Fabrication And Application Of Electrochemical Biosensors Based On Novel Antifouling Materials

In this thesis,different electrochemical biosensors for disease biomarkers were fabricated with different construction procedures,which were mainly based on various novel antifouling materials combined with different conducting polymers.Many different characterization techniques were employed to investigate the antifouling capabilities and biosensing properties of different biosensing interfaces.The application potentials of these biosensors were analyzed in real serum samples,respectively.The main contents of this thesis are summarized as below:(1)A highly biocompatible polymer composite of poly(3,4-ethylenedioxythiophene)(PEDOT)and poly(ethylene glycol)(PEG)derivative was electrodeposited with a simply electrochemical method onto bare glassy carbon electrode(GCE)surface.The surface morphology and electrochemical stability of the PEDOT/PEG composite modified electrode(PEDOT/PEG/GCE)were characterized with scanning electron microscopy(SEM)and cyclic voltammetry(CV),respectively.The PEDOT/PEG modified electrode displayed flake-like nanostructure,and showed outstanding electrochemical stability.In different concentrations of bovine serum albumin(BSA)solutions,the ability in preventing nonspecific protein adsorption of the PEDOT/PEG/GCE was investigated through electrochemical impedance spectroscopy(EIS)method,and the results indicated satisfied capability in eliminating nonspecific adsorption,even in 50.0 mg/mL BSA solution.AuNPs were selfassembled onto the PEDOT/PEG/GCE surface through Au-S bonds for the immobilization of capture probe of alpha-fetoprotein antibody(AFP-Ab)with Au-NH2 bonds to construct AFP electrochemical biosensor.EIS was applied to detect the target(AFP)recognition.The detection range was between 0.001 fg/m L to 10.0 fg/mL,with an ultralow detection limit of 0.0003 fg/mL.The fabricated biosensor manifested high selectivity,sensitivity,and application potential,mainly attributing to the excellent biocompatible,hydrophilicity,stability,and antifouling properties of PEDOT/PEG nanocomposite.(2)Zwitterionic peptide with high antifouling ability from its outstanding hydrophilicity and charge neutrality is becoming one of the most promising antifouling candidate.In this work,antifouling peptide with the sequence of EKEKEKEPPPPC was self-assembled onto gold(Au)electrode surface through Au-S bonds to form antifouling layer.The capability of the constructed peptide layer in preventing nonspecific protein adsorption was surveyed by EIS in different concentrations of single protein samples(HSA and lysozyme)and complex protein-containing solutions(human serum),respectively.Static water contact angle measurement was performed to study the hydrophilic ability of peptide-based layer.Carboxyl group(-COOH)functionalized oligonucleotide sequences(apture probe of breast cancer 1(BRCA1))were attached to peptides(containing-NH2)through the covalent binding to prepare BRCA1 biosensor,based on the electrochemical signal changes induced by hybridization events.The biosensor fabrication procedure was monitored by X-ray photoelectron spectroscopy(XPS)and EIS,respectively.The prepared biosensor exhibited a linear detection range from 1.0 fM to 10.0 pM with a limit of detection of 0.3 fM,associated with antifouling capability,sensitivity,selectivity,and reproducibility,suggesting its potential in practical application.(3)A new zwitterionic peptide(sequence of EESKSESKSGGGGC)as antifouling material was firstly designed,primarily according to the main principle of keeping good hydrophilicity and charge neutrality.It is known that the assembly manner of recognition probe and antifouling material is a key factor affecting the performance of biosensor.Therefore,different fabrication procedures using longchained capture probes(AFP-aptamers)and short-chained antifouling peptides onto gold electrode(Au)surfaces were designed,and the antifouling property and target determination capability of two differently constructed interfaces were investigated by differential pulse voltammetry(DPV)technique.The antifouling property was measured in different concentrations of HSA and human serum solutions.The DPV response range of the biosensor toward AFP with high antifouling capability was from 10.0 fg/m L to 100.0 pg/m L.The fabricated aptasensor exhibited high feasibility for AFP detections in real human serum samples,and the differences between our method and the clinical standard assay were within 6.0% for different serum sample assays.(4)Poly(m-Aminobenzoic acid)was electrodeposited onto bare glassy carbon electrode(GCE)surface through CV technique.Poly(m-Aminobenzoic acid)modified electrode(PmABA/GCE)surface morphology was characterized by scanning electron microscopy(SEM).Taking advantage of the carboxyl(-COOH)groups in PmABA polymers,amino(-NH2)terminated immunoglobulin E aptamers(IgEaptamers)and peptides(sequence of CHHHDDD)were connected to PmABA through the formation of covalent bonds in sequence,to form the biosensing interface.Electrochemical techniques such as CV,EIS and DPV were employed to monitor the construction procedure,antifouling ability and recognition performance of the IgE biosensor.The fabricated biosensing interface(IgE-aptamer/PmABA/GCE)displayed high antifouling capability even in 20%(V/V)fetal bovine serum(FBS)solution.The obtained linear detection range of the biosensor(IgE-aptamer/PmABA/GCE)was from 0.01 ng/m L to 50.0 ng/mL with high specificity.