Zhongwei Xue

A selective fluorogenic sensor for visual detection of nitrite

Determination of nitrite levels is of substantial interest in many applications from monitoring drinking water quality to clinical diagnosis, etc. N-(Rhodamine B)-lactam-o-phenylenediamine (RB-PDA) was identified from a panel of rhodamine-lactams for fluorogenic and visual detection of nitrite in aqueous media via analyte triggered formation of highly fluorescent and deep colored species.

Chromo-fluorogenic detection of aldehydes with a rhodamine based sensor featuring an intramolecular deoxylactam

A chromogenic and fluorogenic detection of aldehydes was achieved via analyte triggered opening of the deoxylactam of N-(rhodamine B)-deoxylactam-ethylenediamine (dRB-EDA). The utility of the sensor was demonstrated by fluorescent labeling of aldehyde-displaying sialoproteins on cell surfaces.

A rhodamine-benzimidazole based sensor for selective imaging of acidic pH

N-(Rhodamine B)-benzimidazole (RB-IM), featuring an intramolecular spiro-benzimidazole, was developed for selective sensing of protons via opening of the spiro-ring to give fluorescent and colored species. The utility of RB-IM was demonstrated by imaging of lysosomes in live cells and staining of the intestine of zebrafish.

Defining cancer cell bioenergetic profiles using a dual organelle-oriented chemosensor responsive to pH values and electropotential changes

Cell fate is largely shaped by combined activity of different types of organelles, which often feature functionally critical parameters that succumb to pathological inducers. We herein report the analysis of cell bioenergetic profiles with a dual organelle-oriented chemosensor (RC-AMI), partitioning in mitochondria to give blue fluorescence and in lysosomes to give red fluorescence. Responsive to lysosomal pH and mitochondrial transmembrane potential (ΔΨm), two parameters crucial to cell bioenergetics, RC-AMI enables dual colored reporting of lysosomal acidity and ΔΨm, revealing upregulated ΔΨm and imbalance dramatically shifted favoring ΔΨm over lysosomal acidity in cancer cells whereas the tendency is reversed in starved cells. Complementing classical homo-organelle-specific sensors, this dual organelle-oriented and fluorescently responsive probe offers a new tool to detect imbalance between lysosomal acidity and mitochondrial ΔΨm, an index critical for cancer bioenergetics.

Centrifugation aided highly sensitive detection of nitrite with a dye-silica conjugate featuring cleavable linkages.

Rhodamine-silica nanocomposite bridged by a cleavable linker was used for highly sensitive nitrite detection via analyte triggered release of rhodamine from silica particles. Centrifugal removal of pristine nanoconjugate from the assay medium effectively decreased background signals in the supernatant whereas rhodamine unleashed from silica platform is retained in the supernatant, enabling facile detection of nitrite with an assay limit of 50 nM which is 400 folds lower than legislated maximum contaminant levels of nitrite in drinking water. Assays based on small molecular chemosensors are often compromised by their intrinsic fluorescence signals and low aqueous compatibility. The performance of water compatible rhodamine-silica nanocomposite suggests broad analytical potentials of centrifugal nanoparticulate systems with dyes conjugated via appropriate cleavable linkers.

Bifunctional Super-resolution Imaging Probe with Acidity-Independent Lysosome-Retention Mechanism

Spatiotemporal imaging is of enormous use to explore organelle biology, necessitating organelle-tracing techniques reliable in varied cell stress. We herein reported lysosomal imaging using rhodamine-X-integrated sialic acid (ROXSA), which is stably maintained in lysosomes irrespective of lysosomal pH changes. Exhibiting bright fluorescence and superior photostability, ROXSA enables 120 h continual tracking of fusion/fission of lysosomes and mitochondrion-lysosome interaction in mitophagy. Relative to conventional acidotropic probes prone to dissipation from stressed lysosomes, ROXSA offers a new route for long-term tracking of stressed lysosomes relevant to diverse pathological conditions.

Organelle-Directed Staudinger Reaction Enabling Fluorescence-on Resolution of Mitochondrial Electropotentials via a Self-Immolative Charge Reversal Probe

Organelles often feature parameters pertinent to functions and yet responsive to biochemical stress. The electropotential across the mitochondrial membrane (ΔΨm) is a crucial mediator of cell fates. Herein we report a bioorthogonal reaction enabled fluorescence-on probing of ΔΨm alterations featuring anionic fluorescein-triphenylphosphonium diad (F-TPP), which is released via intramitochondria Staudinger reaction triggered self-immolation of o-azidomethylbenzoylated F-TPP. Compared to classical cationic mitochondria-specific dyes, F-TPP is hydrophilic and negatively charged. Effectively discerning ΔΨm changes upon diverse stress inducers, the organelle-directed bioorthogonal imaging strategy offers unprecedented choices to probe mitochondrial biology with functional molecules that are otherwise inaccessible via physiological organelle-probe affinity.