| There is a relatively and common malignant blood disease which has serious harm to human health in patients with acute myeloid leukemia (AML) - acute promyelocytic leukemia (acute promyelocytic leukemia, APL). Patients with APL have distinctive t (15; 17) chromosome translocation caused formation of the PML/RARαfusion gene.In the recent years, the electrochemical DNA biosensors have been rapidly developed to be a firenew biological sensor. The electrochemical DNA biosensors have received much attention due to the high sensitivity, specific, rapid response, easy handling and low cost. Since many of the properties that biosensors are supposed to measure and formed on the molecular level. Because of their special structural feature and theirs unique electronic and mechanical properties, combine in a unique way to show high electrical conductivity, high chemical stability, extremely high mechanical strength and modulus, Nanoparticles have attracted increasing attention by scientists all over the world. It has high spicific surface and surface activity center, high catalytic efficiency, high adsorption capability, high surface activity. The electrochemical DNA biosensors constructed at the molecular scale would be extremely sensitive, selective, and responsive. Thus, the potential application value of nanoparticle on biosensors is very huge.To establish the enzyme biosensor having high sensitive, this paper used gold nanoparticles (AuNPs) which have excellent specific surface area and biological compatibility to link with immunosorbent analysis technology, because the AuNPs can combined firmly with oligonucleotide modified by thiol through Au-S bond , the sandwich-type electrochemical enzymes-based AuNPs-modified DNA biosensor was developed for detection of the target gene. In this study,we constructed respectively two different kinds of AuNPs-modified electrochemical sensor for PML/RARαfusion gene in APL, at the same time, investigated the performance such as specific properties and so on.In this article, nano-gold was synthesized and characterized by transmission electron microscope (TEM) and ultraviolet spectrophotometer(UV). Then a nano-gold modified sandwich-type DNA electrochemical biosensor was built successfully and other experimental condition was optimized. The biosensor was developed for detection of PML/RARαfusion gene in acute promyelocytic leukemia (APL) in this study.The results indicated that HRP, as the indicator, showed excellent specificity and can distinguish PML/RARαfusion gene with noncomplementary genes effectively. Under the optimal condition, the sensor was challenged with the target DNA of a series of concentration across the range of 100 fM to 1 nM, and in this range, there was a good linear relationship between the current signal and a non-linear logarithmic function related to complementary DNA concentration..The lower limit was 2.3×10-14 M.In addition, an electrochemical DNA biosensor based on hexaammineruthenium (III) chloride [Ru(NH3)6]3+) as a hybrid indicator was fabricated for detection of PML/RARαfusion gene in acute promyelocytic leukemia (APL) using chronocoulometry (CC). Owing to the different amount of [Ru(NH3)6]3+ caused by electrostatic combination with DNA sequences before and after hybridization,the different charge was formed. The increase of the different charge of [Ru(NH3)6]3+ was observed upon hybridization of the probe with target DNA. The different charge intensity of[Ru(NH3)6]3+ was increased with the increasing of target DNA sequence concentration.Under the optimal condition, experimental results indicated the biosensor showed a good specificity to distinguish the complementary sequence with different mismatch sequences and could detect PML/RARαfusion gene quantitatively. The relationship between the charges of [Ru(NH3)6]3+ and logarithmic of target sequence concentrations (lg C) was linear in the concentration range of 1×10-12 M - 1×10-8 M, and the detection limit had been estimated as 4×10-13 M. Thus the [Ru(NH3)6]3+, as a electrochemical DNA indicator, can indicate the complementary sequence of PML/ RARαfusion gene qualitatively and quantitatively.Finally, amount of single DNA were try to be assembled onto the nano-gold as signal probes. Then capture probes modified sulfhydryl were fixed to the gold electrode. After hybridization, the current signals were amplified by mass signal DNA probes. By this method, PML/RARαfusion gene was detected, and the current value shows the linear correlation with the concentration of the complementary DNA in the range from 1×10-9 to 1×10-14 M. At the same time,one mismatched base mutation and non- complementary can be distinguished.
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