Fluorescent Probe For Live Cell Imaging Research Articles

Recent advances in Si-rhodamine-based fluorescent probes for live-cell imaging.

Fluorescence imaging is a powerful technique for visualizing biological events in living samples with high temporal and spatial resolution. Fluorescent probes emitting far-red to near infrared (NIR) fluorescence are particularly advantageous for in vivo imaging due to their high tissue permeability and low autofluorescence, as well as their suitability for multicolor imaging. Among the far-red to NIR fluorophores, Si-rhodamine is one of the most practical fluorophores for the development of tailor-made NIR fluorescent probes because of the relative ease of synthesis of various derivatives, the unique intramolecular spirocyclization behavior, and the relatively high water solubility and high photostability of the probes. This review summarizes these features of Si-rhodamines and presents recent advances in the synthesis and applications of far-red to NIR fluorescent probes based on Si-rhodamines, focusing on live-cell imaging applications such as fluorogenic probes, super-resolution imaging and dye-protein hybrid-based indicators.

A sustainable green synthesis of functionalized biocompatible carbon quantum dots from Aloe barbadensis Miller and its multifunctional applications

Herein, we demonstrated a sustainable green approach for the preparation of fluorescent biocompatible carbon quantum dots by microwave-assisted reflux synthesis from Aloe barbadensis Miller (Aloe vera) extract. The Transmission Electron Microscopic images reveal that the as-prepared CQDs are spherical with less than 5nm in size. The CQDs are amorphous, showed an excitation-independent behaviour, emitted blue fluorescence and have a fluorescence quantum yield of 31%. The presence of -OH groups contributed to the blue emission and helped CQDs to disperse uniformly in an aqueous solution. The prepared CQDs were employed as a photocatalyst for the environmental remediation to degrade the anionic dye, eosin yellow under visible light irradiation. The results showed that the CQDs exhibited excellent photocatalytic efficiency of 98.55% within 80min and a 100% efficiency within 100min. Further, the cytotoxic properties of as-prepared CQDs are investigated in the MCF-7 breast cancer cell line using MTT assay. The results demonstrated a notable reduction in cell viability in a dose-subjected manner, and the cell viability decreased to 50% (IC50) at a concentration of 52.2±1.35μg/mL. Furthermore, cellular internalization of CQDs in breast cancer cells is studied. As expected, CQDs are found to internalize by the cancer cells with blue emission as revealed by fluorescence microscope. In the end, CQDs in human breast cancer cells demonstrate the anti-proliferative effect and are found to be an impressive fluorescent probe for live-cell imaging, paving a path for its potential biomedical applications.

Silafluorene as a promising core for cell-permeant, highly bright and two-photon excitable fluorescent probes for live-cell imaging

In this study, we report the synthesis, linear and non-linear photophysical studies and live-cell imaging of two two-photon activatable probes based on a silafluorene core: SiFluo-V and SiFluo-L. Thanks to their quadrupolar (A-π-D-π-A) design, these probes exhibit respectively good to impressive two-photon cross-sections (from 210 GM to 2150 GM). TD-DFT calculations support the experimental evidence that SiFluo-L displays far better two-photon absorption properties than SiFluo-V. Moreover, SiFluo-L possesses all requirements for bioimaging as it is water soluble, cell-permeant and presents a low cytotoxicity (IC80 ≥ 10 μM). It labels mitochondria in live-cell imaging at low laser power with high brightness, contrast and photostability. This study demonstrates that silafluorene is a promising core to develop new two-photon fluorophores for live-cell imaging.

Self-Assembly of Highly Stable Zirconium(IV) Coordination Cages with Aggregation Induced Emission Molecular Rotors for Live-Cell Imaging.

The self-assembly of highly stable zirconium(IV)-based coordination cages with aggregation induced emission (AIE) molecular rotors for in vitro bio-imaging is reported. The two coordination cages, NUS-100 and NUS-101, are assembled from the highly stable trinuclear zirconium vertices and two flexible carboxyl-decorated tetraphenylethylene (TPE) spacers. Extensive experimental and theoretical results show that the emissive intensity of the coordination cages can be controlled by restricting the dynamics of AIE-active molecular rotors though multiple external stimuli. Because the two coordination cages have excellent chemical stability in aqueous solutions (pH stability: 2-10) and impressive AIE characteristics contributed by the molecular rotors, they can be employed as novel biological fluorescent probes for in vitro live-cell imaging.

Monitoring Lipid Droplet Dynamics in Living Cells by Using Fluorescent Probes.

We have developed three types of lipid droplet (LD)-specific fluorescent probes for live-cell imaging, Lipi-Blue, Lipi-Green, and Lipi-Red, which exhibit fluorescence upon being incorporated into LDs both of living and of fixed cells. These Lipi-probes are LD-specific probes that contain a pyrene or perylene group as a fluorescent scaffold and can be used to observe dynamics of LD in live cells and also interrelations with other organelles by simultaneous staining with multiple organelle-specific probes. Additionally, Lipi-Blue and Lipi-Green allow monitoring LDs in live cells even for 48 h after the staining. Here we show that newly formed LDs and previously existed LDs can be separately monitored in a single cell by using these probes and that intercellular transfer of whole LDs is observed in KB cells, but not in HepG2 cells under the same culturing condition. These findings indicate that newly developed LD-specific probes are useful to analyze the dynamics of LDs in live cells.

ExTzBox: A Glowing Cyclophane for Live-Cell Imaging.

The ideal fluorescent probe for live-cell imaging is bright and non-cytotoxic and can be delivered easily into the living cells in an efficient manner. The design of synthetic fluorophores having all three of these properties, however, has proved to be challenging. Here, we introduce a simple, yet effective, strategy based on well-established chemistry for designing a new class of fluorescent probes for live-cell imaging. A box-like hybrid cyclophane, namely ExTzBox·4X (6·4X, X = PF6-, Cl-), has been synthesized by connecting an extended viologen (ExBIPY) and a dipyridyl thiazolothiazole (TzBIPY) unit in an end-to-end fashion with two p-xylylene linkers. Photophysical studies show that 6·4Cl has a quantum yield ΦF = 1.00. Furthermore, unlike its ExBIPY2+ and TzBIPY2+ building units, 6·4Cl is non-cytotoxic to RAW 264.7 macrophages, even with a loading concentration as high as 100 μM, presumably on account of its rigid box-like structure which prevents its intercalation into DNA and may inhibit other interactions with it. After gaining an understanding of the toxicity profile of 6·4Cl, we employed it in live-cell imaging. Confocal microscopy has demonstrated that 64+ is taken up by the RAW 264.7 macrophages, allowing the cells to glow brightly with blue laser excitation, without any hint of photobleaching or disruption of normal cell behavior under the imaging conditions. By contrast, the acyclic reference compound Me2TzBIPY·2Cl (4·2Cl) shows very little fluorescence inside the cells, which is quenched completely under the same imaging conditions. In vitro cell investigations underscore the significance of using highly fluorescent box-like rigid cyclophanes for live-cell imaging.

Rational design of reversible fluorescent probes for live-cell imaging and quantification of fast glutathione dynamics.

Alterations in glutathione (GSH) homeostasis are associated with a variety of diseases and cellular functions, and therefore, real-time live-cell imaging and quantification of GSH dynamics are important for understanding pathophysiological processes. However, existing fluorescent probes are unsuitable for these purposes due to their irreversible fluorogenic mechanisms or slow reaction rates. In this work, we have successfully overcome these problems by establishing a design strategy inspired by Mayr's work on nucleophilic reaction kinetics. The synthesized probes exhibit concentration-dependent, reversible and rapid absorption/fluorescence changes (t1/2 = 620 ms at [GSH] = 1 mM), as well as appropriate Kd values (1-10 mM: within the range of intracellular GSH concentrations). We also developed FRET-based ratiometric probes, and demonstrated that they are useful for quantifying GSH concentration in various cell types and also for real-time live-cell imaging of GSH dynamics with temporal resolution of seconds.