Step by step towards understanding gold glyconanoparticles as elements of the nanoworld

Guiding principles in the design of ligand-targeted nanomedicines

Medicines for the treatment of most human pathologies are encumbered by unwanted side effects that arise from the deposition of an effective drug into the wrong tissues. The logical remedy for these undesirable properties involves selective targeting of the therapeutic agent to pathologic cells, thereby avoiding collateral toxicity to healthy cells. Since significant advantages can also accrue by incorporating a therapeutic or imaging agent into a nanoparticle, many laboratories are now combining both benefits into a single formulation. This review will focus on the major guiding principles in the design of ligand-targeted nanoparticles, including optimization of their chemical and physical properties, selection of the ideal targeting ligand, engineering of the appropriate surface passivation and linker strategies to achieve selective delivery of the entrapped cargo to the desired diseased cell.

Influence of ligand presentation density on the molecular recognition of mannose-functionalised glyconanoparticles by bacterial lectin BC2L-A

Polyvalent carbohydrate-protein interactions play a key role in bio- and pathological processes, including cell-cell communication and pathogen invasion. In order to study, control and manipulate these interactions gold nanoparticles have been employed as a 3D scaffold, presenting carbohydrate ligands in a multivalent fashion for use as high affinity binding partners and a model system for oligosaccharide presentation at biomacromolecular surfaces. In this study, the binding of a series of mannose-functionalised gold nanoparticles to the dimeric BC2L-A lectin from Burkholderia cenocepacia has been evaluated. BC2L-A is known to exhibit a high specificity for (oligo)mannosides. Due to the unique structure and binding nature of this lectin, it provides a useful tool to study (oligo)saccharides presented on multivalent scaffolds. Surface plasmon resonance and isothermal titration calorimetric assays were used to investigate the effect of ligand presentation density towards binding to the bacterial lectin. We show how a combination of structural complementarities between ligand presentation and lectin architecture and statistical re-binding effects are important for increasing the avidity of multivalent ligands for recognition by their protein receptors; further demonstrating the application of glyconanotechnology towards fundamental glycobiology research as well as a potential towards biomedical diagnostics and therapeutic treatments.

Glyconanomaterials: synthesis, characterization, and ligand presentation

Glyconanomaterials, nanomaterials carrying surface-tethered carbohydrate ligands, have emerged and demonstrated increasing potential in biomedical imaging, therapeutics, and diagnostics. These materials combine the unique properties of nanometer-scale objects with the ability to present multiple copies of carbohydrate ligands, greatly enhancing the weak affinity of individual ligands to their binding partners. Critical to the performance of glyconanomaterials is the proper display of carbohydrate ligands, taking into consideration of the coupling chemistry, the type and length of the spacer linkage, and the ligand density. This article provides an overview of the coupling chemistry for attaching carbohydrate ligands to nanomaterials, and discusses the need for thorough characterization of glyconanomaterials, especially quantitative analyses of the ligand density and binding affinities. Using glyconanoparticles synthesized by a versatile photocoupling chemistry, methods for determining the ligand density by colorimetry and the binding affinity with lectins by a fluorescence competition assay are determined. The results show that the multivalent presentation of carbohydrate ligands significantly enhances the binding affinity by several orders of magnitude in comparison to the free ligands in solution. The effect is sizeable even at low surface ligand density. The type and length of the spacer linkage also affect the binding affinity, with the longer linkage promoting the association of bound ligands with the corresponding lectins.