On the Role of Specific Interactions in the Diffusion of Nanoparticles in Aqueous Polymer Solutions

Abstract

Understanding nanoparticle diffusion within non-Newtonian biological and synthetic fluids is essential in designing novel formulations (e.g., nanomedicines for drug delivery, shampoos, lotions, coatings, paints, etc.), but is presently poorly defined. This study reports the diffusion of thiolated and PEGylated silica nanoparticles, characterized by small-angle neutron scattering, in solutions of various water-soluble polymers such as poly(acrylic acid) (PAA), poly(N-vinylpyrrolidone) (PVP), poly(ethylene oxide) (PEO), and hydroxyethylcellulose (HEC) probed using NanoSight nanoparticle tracking analysis. Results show that the diffusivity of nanoparticles is affected by their dimensions, medium viscosity, and, in particular, the specific interactions between nanoparticles and the macromolecules in solution; strong attractive interactions such as hydrogen bonding hamper diffusion. The water-soluble polymers retarded the diffusion of thiolated particles in the order PEO > PVP > PAA > HEC whereas for PEGylated silica particles retardation followed the order PAA > PVP = HEC > PEO. In the absence of specific interactions with the medium, PEGylated nanoparticles exhibit enhanced mobility compared to their thiolated counterparts despite some increase in their dimensions.

Kinetics of dispersion of nanoparticles in thin polymer films at high temperature

“…However, this motion is through a confined polymer melt. As mentioned earlier, previous reports from simulations of polymers in thin films indicate that polymer chain diffusivity, normal to the interface is suppressed due to confinement 44,53,61 . In addition, it has been already reported, within a film PS chains remain strongly adsorbed on the silicon substrate in an irreversible manner 51,62 .…”

“…This reduction in density was compensated by the simultaneous increase of electron density of the surface layer and there is a comparably smaller increase in electron density in bulk layer also. These two features can be interpreted as temperature induced diffusion of segregated nanoparticles from interface layer to the surface layer through the intermediate bulk layer [37][38][39][40][41][42][43][44] . Recently we have shown, using coarse grained molecular dynamic (MD) simulation 22 that for a film of thickness comparable to the radius of gyration (R g ) of the matrix polymer chain the PGNPs are pushed out of the interface by the polymers thereby increasing the polymer number density and decreasing the PGNP number density at the interface.…”

Nanoparticle-releasing nanofiber composites for enhanced in vivo vaginal retention

“…Along with changes in fiber dissolution kinetics, nanoparticle properties may also differ under in vivo conditions in the presence of mucus and hydrated polymer gel. The fiber polymer may interact with the nanoparticle directly to slow or speed its diffusion, as has been previously described for dilute polymer solutions [45], but may also alter the properties of mucus itself. Pretreatment of human cervicovaginal mucus with 1% Pluronic® F-127 has been shown to enhance diffusion of conventional polystyrene nanoparticles, likely due to hydrophobic shielding interactions between Pluronic® F-127 and either the hydrophobic portions of mucus or the nanoparticle surface [46].…”

Nanoparticle diffusometry in hydrogels

“…So far, SPT has mainly been used for microrheology experiments, in which the micron-size tracer particles are visible under an optical microscope (Dickinson, 2011). Tracking of sub-micron particles, on the other hand, can be achieved by either detecting scattered light (Filipe et al, 2010), or fluorescence (Braeckmans et al, 2010;Mun et al, 2014). The observation of nanoparticles based on laser diffraction is only possible in systems where no other scattering elements are present.…”

“…SPT is one of two methods discussed that allow direct assessment of the distribution of particle displacements in an ensemble, the other being PFG NMR. Most applications of SPT pertain to assessment of size, concentration and functionality of nanoparticles; only few examples have been given to probe local sub-micron network structure and dynamics (Mun et al, 2014). To our knowledge no application has appeared to assess sub-micron food structures.…”