Surfactant-free Colloidal Particles with Specific Binding Affinity

Abstract

Colloidal particles with specific binding affinity are essential for in vivo and in vitro biosensing, targeted drug delivery, and micrometer-scale self-assembly. Key to these techniques are surface functionalizations that provide high affinities to specific target molecules. For stabilization in physiological environments, current particle coating methods rely on adsorbed surfactants. However, spontaneous desorption of these surfactants typically has an undesirable influence on lipid membranes. To address this issue and create particles for targeting molecules in lipid membranes, we present here a surfactant-free coating method that combines high binding affinity with stability at physiological conditions. After activating charge-stabilized polystyrene microparticles with EDC/Sulfo-NHS, we first coat the particles with a specific protein and subsequently covalently attach a dense layer of poly(ethyelene) glycol. This polymer layer provides colloidal stability at physiological conditions as well as antiadhesive properties, while the protein coating provides the specific affinity to the targeted molecule. We show that NeutrAvidin-functionalized particles bind specifically to biotinylated membranes and that Concanavalin A-functionalized particles bind specifically to the glycocortex of Dictyostelium discoideum cells. The affinity of the particles changes with protein density, which can be tuned during the coating procedure. The generic and surfactant-free coating method reported here transfers the high affinity and specificity of a protein onto colloidal polystyrene microparticles.

Colloid supported lipid bilayers for self-assembly

“…Polymers or surfactants are often employed to stabilize colloidal particles in solution [52][53][54], but may influence the formation and mobility of the bilayer in CSLBs. Here, we test how the presence of, for example, leftover polymers from particle synthesis, affects the bilayer.…”

“…In contrast to SDS, PEGylated lipids can provide colloidal stability through steric repulsions between the PEG moieties while also being easily integrated into the bilayer through their lipid tails [52][53][54]. To test their use for colloidal stabilization, we coated the particles with SUVs that contain a small fraction of the following PEGylated lipids: DOPE-PEG(2000), DOPE-PEG(3000) and DOPE-PEG(5000).…”

Interactions between model inclusions on closed lipid bilayer membranes

“…and (2) by specific receptor-ligand based interactions, e.g. between streptavidin coated beads and GUVs doped with biotinilated lipids [43,35,5,44].…”

Controlled adhesion, membrane pinning and vesicle transport by Janus particles

“…Model membrane systems are commonly implemented for studying such processes. 4 Among these systems are giant unilamellar vesicles (GUVs), 5 which mimic the cell size and the curvature of the plasma membrane without the compositional complexity of live cells (which includes a wide variety of lipid species, proteins or the associated cytoskeleton). 6 When investigating the parameters that dictate particle–membrane interactions, one vital aspect to consider is the role of the particle properties on the interaction potentials.…”