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.

Microstructure induction of quaternary ammonium chitosan microcapsules based on magnetic field and study of their aroma release.

Traditional pressure-sensitive microcapsules used in textiles face challenges of insufficient environmental friendliness in the production process and uncontrollable fragrance release. To address this issue, this study utilized quaternary ammonium chitosan and silica as wall materials to develop a magnetic aromatic microcapsule. The microstructure of the microcapsules was controlled by magnetic field induction, and its evolution pattern was investigated. After magnetic field induction, the microcapsules exhibited a trend of evolving from spherical to asymmetrical shapes, accompanied by significant changes in mechanical properties. Asymmetrical microcapsules showed higher adhesion and lower stiffness. When applied to cotton textiles, the cotton textiles treated with asymmetrical microcapsules released 63.40 % of lavender essential oil after 200 friction cycles, representing an 11.3 % improvement in release efficiency compared to regular microcapsules, indicating better mechanical stimulus responsiveness. Additionally, in antibacterial tests, aromatic cotton exhibited a 96.52 % inhibition ratio against Escherichia coli. In summary, this study explores methods to adjust the mechanical properties of microcapsules and the relationship between mechanical properties and microstructure, providing a new approach for functional textiles.

Mussel-inspired chitosan and its applications in the biomedical field.

Chitosan (CS) has physicochemical properties including solubility, crystallinity, swellability, viscosity, and cohesion, along with biological properties like biocompatibility, biodegradation, antioxidant, antibacterial, and antitumor effects. However, these characteristics of CS are greatly affected by its degree of deacetylation, molecular weight, pH and other factors, which limits the application of CS in biomedicine. The modification of CS with catechol-containing substances inspired by mussels can not only improve these properties of CS, but also endow it with self-healing property, providing an environmentally friendly and sustainable way to promote the application of CS in biomedicine. In this paper, the properties of CS and its limitation in the biomedical filed are introduced in detail. Then, the modification methods and properties of substances with catechol groups inspired by mussels on CS are reviewed. Finally, the applications of modified CS in the biomedical field of wound healing, drug delivery, anticancer therapy, biosensor and 3D printing are further discussed. This review can provide valuable information for the design and exploitation of mussel-inspired CS in the biomedical field.

Inclusion complexes of ß-cyclodextrin with isomeric ester aroma compounds: Preparation, characterization, mechanism study, and controlled release.

Cyclodextrins (CDs) have been discovered to provide an efficient solution to the limited application of ester aroma molecules used in food, tobacco, and medication due to their strong smell and unstable storage. This work combined molecular modeling and experimental to analyze the conformation and controlled release of isomeric ester aroma compounds/ß-CD inclusion complexes (ICs). The investigation revealed that ester aroma compounds could be effectively encapsulated within the ß-CD cavity, forming ICs with low binding affinity. Furthermore, the key driving forces in ICs were identified as hydrogen bonds and van der Waals interactions through theoretical simulation. Results from the Fourier transform infrared (FTIR), nuclear magnetic resonance (NMR) and Isothermal titration calorimetry (ITC) experiments confirmed the intermolecular interaction predicted by the molecular model. Notably, the release rate of aroma compounds from L-menthyl acetate/ß-CD (LMA/ß-CD) IC exceeded that of terpinyl acetate/ß-CD (TA/ß-CD) IC. This difference is attributed to the length of the chain of aroma molecules and the variation in the position of functional groups, influencing the stable formation of ICs with ß-CD. These findings hold potential implications for refining the application of ICs across diverse industries.

Research progress of starch as microencapsulated wall material.

Starch is non-toxic, low cost, and possesses good biocompatibility and biodegradability. As a natural polymer material, starch is an ideal choice for microcapsule wall materials. Starch-based microcapsules have a wide range of applications and application prospects in fields such as food, pharmaceuticals, cosmetics, and others. This paper firstly reviews the commonly used wall materials and preparation methods of starch-based microcapsules. Then the effect of starch wall materials on microcapsule properties is introduced in detail. It is expected to provide researchers with design inspiration and ideas for the development of starch-based microcapsules. Next the applications of starch-based microcapsules in various fields are presented. Finally, the future trends of starch-based microcapsules are discussed. Molecular simulation, green chemistry, and solutions to the main problems faced by resistant starch microcapsules may be the future research trends of starch-based microcapsules.

Recent advances of magnetic chitosan hydrogel: Preparation, properties and applications.

Magnetic chitosan hydrogels are organic-inorganic composite material with the characteristics of both magnetic materials and natural polysaccharides. Due to its biocompatibility, low toxicity and biodegradability, chitosan, a natural polymer has been widely used for preparing magnetic hydrogels. The addition of magnetic nanoparticles to chitosan hydrogels not only improves their mechanical strength, but also endows them with magnetic thermal effects, targeting capabilities, magnetically-sensitive release characteristics, easy separation and recovery, thus enabling them to be used in various applications including drug delivery, magnetic resonance imaging, magnetothermal therapy, and adsorption of heavy metals and dyes. In this review, the physical and chemical crosslinking methods of chitosan hydrogels and the methods for binding magnetic nanoparticles in hydrogel networks are first introduced. Subsequently, the properties of magnetic chitosan hydrogels were summarized including mechanical properties, self-healing, pH responsiveness and properties in magnetic fields. Finally, the potential for further technological and applicative advancements of magnetic chitosan hydrogels is discussed.

Microcapsules based on octenyl succinic anhydride (OSA)-modified starch and maltodextrins changing the composition and release property of rose essential oil.

Octenyl succinic anhydride (OSA)-modified starch and maltodextrins (MDs) are important carbohydrate polymers as wall materials. However, few studies have shown whether these two wall materials affect the composition of core materials. In this work, we investigated the effects of OSA-modified starch and MD on the release property of essential oils. Results showed that among the seven characteristic aroma components (CACs) of rose essential oil (REO), the esters released the fastest, followed by the alcohols, while the release of the phenols was the slowest. Environmental factors such as temperature and relative humidities (RHs) had significant influences on the release kinetics of CACs in REO. This work provides new insights into the use of OSA-modified starch and MDs as wall materials for encapsulating complex and bioactive components.