School of Chemical and Biomedical Engineering, Nanyang Technological University, Singapore.
Anal Chem. 2011 Feb 1;83(3):1124-30. doi: 10.1021/ac1028853. Epub 2010 Dec 23.
Sialic acids with a nine-carbon backbone are commonly found at the terminal position of the glycans structures on cell membranes. The unique distribution and ubiquitous existence of sialic acid on the cell membrane make them important mediators in various biological and pathological processes. We report a new class of imaging probes based on semiconductor quantum dots with small molecular phenylboronic acid tags for highly specific and efficient labeling of sialic acid on living cells. Our results have shown that the use of these probes enables one-step labeling and continuous tracking of the cell surface sialic acid moieties without any pretreatment of living cells. The one-step procedure with fast binding kinetics and the biocompatibility of these probes make it an ideal noninvasive technology for living cell imaging. We also find that the labeled sialic acids undergo quick internalization shortly after surface binding via endocytosis and eventually distribute in the perinuclear region. This distribution pattern is consistent with the notion that sialylated glycoproteins are populated on cell membranes and recycled through the vesicular exocytotic and endocytic pathways. The superior photostability and brightness of quantum dots enable quantitative analysis of the diffusion dynamics of sialic acids, which has been a significant challenge for glycan imaging.
带有九碳主链的唾液酸通常位于细胞膜上聚糖结构的末端位置。唾液酸在细胞膜上的独特分布和普遍存在，使它们成为各种生物和病理过程中的重要介质。我们报告了一类基于半导体量子点的新型成像探针，这些探针带有小分子苯硼酸标签，可高度特异性和高效地标记活细胞上的唾液酸。我们的结果表明，使用这些探针可以一步标记和连续跟踪细胞表面的唾液酸部分，而无需对活细胞进行任何预处理。这种一步法具有快速的结合动力学和探针的生物相容性，使其成为活细胞成像的理想非侵入性技术。我们还发现，标记的唾液酸在通过胞吞作用表面结合后很快被内化，并最终分布在核周区域。这种分布模式与以下观点一致，即唾液酸化糖蛋白存在于细胞膜上，并通过囊泡胞吐和胞吞途径进行循环。量子点的优越的光稳定性和亮度使唾液酸的扩散动力学能够进行定量分析，这对于糖成像来说是一个重大挑战。
