Synthesis Of SERS Probe For Studying About The Correlation Between Tryptophan Metabolites And Colon Cancer

Colon cancer,one of the nine most common cancer in China,is caused by a variety of factors.The prevalence of colon cancer is increasing gradually in most areas of our country.The traditional clinical diagnosis methods of colon cancer mainly include imageological diagnosis,pathological examination and biochemical detection.However,the accuracy of imageological diagnosis for colon cancer is low,leading to detecte for most lesions in the middle and advanced stages.On the other hands,the colorectoscope needs to invade the human body to cause intestinal discomfort or even damage,which is not suitable for people with strong stress responses and elderly patients.Colon cancer treated early has a 90%cure rate.Therefore,in order to improve the survival rate of cancer patients,it is extremely important to construct more convenient diagnostic methods and explore potential indicators for early diagnosis and therapy.Surface-enhanced Raman technology（SERS）is a powerful platform for the detection of biomolecules with the sensitivity in single-molecule level.Due to its advantages such as ultra-sensitivity,high-selectivity and non-invasiveness,many domestic and foreign researches that combined with the current clinical needs of various countries have been carried out on early screening,early diagnosis,treatment and prognosis assessment of cancer based on SERS.The pros and cons of the SERS enhancement effect are related to the material of the corresponding substrate,the provided number and density of"hot spots".Therefore,we constructed SERS sensors to detect Trp and its metabolites in this work,which based on stable gold nanorods（Au NRs）and gold-coated gold nanorods（Au@Au NRs）array of SERS sensors.This research is mainly carried out from the following three aspects:1.Combining SERS with colorimetric assay,the concentration of Trp in serum was determined based on diazo-coupling reaction.Trp was diazo-coupled to form a macromolecule containing-N=N through gold nanorods as the SERS substrate,which increased the contact surface with Au NRs to greatly improve its detection limit.At the same time,the concentration of Trp was quantitatively detected by the intensity of the newly emerged characteristic peaks.In addition,because of obvious change in color of the formed azo dye solution with the concentration variation of tryptophan,a colorimetry was applied for simply,quickly and intuitively detecting Trp.In this work,it was found that the concentration of Trp in the serum of colon cancer patients was higher than that of normal people,which was consistent with the results of high performance liquid chromatography mass spectrometry（HPLC-MS）.2.In this work,Au@EBP@Au NRs arrays prepared by natural evaporation and silver-coated Au NPs structure（Au@MBN@Ag NPs）which both carried with biological silent region signal respectively were developed to construct sandwich sensor for detecting 5-hydroxytryptamine（5-HT）in serum.The Au@EBP@Au NRs arrays and Au@MBN@Ag NPs were modified with N-acetyl-L-cysteine（NLC）and dithio-bis-succinimidyl propionate（DSP）respectively to capture different functional groups of 5-HT,through which realized the quantitative analysis of 5-HT.Finally,this method successfully achieved the detection of 5-HT in complex serum samples.3.A "nuclear satellite"sensor triggered by enzyme was developed for detecting IDO for presence or absence of colon cancer based on SERS,which composed of Au@MBN@Ag NPs functionalized by aptamer,Trp and carboxylated magnetic beads（MNP-COOH）.In addition to the enrichment effect of MNP-COOH,it can also avoid the influence of centrifugal effect on the detection results.Under the action of IDO,the nuclear satellite structure proposed in this work was destroyed,leading to the change of the SERS signal with the concentration of IDO.A standard working curve was established between the concentration of IDO and the SERS intensity of MBN at 2226cm^-1.Additionally,the high-specificity of the detection platform was verified by anti-interference experiments,revealing that it is a potential method in reliable quantitative analysis and detection for IDO.Finally,the spike-and-recovery experiments successfully proved the reliability of the method in practical applications with the help of macrophages and clinical serum samples as objects.