Electrochemical Immunosensor Based On Nanomaterials For Cortisol Detection

As an important marker of stress and depression,cortisol（Cor）plays an important role in human physical and mental health.Depression is one of the mental diseases that seriously affects the healthy life of human beings.The early warning and screening and diagnosis of depression are of great significance for the timely treatment of depression and the physical and mental health of patients.Therefore,the development of a sensitive,convenient,efficient and accurate detection technology is crucial for the early warning,screening and objective diagnosis of depression.In this paper,three electrochemical immunosensors for detecting cortisol were constructed by using nanocomposites with excellent physical and chemical properties as the modified materials of electrochemical immunosensors,and the sensitive detection of cortisol was realized.The research content is mainly divided into the following three parts:（1）Using molybdenum disulfide as the base material,copper tungstate@molybdenum sulfide nanocomposites（CuWO₄@MoS₂）were synthesized by a simple hydrothermal method,and gold nanoparticles（AuNPs）were synthesized by sodium citrate reduction method.AuNPs were ultrasonically dispersed in 2%chitosan（Chit）to obtain Chit-Au.An electrochemical immunosensor was constructed by layer-by-layer modification of CuWO₄@MoS₂and Chit-Auonto a glassy carbon electrode（GCE）for sensitive detection of cortisol.Under the optimal conditions,the sensor has good sensing performance for cortisol,with a linear response range of0.1 fg/mL～1μg/mL,and a detection limit of 0.014 fg/mL.In addition,the prepared sensor was successfully used to detect the cortisol content in human saliva,and the feasibility of the method was verified by comparing with the ELISA results.（2）A conductive MOFs material（NiCo MOFs）with a cubic structure was synthesized using nickel nitrate,potassium cobalt cyanide,and trisodium citrate as raw materials,and SnS₂/NiCo MOFs were synthesized by a simple hydrothermal synthesis method on the basis of NiCo MOFs.The SnS₂/NiCo MOFs were functionalized with L-cysteine and combined with gold nanoparticles to obtain AuNPs@SnS₂/NiCo MOFs.Using AuNPs@SnS₂/NiCo MOFs as a substrate,a novel electrochemical immunosensor for sensitive determination of Cor was fabricated.The results show that the AuNPs@SnS₂/NiCo MOFs/GCE have high specific surface area and excellent electrical conductivity,which can facilitate the electron transfer between the electrolyte and the electrode surface.The electrochemical sensing platform has good stability,repeatability and high selectivity.The constructed immunosensor was applied to the determination of Cor in saliva and obtained satisfactory results.（3）An electrochemical immunosensing strategy was designed using CuCo₂O₄-MWCNT as a sensing platform.The experimental results show that CuCo₂O₄-MWCNT has a good electrochemical response,and the synergy with AuNPs can achieve double amplification of the current signal,which is an effective strategy for sensitive determination of Cor.Cor showed a good linear relationship with the current signal in the concentration range of 10 fg/mL～1μg/mL,and the detection limit was 0.53 fg/mL.The designed electrochemical immunosensor was used to detect the content of Cor in human saliva,and satisfactory results were obtained.The results show that using the highly conductive AuNPs@CuCo₂O₄-MWCNT as an electrochemical immunosensing platform is a very effective strategy,which can effectively achieve signal amplification and open up a broad new field for sensor development.