Lactose In Biological Samples Monitored By Raman Spectroscopy And Its Application

Lactose is widespread natural disaccharides, and often is used carbon source in microorganism culture. Lactose content affects the microbial growth and metabolism especially the real-time monitoring in mediums. Therefore, it is great important for rapid determination of lactose content in biological samples. In similar, the lactose application in many areas has also been paid close attention to rapid determination of lactose content. Currently, a lot of lactose detection methods have been reported, but Raman spectroscopy as a simple, rapid and real-time method has many advantage. To achieve the rapid determination of lactose in microbiological media, crystal violet as the internal standard, this paper studied the relationship between lactose concentration and the peak after have researched the characteristic peak of lactose. At the same time, this paper research the high sensitive method to detection lactose by surface enhancement Raman spectroscopy, which include the uniform, good stability silver nanoparticles were prepared, and indirect detect lactose method in biological samples was been explored by using SERS- reactive molecules.Firstly, in out of the influence of different sugars, nitrogen sources, vitamins and inorganic salts, this experiment chose internal analysis for the routine Raman spectra method of lactose content, which realized the specificity detection of lactose content by normal Raman spectra in biological sample. The COC stretching vibration peak(1085 cm-1) was selected as the characteristic peak for lactose determination while the crystal violet peak(1,173 cm-1) was selected as the internal standard peak in our experiments. Our developed method allowed the detection of lactose at 0.028–0.1 mol/L with a limit of detection of 0.019 mol/L. This method obtained RSD was not greater than 3.38 % that showed has good precision; and recoveries were 89.64 ~ 109.82 % that showed has good recovery rate. It was successfully applied for detecting real biological sample. In medium, the average of lactose content is 1.01%, the recoveries are 89.81~104.53%, and RSD is 1.92%; in milk, the average of lactose content is 4.70%, the recoveries are 90.59~110.00%,and RSD is 2.89%.Next, the fast and sensitive detection lactose method is widely attended in the biological sample and surface enhanced Raman scattering spectrum is a very useful enhancement tool to detect Raman signal. So, preparing uniformity and stability basements are one of the keys to improve Raman signal. The sodium citrate as reducing agent used to prepare silver nanoparticles that are uniform particle size distribution, high concentration and have the same shape in our experiment. The average size of silver sol is around 50 nm, and has high enhancement effect. To study the silver nanoparticles’ temperature and reduction time conditions by UV-Vis spectrum, the researches show that the best temperature is 140 ℃ and the best time is 15 min.Finally, this study chose benzoic acid, benzene acid, hydroquinone and salicylic acid as SERS-active molecules to detect lactose. The four organic molecules all contain benzene ring aromatic. When they respectively combined with silver nano sol have been prepared, they all got great high Raman surface enhancement effect. Then, to explore the indirect detection of lactose content in biological samples, we added appropriate concentration of lactose into mixed solution. Through this experiment can provide a new thought to further lactose content detection that should rapid, sensitive, cheap and real-time in biological samples.