Stepwise Orthogonal Click Chemistry toward Fabrication of Paclitaxel/Galactose Functionalized Fluorescent Nanoparticles for HepG2 Cell Targeting and Delivery

In this report, we used stepwise orthogonal click chemistry (SOCC) involving strain-promoted azide–alkyne cycloaddition (SPAAC) and microwave-assisted Cu­(I)-catalyzed azide–alkyne cycloaddition (CuAAC) to assemble an anticancer drug (paclitaxel, PTX) and a targeting ligand (trivalent galactoside, TGal) on a fluorescent silicon oxide nanoparticle (NP) by using dialkyne linker <b>8</b> as a bridge. The fluorescent <b>NH</b>_<b>2</b><b>@Cy3SiO</b>_<b>2</b><b>NP</b> was fabricated using a competition method to incorporate Cy3 without loss of the original surface amine density on the NPs. The concept of SOCC was first investigated in a solution-phase model study that showed quantitative reaction yield. In the fabrication of <b>TGal-PTX@Cy3SiO</b>_<b>2</b><b>NP</b>, the expensive compound azido-functionalized PTX <b>12</b> used in SPAAC can be easily recovered due to the absence of other reagents in the reaction mixture. High loading of the sugar ligand on the NP surface serves a targeting function and also overcomes the low water solubility of PTX. Confocal fluorescence microscopy and cytotoxicity assay showed that <b>TGal-PTX@Cy3SiO</b>_<b>2</b><b>NP</b> was taken up by HepG2 cells and was affected by the microtubule skeleton in these cells and inhibited the proliferation of these cells in a dose-dependent manner. The presence of a fluorescent probe, a targeting ligand, and an anticancer drug on the multifunctional <b>TGal-PTX@Cy3SiO</b>_<b>2</b><b>NP</b> allows for real-time imaging, specific cancer-cell targeting, and the cell-killing effect which is better than free PTX

Automated Glycan Assembly of Complex Oligosaccharides Related to Blood Group Determinants

Lactotetraosyl (Lc4) and neo-lactotetraosyl (nLc4) are backbones that are common to many glycans. Using automated glycan assembly, these common core structures were constructed and elaborated to access synthetically challenging glycans of biological relevance. The incorporation of α-fucoses is demonstrated for H-type I and II; α­(1,3)-galactose epitopes were prepared, and the pentasaccharide HNK-1 required incorporation of a 3-<i>O</i>-sulfate. In addition to preparing the target structures, essential insights were gained regarding the relationships of glycosylating agents and nucleophiles as well as the linker stability

Analysis of Carbohydrate–Carbohydrate Interactions Using Sugar-Functionalized Silicon Nanoparticles for Cell Imaging

Protein-carbohydrate binding depends on multivalent ligand display that is even more important for low affinity carbohydrate–carbohydrate interactions. Detection and analysis of these low affinity multivalent binding events are technically challenging. We describe the synthesis of dual-fluorescent sugar-capped silicon nanoparticles that proved to be an attractive tool for the analysis of low affinity interactions. These ultrasmall NPs with sizes of around 4 nm can be used for NMR quantification of coupled sugars. The silicon nanoparticles are employed to measure the interaction between the cancer-associated glycosphingolipids GM3 and Gg3 and the associated <i>k</i>_D value by surface plasmon resonance experiments. Cell binding studies, to investigate the biological relevance of these carbohydrate–carbohydrate interactions, also benefit from these fluorescent sugar-capped nanoparticles

Imaging Early Endothelial Inflammation Following Stroke by Core Shell Silica Superparamagnetic Glyconanoparticles That Target Selectin

Activation of the endothelium is a pivotal first step for leukocyte migration into the diseased brain. Consequently, imaging this activation process is highly desirable. We synthesized carbohydrate-functionalized magnetic nanoparticles that bind specifically to the endothelial transmembrane inflammatory proteins E and P selectin. Magnetic resonance imaging revealed that the targeted nanoparticles accumulated in the brain vasculature following acute administration into a clinically relevant animal model of stroke, though increases in selectin expression were observed in both brain hemispheres. Nonfunctionalized naked particles also appear to be a plausible agent to target the ischemic vasculature. The importance of these findings is discussed regarding the potential for translation into the clinic

Synthesis and Evaluation of a Photoactive Probe with a Multivalent Carbohydrate for Capturing Carbohydrate–Lectin Interactions

Lectins are ubiquitous carbohydrate-binding proteins of nonimmune origin that are characterized by their specific recognition of defined monosaccharide or oligosaccharide structures. However, the use of carbohydrates to study lectin has been restricted by the weak binding affinity and noncovalent character of the interaction between carbohydrates and lectin. In this report, we designed and synthesized a multifunctional photoaffinity reagent composed of a trialkyne chain, a masked latent amine group, and a photoreactive 3-trifluoromethyl-3-phenyl-diazirine group in high overall yield. Two well-defined chemistries, Huisgen-Sharpless click chemistry and amide bond coupling, were the key steps for installing the multivalent character and tag in our designed photoaffinity probe. The photolabeling results demonstrated that the designed probe selectively labeled the target lectin, RCA₁₂₀ (Ricinus communis Agglutinin), in an E. coli lysate and an asialoglycoprotein receptor (ASGP-R) on intact HepG2 cell membranes. Moreover, the probe also enabled the detection of weak protein–protein interactions between RCA₁₂₀ and ovalbumin (OVA)

Multivalency at Interfaces: Supramolecular Carbohydrate-Functionalized Graphene Derivatives for Bacterial Capture, Release, and Disinfection

A supramolecular carbohydrate-functionalized two-dimensional (2D) surface was designed and synthesized by decorating thermally reduced graphene sheets with multivalent sugar ligands. The formation of host–guest inclusions on the carbon surface provides a versatile strategy, not only to increase the intrinsic water solubility of graphene-based materials, but more importantly to let the desired biofunctional binding groups bind to the surface. Combining the vital recognition role of carbohydrates and the unique 2D large flexible surface area of the graphene sheets, the addition of multivalent sugar ligands makes the resulting carbon material an excellent platform for selectively wrapping and agglutinating <i>Escherichia coli</i> <i>(E. coli</i>)<i>.</i> By taking advantage of the responsive property of supramolecular interactions, the captured bacteria can then be partially released by adding a competitive guest. Compared to previously reported scaffolds, the unique thermal IR-absorption properties of graphene derivatives provide a facile method to kill the captured bacteria by IR-laser irradiation of the captured graphene–sugar–<i>E. coli</i> complex