Construction Of Metal Sulfide Immunosensor And Application In Colorectal Tumor Markers Assay

Colorectal cancer(CRC)is one of the most common malignant tumors with high mortality rates and poses a serious threat to the health of people everywhere.From 1990 to 2019,the worldwide prevalence of colorectal cancer more than doubled from 0.84 to 2.17 million,and deaths increased from 0.51 to 1.09 million.The incidence of colorectal cancer continues to rise worldwide,especially among young people.In China the burden of colorectal cancer is increasing with 550,000 new cases occurring every year.Colorectal cancer is diagnosed late,complicated clinical tests and expensive diagnostic tools greatly promote the tumor progression.Early detection and diagnosis of CRC and effective evaluation of treatment effect and prognosis can improve the survival rate of patients.The development of new detection techniques can improve the accuracy and specificity of biomarker detection,and play an important role in the prevention and control of CRC.At present,most of the diagnostic markers for CRC are tumor markers.However,the pathogenesis and mechanism of CRC are complex,and the combined detection of multi-dimensional biomarkers can improve the diagnostic performance of CRC disease.Currently,the diagnostic markers for CRC are generally tumor markers.Currently,the biomarkers used for the diagnosis of CRC are generally tumor markers.However,the pathogenesis and mechanism of CRC are relatively complex,and the combined detection of multi-dimensional biomarkers can improve the diagnostic performance of CRC disease.This study conducted a retrospective study on common clinical laboratory test indicators of CRC patients.Carcinoembryonic antigen(CEA),carbohydrate antigen 199(CA199),carbohydrate antigen 724(CA724),carbohydrate antigen 125(CA125),triglyceride(TG),total cholesterol(TC),high density lipoprotein(HDL),low density lipoprotein(LDL),albumin globulin ratio(A/G),and red cell distribution width(RDW),absolute neutrophil count(N),absolute lymphocyte count(L),and neutrophil to lymphocyte ratio(NLR)were evaluated in the value of alone or combination diagnosis.Common clinical detection and analysis methods usually require complex and expensive instruments and professional operation,which limits their wide application.Therefore,it is very important to develop rapid,highly sensitive,highly selective and low-cost detection methods for the detection of colorectal cancer related tumor markers.Immunosensor is a new type of biosensor based on specific immune response and highly sensitive sensing technologies(such as electrochemistry,optics or piezoelectricity)to determine substance content through signal transduction.Various nanomaterials are used to construct immunosensors,such as metal nanoparticles(gold,copper,palladium,cobalt,silver,platinum,etc.),metal oxides(ZnO,SnO2,Fe2O3),semiconductors(silicon,indium,gallium),and quantum dots(CdSe,CdTe,CdSeTe).In this study,metal sulfide nanocomposites were used as the base material to construct immunosensor to realize signal amplification strategy and improve the sensitivity of marker detection.Electrochemical immunosensor is a kind of biosensor based on nanotechnology,electrochemical analysis technology and immunology technology.It has the advantages of simple operation,fast analysis speed,high sensitivity and good selectivity.Due to the excitation light source does not interfere with the detection signal,PEC sensor has a lower background signal,which has higher sensitivity and specificity than traditional electrochemical analysis methods.In this study,CRC tumor markers CEA,CA199 and CA242 were used as detection models,and electrochemical and photoelectrochemical immunosensors were constructed by combining electrochemical analysis technology,photoelectric technology,nanotechnology and immunotechnology,and were used for actual sample detection.The detailed research content of this topic is as follows:(1)Diagnostic value of multiple biological indicators combined detection in colorectal cancerTo explore the diagnostic efficacy of CEA,HDL,NLR and other multi-dimensional biological indicators in CRC.Receiver operating characteristic curve(ROC)was applied to evaluate the diagnostic value of CEA,CA199,CA724,HDL,LDL,A/G,RDW,N,L,NLR and combined tests in CRC patients.Logistic regression was used to analyze the related factors affecting CRC.The results showed that CEA,CA199,CA724,HDL,LDL,A/G,RDW,N,L and NLR in CRC group were significantly different from those in control group.The area under ROC curve for the combined diagnosis of CRC by multiple indicators was 0.9454,the sensitivity was 90.48%,and the specificity was 85.94%.Regression analysis showed that age,CEA,CA199,CA724,RDW,N,and NLR were risk factors for CRC.In addition,by analyzing the relationship between CEA,CA199 and NLR and clinicopathologic features,it was found that the expressions of CEA and CA199 were closely related to tumor stage,and the serum concentrations of CEA and CA199 in patients with advanced CRC were higher than those in patients with early CRC.In conclusion,laboratory routine combined detection of multiple biological indicators is helpful for the diagnosis and risk assessment of CRC patients.(2)A label-free electrochemical immunosensor for CEA detection based on a novel signal amplification platform of Cu2S/Pd/CuO nanocompositesIn this system,Cu2S/Pd/CuO nanocomposites were used as signal amplification platform to construct a labeled electrochemical immunosensor for highly sensitive detection of CEA content in serum.Snowflake cuprous sulfide(Cu2S)has a large specific surface area.Palladium nanoparticles(Pd NPs)have strong electron transport capacity,good biocompatibility,and provide a large number of catalytic active sites.The prepared Cu2S/Pd/CuO nanocomposites can not only increase the antibody load,but also improve the electron transfer efficiency.The electrochemical workstation was used for electrochemical measurement,and hydrogen peroxide(H2O2)was used as the active substrate.After optimizing reaction conditions,the constructed immunosensor had a wide detection range and high sensitivity.The detection range of the immunosensor was 100 fg/mL～100 ng/mL,and the detection limit was 33.11 fg/mL.Performance analysis shows that the electrochemical immunosensor has good repeatability,specificity and stability,and has obtained good results in the detection of clinical serum samples.Therefore,the construction of the immunosensor provides an effective means for the detection of clinical biomarkers.(3)An electrochemical immunosensor based on PdAgPt/MoS2 nanocomposites was used for the detection of CA242A novel label-free electrochemical immunosensor was developed for the detection of tumor marker CA242.The novel nanocomposite was synthesized by loading PdAgPt nanocomposites onto molybdenum disulfide(MoS2)surface with large surface area.PdAgPt nanocomposites had good conductivity and catalysis,and the pleated papery MoS2 increases the electrochemical active site.The PdAgPt/MoS2 had peroxidase-like properties and was used to catalyze hydrogen peroxide(H2O2)and generate high electrical signals.The CA242 electrochemical immunosensor used PdAgPt/MoS2 as signal amplification platform.Through optimizing experimental conditions,the detection range was from 1×10-4 U/mL to 1×102 U/mL,and the detection limit was low(LOD was 3.43×10-5 U/mL).In addition,the designed CA242 immunosensor also performed well in repeatability,selectivity and stability evaluation,and was successfully used for the detection of human serum samples.(4)Construction of photoelectric chemical immunosensor based on SnS2/ZnCdS heterojunction and sensitive detection of CA199Quantum dots SnS2 and ZnCdS were prepared by hydrothermal method,and SnS2/ZnCdS quantum dots were synthesized by calcination at high temperature.An unlabeled photochemical(PEC)immunosensor based on SnS2/ZnCdS was constructed for the detection of tumor marker CA199.The photocurrent time curve showed that the synthesized SnS2/ZnCdS exhibited excellent photocurrent response under visible light irradiation,which was due to the formation of heterojunction promoted electron transfer and inhibited photogenerated electron/hole(e-/h+)recombination.By immobilized the captured antibody to SnS2/ZnCdS photoelectrode,the ultra-sensitive PEC immunosensor for the detection of CA199 was established.The detection range of CA199 was 0.01～1000 U/mL,and the detection limit was 1.00×10-3 U/mL.The constructed CA199 immunosensor had good repeatability,specificity and stability,and had great application potential in improving the sensitivity of CRC tumor marker detection.