Direct Observation of Nanoparticles within Cells at Subcellular Levels by Super-Resolution Fluorescence Imaging

Abstract

Direct observation of nanoparticles with high spatial resolution at subcellular levels is of great importance to understand the nanotoxicology and promote the biomedical applications of nanoparticles. Super-resolution fluorescence microscopy can break the diffraction resolution limit to achieve spatial resolution of tens of nanometers, making it ideal for highly accurate observation of nanoparticles in the cellular world. In this study, we introduced the employment of super-resolution fluorescence imaging for monitoring nanoparticles within cells. Carbocyanine dyes Alexa Flour 647 labeled mesoporous silica nanoparticles (designated as MSNs-AF647) were constructed as the super-resolution imaging nanoplatform in this work as proof of concept. The MSNs-AF647 were incubated with Hela cells, and the nanoparticles within cells were further monitored by super-resolution fluorescence microscopy. The fluorescence images of MSNs-AF647 within cells captured with the super-resolution fluorescence microscopy showed a much higher spatial resolution than that obtained using conventional fluorescence microscopy, showing that super-resolution fluorescence images can provide more accurate information to locate the nanoparticles at the subcellular levels. Moreover, other functional molecules can be easily loaded into the MSNs-AF647 super-resolution imaging nanoplatform, which suggested that super-resolution fluorescence imaging can further be applied to various bioimaging-related areas, such as imaging-guided therapy, with the aid of the MSNs-AF647 nanoplatform. This study demonstrates that super-resolution fluorescence microscopy offers a highly accurate method to study nanoparticles in the cellular world. We anticipate this strategy may further be applied to research areas such as studying the nanotoxicology and optimization of nanoparticle-based bioprobes or drugs by designing new nanostructured materials with multifunctional properties based on MSNs-AF647.

Mesoporous Silica Particles as Drug Delivery Systems—The State of the Art in Loading Methods and the Recent Progress in Analytical Techniques for Monitoring These Processes

“…In comparison to the standard wide-field methods with a diffraction limit of 250 nm, STORM offers impressive improvement of performance (Figure 10). Recently, STORM was employed for direct observation of nanoparticles within cells with high spatial resolution [155]. In order to characterize processes in situ, confocal laser scanning microscopy (CLSM) combined with microfluidics (MFs) was applied for monitoring of protein adsorption onto silica microparticles.…”

Using intracellular plasmonics to characterize nanomorphology in human cells

“…Light microscopy can be used to visualize both NPs and their surrounding environment; however, only clusters of particles can be visualized 5 . Recently, Chen et al 11 developed a superresolution fluorescence imaging technique with a spatial resolution of 10 nm, well below the light diffraction limit. They used this technique to detect silica nanoparticles in HeLa cells, which they visualized in lysosomes and mitochondria.…”

Protein-, polymer-, and silica-based luminescent nanomaterial probes for super resolution microscopy: a review

“…11 . 66 Silica nanoparticles with a metal core show increased brightness due to metal enhanced fluorescence (MEF), which may also play a role in causing photoblinking behavior in dyes that do not otherwise exhibit this behavior, as observed by our group 23,25 and Lu et al 17 when self-blinking nanoparticles were fabricated. The advantages of these self-blinking nanoparticles are that only a single light source is needed, rather than the two lasers normally needed for single particle localization-based super resolution methods, and that the imaging buffers normally required for these methods are not needed to cause the blinking behavior.…”