Screening Of Sarafloxacin Hydrochloride Aptamer Based On Real SELEX And Establishment Of Its Biosensor

Sarafloxacin(SAR)has been widely used in poultry and aquatic animals.However,it may be a residue in milk and foods of animal origin.These residues may cause human health problems and may also promote the development of antibiotic-resistant pathogens.Therefore,it is particularly important to establish a better detection method for SAR residues.In this work,we proposed a novel Real-SELEX screening technology based on real samples.SAR aptamers were obtained by traditional SELEX screening technology and Real-SELEX screening technology of real samples,and then the aptamers were characterized.Meanwhile based on the aptamers screened in the two systems,a fluorescent aptasensor was established,which can detect real milk samples.The specific contents are as follows:Firstly,aptamers screened by the traditional SELEX strategy or other approaches do not undergo the real sample in the selection process,and the environmental inconsistency between selection system and final detection system might influence the aptamer characteristics and discount the final detection performance.Apt-B4 and Apt-F2 with high detection performance were effectively screened by traditional SELEX screening technology and Real-SELEX screening technology.Secondly,through Real-SELEX screening technology based on real samples,we obtained aptamer Apt-F2(48.08±13.38 nM)with higher SAR specificity and affinity than aptamer Apt-B4(84.22 ±27.40 nM)screened by traditional SELEX technology.Meanwhile,Apt-B4 and Apt-F2 could specifically bind to SAR.Compared with Apt-B4,Apt-F2 also showed stronger conformational changes after binding to SAR.Apt-B4 or Apt-F2 was used as a platform for developing fluorescent aptasensor.The limit of detection of Apt-B4-and Apt-F2-based aptasensors for SAR were respectively 0.19 ng/mL and 0.12 ng/mL.Moreover,Apt-F2-based aptasensor also suggested slightly better recovery rate of SAR from spiked milk samples,the detection recovery rate is between 97.6%?107.4%.All of these results indicated the advantage of the real SELEX strategy superior to traditional SELEX strategy,The Apt-F2 aptasensor can detect SAR residues in real milk.