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