Construction Of Antifouling Electrochemical Biosensors And Applications In The Detection Of Protein Biomarkers

Electrochemical biosensors have been widely used for biomarker detection in the past decades because of their simple construction,low cost,and high sensitivity,and play an important role in early diagnosis of diseases.However,in the complex environment of actual samples such as serum,it is easy to adsorb cells and interfering substances such as proteins,which affects the accuracy of the assay and even limits its application in actual samples.Therefore,the design of sensing interfaces with resistance to nonspecific adsorption is important for the construction of biosensors.In this thesis,three label-free sensing strategies based on materials with antifouling properties such as bovine serum albumin and amphoteric ions,combined with materials with excellent electrochemical properties such as MXene and gold nanoparticles（Au NPs）,were constructed to achieve highly sensitive and specific detection of immunoglobulin G（IgG）and glycoantigen 125（CA125）in complex samples.The three main schemes include the following:1.The urea-denatured bovine serum albumin（BSA）hydrogel was combined with the two-dimensional nanomaterial MXene and modified on the electrode surface by drop coating to obtain an anti-pollution sensing interface,and then the immunoglobulin G（IgG）capture peptide was modified onto the anti-pollution surface to construct a highly selective anti-pollution electrochemical biosensor for the detection of IgG.Due to the large specific surface area and good electrical conductivity of the hydrogel doped with MXene,the biosensor has a high sensitivity,and the hydrogel formed by the peptide chain obtained from BSA cleavage has better hydrophilicity compared with the sensor usually blocked with BSA,therefore,the sensor shows a more excellent anticontamination performance in human serum,which provides the conditions for the accurate staining of IgG in complex real samples.The sensor showed better resistance to contamination in human serum,which provided the conditions for accurate IgG staining in complex real samples.Compared with previously reported IgG electrochemical sensors,the constructed sensing strategy has better detection performance with a limit of detection of 23 pg m L^-1.It is worth mentioning that the strategy can be constructed in only two steps,which provides a new idea for the development of practical electrochemical biosensors without the use of expensive anti-fouling materials and complex processes,and is expected to achieve direct detection of biomarkers in complex samples.The strategy is expected to enable the direct detection of biomarkers in complex samples.2.A copolymer（PSN）of amphoteric betaine methanesulfonate（SBMA）and hydrophobic N-isopropylacrylamide（NIPAM）was synthesized by a simple free radical polymerization reaction,based on which a label-free anti-pollution electrochemical biosensor with long-term stability and high sensitivity was constructed,effectively avoiding the non-specific adsorption of proteins and other biomolecules on the sensor surface,and achieving the The accurate detection of CA125,a biomarker of ovarian cancer in complex biological environments,was achieved.Firstly,polyaniline（PANI/GCE）was electrodeposited on the surface of the glassy carbon electrode,enhancing the sensor’s electrochemical properties and serving as a signal for detection by its redox current.Due to the electroneutral and hydrophilic nature of the amphiphilic polymer,the sensing interface exhibits good resistance to contamination in serum as well as protein solutions.The sensor was further modified with aptamers to achieve direct quantification of CA125 in serum samples with a detection limit of 2.7m U m L^-1.The sensor can be stable in buffered solutions for up to 15 days and has potential applications in clinical diagnostics.3.The amphoteric thiophene derivative EDOT-Asp was synthesized by the condensation reaction between aspartic acid（Asp）and EDOT-NH₂,and the thiophene backbone in this derivative can form a sensing interface（PEDOT-Asp/GCE）on the electrode surface through controlled modification of electropolymerization.The amphiphilic ions in aspartic acid residues can form a hydrated layer at the sensing interface,which effectively prevents the non-specific binding of hydrophobic proteins,while the electroneutrality of the sensing interface can hinder the adsorption of charged molecules.Therefore,the sensing interface exhibits better contamination resistance and biocompatibility than the bare glassy carbon electrode and the PEDOT-modified glassy carbon electrode.Subsequent electrodeposition of gold nanoparticles on the sensing interface increases the specific surface area and electrochemical properties of the sensing interface and enables the trapping of CA125 aptamer chains via Au-S.When CA125 is specifically recognized by the aptamer chain,the large spatial site resistance impedes electron transfer,and the DPV signal decreases proportionally to the concentration of CA125,enabling its quantitative detection.The sensor can achieve the anti-pollution modification of the sensing interface by one-step electropolymerization,which provides a new idea for anti-pollution sensing strategy.