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Composite nanoparticles co-encapsulate organic materials with inorganic primary colloids. Producing “stoichiometric NPs”, where all NPs contain organic and inorganic species at similar ratios, requires matched diffusion-aggregation time scale. 

Cannabidiol (CBD) is viewed as a promising therapeutic agent against a variety of health ailments; however, its efficacy is limited by poor aqueous solubility. Amorphous solid dispersions (ASDs) can enhance the solubility of therapeutics by distributing them throughout a polymer matrix. In consideration of ASD formulations with CBD, we investigate the interactions of CBD with various polymers: poly(vinylpyrrolidone) (PVP), poly(vinylpyrrolidone)/vinyl acetate (PVP/VA) copolymer, hydroxypropyl methylcellulose phthalate (HPMCP), hydroxypropyl methylcellulose acetate succinate (HPMCAS), and poly(methyl methacrylate) (PMMA). Both the experiment and molecular dynamics simulation reveal diverse mixing behavior among the set of polymers. Detailed structural and nanoscale interaction analyses suggest that positive deviations from ideal mixing behavior arise from the formation of stable polymer–CBD hydrogen bonds, whereas negative deviations are associated with disruptions to the polymer–polymer hydrogen bond network. Polymer–water interaction analyses indicate the significance of polymer hydrophobicity that can lead to poor dissolution of CBD. These results have implications for drug dissolution rates based on how CBD and water interact with each polymer. Furthermore, these insights may be used to guide ASD formulations for CBD or other small-molecule therapeutic agents. 

In addition to the repulsive and attractive interaction forces described by Derjaguin–Landau–Verwey–Overbeek (DLVO) theory, many charged colloid systems are stabilized by non-DLVO contributions stemming from specific material attributes. Here, we investigate non-DLVO contributions to the stability of polymer colloids stemming from the intra-particle glass transition temperature ( T g ). Flash nanoprecipitation is used to fabricate nanoparticles (NPs) from a library of polymers and dispersion stability is studied in the presence of both hydrophilic and hydrophobic salts. When adding KCl, stability undergoes a discontinuous decrease as T g increases above room temperature, indicating greater stability of rubbery NPs over glassy NPs. Glassy NPs are also found to interact strongly with hydrophobic phosphonium cations (PR 4 + ), yielding charge inversion and intermediate aggregation while rubbery NPs resist ion adsorption. Differences in the lifetime of ionic structuration within mobile surface layers is presented as a potential mechanism underlying the observed phenomenon. 

Functionalized cellulosics have shown promise as naturally derived thermoresponsive gelling agents. However, the dynamics of thermally induced phase transitions of these polymers at the lower critical solution temperature (LCST) are not fully understood. Here, with experiments and theoretical considerations, we address how molecular architecture dictates the mechanisms and dynamics of phase transitions for cellulose ethers. Above the LCST, we show that hydroxypropyl substituents favor the spontaneous formation of liquid droplets, whereas methyl substituents induce fibril formation through diffusive growth. In celluloses which contain both methyl and hydroxypropyl substituents, fibrillation initiates after liquid droplet formation, suppressing the fibril growth to a sub-diffusive rate. Unlike for liquid droplets, the dissolution of fibrils back into the solvated state occurs with significant thermal hysteresis. We tune this hysteresis by altering the content of substituted hydroxypropyl moieties. This work provides a systematic study to decouple competing mechanisms during the phase transition of multi-functionalized macromolecules. 

ABSTRACT: The dosing of peptide and protein therapeutics is complicated by rapid clearance from the blood pool and poor cellular membrane permeability. Encapsulation into nanocarriers such as liposomes or polymersomes has long been explored to overcome these limitations, but manufacturing challenges have limited clinical translation by these approaches. Recently, inverse Flash NanoPrecipitation (iFNP) has been developed to produce highly loaded polymeric nanocarriers with the peptide or protein contained within a hydrophilic core, stabilized by a hydrophobic polymer shell. Encapsulation of proteins with higher-order structure requires understanding how processing may affect their conformational state. We demonstrate a combined experimental/simulation approach to characterize protein behavior during iFNP processing steps using the Trp-cage protein TC5b as a model. Explicit-solvent fully atomistic molecular dynamics simulations with enhanced sampling techniques are coupled with two-dimensional heteronuclear multiple-quantum coherence nuclear magnetic resonance spectroscopy (2D-HMQC NMR) and circular dichroism to determine the structure of TC5b during mixed-solvent exposure encountered in iFNP processing. The simulations involve atomistic models of mixed solvents and protein to capture the complexity of the hydrogen bonding and hydrophobic interactions between water, dimethylsulfoxide (DMSO), and the protein. The combined analyses reveal structural unfolding of the protein in 11 M DMSO but confirm complete refolding after release from the polymeric nanocarrier back into an aqueous phase.