Characterization of mechanical parameters of microbeads by means of analytical centrifugation

Regulation of mechanical properties of microcapsules and their applications

Microcapsules encapsulating payloads are one of the most promising delivery methods. The mechanical properties of microcapsules often determine their application scenarios. For example, microcapsules with low mechanical strength are more widely used in biomedical applications due to their superior biocompatibility, softness, and deformability. In contrast, microcapsules with high mechanical strength are often mixed into the matrix to enhance the material. Therefore, characterizing and regulating the mechanical properties of microcapsules is essential for their design optimization. This paper first outlines four methods for the mechanical characterization of microcapsules: nanoindentation technology, parallel plate compression technology, microcapillary technology, and deformation in flow. Subsequently, the mechanisms of regulating the mechanical properties of microcapsules and the progress of applying microcapsules with different degrees of softness and hardness in food, textile, and pharmaceutical formulations are discussed. These regulation mechanisms primarily include altering size and morphology, introducing sacrificial bonds, and construction of hybrid shells. Finally, we envision the future applications and research directions for microcapsules with tunable mechanical properties.

Pickering emulsion stabilization with colloidal lignin is enhanced by salt-induced networking in the aqueous phase

We study the effect of electrolytes on the stability in aqueous media of spherical lignin particles (LP) and its relevance to Pickering emulsion stabilization. Factors considered included the role of ionic strength on morphology development, LP size distribution, surface charge, interfacial adsorption, colloidal and wetting behaviors. Stable emulsions are formed at salt concentrations as low as 50 mM, with the highest stability observed at a critical concentration (400 mM). We show salt-induced destabilization of LP aqueous dispersions at an ionic strength >400 mM. At this critical concentration LP flocculation takes place and particulate networks are formed. This has a profound consequence on the stability of LP-stabilized Pickering emulsions, affecting rheology and long-term stability. The results along with quartz microgravimetry and confocal microscopy observations suggest a possible mechanism for stabilization that considers the interfacial adsorption of LP at oil/water interfaces. The often-unwanted colloidal LP destabilization in water ensues remarkably stable Pickering emulsions by the effect of network formation.

Assessing contamination of microplastics in the Ghanaian coastal sea using a self-constructed LADI trawl

Almost everywhere in the marine ecosystem contains microplastics. Although their environmental contamination is a global problem, relatively little is known about their distribution and abundance in the Gulf of Guinea. This study looked at the spatial dynamics of microplastics in the sea surface water off the coast of Ghana. Four chosen areas were found to have non-variable concentrations ranging from 1.14 to 2.79 particles m^-3 using a self-constructed Low-Tech Aquatic Debris Instrument (LADI) trawl (333 μm mesh). The most abundant shapes were fragments and pellets, while the most common colors were colored and transparent particles. The polymer types found in the microplastics selected for investigation using Fourier Transform Infrared spectroscopy in Attenuated Total Reflectance mode (ATR-FT-IR) were Polypropylene, Polyethylene, and Polystyrene. These results provide an important baseline on microplastic pollution along the Ghanaian coast suggesting the LADI trawl as an accurate quantitative sampling tool for microplastics from sea surface water.

A Study of the Printability of Alginate-Based Bioinks by 3D Bioprinting for Articular Cartilage Tissue Engineering

Three-dimensional bioprinting combined with natural hydrogels is a promising technology for the treatment of several pathologies and different tissue regeneration. One of the most studied tissues is cartilage, a complex and avascular tissue that displays a limited self-repair capacity after injuries. Herein, the development of alginate-based hydrogels and scaffolds containing different microstructure is presented and the printability of alginate by 3D bioprinting is studied. Rheological characterization was performed for the determination of viscosity and viscoelastic properties of hydrogels and mechanical characterization was carried out for the determination of compressive modulus of alginate hydrogels. All these characteristics were correlated with alginate behaviour during 3D bioprinting process. For the printability evaluation filament diameter, perimeter of the pores, area of the pores and shrinkage of alginate scaffolds were measured. The results demonstrate that alginate microstructure has a great influence on its printability and on hydrogels' physicochemical properties. Molecular weight of alginate determines its viscosity while M/G ratio determines cross-linking conditions and mechanical properties that vary with cross-linking density. These results suggest the importance of an exhaustive control of the viscoelastic and mechanical properties of alginate hydrogels to obtain structures with high resolution and precision.

Tentacle-type poly(hydroxamic acid)-modified macroporous cellulose beads: Synthesis, characterization, and application for heavy metal ions adsorption

Herein, a facile yet efficient template method to fabricate macroporous cellulose beads (MCBs) is reported. In this method, micro-size CaCO₃ is utilized to create macroporous structure for fast mass transfer, and tentacle-type poly(hydroxamic acid) as adsorption ligand is immobilized on the MCBs to improve adsorption capacity. The obtained tentacle-type poly(hydroxamic acid)-modified MCMs (TP-CMCBs) show uniform spherical shape (about 80 μm), bimodal pore system (macropores≈3.0 μm; diffusional pores≈14.5 nm), and high specific surface area (52.7 m²/g). The adsorption performance of TP-CMCBs is evaluated by heavy metal ions adsorption. TP-CMCBs exhibit not only high adsorption capacities (342.5, 261.5 and 243.2 mg/g for Cu²⁺, Mn²⁺ and Ni²⁺, respectively.), but also fast adsorption rate (>70% of its equilibrium uptake within 30 min). Additionally, TP-CMCBs have excellent reusability, as evidenced by that the adsorption capacities have no obvious change even after five-time consecutive adsorption-desorption cycles. All results demonstrate that the proposed TP-CMCBs have great potential in removal of heavy metal ions.

Pelagic microplastics in surface water of the Eastern Indian Ocean during monsoon transition period: Abundance, distribution, and characteristics

Microplastics (MPs) have been documented in almost all marine environments, including coastal regions, the open ocean, and the deep sea. However, relatively little knowledge was available about MP pollution in the open ocean, especially the Indian Ocean. We conducted field observations at 36 stations in the Eastern Indian Ocean (EIO), using a typical manta trawl with a mesh size of 330 μm for surface water sampling. Ours is the first study to obtained comprehensive and comparable baseline data about MPs in the EIO, including abundance, spatial distribution and characteristics. Abundance of MPs in the EIO varied from 0.01 items m^-2 to 4.53 items m^-2, with an average concentration of 0.34 ± 0.80 item m^-2. The mean concentration of MPs in the Bay of Bengal (BoB) was 2.04 ± 2.26 items m^-2 and 0.16 ± 0.17 items m^-2 in the open ocean of the EIO. These results illustrate the high spatial heterogeneity of MPs distribution. Micro-FTIR analysis of polymer composition showed that the vast majority of MPs consisted of polypropylene (PP, 51.11%) and polyethylene (PE, 20.07%). Our data show that MP pollution in the EIO, whether in the epeiric sea or the open ocean, is among the highest of the world's oceans. The BoB is likely to become a MP hotspot due to the vast input of land-based plastics and the presence of multiscale recirculation gyres. These results are absolutely thought provoking: The EIO needs more attention on MPs.

Preparation and characterization of highly porous cellulose-agarose composite chromatographic microspheres for enhanced selective separation of histidine-rich proteins

In this work, the porous cellulose-agarose microspheres with high specific surface area and enhanced mechanical strength are prepared by a novel chemical crosslinking method. The crosslinking reaction homogeneously proceeds between polysaccharides, and the covalent bonding network is generated to replace the inherent hydrogen bonding network of cellulose. The prepared microspheres exhibit low crystallinity of 12.45%, which means high content of amorphous regions. The micro-meso-macroporous structure of microspheres in morphology is conducive to high permeability and adsorption capacity, and the microspheres possess high specific surface area of 183.81 m²/g. The affinity chromatographic microspheres are prepared by immobilizing Cu²⁺, which exhibits high adsorption capacity of 197.65 mg/g for bovine hemoglobin (BHb), fast adsorption rate wihin 40 minutes, well-selectivity, and excellent recyclability in ten cycles. We expect that this work to provide an outstanding candidate for the high performance of biomacromolecular purification.