Efficient Endocytosis of Inorganic Nanoparticles with Zwitterionic Surface Functionalization

Abstract

PEGylation, which has traditionally been the method of choice to enhance the colloidal stability of nanostructures designed for biological applications, and to prevent non-specific protein adsorption, is now being challenged by short zwitterionic ligands. Inspired by the zwitterionic nature of cell membranes, these ligands have the potential to push forward the field of nanoparticles for nanomedicine. In this work, we report a thorough analysis of the surface chemistry of silica coated luminescent CdSe/CdS quantum dots functionalized with either PEGsilane or zwitterionic sulfobetaine-silane by quantitative nuclear magnetic resonance spectroscopy. We demonstrate the differences in the cellular uptake propensity between particles with these two ligands. While both ligands offer good colloidal stability in crowded cell culture medium, the zwitterionic functionalized nanoparticles with an optimized ligand density showed to be more easily endocytosed by HeLa cells. This approach can readily be transferred to other nanoparticle systems offering a wealth of unique properties, with great potential for intracellular bioapplications. IntroductionDiagnostic and therapy techniques in modern nanomedicine have benefited in the past decades from the growing interest and significant advancement in the development of functional nanoparticles (NPs). [1][2][3] New generation NPs have emerged as important players in the development of high contrast bioimaging and in offering novel diagnostic and therapeutic opportunities. Due to their unique properties (luminescent, magnetic, plasmonic, etc.), and in combination with specific surface functionalization, NPs have become an interesting class of materials for cell labeling, selective targeting of biomolecules, sensitive biosensing, smart drug delivery strategies and other theranostics applications. [4][5][6] To achieve their full potential, NPs developed for biological applications should meet important criteria, including a robust colloidal stability in a variety of complex environments. Indeed, the colloidal stability observed for inorganic NPs in a simple solvent system is often challenged once in dense and crowded biological media. On the other hand, for NPs specifically designed for intracellular applications, an efficient cellular uptake is also required, which is commonly achieved via endocytic pathways. 5 Several approaches have been

Nanoparticle Surface Functionalization: How to Improve Biocompatibility and Cellular Internalization

“…cancer cells) (Breus et al, 2009;Muro et al, 2010;Zhang et al, 2011). An example of the zwitterionic ligands useful to enhance NPs uptake is reported by Drijvers et al (2019). In this work, silica coated CdSe/CdS quantum dots were biofunctionalized with PEG and with sulfobetaines in order to evaluate the impact of these modifications on the NPs cellular uptake.…”

Quo Vadis, Nanoparticle-Enabled In Vivo Fluorescence Imaging?

“…[118][119][120][121][122] Simply put, a successful surface functionalization boils down to finding the right balance between minimizing interactions with biological components that elicit an immune response (and hence premature clearance of the NPs), while prompting selective recognition and interaction with cells that form the tissue of interest. Silica coating, [123][124][125] as well as the use of zwitterionic molecules 126,127 or polymers 128 are amongst the most explored strategies to enhance biocompatibility and extend NP circulation time. Decoration with polyethylene glycol (PEG), in particular, is often regarded as the golden standard for imparting "stealth" properties to NPs.…”

Recent Developments in the Design of Non-Biofouling Coatings for Nanoparticles and Surfaces

“…Indeed, the use of zwitterionic coatings, due to their non-fouling and stealth properties, prevented cellular uptake and hence increased the circulation time of those NPs in vivo. However, Drijvers et al [72] found that the internalization could be tuned through the ligand density. For 15 nm QDs coated with a silica shell functionalized with sulfobetaines, substantial cellular uptake was detected by both confocal microscopy and flow cytometry when using up to 1 ligand per nm 2 .…”

“…Fluorescence confocal microscopy images of zwitterion-functionalized quantum dots (QDs) (A) versus PEGylated QDs (B) and the correlation between a positive cell percentage (PCP) and ligand type and density (C). Reprinted with permission from reference[72]. Copyright (2019) American Chemical Society.…”