Multimodal Detection Of Cancer Biomarkers PSA Based On Noble Metal Nanocomposites

Cancer biomarker is a kind of biomarker that is produced or increased by the secretion of cancer cells or the abnormal response of human body to tumor during the occurrence and proliferation of malignant tumor,and one of the substances that reflect the existence and growth of tumor.Cancer markers are usually associated with cancer risk and can be used for cancer prevention,diagnosis and efficacy monitoring.Therefore,the accurate,highly sensitive and highly specific detection of cancer markers is of great significance and value.Due to the extremely high molar extinction coefficient of noble metal nanoparticles,the local surface plasmon resonance effect of noble metal nanoparticles shows extremely high sensitivity to the local environment in which the particles are located,which makes them show different colors in different states and has attracted widespread attention.Based on the existing colorimetric detection using precious metal nanoparticles,this paper integrates fluorescence and photothermal output modes to realize simple and sensitive detection of cancer markers according to two or more signal output modes,and improves the accuracy of the results by correcting the contrast color results of other signal results.The results are as follows:（1）A carbon dots（CDs）encapsulated plasma core-satellite single nanoprobe（CDs/Ag-Au NPs）was constructed using a sequential in situ reduction strategy without the need of additional reducing agents.Under the etching action of H₂O₂,the color of the solution changed from yellow to pink,and the fluorescence intensity gradually increased,which produced significant colorimetric and fluorescence signals.Inspired by this dual responsiveness,we further utilized this integrated nanoprobe as the signal reporter in the glucose oxidase-involved immunoassay for prostate-specific antigen（PSA）.Both the clear changes in the localized surface plasmon resonance peak and remarkable fluorescence enhancement were closely correlated with the target concentration,thus achieving highly sensitive and reliable dual-mode detection of PSA in a simple manner.The detection range of PSA in colorimetric and fluorescent channels was 0.05-20 ng/m L and 0.005-20 ng/m L respectively,and the limit of detection（LOD）was 2.3 pg/m L and 0.84 pg/m L respectively.At the same time,the method realizes the dual-mode visual detection and evaluation of PSA level in human serum samples,indicating that the method has potential application.（2）To further improve the portability of PSA detection and for immediate detection in resource-limited environments.We constructed a colorimetric and photothermal immunoassay to quantitatively detect PSA by reading the color and temperature of the solution directly.The PDA-Au nanoprobe with nuclear-satellite structure was synthesized by linking polyamine（PDA）with gold seeds via cysteine.When ascorbic acid（AA）is present in the solution,PDA and AA can synergistically reduce chloroauric acid,mediate the growth of gold seeds on the surface of PDA,and cause the red shift of the local surface plasmon resonance peak of the nanosensor.The color of the solution changes from pink to blue.At this time,the photothermal conversion efficiency of the nanoprobe is increased,and the temperature of the solution after irradiation by the near infrared laser is increased,and the temperature change can be read by the digital thermometer.This method can also be combined with sandwich immunoassay to construct a colorimetric and photothermal dual mode enzyme-linked immunosorbent assay（ELISA）based on alkaline phosphatase for highly sensitive and accurate detection of PSA.The detection range of PSA in colorimetric and photothermal channels was 0.05-100 ng/m L and 0.5-150 ng/m L respectively,and the LOD was 6.71 pg/m L and 0.13 ng/m L respectively.The accurate detection of PSA level in serum samples shows that our dual-mode colorimetric and photothermal immunoassay have great potential in the diagnosis of cancer biomarkers at the early clinical stage.（3）Although colorimetric and photothermal dual-mode detection can improve the portability of the method,the sensitivity of the detection method based on gold nanoparticles growth is reduced.In order to improve the detection sensitivity while preserving the advantages of high portability,we proposed a method to construct a three-mode PSA detection system mediated by glucose oxidase based on the changes of LSPR peak,fluorescence intensity and photothermal efficiency caused by CDs/Au NRs etching.The CDs and Au NRs were synthesized.The electrostatic interaction made CDs adsorbed on Au NRs to form CDs/Au NRs probes.CDs/Au NRs was etched to different degrees by Fenton reaction,resulting in changes of colorimetric,fluorescent and photothermal signals.Combining this reaction with ELISA,H₂O₂ produced by the reaction of glucose oxidase and glucose produces·OH through Fenton reaction,which etches CDs/Au NRs,resulting in changes in the aspect ratio.At this time,the color of the solution changes,the free CDs in the solution increase,and the photothermal conversion efficiency decreases.The change degree of these three signals was related to the concentration of antigen,thus realizing the accurate and sensitive detection of target antigen PSA.Under the optimal conditions,the detection range of PSA by the sensor in three channels is 0.05-40 ng/m L（colorimetric）,0.005-20 ng/m L（fluorescent）,and 0.1-20 ng/m L（photothermal）.The LOD was 1.47 pg/m L（colorimetric）,0.29 fg/m L（colorimetric）and 49 pg/m L（photothermal）respectively.Due to the specific binding between antigen and antibody,the multi-channel sensor has high selectivity.Finally,the concentration of PSA in human serum samples was determined by standard addition method.The recoveries obtained by the three methods were basically consistent with the results of commercial kits.