Surface-enhanced Raman Spectroscopy And Its Application In Living Cells

Surface-enhanced Raman scattering (SERS) means that when the substance placed on or near the surface of metal nanostructures, its Raman scattering signal intensity can be greatly enhanced. SERS is a spectroscopic technique which is of high sensitivity, low aqueous interference, little damage for cell. These properties enable SERS to be widely used in biological system research field, especially for the single living cell analysis. Herein, we will introduce our work in this field from several kinds of the fabrication of metallic nanoparticles to SERS application in nanoparticles and the interaction of red blood cells. The purpose is to combine Raman spectroscopy technology with nanometer technology, fully making use of the complementary advantages between the disciplines, taking the unique advantages of SERS spectroscopy, and realizing the application of innovation and breakthrough. The main contents are listed as follows:1. Use sodium citrate reduction method to fabricate the gold and silver nanoparticles, and fabricate the gold-core silver-shell nanoparticles (Ag@AuNPs) using the gold nanoparticles as the seed. On the basis, we try to study the fabrication of gold nanorods and gold-core silver-shell nanorods. The surface plasmon resonance peak of nanoparticles with different sizes and stability were studied by using UV-Vis spectroscopy. Moreover, the SERS enhancement of Raman dye crystal violet (CV) with different nanoparticles was studied, and the result will facilitate the SERS applications in single living cell analysis.2. Study the relationship of Ag@AuNPs to CV signal enhancement effect and time. Use the new nanomaterials Ag@AuNPs as Raman enhancement substrate, SERS spectroscopy of CV using 785nm laser excitation, statistical spectral characteristic peak intensity trends. The spectra analysis results show the intensity of CV peaks 725、801、914、1177、1392.1588cm-1 increase with time (0-30min), essentially unchanged with time after Reached a plateau (30-36min). Thus, we know that the best fastest measurement time for SERS spectrum of CV was 30min, this greatly improves the period of related SERS studies.3. Tracking the process which erythrocyte endocytoses Ag@AuNPs wrapped in CV with laser tweezers Raman technique is studied:every 20 seconds we imprisoned erythrocytes by optical tweezers, and then collected the Raman spectra of both erythrocytes and the adjacent solutions. Results show the spectra of erythrocytes collected included the characteristic peaks of belonging to erythrocyte and CV. The intensity of peaks 1001,1128,1213cm-1 of erythrocyte and peaks 915,1177,1370,1586,1619 cm-1 of CV increases with time. It means, in the process of co-culture with erythrocytes and nanoparticles, Ag@AuNPs could increase the signal of erythrocyte and nanoparticles were accumulated in erythrocytes. By analyzing the spectra D-value between erythrocytes and its adjacent solutions, we found that 913,1179, 1586cm-1 spectral characteristic peaks belonging to CV changed like cosine with time. This indicates that the nanoparticles in erythrocyte decreased after the first increment and then increased again. We can calculate the time range where nanoparticles began to enter erythrocyte and its speed, and the rate of lysosome degrading nanoparticles wrapped in CV. This study shows that SERS spectroscopy can provide a new idea and an experimental method for the study of foreign objects (such as nanoparticles, drugs) into to cells.