Roque J. Minari

Thermoresponsive nanogels with film-forming ability

Thermoresponsive nanogels (NGs) with film-forming ability could have great potential in delivery system platforms with controlled and targeted release of drugs or proteins, such as in topical treatment. This platform offers the opportunity of combining both the high loading capacity of an NG dispersion and the delivery capability from a film, which could be previously obtained or directly formed onto the surface where the release is required. Therefore, this article investigates the synthesis of NGs based on poly(N-vinylcaprolactam), a thermoresponsive polymer, and poly(butyl acrylate), which promotes particle coalescence and cohesivity (i.e., film forming). The synthesized NGs have low cytotoxicity and are able to form flexible and smooth films, conserving the thermoresponsivity of the particulated system. The obtained films loaded with a model protein show delivery profiles responsive to temperature changes.

Crosslinked casein-based micelles as a dually responsive drug delivery system

New types of biodegradable nanocarriers for drug delivery were prepared using casein (CAS) micelles as particle templates and glyceraldehyde (GAL) as a crosslinking agent. We found that highly crosslinked casein micelles (CCM) maintained their structural integrity at pH 7.4 (plasma conditions) but were easily degraded in the presence of proteases at pH 5 (lysosomal conditions). Nile red (NR) was chosen as a hydrophobic model drug inspired by the natural role of casein as lipophilic nutrient nanotransporter. The cumulative release of the NR-loaded micelles showed marginal dye leakage at pH 7.4 but was significantly accelerated by protease and pH-mediated degradation of the nanocarriers in a dual-responsive fashion. The prepared nanocarriers possess many favorable features for drug delivery: excellent biocompatibility and biodegradability, high stability in physiological conditions, remarkable capacity for the encapsulation of hydrophobic drugs, minimal drug leakage under extracellular conditions, and rapid drug release in response to the endo-lysosomal levels of pH and proteases. In this regard, the prepared CCM represent a promising candidate for the delivery and triggered release of anti-cancer drugs in lysosomal environments.

Poly( n -butyl acrylate)–Casein Nanocomposites as Promising Candidates for Packaging Films

Partially degradable materials, offer an interesting sustainable alternative for short-term use applications where their environmental impact could be importantly reduced. This article investigates the preparation of a series of poly(n-butyl acrylate)–casein nanocomposites with varied bio-component content via emulsifier-free emulsion polymerization. The influence of casein content on the morphological and film properties of the natural/synthetic materials is discussed. Film performance was analyzed in terms of water and vapor resistance, biodegradability in composting conditions, mechanical behavior, opacity, and thermal stability. The obtained results suggest that poly(n-butyl acrylate)–casein nanocomposites, with grafting of acrylic chains onto protein molecules, have great potential as bio-defragmentable packaging materials.

Enhancing the coating properties of acrylic/casein latexes with high protein content

Casein-derived materials are highly attractive as a consequence of their environmental friendliness and excellent film-forming properties. Due to the casein hydrophilicity, films containing a large protein content are highly susceptible to water, thus limiting their use in coating applications. A novel approach for synthesizing waterborne acrylic–casein latexes with large content of protein and high degree of compatibilization between both components is presented. The employed synthesis strategy involves the use of a highly methacrylated casein in an emulsifier-free emulsion polymerization of acrylic monomers with the aim of controlling both the fraction of grafted biomaterial and the amount of acrylic chains linked onto the protein backbone. The performance of the resulting materials was evaluated in a water-based coating application. The used methacrylation approach allowed the maximum compatibilization of 33% of casein in the hybrid polymer. The as-obtained casein-derived films were proven to exhibit superior water resistance, which would open a new possibility for designing biobased coatings in several fields.

Analysis by size exclusion chromatography of the graft terpolymer present in MBS

The molar mass distribution (MMD) and branching distribution (BD) of the graft terpolymer present in MBS (methyl methacrylate-butadiene-styrene, MMA-B-St) were estimated by size exclusion chromatography (SEC) with a series of three detectors: a UV photometer, a specific viscometer (SV), and a differential refractometer (DR). A solvent extraction procedure was employed to isolate the main MBS constituents: unreacted polybutadiene (PB), a PMMA-PS free copolymer (FC), and the PB-g-(PMMA-PS) graft terpolymer (GT). The FC was analyzed by UV + DR, yielding an almost uniform St mass fraction. The analysis of the GT involved the following assumptions: (i) the composition of the grafted branches coincides with that of the FC; (ii) the volumetric contractions of the molecules are represented by the Zimm–Stockmayer equations for randomly branched homopolymers; (iii) the low molar mass fraction exhibits a single branch per molecule; and (iv) the Mark–Houwink–Sakurada (MHS) parameters of the hypothetical homologous linear terpolymer are estimated by weighting the MHS constants of the PB and FC according to their mass fractions in the GT. The data treatment employed also enabled the branching exponent (ε) that relates the geometric and hydrodynamic contraction factors to be estimated, yielding ε ≈ 1.45.