The Research Of DNA Sensor Multiplied And Modified Surface With Gold Nanoparticles

With the reveal of human genetic code by human genome scheme and the illumination about complex gene mechanism of tumour by molecule epidemiology, the research of DNA will play a important role in disease defend, early diagnosis, and therapy. Investigation indicates that the appearance of the malignant tumor is highly correlative with the DNA mutation. It has become an important topic of the cancer study to detect the gene mutation and look for the relation between mutation and pathological change at the molecular level. Rapid detection for trace gene mutation can provide basic data for diagnose disease. Therefore, looking for a rapid and simple method used for detecting trace mutation is very important and pressing.QCM is a simple, rapid and real-time measurement of DNA binding and hybridization at the sub-nanogram level, so it is applied widely in gene diagnostic, becoming the best of all effective means at molecule biology and microchemistry. The gold nanoparticle has become a research emphasis since it has revealed simple operation, size-controlled, prominent size quantum effect, and good properties of biologic consistent, so it has special multiplied effect in biosensors. So some scientists combined gold nanoparticle with the quartz crystal microbalance technique in order to design a DNA biosensor named sandwich-type ternary that constructed with an oligodeoxynucleotide immobilized on a QCM electrode, a target DNA, and a gold nanoparticle modified by an oligonucleotide, therefore it resolved the problem of low detection sensitivity when used the QCM technology. The prophase researches of laboratory have show that multiplied effect with DNA detection enhanced with the size increase of gold nanoparticle about the sandwich-type ternary DNA biosensor, however multiplied effect began to decrease when the size of gold nanoparticle has more than fifty nanometer. Combining the technology of nanoparticle modification on QCM surface with the application of gold narnoparticle amplifier can improve the detection limit of DNA. And this method can enhance the amplification effect even if the amplifier size is more than fifty nanometers.These methods are far from practice application because the high sensitivity is received when the chain length of target DNA is shorter. Hybridization hasthree steps at remaining the special property of nucleic acid hybridization.Increased the chain length of probe DNA and target DNA, at the same time, weuse a cantilever that is composed of mismatching base with target DNA to connectgold nanopartical as amplifier. Gold nanopartical can away from the double chainof hybridization, so it can avoid the spatial hindrance owing to gold nanopartical svolume for the form of double chain, and the increased length of target DNAcould remain the former sensitivity. Accordingly, the celerity, high sensitivity, nearpractice application detection method of DNA mutation is afforded.1. We used two same bases and five same bases as a cantilever, gold nanoparticalwith fifty nanometers as a amplifier, detection limit is improved from10-14mol L-1 to 10-15 mol L-1successfully, and the chain length of target DNA isincreased from 17mer to 33mer.2.When used gold nanopartical of fifty nanometers as signal amplifier to detect target DNA, detection effect of the cantilever with five bases is better than the cantilever with two bases. Multiplied quality when use the longer cantilever is higher than the latter about lOng. So the longer cantilever has active effect to amend the spatial hindrance of gold nanoparticals in hybridization. 3.We used the gold nanopartical-DNA bond composed of fifty nanometers and thirty nanometers respectively to multiply quality when used the longer cantilever. The gold nanopartical with the diameters of fifty nanometers have a better effect. Gold nanopartical-DNA bond can away from the double hybridization chain for the cantilever, so it can avoid the spatial hindrance. Gold nanoparticals of large size have better multiple effects than the smaller.4. Gold nanoparticals modified QCM can enlight...