In recent years, the demand for non-surfactant based Pickering emulsions in many industrial applications has grown significantly because of the option to select biodegradable and sustainable ...materials with low toxicity as emulsion stabilisers. Usually, emulsions are a dispersion system, where synthetic surfactants or macromolecules stabilise two immiscible phases (typically water and oil phases) to prevent coalescence. However, synthetic surfactants are not always a suitable choice in some applications, especially in pharmaceuticals, food and cosmetics, due to toxicity and lack of compatibility and biodegradability. Therefore, this review reports recent literature (2018-2021) on the use of comparatively safer biodegradable polysaccharide particles, proteins, lipids and combinations of these species in various Pickering emulsion formulations. Also, an overview of the various tuneable factors associated with the functionalisation or surface modification of these solid particles, that govern the stability of the Pickering emulsions is provided.
In a Pickering emulsion, solid particles accumulate at the interface between two immiscible phases to reduce coalescence by forming a physical barrier. Using bioderived particles is becoming popular to generate more sustainable Pickering emulsions.
An overview of microspheres manufactured for use in biomedical applications based on recent literature is presented in this review. Different types of glasses (i.e. silicate, borate, and phosphates), ...ceramics and polymer-based microspheres (both natural and synthetic) in the form of porous , non-porous and hollow structures that are either already in use or are currently being investigated within the biomedical area are discussed. The advantages of using microspheres in applications such as drug delivery, bone tissue engineering and regeneration, absorption and desorption of substances, kinetic release of the loaded drug components are also presented. This review also reports on the preparation and characterisation methodologies used for the manufacture of these microspheres. Finally, a brief summary of the existing challenges associated with processing these microspheres which requires further research and development are presented.
•Highly porous 3D scaffolds were fabricated from chitosan-agarose blends.•Pore sizes for the blended scaffolds were significantly smaller than for agarose and chitosan only.•The blended scaffolds ...showed enhanced mechanical properties.•FTIR analysis suggested a hydrogen bonding interaction between chitosan and agarose.•All wet blend scaffolds showed instant full recovery after near full compression.
This study aimed to explore the correlation between mechanical and structural properties of chitosan-agarose blend (Ch-Agrs) scaffolds. Porosity of Ch-Agrs scaffolds was constant at 93%, whilst pore sizes varied between 150 and 550 μm. Pore sizes of the blend scaffolds (150–300 μm) were significantly smaller than for either agarose or chitosan scaffolds alone (ca. 500 μm). Ch50-Agrs50 blend scaffold showed the highest compressive modulus and strength values (4.5 ± 0.4 and 0.35 ± 0.03 MPa) due to reduction in the pore size. The presence of agarose improved the stability of the blends in aqueous media. The increase in compressive properties and residual weight after the TGA test, combined with the reduction in the swelling percentage of the blend scaffolds suggested an interaction between chitosan and agarose via hydrogen bonding which was confirmed using FTIR analysis. All wet blend scaffolds exhibited instant recovery after full compression. This study shows the potential of Ch-Agrs scaffolds for repairing soft tissue.
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Orthobiologics is a rapidly advancing field utilising cell-based therapies and biomaterials to enable the body to repair and regenerate musculoskeletal tissues. This paper reports on ...a cost-effective flame spheroidisation process for production of novel porous glass microspheres from calcium phosphate-based glasses to encapsulate and deliver stem cells. Careful selection of the glass and pore-forming agent, along with a manufacturing method with the required processing window enabled the production of porous glass microspheres via a single-stage manufacturing process. The morphological and physical characterisation revealed porous microspheres with tailored surface and interconnected porosity (up to 76 ± 5%) with average pore size of 55 ± 8 µm and surface areas ranging from 0.34 to 0.9 m2 g−1. Furthermore, simple alteration of the processing parameters produced microspheres with alternate unique morphologies, such as with solid cores and surface porosity only. The tuneable porosity enabled control over their surface area, degradation profiles and hence ion release rates. Furthermore, cytocompatibility of the microspheres was assessed using human mesenchymal stem cells via direct cell culture experiments and analysis confirmed that they had migrated to within the centre of the microspheres. The novel microspheres developed have huge potential for tissue engineering and regenerative medicine applications.
This manuscript highlights a simple cost-effective one-step process for manufacturing porous calcium phosphate-based glass microspheres with varying control over surface pores and fully interconnected porosity via a flame spheroidisation process. Moreover, a simple alteration of the processing parameters can produce microspheres which have a solid core with surface pores only. The tuneable porosity enabled control over their surface area, degradation profiles and hence ion release rates. The paper also shows that stem cells not only attach and proliferate but more importantly migrate to within the core of the porous microspheres, highlighting applications for bone tissue engineering and regenerative medicine.
Oil-in-water emulsions have been stabilized by functionalized cellulose nanofibrils bearing either a negative (oxidized cellulose nanofibrils, OCNF) or a positive (cationic cellulose nanofibrils, ...CCNF) surface charge. The size of the droplets was measured by laser diffraction, while the structure of the shell of the Pickering emulsion droplets was probed using small-angle neutron scattering (SANS), confocal laser scanning microscopy (CLSM), scanning electron microscopy (SEM), and rheology measurements. Both OCNF- and CCNF-stabilized emulsions present a very thick shell (>100 nm) comprised of densely packed CNF. OCNF-stabilized emulsions proved to be salt responsive, influencing the droplet aggregation and ultimately the gel properties of the emulsions, while CCNF emulsions, on the other hand, showed very little salt-dependent behavior.
This study aimed to quantify the influence of clays and partially oxidised cellulose nanofibrils (OCNF) on gelation as well as characterise their physical and chemical interactions. Mixtures of ...Laponite and montmorillonite clays with OCNF form shear-thinning gels that are more viscous across the entire shear range than OCNF on its own. Viscosity and other rheological properties can be fine-tuned using different types of clay at different concentrations (0.5–2 wt%). Laponite particles are an order of magnitude smaller than those of montmorillonite (radii of 150 Å compared to 2000 Å) and are therefore able to facilitate networking of the cellulose fibrils, resulting in stronger effects on rheological properties including greater viscosity. This work presents a mechanism for modifying rheological properties using renewable and environmentally-friendly nanocellulose and clays which could be used in a variety of industrial products including home and personal care formulations.
An overview of the formation of calcium phosphate under in vitro environment on the surface of a range of bioactive materials (e.g. from silicate, borate, and phosphate glasses, glass-ceramics, ...bioceramics to metals) based on recent literature is presented in this review. The mechanism of bone-like calcium phosphate (i.e. hydroxyapatite) formation and the test protocols that are either already in use or currently being investigated for the evaluation of the bioactivity of biomaterials are discussed. This review also highlights the effect of chemical composition and surface charge of materials, types of medium (e.g. simulated body fluid, phosphate-buffered saline and cell culture medium) and test parameters on their bioactivity performance. Finally, a brief summary of the biomedical applications of these newly formed calcium phosphate (either in the form of amorphous or apatite) is presented.
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•Am and Pu were adsorbed and separated using a single extraction chromatography DGA column.•Pu was eluted from the column completely using on-column reduction of Pu(IV) to ...Pu(III).•241Am and 239,240Pu measurements by accelerator mass spectrometry (AMS) agree with the certified values in two SRMs.
A simple method was developed to separate Pu and Am using single column extraction chromatography employing N,N,N′,N′-tetra-n-octyldiglycolamide (DGA) resin. Isotope dilution measurements of Am and Pu were performed using accelerator mass spectrometry (AMS) and alpha spectrometry. For maximum adsorption Pu was stabilized in the tetra valent oxidation state in 8M HNO3 with 0.05M NaNO2 before loading the sample onto the resin. Am(III) was adsorbed also onto the resin from concentrated HNO3, and desorbed with 0.1M HCl while keeping the Pu adsorbed. The on-column reduction of Pu(IV) to Pu(III) with 0.02M TiCl3 facilitated the complete desorption of Pu. Interferences (e.g. Ca2+, Fe3+) were washed off from the resin bed with excess HNO3. Using NdF3, micro-precipitates of the separated isotopes were prepared for analysis by both AMS and alpha spectrometry. The recovery was 97.7±5.3% and 95.5±4.6% for 241Am and 242Pu respectively in reagents without a matrix. The recoveries of the same isotopes were 99.1±6.0 and 96.8±5.3% respectively in garden soil. The robustness of the method was validated using certified reference materials (IAEA 384 and IAEA 385). The measurements agree with the certified values over a range of about 1–100Bqkg−1. The single column separation of Pu and Am saves reagents, separation time, and cost.
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