Preparation And Detection Application Of Molecularly Imprinted Photonic Crystal Sensor

In our country,the food safety system is still in the establishment stage.The safety problems,especially the drug residues in animal source foods occur frequently,which has aroused the attention of numerous consumers.Enrofloxacin?ENRO?,one kind of broad-spectrum bactericidal drugs,is widely used in livestock and aquaculture.The big amount use of ENRO may occur cumulative effects,it can be trapped in animals'kidneys and livers.The residual enrofloxacin and its metabolite ciprofloxacin are discharged into the sewage treatment plant along with the aquaculture wastewater and domestic sewage.The existing water treatment technology is difficult to remove them effectively,so it may lead to water and soil pollution,even drug-resistant strains.Benzocaine is one of the most commonly used anesthetics for fish.It can reduce the stress response,improving the survival rate of fish in the long distance transportation.Fish anaesthetics have withdrawal time,which is defined as the time required after administration of a drug to the fish needed to assure that drug residues in the marketable fish is below a determined maximum residue limit?MRL?.Further more,when the fish died,the concentration of anesthetics would not decrease any more.It may cause harm to human health after eating these fish with high drug residues.At present,there is a lack of relevant laws and regulations,application standards and detection standards of anesthetic drugs for fish in our country.Therefore,the irregular use or abuse may occur in the market.The problem of drug residues and safety of fish anesthetics has aroused great attention of consumers.In a word,the drug residues in animal source foods have great potential risks to human health and ecological environment.Long-term consumption of these foods may lead to chronic poisoning,allergic reactions and other symptoms,or even cause cancer,birth defects and mutation.It is really significant to take more effective supervision and testing measures.The existing instrument testing methods have the shortcomings of expensive instruments and high requirements for operators,and it is difficult to meet the requirements of field real-time testing.Molecular imprinting technology has the characteristics of predetermination,specificity recognition and practicability,which can design different molecularly imprinted polymers?MIPs?according to the different needs.MIPs have strong stability and long service life.Responsive photonic crystal have the characteristic of signal self-expression,it can quickly respond to target molecules.This study combines molecular imprinting technology with specific identification and responsive photonic crystals with signal self-expression to build portable molecularly imprinted photonic crystal?MIPC?sensors,the template molecules of which are enrofloxacin and benzocaine.The specific research work is as follows:?1?Silicon dioxide?SiO₂?and polystyrene?PS?microspheres were prepared by modified Stober method and emulsion polymerization.The synthesis conditions were optimized.And we prepared SiO₂ and PS photonic crystals by vertical sedimentation self-assembly method.Both SiO₂ and PS photonic crystals form face-centered cubic structures and have bright structural colors.We found that the wavelength of diffraction peak appeared redshift with the increase of particle size.It provides a good template for the preparation of inverse opal MIPC sensor.?2?Preparation of Enrofloxacin?ENRO?inverse opal MIPC sensor.We optimized the molecular imprinting system to ensure the most suitable functional monomer,solvent,crosslinker and eluent.The experimental results show that the different polymerization conditions have great influence on MIPC recognition performance.Finally,acrylic acid?AA?was selected as the functional monomer,methanol as the solvent,the optimal amount of crosslinking agent EGDMA was 57?L,the optimal molar ratio of template molecule,functional monomer and crosslinking agent was 1:6:3,0.01 mol/L NaOH solution:methanol=2:3?V:V?was used as the eluent.The enrofloxacin inverse opal MIPC can identify the target molecule quickly and efficiently,showing good response performance.?3?Preparation of benzocaine inverse opal MIPC sensor.We optimized the recognition performance,and finally applied it to the actual samples?fish?detection.The experimental results show that the benzocaine MIPC can quickly identify the target molecules,and can be reused many times.With the increase of concentration of benzocaine,MIPC diffraction peaks redshift about 35 nm,and the color change from green to yellow,successfully realizing“visual detection”.The minimum detection limit of benzocaine MIPC is 0.001 mol/L?165mg/L?.However,the diffraction peaks redshift of non-imprinted photonic crystal is only 19nm.When detecting fish samples,the standard addition recovery rate of the two methods MIPC and HPLC are basically identical.It confirms the feasibility of determination of benzocaine in practical sample preliminary screening and routine analysis by the MIPC sensor.The sucessful research and development of enrofloxacin and benzocaine inverse opal MIPC sensors has practical research value for detecting the drug residues in animal source foods.It makes exploratory work and provides a new train of thought to further establish automatic analysis instruments of the drug residues in animal source foods.In a word,it is expected to eventually applied the MIPC sensors in real-time and on-site rapid detection,which has profound social importance to protect human health.