Rongjin Zeng

Selective visualization of endogenous hypochlorous acid in zebrafish during lipopolysaccharide-induced acute liver injury using a polymer micelles-based ratiometric fluorescent probe

The development of effective method for monitoring of endogenous hypochlorous acid (HClO) in vivo is of great significance for early diagnosis of lipopolysaccharide (LPS) induced acute liver injury. Herein, we report a polymer micelles-based ratiometric fluorescent probe (PM) based on the combination of intramolecular charge transfer (ICT) mechanism and fluorescence resonance energy transfer (FRET) principle for selective visualization of endogenous HClO in vivo. Upon the reaction of PM with HClO, the electron-donating thiourea moiety is oxidized and transformed into imidazoline moiety (electron-withdrawing group), resulting in a dramatic blue shift (˃100nm) in the fluorescence emission. The as-prepared PM shows good water dispersibility (100% aqueous media), fast response (<40s), high sensitivity (a detection limit of 1.75nM), and outstanding selectivity toward HClO over other ROS/RNS (50 equiv.). In addition, the vivo imaging experiments demonstrate that PM facilitates the visualization of endogenous HClO generation with LPS induced acute liver injury in zebrafish model.

Self-Assembled Fluorescent Bovine Serum Albumin Nanoprobes for Ratiometric pH Measurement inside Living Cells

In this work, we demonstrated a new ratiometric method for the quantitative analysis of pH inside living cells. The structure of the nanosensor comprises a biofriendly fluorescent bovine serum albumin (BSA) matrix, acting as a pH probe, and pH-insensitive reference dye Alexa 594 enabling ratiometric quantitative pH measurement. The fluorescent BSA matrix was synthesized by cross-linking of the denatured BSA proteins in ethanol with glutaraldehyde. The size of the as-synthesized BSA nanoparticles can be readily manipulated from 30 to 90 nm, which exhibit decent fluorescence at the peak wavelength of 535 nm with a pH response range of 6-8. The potential of this pH sensor for intracellular pH monitoring was demonstrated inside living HeLa cells, whereby a significant change in fluorescence ratio was observed when the pH of the cell was switched from normal to acidic with anticancer drug treatment. The fast response of the nanosensor makes it a very powerful tool in monitoring the processes occurring within the cytosol.

Selective visualization of endogenous hydrogen sulfide in lysosomes using aggregation induced emission dots

The development of novel fluorescent probes for selective detection of endogenous hydrogen sulfide (H2S) in lysosomes is imperative for elucidating its functions associated with diseases. Nevertheless, the reported fluorescent probes for lysosomal H2S detection usually undergo an aggregation caused quenching (ACQ) phenomenon in the aggregate state and cause the self-quenching of fluorescence due to the “self-absorption” effect with a small Stokes shift, which largely limited their sensing application. To solve this problem, we present the aggregation induced emission dots (AIED) for selective visualization of endogenous H2S in lysosomes via a simple co-precipitation method. It is worth noting that AIED with excellent AIE properties and large Stokes shift (∼150 nm) could effectively prevent the notorious ACQ phenomenon and the self-quenching of fluorescence. In addition, the as-prepared AIED exhibits favorable features including good water dispersibility, high sensitivity (∼43.8 nM), outstanding selectivity toward H2S over other thiols, long-term stability (>15 weeks) and good biocompatibility. Significantly, the resultant AIED with good membrane permeability has been successfully employed to visualize the endogenous H2S in lysosomes in living cells. We expect that AIED can serve as a useful tool to investigate the roles of lysosomal H2S in H2S-associated diseases.

Real-time monitoring of endogenous cysteine levels in living cells using a CD-based ratiometric fluorescent nanoprobe

AbstractA simple and readily available fluorescent probe is needed for the real-time monitoring of endogenous cysteine (Cys) levels in living cells, as such a probe could be used to study the role of Cys in related diseases. Herein, we report the first fluorescent probe based on carbon dots (CDs-FITA) for the selective and ratiometric imaging of endogenous Cys in live cells. In this ratiometric fluorescent probe, a fluorescein derivative (FITA) that recognizes Cys is covalently linked to the surfaces of carbon dots (CDs); employing CDs greatly improves the water solubility of the probe. Acrylate on FITA is selectively cleaved by Cys in aqueous solution under mild conditions, leading to a dramatic increase in the fluorescence from fluorescein. The probe therefore allows the highly selective ratiometric fluorescent detection of Cys even in the presence of various interferents. The as-prepared CDs-FITA showed excellent performance when applied to detect Cys in blood serum. In addition, due to its negligible cytotoxicity, the CDs-FITA can also be utilized for the real-time monitoring of endogenous cysteine (Cys) levels in living cells. Graphical abstractIllustration of the CD-based probe for Cys imaging in living cells

Switchable single fluorescent polymeric nanoparticles for stable white-light generation

The development of switchable white-light emitters is extremely challenging but urgently needed for various applications. We describe a class of switchable fluorescent polymeric nanoparticles (SFPNs) that can alternate their emission color among stable white, cyan, or pink. These SFPNs consist of a dye with cyan-light emission and a spiropyran (SP) derivative with photochromism. When the SP derivative is transferred to its merocyanine state, fluorescence resonance energy transfer (FRET) occurs from the cyan dye to the merocyanine one. In a rational design of transfer efficiency, a stable white-light emission is achieved. This white-light emission can be switched to the cyan-light one upon photoirradiation or pink-light one by solvent-induced swelling. Such multi-color fluorescent alternation is reversible and therefore allows for data encryption. Because of the facile synthesis, excellent long-term stability, fast photo-responsibility, high-contrast fluorescence, and outstanding switchability of these nanoparticles, we envision that they should have great potential in various applications such as high-resolution imaging, white luminescence, and data encryption.