Surface Enhanced Raman Scattering For Glucose Sensing Research

With the improvement of people’s living standard, health problems have become a hot topic for many people. Diabetes mellitus is one of the metabolic diseases that endanger human health. In the worldwide, the number of people with diabetes has been reached to 3.82 hundred million up to now, of which China is the most populous reaching to 1.14 hundred million. Diabetes is harmful for the heart, blood vessels, nerves, seriously causing death. The main factor of diabetes is the high blood sugar levels, so the level of blood sugar levels of clinical diagnosis and treatment of diabetes has important significance for treating the diabetes.Surface enhanced Raman spectroscopy(SERS) is not only used as a fingerprint identification spectrum for analyzing the structure of substance, but also has a wide range of applications in the analysis of the sensing field, which is applied to the detection for environmental pollutant, food additives, and the biological molecules such as cell, protein, glucose and so on. SERS has many advantages of sensor filed, which is included the sample without pretreatment, trace, in situ, real-time on-line detection carried out, high sensitivity, and the detection of single molecule has been realized. Thus, it can be used for detection of glucose.Due to small scattering area and the weak Raman activity of glucose, so it is difficult to directly determine the glucose Raman signals, even the SERS signal is unpredictable to detect. It is very difficult to modify on the surface of noble metal(, Ag) for glucose, and most of methods of modifying on the surface of noble metal(, Au) for glucose is physical adsorption, but the selectivity of this method is relatively poor. This paper was applied the SERS tags to realize the indirect detection of glucose. Using self assembling method to prepare the glucose SERS sensor chip and the sensor chips have interacted with containing glucose solution to produce Hydrogen peroxide and glucose acid, which can impact SERS signal of sensor chip marked the SERS tags, to achieve glucose indirect detection. The main content as the following:The silver nanoparticle self assembly film is used as a SERS substrate, on which the probe molecule has been decorated to form a glucose SERS sensor chip. On the one method is the chemical bond modification method. The 4-MPY was decorated on the Ag NPs film through the Ag-S bond. This method of covalent bonding makes acting force more reliable between the SERS tags and substrate, which is easy to implement. On the other methods of chemical modification is electrostatic force. As we known, the Ag NPs coated with citrate owning a certain negative, so glucose oxidase(GOx) molecules can be assembled on the surface of Ag NPs by electrostatic self-assembly method to form charged probe molecular marker of active substrate. This modification method does not change the physical and chemical properties of glucose oxidase, which is not easy to damage the structure of the enzyme.Ag NPs active substrate modified can be interacted with the products of glucose oxidation reaction(hydrogen peroxide, glucose acid) and the SERS signal of probes labeled on the SERS chip have been obviously changed, so we based on the interaction between the products and the Raman reporter of SERS sensor chips to indirectly realize the detection of glucose. One kind of sensing mechanism is that the Ag NPs film can be etched by the, hydrogen peroxide, thus the SERS signal of the Raman reported is weakened. The other sensing mechanism is due to produce gluconic acid which can change the potential of glucose oxidase, so that acting force weakens between the GOx and bridging molecule(PDDA), the glucose oxidase was partially dissociated down from the substrate, the probe molecule SERS signal were weakened. In our study, we respectively study the mechanisms of sensing, response time, selectivity, sensitivity, and reproducibility of the method. We have established a method for the detection of glucose based on glucose oxidation system,, and realized the high sensitivity detection of glucose.In our paper, our methods have some advantage such as the simple and easy to operate, high sensitivity, response time being faster comparing to others. Because glucose oxidase is a kind of protein, which has no toxicity to organisms, so glucose oxidase as the probe molecule for the future detection of blood glucose in vivo has done an important foundation.