Molecular Engineering of Glycoaptamer Dual-Target Radionuclide Probes for PET/CT Imaging of Triple-Negative Breast Cancer

Triple-negative breast cancer (TNBC) is one of the most malignant cancer types, characterized by a lack of efficient diagnostic and treatment methods in clinical practice. The development of effective targeted diagnosis and treatment for TNBC has become an important research focus. Here, we report the first proof-of-concept evidence of a glycoaptamer dual-target radionuclide probe (GDRP) for positron emission tomography/computed tomography (PET/CT) imaging of TNBC. The GDRP was created through precise molecular engineering of the aptamer AS1411, combined with three mannose ligands. The GDRP exhibited significantly increased serum stability and a high affinity for TNBC cells through a dual targeting mode. The advantages of our developed GDRP were further demonstrated by its excellent in vivo PET/CT dynamic imaging performance, featuring a long imaging window and high spatiotemporal resolution. This flexible method allows for the preparation of glycosylated functional nucleic acid molecular probes with high serum stability and tumor specificity. We anticipate that this PET/CT molecular probe will expand the development of glycoaptamer-based radioactive drugs and provides molecular tools for the clinical diagnosis of TNBC.

Emergence of Fluorescent Glycodots for Biomedical Applications

Carbohydrate-functionalized quantum dots exhibit excellent physical characteristics and enhance the steric interaction with biological cells and tissues. Glycoconjugation of quantum dots promotes aqueous solubility, stability, and reduced immunogenicity. Carbohydrate-protein interactions are involved in various vital processes and provide insight into cellular recognition, cell-to-cell communication, pathogenicity, antigen-antibody recognition, and enzymatic action. Quantum dots are fluorescent materials with rich quantum mechanical and unique optical properties, making them valuable for biomedical applications. Recent advancements in quantum dot materials as biomedical tools have led to the development of carbohydrate-conjugated glyco-functionalized quantum dots. These innovations promise application as nanocarriers, imaging agents, fluorescent probes, and theranostics. This review provides an overview of glyco nanotechnology, emphasizing carbohydrate-conjugated metal-, silicon-, and carbon-based quantum dots as glyco dots and their potential biomedical uses. We hope that this study will address the gap in this field and provide a more precise understanding of the subject.

Carbohydrate-Functionalized Anthracene Carboximides as Multivalent Ligands and Bio-Imaging Agents

Anthracene carboximides (ACIs) conjugated with gluco-, galacto- and mannopyranosides are synthesized, by glycosylation of N-hydroxyethylanthracene carboximide acceptor with glycosyl donors. Glycoconjugation of anthracene carboximide increases the aq. solubility by more than 3-fold. The glycoconjugates display red-shifted absorption and emission, as compared to anthracene. Large Stokes shift (λabs/λem=445/525 nm) and high fluorescence quantum yields (Φ) of 0.86 and 0.5 occur in THF and water, respectively. The ACI-glycosides undergo facile photodimerization in aqueous solutions, leading to the formation of the head-to-tail dimer, as a mixture of syn and anti-isomers. Solution phase and solid-state characterizations by dynamic light scattering (DLS), microscopic imaging by atomic force (AFM) and transmission electron (TEM) microscopies reveal self-assembled vesicle structures of ACI glycosides. These self-assembled structures act as multivalent glycoclusters for ligand-specific lectin binding, as evidenced by the binding of Man-ACI to Con A, by fluorescence and turbidity assays. The conjugates do not show cellular cytotoxicity (IC50) till concentrations of 50 μM with HeLa and HepG2 cell lines and are cell-permeable, showing strong fluorescence inside the cells. These properties enable the glycoconjugates to be used in cell imaging. The non-selective cellular uptake of the glycoconjugates suggests a passive diffusion through the membrane.

Linker length-dependent morphologies in self-assembled structures of anthracene glucosides

Anthracenemethyl glucosides, that possess ethylene glycol linkers connecting the glucoside with anthracene moiety, are studied herein. Koenigs-Knorr glycosylation of ethylene glycol-tethered anthracene with acetobromo glucose, followed by removal of the protecting groups, lead to the facile formation of the target glucosides. Aq. solutions of these anthracene glucosides readily undergo self-assembly, with critical aggregation concentration varying between 0.4 and 1 mM, depending on the linker, being ethylene-, di- and tetraethylene glycol, as assessed by photophysical evaluations. Circular dichroism spectra show chiral self-assembled structures for these glucosides in solution, from which a left-handed chirality is adjudged. Morphologies of the self-assembled structures of these glucosides are controlled by the linker length. With the ethylene glycol linker, vesicles form initially, around which tendrils start to grow as the concentration of the glucoside is increased. Whereas, di- and tetraethylene glycol-spaced glucosides prefer agglomerated fractal-like structures, as assessed by microscopies. The aggregation phenomenon in the latter glucosides appears to be under the non-equilibrium-driven, dissipative control.

Green Synthesis of Carboxymethyl Chitosan-Based CuInS2 QDs with Luminescent Response toward Pb2+ Ion and Its Application in Bioimaging

Polysaccharide-based QDs have attracted great attention in the field of biological imaging and diagnostics. How to get rid of the high heavy metal toxicity resulting from conventional Cd- and Pb-based QDs is now the main challenge. Herein, we offer a simple and environmentally friendly approach for the "direct" interaction of thiol-ending carboxymethyl chitosan (CMC-SH) with metal salt precursors, resulting in CuInS2 QDs based on polysaccharides. A nucleation-growth mechanism based on the LaMer model can explain how CMC-CuInS2 QDs are formed. As-prepared water-soluble CMC-CuInS2 QDs exhibit monodisperse particles with sizes of 5.5-6.5 nm. CMC-CuInS2 QDs emit the bright-green fluorescence at 530 nm when excited at 466 nm with the highest quantum yield of ∼18.0%. Meanwhile, the fluorescence intensity of CMC-CuInS2 QD aqueous solution is quenched with the addition of Pb2+ and the minimal limit of detection is as little as 0.4 nM. Furthermore, due to its noncytotoxicity, great biocompatibility, and strong biorecognition ability, CMC-CuInS2 QDs can be exploited as a possible cell membrane imaging reagent. The imaging studies also demonstrate that CMC-CuInS2 QDs are suitable for Pb2+ detection in live cells and living organisms (zebrafish). Thus, this work offers such an efficient, green, and practical method for creating low-toxicity and water-soluble QD nanosensors for a sensitive and selective detection of toxic metal ion in live cells and organisms.

Anthracenemethyl Glycosides as Supramolecular Synthons for Chiral Self-Assembly and as Probes in Cell Imaging

Chiral self-assembly of molecules warrants optimal structural features of synthons that promote formation of such self-assembled structures. A polyaromatic moiety coupled with hydrophilic, chiral-rich carbohydrates leads to segmentation of the regions and the self-assembly to supramolecular structures. Thermodynamic stability is augmented further through chiral self-assembly of the molecules, and formation of the desired chiral supramolecular structures is achieved. In the present study, we develop anthracene glycosides as efficient synthons that, in aqueous solutions, undergo facile self-assembly and lead to chiral supramolecular structures. Anthracenemethyl O-glycosides, installed with mono- and disaccharides, are studied for their self-assembly properties. Emerging chiral structures follow the configuration of the attached sugar moiety. Monosaccharide d- and l-glycopyranoside-containing derivatives alternate between left- and right-handed chiral structures, respectively. Disaccharide-containing derivatives do not exhibit chirality, even when self-assembly occurred. Photochemical [4π + 4π] cycloaddition occurs in the self-assembled structure in aqueous solution. Cell viability assay using HeLa cells shows above 80% viable cells at a concentration of 50 μM. Bioimaging assays reveal a significant imaging of HeLa cells for anthracenemethyl d-glucopyranoside; bright imaging was observed at the perinuclear region of the cells, suggestive of an active transport of the molecules through the cell membrane. d-Galactopyranoside and l-glucopyranoside-containing derivatives show weak imaging potencies.

Cu(I)-Catalyzed Click Chemistry in Glycoscience and Their Diverse Applications

Copper(I)-catalyzed 1,3-dipolar cycloaddition between organic azides and terminal alkynes, commonly known as CuAAC or click chemistry, has been identified as one of the most successful, versatile, reliable, and modular strategies for the rapid and regioselective construction of 1,4-disubstituted 1,2,3-triazoles as diversely functionalized molecules. Carbohydrates, an integral part of living cells, have several fascinating features, including their structural diversity, biocompatibility, bioavailability, hydrophilicity, and superior ADME properties with minimal toxicity, which support increased demand to explore them as versatile scaffolds for easy access to diverse glycohybrids and well-defined glycoconjugates for complete chemical, biochemical, and pharmacological investigations. This review highlights the successful development of CuAAC or click chemistry in emerging areas of glycoscience, including the synthesis of triazole appended carbohydrate-containing molecular architectures (mainly glycohybrids, glycoconjugates, glycopolymers, glycopeptides, glycoproteins, glycolipids, glycoclusters, and glycodendrimers through regioselective triazole forming modular and bio-orthogonal coupling protocols). It discusses the widespread applications of these glycoproducts as enzyme inhibitors in drug discovery and development, sensing, gelation, chelation, glycosylation, and catalysis. This review also covers the impact of click chemistry and provides future perspectives on its role in various emerging disciplines of science and technology.

Supramolecular Assembly of TPE-Based Glycoclusters with Dicyanomethylene-4H-pyran (DM) Fluorescent Probes Improve Their Properties for Peroxynitrite Sensing and Cell Imaging

Two red-emitting dicyanomethylene-4H-pyran (DM) based fluorescent probes were designed and used for peroxynitrite (ONOO^- ) detection. Nevertheless, the aggregation-caused quenching effect diminished the fluorescence and restricted their further applications. To overcome this problem, tetraphenylethylene (TPE) based glycoclusters were used to self-assemble with these DM probes to obtain supramolecular water-soluble glyco-dots. This self-assembly strategy enhanced the fluorescence intensity, leading to an enhanced selectivity and activity of the resulting glyco-dot comparing to DM probes alone in PBS buffer. The glyco-dots also exhibited better results during fluorescence sensing of intracellular ONOO^- than the probes alone, thereby offering scope for the development of other similar supramolecular glyco-systems for chemical biological studies.

Fluorescent glycoconjugates and their applications

Fluorescent glycoconjugates are discussed for their applications in biology in vitro, in cell assays and in animal models. Advantages and limitations are presented for each design using a fluorescent core conjugated with glycosides, or vice versa.

Thiophenol detection using an AIE fluorescent probe through self-assembly with TPE-based glycoclusters

We describe a novel green-emitting tetraphenylethylene-dicyanomethylene-4H-pyran (TPE-DCM) based fluorescent probe (TD-1). Conjugating TPE and DCM moieties allowed TD-1 to display high selectivity for thiophenol with excellent AIE properties in aqueous solution. Nevertheless, the poor water solubility of the hydrophobic structure resulted in a weak and unstable emission intensity. The non-covalent self-assembly of TD-1 with a TPE glycocluster (TPE2S) led to a largely improved water solubility producing a reliable and stable sensing system. The corresponding glyco-probe could sensitively detect exogenous thiophenol concentrations in PBS buffer or environmental water samples.

Tetraphenylethylene-based glycoclusters with aggregation-induced emission (AIE) properties as high-affinity ligands of bacterial lectins

TPE-based glycoclusters are fluorescent through aggregation induced emission (AIE) in water.

Perylenediimide-based glycoclusters as high affinity ligands of bacterial lectins: synthesis, binding studies and anti-adhesive properties

Rapid access to perylenediimide-based glycoclusters allowed their evaluation as high affinity ligands of bacterial lectins and their potential as anti-adhesive antibacterials.