Research Of Electrochemical Aptamer Sensor For Detection Of Tetracycline Antibiotic Residues In Milk Based On Graphene-based Compounds

Tetracycline antibiotics（TCs）are widely used in the field of veterinary medicine and food because of their high antibacterial efficiency,low cost,and excellent performance in improving growth rate and feed efficiency.They can accumulate in the human body through the food chain and may cause harmful effects on human health even at low doses.Many techniques,such as chromatography and electrophoresis,are used to detect TCs.Although their accuracy is high,they have disadvantages such as long time-consumption and expensive instruments,which limit their wide application.Electrochemical sensors are promising,innovative,complementary,or alternative analytical techniques for the detection of tetracycline antibiotics due to their advantages of high sensitivity and selectivity,rapid detection,easy operation,and in situ application.Graphene and graphene-based materials have become the focus of much research due to their excellent mechanical,electrical,and thermal properties.Three electrochemical aptamer sensors were constructed and used for the detection of tetracycline antibiotic residues in milk samples.The main contents are as follows:（1）Reduced graphene oxide（rGO）,gold nanoparticles（Au NPs）,and Cu-MOF modified screen-printed carbon electrode（SPCE）used as a test platform,an electrochemical method-based aptamer sensor was constructed and successfully applied to the detection of oxytetracycline（OTC）.rGO had good electrical conductivity and Cu-MOF had a large specific surface area.The combination of rGO and Cu-MOF not only promoted the electron transfer rate on the electrode surface but also provided more binding sites for OTC aptamers,thus realizing the sensitive detection of OTC.Under optimal conditions,the detection limit（LOD）of the aptamer sensor for OTC was 0.03 ng/m L（S/N=3）.（2）In order to broaden the detection range,three kinds of TCs were detected based on rGO materials.A multi-detection method was designed using broad-spectrum aptamers of tetracycline antibiotics.An electrochemical aptasensor based on the specific recognition of tetracycline（TET）,doxycycline（DOC）,and OTC was developed using flower-like zinc oxide/rGO/Au NPs.The surface of the glassy carbon electrode used the flower-like zinc oxide/rGO/Au NPs as a platform,which improved the electron transport rate,enhanced the electrochemical sreetrength,and provides enough active sites for the capture of aptamers.Under optimal conditions,the LOD of aptasensors for TET,DOC,and OTC were 0.33,0.23,and 0.3 ng/m L（S/N=3）,respectively.（3）In order to improve the sensitivity,the method of signal amplification was explored based on graphene materials.Signal amplification strategies were essential to improve the detection sensitivity of target ions or molecules with important biological functions,and few studies had used more than two signal amplification strategies.In this chapter,the simultaneous coordination triple signal amplification strategy was adopted to detect tetracycline by electrochemical method.Carbon material with strong conductivity being used as a carrier,the electron transmission channel was increased to realize initial signal amplification.Exo I could specifically digest single-stranded DNA in the 3’-5’direction,so it could be used to assist target recovery and achieve secondary signal amplification.Finally,the gold nanoprobe was bound to the c DNA on the electrode surface by a specific base pairing.Through the catalytic action of peroxidase enzyme,the strong electrochemical signal was generated and the three-stage signal amplification was realized.Under optimized conditions,the detection limit was 3.3×10^-4 ng/m L,and the range was 1×10^-3 ng/m L to1×10³ ng/m L.In addition,the sensor has high specificity,good repeatability,good stability,and good reliability.It has good application potential.