Construction Of Antifouling Electrochemical Sensors And The Applications In Biomolecule Detection

Cancer is a huge threat to our lives,and effective early detection and treatment strategies can greatly reduce the incidence and mortality of cancer.Electrochemical biosensors are widely used to detect cancer markers due to their low cost,simple structure and high sensitivity.However,in complex samples,the detection of electrochemical biosensors can reduce their accuracy due to biological fouling.For this reason,it is necessary to study antifouling sensing interfaces that can avoid non-specific adsorption,thereby improving the feasibility of clinical application of electrochemical biosensors.In this thesis,three antifouling electrochemical biosensors were constructed based on antifouling materials such as hydrogels and peptides,combined with signal amplification strategies and dual-mode detection methods.The plans are as follows:(1)In chapter two,a kind of conductive supramolecular polymer hydrogel(CSPH)based on polyaniline(PANI)was synthesized.After the electrochemical copolymerization of aniline(AN)and 3-aminophenylboronic acid(ABA)on glassy carbon electrode(GCE),the electrode was then inserted into the polyvinyl alcohol(PVA)solution to obtain robust CSPH through boric acid groups incorporated onto PANI to cause gelation of PVA solution,owing to the hydrophilicity of CSPH and nearly electrical neutrality,the modified electrode not only has good electrical conductivity and biocompatibility,but also has antifouling performance,and it is no longer necessary to modify the antifouling material.Then,the thrombin aptamer 1(TBA1)was modified on CSPH through amide bond,and the modified magnetic nanoparticle(MNP-TBA2)and thrombin aptamer 2 were used to construct a sandwich electrochemical aptasensor.Due to the amplification of nanomaterials,the aptasensor has good sensitivity,with a linear range of 1 pmol/L to 10 nmol/L and a detection limit as low as 0.64 pmol/L.In addition,due to the antifouling performance of the CSPH membrane,the sensor has high selectivity that it can realize the identification and detection of thrombin in actual samples and has a good clinical application prospect.(2)In chapter three,a dual-mode antifouling electrochemical sensing platform forthe detection of prostate-specific antigen(PSA)based on two kinds of antifouling peptides functionalized with graphene oxide-Fe3O4-thionine(GO-Fe3O4-Thi)probe and internal reference Ferrocene(Fc)was constructed,respectively.The longer peptide(Pep1)modified with GO-Fe3O4-Thi probe was designed to contain an antifouling sequence(DKDKDKD)and a peptide sequence(HSSKLQK)capable of being recognized and cut by PSA.The GO-Fe3O4-Thi probe displays not only as mimicked peroxidase(GO-Fe3O4),but also worked as an electrochemical probe due to the presence of thionine(Thi).The concentration of PSA can be measured through both the increase of differential pulse voltammetry(DPV)signal change of Thi and the decrease of chronoamperometry(CA)signal of the reduction of H2O2 electrocatalyzed by GO-Fe3O4.The shorter antifouling peptide(Pep2)was tagged with Fc,whose DPV signal remained constant and did not change with the change of PSA concentration,and it was used as an internal reference to ensure the reliability and accuracy of the measurement.More importantly,owing to the antifouling capability of the designed peptides,the biosensor performances remained operable even in human serum,indicating feasibility of the electrochemical biosensor for practical PSA quantification in complex samples.(3)In Chapter four,an antifouling electrochemical biosensor for detecting PSA based on a novel composite material MXene-Au-MB and antifouling peptides modified by the electrochemical signal probe Fc was constructed.The sensor interface used MXene-Au-MB as the substrate,then anchors the peptide chain and finally modified the electrochemical signal probe Fc.Based on the two-dimensional(2D)nanomaterial MXene's high conductivity,high specific surface and high hydrophilicity,a new composite material MXene-Au-MB was synthesized for the first time.While retaining the excellent performance of MXene,methylene blue(MB)as an internal standard molecule was introduced through electrostatic adsorption,while gold nanoparticles further improved the electrocatalytic activity and sensitivity of electrochemical biosensors and provided a large number of binding sites for peptides to improve the sensitivity.The designed peptide chain included antifouling sequences and sequences that recognized and cut by PSA,and served as an antifouling layer in the sensing interface to capture the electrochemical signal probe carboxyferrocene(Fc-COOH)through an amide bond.The concentration of PSA could be measured by an increase in the change in the DPV signal of the Fc.When PSA is present,the signal of MB remains unchanged,and the use of electrochemical internal standard method can improve the accuracy of the biosensor.Because of its excellent sensitivity,accuracy and selectivity,the electrochemical biosensor can be used for the quantitative detection of actual PSA in complex samples and can be extended to a universal mechanism for the detection of other biomolecules.