The Research Of Aptasensor For Antibiotics Determination Based On Enzyme Signal Amplification

Antibiotics are mainly used to kill or inhibit microbes and bacteria to treat diseases caused by various bacteria.But the antibiotics can accumulate through the food chain in the human body,which may have a negative impact on human and animal health even at low concentration.In addition,their abuse causes humans to produce the super bacteria with tolerance to antibiotics,which will reduce the efficiency of disease treatment.Antibiotic-resistant bacteria may spread to other microbial populations that pose a potential threat to human and animal health.So,it is essential to control the intake of antibiotic.But the existing traditional way to detect the antibiotics is limited to a variety of external and internal conditions.For example,the reagents need to be pretreated,the professional operator trained and cumbersome testing procedures.Therefore,in this paper,by using aptamers and enzymes to design a series of biosensors for rapid,low-cost,high-sensitivity to detect antibiotics.The main contents of this work were shown in the following:1.The portable,efficient and accurate colorimetric biosensing was constructed and applied to detect of kanamycin highly sensitive based on split peroxidase DNAzyme coupled with dual nicking enzyme signal amplification?NESA?.In order to avoid produce the background signal by the self-assembly of G-quadruplex,two hairpin probes were specifically designed to enclose two G-rich fragments.When the target is present in the system,the cleavage reaction of the hairpin probe is initiated by the nicking enzyme,and two separated G-rich fragments are released.Under the action of the helper DNA and hemin,the peroxidase-mimicking DNAzyme,which can catalyze the oxidation of ABTS^2-mediated by H₂O₂ to generate the colored radical anion ABTS^·-,allowing to low cost and visual detection of antibiotic by the naked eye to achieve the optical absorption quantitative detection.Under optimized conditions,the results revealed the proposed biosensor exhibits excellent specificity and sensitivity toward kanamycin with a detection limit as low as 14.7 pM.2.The simple,rapid,and low-background colorimetric method for the detection of ampicillin based on target-recycle peroxidase DNAzyme with isothermal enzyme signal amplification.In order to improve the specificity of detected ampicillin,the hairpin was designed contains the ampicillin's aptamer.When the target is present in the system,the target binds to aptamer to initiate the chain-growth reaction of the polymerase.The dropped target can continue to react.At the same time,the trigger can release the G-rich probe,which blocked by the hairpin probe.In the action of hemin and nicking enzyme to produce G-quadruplex DNAzyme catalyze chromogenic substrates for naked eye observations.The results revealed the proposed biosensor exhibits excellent specificity and sensitivity toward ampicillin with a detection limit as low as 54.7 pM.3.The low-cost,simple chemiluminescent DNA sensor for sensitive and rapid detecting antibiotics was constructed Based on the Exo III-assisted signal amplification technique.In order to improve the sensitivity and accuracy of sensor,the hairpin probe contains target's aptamer.When the target is present in the system,the hairpin probe is destroyed to activate exonuclease III to hydrolyze DNA single-strands and the secondary target and the trigger chain are capable of cyclic reaction to produce a large number of G-rich sequences.In the presence of hemin,the formation of heme/G-quadruplex DNAzyme can catalyze hydrogen peroxide-luminol System to generate chemiluminescent signals.Under the optimal conditions of the experiment,we can know that the minimum detection limit of this work can reach 0.0005ng_?mL^-1.