Detection Of Hexose By SERS Based On Frame-structured Composite Substrates

Carbohydrate is an essential energy source for organisms and plays an important role in the construction of organisms and the maintenance of physiological functions.However,excessive sugar intake can lead to a variety of health problems.At present,the improvement of modern living standards has led to some sugar-related diseases.For example,the number of people with diabetes is increasing year by year,and the age of onset is younger.Among the many sugars,glucose,fructose and galactose are directly absorbed by the body.These three sugars are classified as hexose and have a structural formula of C₆H₁₂O₆,which is more closely related to human metabolism.Therefore,the development of hexose detection methods and techniques for food,blood and urine has become a hot research topic.Surface enhanced Raman spectroscopy（SERS）has been widely used in the selective detection of small molecules in complex environments due to its high sensitivity,high signal-to-noise ratio and"fingerprint spectrum"characteristics.However,common saccharide substances,including hexose,belong to Raman inert molecules,and the Raman signals of saccharide molecules are difficult to be directly observed,and simultaneously,it is difficult to directly enhance the Raman signals of saccharide molecules through a traditional SERS substrate,so the enhancement performance of the substrate is improved by the introduction of the framework structure.Considering various interferences in the actual detection environment,a detection method with selectivity and good anti-interference ability was designed according to the spectral characteristics and structural characteristics of different hexose molecules.Based on SERS,three kinds of composite SERS substrates were designed and prepared,and three detection methods were proposed to realize the quantitative detection of glucose,fructose and galactose,which are the most common hexose.1.A composite SERS probe was prepared by combining a signal molecule with a silver-coated covalent organic framework material,and the detection of glucose in the beverage environment was realized.In this study,the covalent organic framework materials with excellent porosity and large specific surface area were used to adsorb the glucose molecules effectively,and the glucose was interacted into the hot spot area of the substrate surface.The signal molecule 3,3’,5,5’-tetramethylbenzidine is introduced,the generated SERS signal can be sensitively changed,and has a good linear relationship with the glucose concentration,so that the sensitivity of glucose detection is greatly improved.The detection limits of glucose in water and beverage were 0.069μg/m L and 0.096μg/m L,respectively.The results showed that the probe could detect glucose in beverage accurately and sensitively.2.Boric acid-functionalized silver SERS substrate was synthesized and used to detect fructose in artificial urine.In this work,boric acid-functionalized silver nanoparticles as SERS substrates were synthesized by self-assembly reaction under mild conditions with the help of the high affinity of the thiol functional group at one end of the probe molecule 4-thiophenylboronic acid with silver surface.The boronic acid functional group has strong interaction with the fructose molecule and can combine to form an ester complex,which induces the deboronation reaction in the system,thereby indirectly realizing the quantitative detection of fructose.The detection limits of fructose in water and artificial urine were 0.084μM and 0.535μM,respectively.The results showed that the substrate had good response to fructose in artificial urine.3.Silver and metal-organic framework composite SERS substrate was designed to detect galactose in cascade with enzyme.In this work,a method for the detection of galactose by nano-enzyme and natural enzyme cascade was proposed.A composite SERS substrate with peroxidase-like activity was prepared by synthesizing a metal-organic framework MIL-53material and coating silver nanoparticles on the surface of MIL-53 material through a thermal reduction reaction,thereby realizing the sensitive detection of hydrogen peroxide.Then galactose is oxidized and decomposed into hydrogen peroxide by galactose oxidase,so that the enzyme cascade detection of galactose can be realized.The method was applied to the detection of galactose in water environment,and the detection limit was 0.095μM.The detection results showed that the method of nano-enzyme and natural enzyme cascade detection of galactose was effective.In this study,three kinds of composite SERS substrates were synthesized,and a series of SERS-based hexose detection methods were established.The quantitative detection of three hexoses was successfully realized,which extended the application of SERS technology in food detection and biosensor,and provided a new idea for the practical application of saccharide detection methods.