Label-free Aptamer Sensors For Antibiotics Detection In Wastewater Based On Different Signal Amplification Strategy

Bacterial infection used to be the leading cause of death in humans.Fortunately,the discovery of antibiotics that acts on bacteria makes people light up the hope of life and restore the faith of life,prompting antibiotics to become the most widely used,the fastest developing and the most varied drugs in the world at present.However,the abuse of antibiotics is alarming and leads to the existence of antibiotic residues in food and ecological environment,which is a great threat to not only the physical and mental health but also the living environment of human beings.Therefore,it is of great significance to establish a rapid and effective detection method for the preliminary rapid screening of antibiotic residues in complex environments.With the rapid development of scientific research,a variety of analytical instruments and new detection methods have emerged.Due to the advantages of fast response,low cost and high efficiency,fluorescent sensors stand out among these methods and have been widely developed and applied in the fields of food safety,environmental monitoring and clinical diagnosis.In order to further improve the detection performance of these sensors,this thesis constructed three simple,fast and low-cost novel fluorescent aptamer sensors for antibiotics based on different signal amplification technology such as nuclease,nanomaterials and hybrid chain reaction(HCR).The main contents of this paper are as follows:(1)A label-free fluorescent aptamer sensor for kanamycin detection based on exonuclease III-aided signal amplification.The exonuclease III can specifically hydrolyze ds DNA to oligonucleotides.Taking the advantage of exonuclease III and nucleic acid dye SYBR Gold(SG)as the indicator,we constructed a fluorescent aptamer sensor for detecting kanamycin with exonuclease III-aided target recycling.This method has a good ability to detect kanamycin not only in buffer solution but also in complex samples,and has a high specificity in the detection process.This strategy provides an accurate and reliable method for monitoring the pollution degree of kanamycin in the water environment.(2)Graphene oxide-regulated low-background aptasensor for the turn-on detection of tetracycline.Graphene oxide(GO)is a new type of carbon nanomaterials,which not only has excellent specific surface area and affinity but also can strongly adsorb singlestranded DNA through π-π stack interaction.In this study,an turn on aptamer sensor was constructed to detect tetracycline based on GO-regulated low background signals.In the presence of tetracycline,the single-stranded aptamer was divorced from graphene and enhance the fluorescence of nucleic acid dye SG.When the target was not present,the aptamers were adsorbed by graphene and could not enhance the fluorescence of the SG.This “turn on” strategy showed a higher(4 orders of magnitude)detection limit than that in “turn off” mode.In addition,the sensor has good stability and repeatability,and can be successfully detected in actual samples such as milk and wastewater,indicating the practicability and applicability of this strategy in food safety and environmental protection.(3)Label-free detection of tetracycline based on aptamer recognition and hybrid chain reaction.Hybrid chain reaction is a commonly used signal amplification technology that uses the principle of base complementary pairing to form an ultra-long and stable ds DNA structure.On the basis of the second study,a new aptamer sensor was constructed for tetracycline detection based on graphene oxide and hybrid chain reaction amplification strategy.The strategy is simple to operate,fast in response,low in cost,and exhibits good specificity,stability,and repeatability.The establishment of this method will have potential application prospects for the monitoring and analysis of tetracycline in the actual water environment.