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以NaYF_4为代表的上转换纳米晶作为细胞及组织标记的研究越来越热。但易团聚,水溶性、生物兼容性差,没有与生物偶联官能团等缺点限制了其应用,因而表面修饰显得尤为重要。作者通过水热和共沉淀相结合方法,制备了NaYF_4:Yb~(3+),Er~(3+)上转换纳米晶,并对其包覆二氧化硅壳层。SEM表征硅包覆前后分别为25和250 nm的单分散粒子,说明硅已成功地包覆于纳米晶表面。980 nm激光照射下,样品的PBS胶体溶液呈可视上转换绿光。上转换荧光光谱和寿命均表明二氧化硅壳层对其发光性质影响很小。圆二色谱说明蛋白分子通过戊二醛与纳米晶偶联前后的二级结构基本不变。基于硅片上的抗原抗体荧光免疫识别试验进一步验证了偶联蛋白分子的特异性,表明该上转换纳米晶适合于生物标记。
Up-conversion nanocrystals, represented by NaYF_4, are becoming more and more hot as cells and tissue markers. However, the surface modification is particularly important because of its poor reunion, water solubility, poor biocompatibility, and lack of biological coupling functional groups. The authors prepared NaYF_4: Yb ~ (3 +) and Er ~ (3+) upconverting nanocrystals by a combination of hydrothermal and coprecipitation methods, and coated them with silica shell. SEM characterization of monodisperse particles of 25 and 250 nm respectively before and after the silicon coating shows that the silicon has been successfully coated on the surface of the nanocrystal. Under the 980 nm laser irradiation, the PBS colloidal solution of the sample was visually up-converted green light. Both up-conversion fluorescence spectra and lifetime show that the silica shell has little effect on its luminescence properties. Circular dichroism shows that the secondary structure of protein molecules before and after conjugation of glutaraldehyde and nanocrystals is basically unchanged. The specificity of the coupled protein molecules was further verified by fluorescence immunoassay based on the antigen on the silicon chip, indicating that the up-converting nanocrystals are suitable for biomarker.