Xiao Peng He

Fluorescent glycoprobes: a sweet addition for improved sensing

The development of small-molecule fluorescent probes for the detection of ions and biomacromolecules and for cellular and in vivo imaging has been a very active research area. Nevertheless, many problems exist for traditional probes including their poor water solubility, toxicity and the inability to target specific tissues. Because of the enhanced water solubility, biocompatibility and targeting ability for specific cells, there has been an emerging movement to use carbohydrates as either the backbone or as a warhead to decorate conventional fluorescent probes, producing glycoprobes with enhanced properties. This feature article provides an overview of recently developed glycoprobes for ion and protein detection as well as targeted (receptor targeting) cellular imaging and theranostics. Here, we summarise the tactics for preparing small molecular glycoprobes and their supramolecular 2D material composites.

Colorimetric and plasmonic detection of lectins using core-shell gold glyconanoparticles prepared by copper-free click chemistry.

This study describes the simple preparation of core-shell glycosyl gold nanoparticles (AuNPs) using stepwise, copper-free click chemistry-promoted self-assembly. The as-formed glyco-AuNPs can be used for the selective detection of sugar-lectin interactions, which are vital to many important physiological and pathological processes. The approach uses AuNPs as bioprobes since they produce, sensitively, changes in both color visible to the naked eye and surface plasmon resonance (SPR), on aggregation. Strain-promoted click reaction of an azido galactoside with a lipid cyclooctyne affords a galactolipid that can be embedded into polyethylene glycol (PEG)-coated AuNP via self-assembly. Subsequently, using naked-eye and plasmon resonance scattering spectroscopy, we were able to observe the colorimetric and plasmonic variations of the glyco-AuNPs, respectively, in the presence of a selective lectin over other proteins.

Receptor-targeting fluorescence imaging and theranostics using a graphene oxide based supramolecular glycocomposite

Intercellular glycoligand-receptor interactions are implicated in a number of disease-related processes. Effective tools that target these receptors may facilitate disease theranostics. However, owing to their low binding affinity, multivalent presentation of glycoligands is needed to increase the avidity with transmembrane receptors. While previous strategies focus on the covalent coupling of glycoligands to a synthetic backbone, we show here that the use of graphene oxide (GO) greatly enhances the cellular and tissue imaging ability of a small-molecule fluorescence glycoprobe. We determine that GO with an optimum size may serve as a clustering platform to reinforce the interaction of the glycoprobe with its selective receptor on a cancer cell. This phenomenon has been consistently observed with the xenograft tissue of a tumor-bearing mouse. Using this principle we have further constructed a supramolecular glycocomposite by co-assembling the glycoprobe and an anticancer drug onto a single GO surface. In addition to imaging ability, this material displays improved toxicity for liver cancer cells that over express the glycoprotein receptor, when compared to the control cells.

A supramolecular pyrenyl glycoside-coated 2D MoS2 composite electrode for selective cell capture

Here we demonstrate the simple construction and characterization of a pyrenyl glycoside-coated 2D MoS2 material composite capable of selectively capturing proteins and live cells on an electrode, as determined by differential pulse voltammetry.

Supramolecular Polymer Dot Ensemble for Ratiometric Detection of Lectins and Targeted Delivery of Imaging Agents

A supramolecular, polymer-dot-based ensemble has been developed for the ratiometric detection of lectins and targeted delivery of glycoprobes. Self-assembly between a blue-emitting polymer dot and a red-emitting glycoprobe, results in an ensemble that shows red emission upon excitation of the polymer dot because of Förster resonance energy transfer. Resulting in ratiometric detection of lectins in buffer solution as well as targeted delivery of the glycoprobe to cells that highly express a sugar receptor. Unlike conventional systems where both the agent and vector are codelivered intracellularly, our ensemble developed here shows a receptor-controlled dissociation on the cell membrane.

Erratum:Glycosylation enhances the aqueous sensitivity and lowers the cytotoxicity of a naphthalimide zinc ion fluorescence probe (Chem. Commun. (2015) DOI: 10.1039/c5cc04357c)

With this research we demonstrate that glycosylation of a naphthalimide zinc ion probe, using click chemistry, leads to an improvement of the aqueous sensitivity, working pH range and targeting ability for specific cells, together with significantly reduced cytotoxicity.