On the Stability of Polymeric Nanoparticles Fabricated through Rapid Solvent Mixing

Abstract

We study the stability of polymeric nanoparticles fabricated through the rapid mixing of polymers in a good solvent with a poor solvent that is miscible with the good solvent. In previous experiments where water was used as the poor solvent, a negative surface charge was measured on the precipitated nanoparticles, which led to the long-time stability of the dispersion. It was argued that these charges originate presumably from either water or hydroxide adsorption at the hydrophobic nanoparticle surface or from impurities in the feed streams that preferentially adsorb on the precipitated nanoparticles. To elucidate the origin of this stabilization mechanism, we performed experiments wherein we replaced water with a nonpolar poor solvent. The polymers aggregated into stable nanoparticles for a range of processing parameters. We investigated theoretically three possible explanations for this stability, i.e., electrostatic stabilization, conditional thermodynamic equilibrium, and steric stabilization. Our experiments and considerations suggest that steric stabilization is the most likely candidate.

Biodegradable Polymeric Nanoparticles for Drug Delivery to Solid Tumors

“…Therefore, resistance against aggregation is desirable in order to obtain a long shelf life for polymeric nanoparticles. Electrostatic and steric stabilization are the two mechanisms through which nanoparticles are stabilized (Morozova et al, 2019). The former is based on the mutual repulsion of similar electrical charges and depends on the balance of forces between charged surfaces and various interfaces, namely, the attracting van der Waals forces (resulting from dipole-dipole interactions) and the repulsive electrostatic forces of the electrical double layers surrounding the particles in the medium (Morozova et al, 2019).…”

“…Electrostatic and steric stabilization are the two mechanisms through which nanoparticles are stabilized (Morozova et al, 2019). The former is based on the mutual repulsion of similar electrical charges and depends on the balance of forces between charged surfaces and various interfaces, namely, the attracting van der Waals forces (resulting from dipole-dipole interactions) and the repulsive electrostatic forces of the electrical double layers surrounding the particles in the medium (Morozova et al, 2019). Steric stabilization, on the other hand, is a protective barrier provided by the adsorption or conjugation of polymers or surfactants onto the surfaces of the nanoparticles (Mo et al, 2016).…”

Synthetic advances of internally nanostructured polymer particles: From and beyond block copolymer

“…The colloidal stability was maintained through amphiphilic polymers adsorbed on the surface that act as a steric barrier, and their charged end groups as well. [39] Normally, the particle size has a close relationship with the chemical composition and molecular weight of the polymer in colloidal particles. In addition, the density of polymer brushes on the particle surface is dependent on the processing parameters in FNP.…”

“…The colloidal stability was maintained through amphiphilic polymers adsorbed on the surface that act as a steric barrier, and their charged end groups as well. [ 39 ]…”

Evolution of Polymer Colloid Structure During Precipitation and Phase Separation

“…For example, the presence of distinct surface patches on colloids imparts them with the ability to selectively adsorb at liquid interfaces, forming Pickering emulsions. 11 − 14 In drug delivery applications, compartmentalization within a colloid can control the release profile of internally sequestered drug molecules. 15 , 16 Thus, an understanding of the mechanism and kinetics of phase separation is vital to controlling the internal and external structure of polymeric colloids.…”