School of Biomedical Engineering, Science and Health Systems, Drexel University, 3141 Chestnut Street, Bossone 718, Philadelphia, PA 19104, USA.
Analyst. 2013 Nov 12;138(24):7316-25. doi: 10.1039/c3an01198d.
Quantum dots (QDs) are photoluminescent nanoparticles that can be directly or indirectly coupled with a receptor such as an antibody to specifically image a target biomolecule such as an antigen. Recent studies have shown that QDs can be directly made at room temperature and in an aqueous environment (AQDs) with 3-mercaptopropionic acid (MPA) as the capping ligand without solvent and ligand exchange typically required by QDs made by the organic solvent routes (OQDs). In this study, we have synthesized CdSe AQDs and compared their conjugation efficiency and imaging efficacy with commercial carboxylated OQDs in HT29 colon cancer cells using a primary antibody-biotinylated secondary antibody-streptavidin (SA) sandwich. We showed that the best imaging condition for AQDs occurred when one AQD was bound with 3 ± 0.3 SA with a nominal SA/AQD ratio of 4 corresponding to an SA conjugation efficiency of 75 ± 7.5%. In comparison, for commercial CdSe-ZnS OQDs to achieve 2.7 ± 0.4 bound SAs per OQD for comparable imaging efficacy a nominal SA/OQD ratio of 80 was needed corresponding to an SA conjugation efficiency of 3.4 ± 0.5% for CdSe-ZnS OQDs. The more than 10 times better SA conjugation efficiency of the CdSe AQDs as compared to that of the CdSe-ZnS OQDs was attributed to more capping molecules on the AQD surface as a result of the direct aqueous synthesis. More capping molecules on the AQD surface also allowed the SA-AQD conjugate to be stable in cell culture medium for more than three days without losing their staining capability in a flowing cell culture medium. In contrast, SA-OQD conjugates aggregated in cell culture medium and in phosphate buffer saline solution over time.
量子点（QD）是可以直接或间接地与受体（如抗体）偶联以特异性地成像靶生物分子（如抗原）的荧光纳米颗粒。最近的研究表明，在室温下并且在以巯基丙酸（MPA）作为封端配体的水性环境（AQD）中，可以直接合成量子点，而无需通常由有机溶剂路线（OQD）合成量子点所需的溶剂和配体交换。在这项研究中，我们合成了 CdSe AQD，并在 HT29 结肠癌细胞中使用针对生物素化的二级抗体的一抗-生物素化二级抗体-链霉亲和素（SA）夹心，比较了它们与商业羧基化 OQD 的偶联效率和成像效果。我们表明，AQD 的最佳成像条件是一个 AQD 与 3 ± 0.3 SA 结合，SA/AQD 比为 4，对应于 75 ± 7.5%的 SA 偶联效率。相比之下，对于商业 CdSe-ZnS OQD，要达到 2.7 ± 0.4 个结合的 SAs/OQD 以获得可比的成像效果，需要 80 的名义 SA/OQD 比，对应于 3.4 ± 0.5%的 CdSe-ZnS OQD 的 SA 偶联效率。与 CdSe-ZnS OQD 相比，CdSe AQD 的 SA 偶联效率高 10 倍以上，这归因于直接水性合成导致 AQD 表面有更多的封端分子。AQD 表面的更多封端分子也允许 SA-AQD 缀合物在细胞培养液中稳定存在超过三天，而不会在流动的细胞培养液中失去其染色能力。相比之下，SA-OQD 缀合物随时间在细胞培养液和磷酸盐缓冲盐溶液中聚集。
