The Fabrication and Application of Several Stimuli-responsive Molecularly Imprinted Electrochemical Biosensors

Author:Wei Zuo Bo

Supervisor:wang li shi

Database:Doctor

Degree Year:2019

Download:54

Pages:155

Size:9531K

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Molecularly imprinted polymers(MIPs)are the novel intelligent materials,which have selective recognition sites for target molecules,have been applied to various applications in separation science,solid phase extraction,biosensing,mimic enzymes catalysis,and drug delivery.MIPs have been successfully developed against a wide range of small protein molecules.However,the molecular size,conformational flexibility,and solubility factors of the relatively large globular protein make it a challenging task to fabricate accessible binding sites with high specificity and affinity toward target proteins.Stimulus-responsive molecularly imprinted electrochemical biosensors(SR-MIPs/GCE)were developed to achieve target proteins efficiently and rapidly capture and release,which can be achieved by regulating the interaction between the stimulus-responsive molecular imprinted polymers(SR-MIPs)and the protein.This strategy not only improves the elution efficiency and mass transfer rate of proteins,but also enhances the imprinting efficiency of the biosensor.The main contents and conclusions are as follows.1)A high sensitivity bovine serum albumin(BSA)imprinted thermo-responsive electrochemical biosensor(T-MIPs/GCE)was fabricated by free radical polymerization.The poly(N-isopropylacrylamide)(PNiPAAm)chain in T-MIPs/GCE undergoes a hydrophilic/hydrophobic conformational transition at a lower critical solution temperature(LCST),so the interaction between template and monomer were inhibited.Based on the thermo-responsive ability of T-MIPs,the sensor gains the self-cleaning function to the template molecules by using potential cycling in a range of-0.8 V to+0.8 V for 14 cycles at37°C in a PBS buffer without the help of washing solvents.During the self-cleaning,BSA molecules can be efficiently removed from the MIPs and the remained film still maintains a stably structure for further sensing application.The binding isotherms of BSA were assessed for the T-MIPs/GCE within the scope of the effective concentration from 0.02 to 10μmol L-1,with a detection limit of 0.012μmol L-1.The proposed method was applied to the enrichment and determination of BSA in milk samples with a recovery of 98.2%103.1%.2)A high sensitivity electric field-responsive imprinted electrochemical sensor(E-MIPs/GCE)for human serum albumin(HSA)was fabricated by free radical polymerization.The self-cleaning of HSA is realized by providing overpotential to the HSA-E-MIPs/GCE.The hydrogen evolution reaction can be triggered by an electric field stimulus,providing the functionality of pH control.The binding isotherms of HSA were assessed for the E-MIPs/GCE within the scope of the effective concentration from 0.05 to 5.0μmol L-1,with a detection limit of 0.024μmol L-1.The proposed method was applied to the enrichment,separation and determination of HSA in serum samples with a recovery of92.4%101.2%.This method not only solves the salt accumulation in the solution by external adding acids or alkalis on these pH-responsive MIPs,but also accelerates the mass transfer rate of proteins.3)Based on the reversible configuration transition of N,N’-dimethylaminoethyl methacrylate(DMAEMA)in aqueous solution by alternating with CO2/N2,a gas-responsive HSA imprinted electrochemical sensor(G-MIPs/GCE)was fabricated by free radical polymerization.The biosensor exhibited unique self-clean and self-recognition properties toward HSA proteins basing on reversible conformational changes driven by N2/CO2 stimuli.The gas-responsive characteristics of DMAEMA,G-MIPs,and G-MIPs/GCE were characterized by hydrogen nuclear magnetic resonance spectroscopy(1H NMR),scanning electron microscopy(SEM)and contact angle,cyclic voltammetry(CV)and electrochemical impedance spectroscopy(EIS).The binding isotherms of HSA were assessed for the G-MIPs/GCE within the scope of the effective concentration from 0.015 to 5.0μmol L-1,with a detection limit of 0.016μmol L-1.The proposed method was applied to the enrichment,separation,and determination of HSA in serum samples with a recovery of 92.5%112.1%.4)A novel photo-responsive magnetic electrochemical imprinting sensor for the selective extraction of paracetamol(PCM)from biological samples was designed.In particular,nanosized photoresponsive molecular imprinted polymers were prepared on the surface of magnetic Fe3O4 nanoparticles through living radical polymerization of azobenzene.The introduction of a magnetic-controlled glassy carbon electrode makes the immobilization and removal of nanosized photo-responsive molecular imprinted polymers on the magnetic-controlled glassy carbon electrode surface facilely operational.Simultaneously,these processes are monitored by the photo-responsive changes of electrochemical signal from PCM.The binding isotherms of PCM were assessed for the sensor within the scope of the effective concentration from 0.001 to 7 mmol L-1,with a detection limit of 0.00043 mmol L-1.The proposed method was applied to the enrichment,separation,and determination of PCM in urine samples with a recovery of 87.5%93.3%.This method effectively solves the problems of low template release efficiency after sample extraction and poor reusability of traditional molecularly imprinted solid phase extraction adsorbent.5)A near-infrared(NIR)light-responsive imprinting biosensor with excellent conductivity and tensibility was designed by incorporation graphene oxide/polyaniline(GO/PANI)with T-MIPs/GCE.In this design,GO/PANI acts as a physically cross-linker,providing hydrogen bond interaction with amide groups in the PNiPAAm.It is functioned to enhance the strength of imprinted hydrogel networks.As a NIR radiation trigger gate,the obtained biosensor not only has a function of IR-based cleaning toward BSA in the absence of elution solution,but also a function of proteins releasing and uptaking,basing on reversibly conformational changes with 808 nm NIR light.The binding isotherms of PCM were assessed for the biosensor within the scope of the effective concentration from 0.02 to 10μmol L-1,with a detection limit of 0.015μmol L-1.The proposed method was applied to the enrichment,separation,and determination of BSA in serum samples with a recovery of 90.9%104.4%.