Preparation of starch/PVA nanoparticles and evaluation of their ability to stabilize Pickering emulsions.

Biodegradable and biocompatible polymer-based nanoparticles (NPs) hold great promise for various industries. We report the first development of composite NPs consisting of starch (St) and polyvinyl alcohol (PVA) using the nanoprecipitation technique with ethanol as an antisolvent. We varied the St:PVA ratios in the precursor solutions to evaluate their impact on the structure and properties of the composite NPs. The ratios used were 4:1, 1:1, and 1:4. Characterization by X-ray diffraction, differential scanning calorimetry, and thermogravimetric analysis revealed distinct XRD and TGA patterns for the composite St/PVANPs compared to their corresponding physical blends. This indicated the presence of mixed St/PVA crystallites within their structures. Additionally, the crystallinity of St/PVANPs increased with rising St content. Dynamic light scattering and scanning electron microscopy showed that nanoparticle sizes increased with higher PVA proportions. The St/PVANPs showed superior performance as stabilizers in Pickering emulsions, forming denser continuous networks in the gel-like structure of the emulsions. Additionally, increasing the PVA content in the composition of St/PVANPs strengthened the structure of Pickering emulsions. The emulsion stabilized by St20/PVA80NPs showed exceptional stability for one month. These findings highlight the potential of St/PVANPs as innovative materials for various applications, including emulsion stabilization.

Design of Dosage Forms with Improved Biopharmaceutical Properties.

The development of a pharmaceutical product consists of giving a drug an optimal dosage form (a certain state of aggregation, consistency, structural, mechanical, physicochemical, and functional properties), which ensure stability, the possibility of accurate dosage, the required pharmacological effect, and ease of administration with minimal side effects [...].

ß-Cyclodextrin Modified Hydrogels of Kappa-Carrageenan for Methotrexate Delivery.

This work is aimed at developing a kappa-carrageenan (kCR) gel with increased methotrexate (MTX) content. ß-Cyclodextrin (ßCD), which is able to inclusion complex formation with MTX, has been used to increase the drug concentration in the hydrogel. The rheological behavior of the designed gels was investigated and the influence of MTX and ßCD on the viscoelastic properties of kCR gel was studied in detail. The effect of ßCD and its concentration on the MTX-releasing rate from the kCR gels was examined. The properties of kappa- and iota-carrageenans loaded with MTX were compared and the differences observed were explained in terms of different binding affinities of MTX to these polymers. The obtained gels provided desirable viscoelastic properties useful for topical application.

Photocatalytic Activity of Fibrous Ti/Ce Oxides Obtained by Hydrothermal Impregnation of Short Flax Fibers.

Fibrous Ti/Ce oxide photocatalysts were prepared for the first time by a biomimetic solution process using short flax fibers (flax straw processing waste) as a biotemplate. Titanium polyhydroxy complex solutions with 3% and 5% cerium were used as precursors. Flax fibers were impregnated in an autoclave under hydrothermal conditions. Ti/Ce oxides were obtained from the biotemplate by annealing at 600 °C. The photocatalytic activity of the Ti/Ce oxides was studied by the adsorption and decomposition of the dye rhodamine B under UV irradiation. The photocatalytic decomposition of the dye was 50% and 75% faster for Ti/Ce oxides with 3% and 5% Ce, respectively, than for the analogous undoped fibrous TiO2. The morphologies, textures, and structures of the photocatalysts were studied by scanning electron microscopy, low temperature N2 adsorption/desorption, UV-Vis spectroscopy, and X-ray and XPS analytical methods. It was shown that the introduction of Ce into the precursor solution increased the surface irregularity of the Ti/Ce oxide crystallites compared to pure TiO2. This effect scaled with the Ce concentration. Ce improved the UV light absorption of the material. The Ti/Ce oxides contained Ce4+/Ce3+ pairs that played an important role in redox processes and intensified the photocatalytic activity.

Structure and properties of biodegradable maize starch/chitosan composite films as affected by PVA additions.

The aim of this work was to develop environmentally safe multi-purpose composite films based on maize starch (St), low weight chitosan (Chit), and Polyvinyl Alcohol (PVA). To this end the structural features and functional characteristics of the films were evaluated. The PVA content in the blends was varied in the range of 0-40 wt% (based on the total weight of the blend), the St/Chit ratio was fixed at 70/30 in weight. The results of the St/Chit/PVA composite films analysis by X-ray diffraction, FTIR spectroscopy, and SEM methods showed that the PVA concentration increase in the compositions resulted in phase separation between PVA and two other components of the blends, while the intermolecular interactions between St and Chit grew. The mechanical characteristics of the composite films improved with an increase in the PVA concentration. The UV-protective ability and biodegradation rate of St/Chit/PVA films decreased as the PVA content grew. The results of this systematic study enabled us to recommend the 10-20 wt% PVA additions to the St/Chit (70/30) matrix as an optimal supplement ensuring the formation of the films with advanced mechanical and functional characteristics without loss of biodegradability.

Effect of fibrous TiO2 filler on the structural, mechanical, barrier and optical characteristics of biodegradable maize starch/PVA composite films.

The work focuses on producing and evaluating "green" multifunctional film materials based on a mixed eco-friendly starch/PVA matrix and filled with fibrous TiO2 particles formed by the ultrasound-assisted biotemplate method. Starch/PVA/TiO2 film-forming dispersions were prepared by heating and intensively mixing the components at the same time, and then composite films were obtained by the casting method. The influence of the TiO2 filler content on the morphological and structural characteristics of the composites was studied by the optical microscopy, X-ray diffraction, DSC and FTIR spectroscopy methods. The compatibility of the polymer components was improved by incorporating a small amount of the filler (0.01 and 0.05 wt% of the dry polymer weight). The dependence of tensile strength and water vapor permeability on the filler content was shown to have a maximum at the TiO2 concentration of 0.05 wt%. The UV- protective ability of the composite films rose as the TiO2 concentration increased. The presence of TiO2 in the biodegradable starch/PVA matrix had little effect on the soil burial biodegradation rate of the composite films. Thus, the obtained results show that fibrous TiO2 particles at optimum concentration of 0.01 and 0.05 wt% can improve starch/PVA films properties and extend their functionality.

Preparation and Characterization of Polyvinylpyrrolidone/Cellulose Nanocrystals Composites.

Composite films and aerogels of polyvinylpyrrolidone/cellulose nanocrystals (PVP/CNC) were prepared by solution casting and freeze-drying, respectively. Investigations into the PVP/CNC composite films and aerogels over a wide composition range were conducted. Thermal stability, morphology, and the resulting reinforcing effect on the PVP matrix were explored. FTIR, TGA, DSC, X-ray diffraction, SEM, and tensile testing were used to examine the properties of the composites. It was revealed PVP-assisted CNC self-assembly that produces uniform CNC aggregates with a high aspect ratio (length/width). A possible model of the PVP-assisted CNC self-assembly has been considered. Dispersibility of the composite aerogels in water and some organic solvents was studied. It was shown that dispersing the composite aerogels in water resulted in stable colloidal suspensions. CNC particles size in the redispersed aqueous suspensions was near similar to the CNC particles size in never-dried CNC aqueous suspensions.

Photocatalytic and adsorption properties of TiO2-pillared montmorillonite obtained by hydrothermally activated intercalation of titanium polyhydroxo complexes.

We report on a new approach for the synthesis of TiO2-pillared montmorillonite, where the pillars exhibit a high degree of crystallinity (nanocrystals) representing a mixture of anatase and rutile phases. The structures exhibit improved adsorption and photocatalytic activity as a result of hydrothermally activated intercalation of titanium polyhydroxo complexes (i.e., TiCl4 hydrolysis products) in a solution with a concentration close to the sol formation limit. The materials, produced at various annealing temperatures from the intercalated samples, were characterized by infrared spectroscopy, differential scanning calorimetry (DSC)/thermogravimetric analysis (TGA), X-ray diffraction, dynamic light scattering (DLS) measurements, and liquefied nitrogen adsorption/desorption. The photocatalytic activity of the TiO2-pillared materials was studied using the degradation of anionic (methyl orange, MO) and cationic (rhodamine B, RhB) dyes in water under UV irradiation. The combined effect of adsorption and photocatalysis resulted in removal of 100% MO and 97.5% RhB (with an initial concentration of 40 mg/L and a photocatalyst-sorbent concentration of 1 g/L) in about 100 minutes. The produced TiO2-pillared montmorillonite showed increased photocatalytic activity as compared to the commercially available photocatalyst Degussa P25.