| DNA is an important genetic material. It determines the heredity and variation of biology. Deleting, replacing or inserting bases in DNA sequence will lead to the gene mutation and illness. Therefore, the sensitive detection of genetic variations will generate a far-reaching significance in genetic screening, drug research, genetic disease diagnosis and treatment. Endocrine disruptors such as17β-estradiol or bisphenol A will enter the human body by atmosphere, food or water. They will cause the endocrine disorder of human body and trigger a variety of cancers. So the analysis of environmental hormones in food and daily necessities play an important role in human health and environmental protection. At present, the usual methods of the detection of DNA or environmental hormone included colorimetric, fluorescence, chemiluminescence, surface enhanced Raman scattering and electrochemical analysis methods etc. The electrochemical methods were more popular because they had the advantages of simplicity, low cost, good selectivity and high sensitivity etc. With the increasing requirement for DNA and environmental hormone detection, the electrochemical methods need to solve some targets, such as cutting down testing time, increasing the selectivity and sensitivity. In order to solve these problems, we synthesized several layered transition metal chalcogenides, which have large specific surface area. Besides, we used aptamer to build sensors for the detection of17β-estradiol, because aptamer has advantages of high specificity and affinity, non-toxic and good stability etc. In addition, we combined the technology of signal amplification such as enzyme catalysis signal amplification and the hybridization chain reaction signal amplification etc. The main works are listed as follows:(1) MoS2-MWCNTs composite was synthesized by hydrothermal method. This composite combined the large specific surface area of MoS2and the good electrical conductivity of MWCNTs. As the electrode substrate, it greatly improved the current response of the sensor. On the other hand, MoS2-MWCNTs can facilitate the direct electron transfer of GOD on the electrode. The multiple signal amplification strategy produced an ultrasensitive electrochemical detection of DNA down to0.8fM.(2)WS2-MWCNTs composite was synthesized by hydrothermal method, and used as the electrode substrate. Herein, we demonstrated an ultrasensitive detection platform for DNA by combining the nanocomposite and hybridization chain reaction amplification. The signal was amplified by Avidin-HRP on the long DNA polymeric chain. The proposed biosensor showed a very high sensitivity and good selectivity for the detection of target DNA.(3) VS2composite was synthesized by hydrothermal method, and its morphology was identified by scanning electron microscopy (SEM) and transmission electron microscopy (TEM). From the SEM and TEM, it was found the VS2composite had ordered nanosheets stacking flower-structure. The structure can offer a large number of binding sites for AuNPs, and greatly increase the modified quantities of aptamer. The aptamer sensor exhibited a high sensitivity and remarkable reproducible analytical performance.(4) CoS composite was synthesized by a simple hydrothermal method with L-cysteine as sulfur donor. A guanine-rich complementary DNA sequence (cDNA) was designed to hybrid with the17β-estradiol aptamer for signal amplification. cDNA may compete with17β-estradiol for the immobilized aptamer on the electrode surface. Methylene blue was chosen as a tracer because it could specific binding to guanine bases in DNA sequence. The method had demonstrated a detection limit of0.7pM. Besides, the fabricated aptasensor exhibited good selectivity toward17β-estradiol. |
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