In Vitro Tracking of Human Umbilical Vein Endothelial Cells Using Ultra-Sensitive Quantum Dot-Embedded Silica Nanoparticles

Abstract

The nanoscale spatiotemporal resolution of single-particle tracking (SPT) renders it a powerful method for exploring single-molecule dynamics in living cells or tissues, despite the disadvantages of using traditional organic fluorescence probes, such as the weak fluorescent signal against the strong cellular autofluorescence background coupled with a fast-photobleaching rate. Quantum dots (QDs), which enable tracking targets in multiple colors, have been proposed as an alternative to traditional organic fluorescence dyes; however, they are not ideally suitable for applying SPT due to their hydrophobicity, cytotoxicity, and blinking problems. This study reports an improved SPT method using silica-coated QD-embedded silica nanoparticles (QD2), which represent brighter fluorescence and are less toxic than single QDs. After treatment of QD2 in 10 μg/mL, the label was retained for 96 h with 83.76% of labeling efficiency, without impaired cell function such as angiogenesis. The improved stability of QD2 facilitates the visualization of in situ endothelial vessel formation without real-time staining. Cells retain QD2 fluorescence signal for 15 days at 4 °C without significant photobleaching, indicating that QD2 has overcome the limitations of SPT enabling long-term intracellular tracking. These results proved that QD2 could be used for SPT as a substitute for traditional organic fluorophores or single quantum dots, with its photostability, biocompatibility, and superior brightness.

The utilization of quantum dot labeling as a burgeoning technique in the field of biological imaging

“… 46,47 These nanoscale semiconductor crystals stand out in the field of biological imaging because of their excellent brightness and long-term stability. 48 Quantum dots emit light with wide absorption and narrow emission spectrum, which makes it possible to track multiple tags in complex biological systems at the same time. 49 By precisely adjusting their size, researchers can obtain the required specific fluorescence characteristics, which can be used in the dynamic observation of intracellular molecules, the study of intracellular molecular interactions, and revealing the mechanism of intracellular transport.…”

Silica Encapsulation of Hydrophobic Optical NP-Embedded Silica Particles with Trimethoxy(2-Phenylethyl)silane

“…Finally, the silica shell provides flexibility for surface modification. Silanol groups can easily react with various silanol precursors with functional groups, such as amine or thiol groups; therefore, various functional groups like amine or thiol groups can be introduced with other silylether-containing compounds, such as 3-aminopropyl triethoxysilane (APTES), 3-chloropropyl trimethoxysilane (CPTMS), 3-glycydoxypropyl trimethoxysilane (GPTS), or 3-mercaptopropyl trimethoxysilane (MPTS) [ 12 , 13 , 14 , 15 ].…”

Functional Optical Nano/Micromaterials

“…SiO 2 @QDs labeling efficiency was retained for 96 h with minimal cytotoxicity and did not impair cell function. This technique was successfully used to visualize in situ endothelial vessel formation without real-time staining [ 18 ].…”