Determination Of Tumor Markers In Human Urine By Chemical Reaction Assisted SERS Technology

Urinary 5-hydroxyindole-3-acetic acid(5-HIAA)is a tumor marker for diagnosis of patients with carcinoid.3-methoxy-4-hydroxymandelic acid(VMA),also present in human urine,is a tumor marker for neuroblastoma and pheochromocytoma.All of them are belong to neuroendocrine tumors(NENs),which are characterized by difficulty in diagnosis due to the absence of specific symptoms in the early stage,and poor prognosis in the late stage.Early screening and diagnosis of NENs is very important to improve the survival rate and reduce the cost and complexity of treatment.In order to achieve the goal of early screening and diagnosis of NENs,several new types of chemical reaction-assisted surface enhanced Raman scattering(SERS)technology were proposed to quantitatively detect 5-HIAA,VMA,and their mixture in urine.(1)In clinical practice,a simple colorimetric assay has widely been utilized for urinary5-HIAA via its reaction with 1-nitroso-2-naphthol in nitrous acid medium.However,this colorimetric assay has been criticized for lack of specificity.Herein,we proposed a novel SERS-based method for selective detection of urinary 5-HIAA by the use of a modified nitrosonaphthol reaction,in which hydrochloric acid is substituted for nitric acid to control the reaction conditions.The chloride-aggregated Ag colloids not only create enormous hot spots for SERS enhancement,but also improve the chemical stability of Ag NPs in acidic environment.Under optimized conditions,the present method can detect 5-HIAA within 12 min at concentrations as low as 1.2 ng/m L,which is 1000 times lower than that of conventional colorimetric method.And more importantly,the present method exhibits specific response toward 5-HIAA against other metabolites with similar structures in the urine.Furthermore,several healthy person’s urine samples were also analyzed using the present method,and experimental results are in compliance with the levels recorded in a healthy population.On the basis of these results,we can conclude that the present SERS-based method can provide a valuable alternative to conventional colorimetric assay for clinical diagnosis,evaluating prognosis,and monitoring of treatment in carcinoid.(2)The above method only can be used to detect 5-HIAA,and thus another type of chemical reaction-assist SERS technology was proposed to realize the simultaneous detection of VMA and 5-HIAA.Both of VMA and 5-HIAA can react with the diazonium salt of p-nitroaniline,and the characteristic peaks of their products in SERS spectrum are significantly different.The relative intensities of the characteristic peaks are correlated with their concentration in the measured substance.Accordingly,VMA and 5-HIAA in healthy urine samples can be detected by this new method,and our experimental results are in compliance with the levels recorded in healthy population.Based on the above results,this method can be used for the simultaneous detection of two types of tumor marker with high selectivity.Our works have demonstrated that chemical reaction-assisted SERS technology has great potential for the simultaneous detection of various tumor marker in urine.