Theoretical And Experimental Study Of Surface-enhanced Raman Scattering Detection For Prostate Cancer Markers

Prostate cancer is the second leading death-related cancer in middle-aged and old men.A large number of studies have shown that the concentration of Zn²⁺ or citrate ions in the prostate and its secretions of patients with prostate cancer are significantly lower than those of the normal in the early stage.Therefore,acurate detection of Zn²⁺ and citrate may provide a strong evidence for clinical diagnosis of prostate cancer.This work focused on establishing a surface-enhanced Raman scattering?SERS?method for detection of prostate cancer marker Zn²⁺,with 2-carboxyl-2'-hydroxy-5'-sulfonated formyl benzene?Zincon?as the SERS probe and liquid-liquid self-assembled Au nanoarrays as the SERS substrate.Meanwhile,combined with DFT,it showed that the proposed method exhibited excellednt selectivity for Zn²⁺ detection from the aspects of theory and experiment.Moreover,the liquid-liquid self-assembled Ag nanoarrays was prepared and transferred to the working electrode of the screen-printed electrode?SPE?to realize the quantitative detection of citrate through electrochemical surface-enhanced Raman spectroscopy?EC-SERS?.The details are as follows:Firstly,the structures of Zincon and its complexes with Zn²⁺,Cu2+,Co2+ and Ni2+ were optimized by DFT theoretical calculation.Meanwhile,the vibration of chemical bonds in these molecules was calculated theoretically.Experimentally,Au nanoparticles?Nps?was synthesized by chemical reduction method and then self-assembled Au nanoarrays was prepared at the liquid-liquid interface of n-hexane/Au colloids through simple vortex mixing and used to realize the recording of SERS spectra of Zincon and its four complexes.Au nanoarrays were characterized by SEM and UV-Vis.By comparing the theoretical Raman spectrum,normal Raman spectrum?NRS?and SERS spectrum of Zincon and its four metal complexes,the characteristic vibration peaks of them were studied and their peaks were identified in detail,which theoretically proved the feasibility of using Zincon as the probe to specifically detect Zn²⁺ by SERS method.Secondly,a sensitive and highly selective SERS method to detect Zn²⁺ in human prostatic fluids by utilizing water-insoluble Zincon as a SERS probe based on self-assembled Au nanoarrays at a liquid�liquid interface between n-hexane and Au colloids was proposed.The spectra showed remarkably different SERS bands of Zincon before and after coordinating Zn²⁺ in the controlled conditions?70 ?L of ethanol,500 ?L of n-hexane,p H value of 7.1 and 10 s of vortex mixing time?,which can be used in quantifying Zn²⁺ with characteristic peaks.The proposed SERS method presented a good linear relationship ranging from 0.500 to 10.0 ?mol/L and a satisfactory detection limit of 0.127 ?mol/L as well as low interference with other metal ions.And the recovery of 81.0%-101% was obtained.Moreover,the detection results were close to those of the conventional standard atomic absorption spectroscopy?AAS?method?accurancy 93.7%?,which verifies the accuracy and reliability of the proposed method.Finally,Ag Nps were synthesized by chemical reduction method and self-assembled Ag nanoarrays were prepared at the n-hexane/Ag colloids interface under the induction of cetyl trimethyl ammonium bromide?CTAB?.Ag nanoarrays were then transferred to the surface of the working electrode of the SPE to obtain Ag nanoarray@SPE.Meanwhile,malachite green?MG?was used as the SERS probe to investigate its enhancement factor and signal reproducibility,and the experimental results showed that it had a good SERS performence.After optimization of the applied potential?0.100 V vs.Ag/Ag Cl?,the time of applying the controlled potential?400 s?,p H value of the solution?p H 8?,quantitative detection of citrate in aqueous solution was realized in in situ EC-SERS platform.The proposed EC-SERS method presented a good linear relationship ranging from 0.100 to 2.00 mmol/L with R = 0.989,a detection limit of 0.0513 mmol/L,and the recovery of 92.0% to 111%.The results showed that the method has good accuracy and reliability.