A Label-free Electrochemical Immunosensor Based On A Gold–vertical Graphene/TiO₂ Nanotube Electrode For CA125 Detection In Oxidation/Reduction Dual Channels

Tumor markers（CA125）are the"gold standard"for ovarian cancer.Therefore,the CA125 immunosensor,which has many advantages such as simple electrode process,low cost,high sensitivity and selectivity,is of great significance in clinical applications such as screening and diagnosis of ovarian cancer.In this paper,an unlabeled immunosensor electrode based on Au-VG/TiO₂was constructed to detect serum CA125 in a redox dual pathway.In this sensing system,Au-VG/TiO₂ electrode was used as signal amplification platform,cytosine（Cyt）was used as the probe of oxidation pathway,and dopamine（DA）was used as the probe of reduction pathway.First,with the TiO₂ nanotube array as the substrate,the VG nanosheets are synthesized on it by chemical vapor deposition technology.After that,using electrodeposition technology,gold nanoparticles are buried deep on the surface and roots of VG nanosheets to prepare Au-VG/TiO₂electrodes.Due to the adsorption of gold nanoparticles and vertical graphene,the specific surface area,conductivity and biocompatibility of the working electrode are improved.Secondly,through the optimization of probe concentration,antibody concentration,antibody incubation time and antigen incubation time,the optimal experimental conditions and quantitative detection methods for constructing highly reliable immune sensors were studied.Therefore,the most efficient experimental data of the CA125quantitative detection model were obtained.In the oxidation and reduction pathways,CA125 antibody had the same concentration range(0.1～1000 mU·mL^-1)in response to the determination of CA125 antigen by AU-VG/TiO₂immunoelectrode.For both pathways,we found that the oxidation pathway was not only sensitive,but also had a lower detection limit(0.0001 mU·mL^-1)than the reduction pathway（0.0026 mU·mL^-1）.We tested the prepared immunosensors for a number of stability aspects,such as reproducibility,reproducibility,specificity,and stability tests for up to four weeks.According to the experimental data,the effect of the oxidation path is significantly better than that of the reduction path,especially in terms of long-term stability and performance deviation.Finally,we also tested for tumor markers（CA125）in serum,and the results were also very impressive.