Abstract
Glyco-functionalized gold nanoparticles have great potential as biosensors and as inhibitors due to their increased binding to carbohydrate-recognizing receptors such as the lectins. Here we apply previously developed solid phase polymer synthesis to obtain a series of precision glycomacromolecules that allows for straightforward variation of their chemical structure as well as functionalization of gold nanoparticles by ligand exchange. A novel building block is introduced allowing for the change of spacer building blocks within the macromolecular scaffold going from an ethylene glycol unit to an aliphatic spacer. Furthermore, the valency and overall length of the glycomacromolecule is varied. All glyco-functionalized gold nanoparticles show high degree of functionalization along with high stability in buffer solution. Therefore, a series of measurements applying UV-Vis spectroscopy, dynamic light scattering (DLS) and surface plasmon resonance (SPR) were performed studying the aggregation behavior of the glyco-functionalized gold nanoparticles in presence of model lectin Concanavalin A. While the multivalent presentation of glycomacromolecules on gold nanoparticles (AuNPs) showed a strong increase in binding compared to the free ligands, we also observed an influence of the chemical structure of the ligand such as its valency or hydrophobicity on the resulting lectin interactions. The straightforward variation of the chemical structure of the precision glycomacromolecule thus gives access to tailor-made glyco-gold nanoparticles (glyco-AuNPs) and fine-tuning of their lectin binding properties.
Highlights
As a major component of most cell surfaces, carbohydrates participate in various cell-cell interactions e.g., in cellular communication and pathogen recognition where they act as ligands for different receptors such as the lectins [1,2]
All building blocks are equipped with a terminal carboxy and a terminal Fmoc-protected amine group allowing for solid phase assembly via well-established Fmoc-peptide coupling protocols
A glycine was introduced by employing a pre-loaded resin giving a free carboxy group at the other chain end that should support colloidal stability of the final glyco-AuNPs by electrostatic stabilization
Summary
As a major component of most cell surfaces, carbohydrates participate in various cell-cell interactions e.g., in cellular communication and pathogen recognition where they act as ligands for different receptors such as the lectins [1,2]. An important concept underlying carbohydrate lectin interactions is multivalency, where multiple binding epitopes of the carbohydrate ligand interact with multiple binding sites of the protein [3,4]. In this way, the overall binding strength of the otherwise weak interactions of single carbohydrate ligands substantially increases, known as the cluster glycoside effect [5,6]. Quantum dots [25,26,27,28,29] serve as platforms for multivalent presentation Among these various macromolecular scaffolds, especially gold nanoparticles (AuNPs) are promising glycan displays. They are inexpensive and with their ease of synthesis and functionalization various glycoconjugates can Polymers 2017, 9, 716; doi:10.3390/polym9120716 www.mdpi.com/journal/polymers
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