Assessment of the delivery of citronella oil from microcapsules supported on wool fabrics

Preparation and sustained-release of chitosan-alginate bilayer microcapsules containing aromatic compounds with different functional groups

This study investigated the release of aromatic compounds with distinct functional groups within bilayer microcapsules. Bilayer microcapsules of four distinctive core materials (benzyl alcohol, eugenol, cinnamaldehyde, and benzoic acid) were synthesized via freeze-drying. Chitosan (CS) and sodium alginate (ALG) were used as wall materials. CS concentration, using orthogonal experiments with the loading ratio as a metric. Under optimal conditions, three other types of microcapsules (cinnamic aldehyde, benzoic acid, and benzyl alcohol) were obtained. The four types of microcapsules were characterized using Fourier-transform infrared (FTIR) spectroscopy, scanning electron microscopy (SEM), transmission electron microscope (TEM), and thermogravimetric analysis (TGA), and their sustained release characteristics were evaluated. The optimal conditions were: CS dosage, 1.2 %; CS-to-eugenol mass ratio, 1:2; and CS-to-ALG mass ratio, 1:1. By comparing the IR spectra of the four types of microcapsules, wall material, and core material, the core materials were revealed to be encapsulated within the wall material. SEM results revealed that the granular protuberances on the surface of the microcapsules were closely aligned and persistent when magnified 2000×. The TEM results indicated that all four microcapsules had a spherical and bilayer structure. The thermal stability and sustained release results showed that the four microcapsules were more resilient and less volatile than the four core materials. The release conformed to first-order kinetics, and the release ratios of the four microcapsules were as follows: benzyl alcohol microcapsules ˃ eugenol microcapsules ˃ cinnamaldehyde microcapsules ˃ benzoic acid microcapsules. The prepared bilayer microcapsules encapsulated four different core materials with good sustained release properties.

Reservoir Effect of Textile Substrates on the Delivery of Essential Oils Microencapsulated by Complex Coacervation

Microcapsules are being used in textile substrates increasingly more frequently, availing a wide spectrum of possibilities that are relevant to future research trends. Biofunctional Textiles is a new field that should be carefully studied, especially when dealing with microencapsulated essential oils. In the final step, when the active principle is delivered, there are some possibilities to quantify and simulate its doses on the skin or in the environment. At that stage, there is a phenomenon that can help to better control the delivery and the reservoir effect of the textile substrate. Depending on the chemical characteristics of the molecule to be delivered, as well as the structure and chemical nature of the fabric where it has been applied, there is physicochemical retention exerted by fibers that strongly controls the final rate of principle active delivery to the external part of the textile substrate. The study of this type of effect in two different substrates (cotton and polyester) will be described here regarding two different essential oils microencapsulated and applied to the substrates using padding technology. The experimental results of the final drug delivery demonstrate this reservoir effect in both essential oils.

Preparation and characterization of a modified Canna starch as a wall material for the encapsulation of methyleugenol improves its antifungal activity against Fusarium trichothecioides

In this study, α-amylase (α-A) and 2-octenylsuccinic anhydride (OSA)-modified Canna starch (Cs) were prepared and characterized as wall materials and encapsulated with methyleugenol (α-A-OSA-Cs-methyleugenol); their in vitro antifungal activity against Fusarium trichothecioides (F. trichothecioides) was also investigated. The encapsulation efficiency under optimal encapsulation conditions was 83.98%. The results of particle size, polydispersity index (PDI), zeta potential, electron scanning microscopy and Fourier transform infrared spectroscopy showed that the modified Cs had superior physicochemical properties; it was also demonstrated that methyleugenol successfully entered the pores of Cs. The in vitro release study showed that α-A-OSA-Cs could effectively reduce their volatility under different temperature environments. α-A-OSA-Cs have excellent performance as slow-release wall materials, and after encapsulation with methyleugenol, the inhibition ability of F. trichothecioides mycelium growth was dose-dependent and improved, extending the shelf life of potatoes, which has good commercial value in the field of slow-release preservatives.

Design of gum Arabic/gelatin composite microcapsules and their cosmetic applications in encapsulating tea tree essential oil

Microencapsulation has been widely used to protect essential oils, facilitating their application in cosmetics. In this study, gelatin, gum arabic and n-butyl cyanoacrylate were used as wall materials, and composite microcapsules of tea tree essential oil (TTO) were prepared using a combination of composite coagulation and in situ polymerization methods. When the ratio of gelatin to gum arabic is 1 : 1, the ratio of TTO to n-butyl cyanoacrylate is 4 : 1, the curing time is 10 h, and the encapsulation efficiency (EE) under these conditions is 73.61%. Morphological observation showed that the composite capsule was a micron-sized spherical particle with an average particle size of 10.51 μm, and Fourier transform infrared spectroscopy (FT-IR) confirmed a complex coagulation reaction between gelatin and gum arabic, and the disappearance of the n-butyl cyanoacrylate peak indicated that the film was formed in a condensation layer. The thermogravimetric analysis (TGA) results showed that the composite capsule greatly improved the thermal stability of TTO. Rheological testing showed that the viscosity and viscoelasticity of the surface composite capsules have been improved. In addition, the composite capsule showed good stability in the osmotic environment and has good sustained-release performance and antioxidant capacity in the average human skin environment.

Characterization, Thermal Stability and Antimicrobial Evaluation of the Inclusion Complex of Litsea cubeba Essential Oil in Large-Ring Cyclodextrins (CD9-CD22)

Food safety issues are becoming increasingly important as a result of contamination with foodborne pathogenic bacteria. Plant essential oil is a safe and non-toxic natural antibacterial agent that can be used to develop antimicrobial active packaging materials. However, most essential oils are volatile and require protection. In the present study, LCEO and LRCD were microencapsulated through coprecipitation. The complex was investigated using GC-MS, TGA, and FT-IR spectroscopy. According to the experimental results, it was found that LCEO entered the inner cavity of the LRCD molecule and formed a complex with LRCD. LCEO had a significant and broad-spectrum antimicrobial effect against all five microorganisms tested. At 50 °C, the microbial diameter of the essential oil and its microcapsules showed the least change, indicating that this essential oil has high antimicrobial activity. In research on microcapsule release, LRCD has proven to be a perfect wall material for controlling the delayed release of essential oil and extending the duration of antimicrobial activity. LRCD effectively extends antimicrobial duration by encasing LCEO, thus improving its heat stability and antimicrobial activity. The results presented here indicate that LCEO/LRCD microcapsules can be further utilized in the food packaging industry.

Application of Lavender-Oil Microcapsules to Functionalized PET Fibers

Surface treatments for textile substrates have received significant attention from researchers around the world. Ozone and plasma treatments trigger a series of surface alterations in textile substrates that can improve the anchoring of other molecules or particles on these substrates. This work aims to evaluate the effect of ozone and plasma treatments on the impregnation of polymeric microcapsules containing lavender oil in polyester fabrics (PES). Microcapsules with walls of chitosan and gum arabic were prepared by complex coacervation and impregnated in PES, plasma-treated PES, and ozone-treated PES by padding. The microcapsules were characterized for their size and morphology and the surface-treated PES was evaluated by FTIR, TGA, SEM, and lavender release. The microcapsules were spherical in shape, with smooth surfaces. The FTIR analyses of the textile substrates with microcapsules showed bands referring to the polymers of the microcapsules, but not to the lavender; this was most likely because the smooth surface of the outer wall did not retain the lavender. The mass loss and the degradation temperatures measured by TGA were similar for all the ozone-treated and plasma-treated polyester samples. In the SEM images, spherical microcapsules and the impregnation of the microcapsules of larger sizes were perceived. Through the lavender release, it was observed that the plasma and ozone treatments interfered both with the amount of lavender delivered and with the control of the delivery.

Preparation and characterization of Perilla essential oil composite microcapsule based on the complex coacervation and interface polymerization

In this paper, we prepared a novel double-layer Perilla essential oil composite membrane microcapsule (PEOCM) by the composite methods of complex coacervation and interface polymerization. The particle size distribution, morphology, pressure resistance, thermal stability, and elemental proportions of the microcapsule shell of the obtained microcapsules were characterized by laser particle size analyzer, scanning electron microscopy (SEM), dynamic rheometer, thermogravimetric analysis (TGA), and energy spectrometer. In order to further examine the application effect of the PEOCM, we carried out a fresh-keeping experiment on nectarines. The results showed that the average volume diameter of the microcapsules was 226.9 µm, with a completely spherical shape and a slight depression on the surface and had good pressure resistance and thermal stability. The results also demonstrated that microencapsulation does not change the composition of Perilla essential oil, and the polyurea membrane with amide structure (-NH-CO-NH-) was formed successfully. Furthermore, the total soluble solids content and peroxidase activity of nectarines indicated that the PEOCM can be a preservative of food. PRACTICAL APPLICATION: We prepared a double-layer Perilla essential oil composite membrane microcapsule by the composite methods of complex coacervation and interface polymerization. The encapsulation conditions of the microcapsules were optimized, the structure of the microcapsule was characterized, and the fresh-keeping effects of the microcapsule on nectarine were studied. The results showed that microcapsules had a completely spherical shape and a slight depression on the surface and had good pressure resistance, good thermal stability, and good fresh-keeping ability. The above characteristics indicated that the double-layer microcapsules have good application prospect and plays an important role in food fresh-keeping and the preservation of essential oils.

Encapsulated Microstructures of Beneficial Functional Lipids and Their Applications in Foods and Biomedicines

Beneficial functional lipids are essential nutrients for the growth and development of humans and animals, which nevertheless possess poor chemical stability because of heat/light-sensitivity. Various encapsulation technologies have been developed to protect these nutrients against adverse factors. Different microstructures are exhibited through different encapsulation methods, which influence the encapsulation efficiency and release behavior at the same time. This review summarizes the effects of preparation methods and process parameters on the microstructures of capsules at first. The mechanisms of the different microstructures on encapsulation efficiency and controlled release behavior of core materials are analyzed. Next, a comprehensive overview on the beneficial functional lipids capsules in the latest food and biomedicine applications are provided as well as the matching relationship between the microstructures of the capsules and applications are discussed. Finally, the remaining challenges and future possible directions that have potential interest are outlined. The purpose of this review is to convey the construction of beneficial functional lipids capsules and the function mechanism, a critical analysis on its current status and challenges, and opinions on its future development. This review is believed to promote communication among the food, pharmacy, agronomy, engineering, and nutrition industries.

Microencapsulation for Functional Textile Coatings with Emphasis on Biodegradability—A Systematic Review

The review provides an overview of research findings on microencapsulation for functional textile coatings. Methods for the preparation of microcapsules in textiles include in situ and interfacial polymerization, simple and complex coacervation, molecular inclusion and solvent evaporation from emulsions. Binders play a crucial role in coating formulations. Acrylic and polyurethane binders are commonly used in textile finishing, while organic acids and catalysts can be used for chemical grafting as crosslinkers between microcapsules and cotton fibres. Most of the conventional coating processes can be used for microcapsule-containing coatings, provided that the properties of the microcapsules are appropriate. There are standardised test methods available to evaluate the characteristics and washfastness of coated textiles. Among the functional textiles, the field of environmentally friendly biodegradable textiles with microcapsules is still at an early stage of development. So far, some physicochemical and physical microencapsulation methods using natural polymers or biodegradable synthetic polymers have been applied to produce environmentally friendly antimicrobial, anti-inflammatory or fragranced textiles. Standardised test methods for evaluating the biodegradability of textile materials are available. The stability of biodegradable microcapsules and the durability of coatings during the use and care of textiles still present several challenges that offer many opportunities for further research.

Synthesis and Characterization of a Multifunctional Sustained-Release Organic-Inorganic Hybrid Microcapsule with Self-Healing and Flame-Retardancy Properties

As their service life increases, cement-based materials inevitably undergo microcracking and local damage. In response to this problem, this study used phacoemulsification-solvent volatilization to prepare a multifunctional sustained-release microcapsule (SFRM) with self-healing and flame-retardant characteristics. The synthesis of SFRM is based on the modification of ethyl cellulose with nano-SiO₂ particles and cross-linking with a silane coupling agent to form an organic-inorganic hybrid wall material. The epoxy resin is blended with hexaphenoxy cyclotriphosphazene (HPCTP) to form a composite core emulsion. The surface morphology, particle size distribution, core-shell composition, and thermal stability of SFRM were analyzed via scanning electron microscopy (SEM), energy-dispersive spectrometry (EDS), Malvern, Fourier-transform infrared (FT-IR), and TD-DSC-DTG. It is concluded that SFRM was successfully synthesized with superior particle size distribution and thermal stability. When the ratio of SiO₂ solution and EC alcohol solution reached 1:2, the particle size distribution of the microcapsules was 30-190 μm, and the D₅₀ decreased to 70 μm. The core material content, slow-release performance, and flame retardancy of SFRM were measured using a UV-1800 spectrophotometer and Hartmann tubes, and the compressive and repair properties of SFRM were evaluated by uniaxial compression tests. The results demonstrate that SFRM has satisfactory slow-release and flame-retardancy properties, the LC is 67%, and the first-order kinetic model shows the best fit and conforms to the non-Fickian diffusion mechanism. The SFRM repair rate can reach approximately 61%. This is of substantial significance to the field of self-repairing cement-based materials.

Mosquito-repellent controlled-release formulations for fighting infectious diseases

Malaria is a principal cause of illness and death in countries where the disease is endemic. Personal protection against mosquitoes using repellents could be a useful method that can reduce and/or prevent transmission of mosquito-borne diseases. The available repellent products, such as creams, roll-ons, and sprays for personal protection against mosquitoes, lack adequate long-term efficacy. In most cases, they need to be re-applied or replaced frequently. The encapsulation and release of the repellents from several matrices has risen as an alternative process for the development of invention of repellent based systems. The present work reviews various studies about the development and use of repellent controlled-release formulations such as polymer microcapsules, polymer microporous formulations, polymer micelles, nanoemulsions, solid-lipid nanoparticles, liposomes and cyclodextrins as new tools for mosquito-borne malaria control in the outdoor environment. Furthermore, investigation on the mathematical modelling used for the release rate of repellents is discussed in depth by exploring the Higuchi, Korsmeyer-Peppas, Weibull models, as well as the recently developed Mapossa model. Therefore, the studies searched suggest that the final repellents based-product should not only be effective against mosquito vectors of malaria parasites, but also reduce the biting frequency of other mosquitoes transmitting diseases, such as dengue fever, chikungunya, yellow fever and Zika virus. In this way, they will contribute to the improvement in overall public health and social well-being.

Vehiculation of Methyl Salicylate from Microcapsules Supported on Textile Matrix

In recent years, textile industries have focused their attention on the development of functional finishing that presents durability and, consequently, controlled release. However, in the case of methyl salicylate microcapsules supported on a textile matrix, studies indicate only the interactions between substrate and microcapsules and the drug delivery system, not applying the release equations. This study reports the mechanism and kinetics of controlled release of microcapsules of gelatin and gum Arabic containing methyl salicylate as active ingredient incorporated into textile matrices. According to the results presented, it was possible to verify that the wall materials participated in the coacervation process, resulting in microcapsules with well-defined geometry, besides promoting the increase of the thermal stability of the active principle. The samples (100% cotton, CO, and 100% polyamide, PA) functionalized with microcapsules released methyl salicylate in a controlled manner, based on the adjustment made by the Korsmeyer–Peppas model, indicating a Fickian mechanism. The influence of temperature was noticeable when the samples were subjected to washing, since with higher temperature (50 °C), the release was more pronounced than when subjected to lower temperature (37 °C). The results presented in this study indicate that the mechanism of backbone release is influenced by the textile matrix and by the durability of the microcapsule during the wash cycles.

Encapsulation of Flavours and Fragrances into Polymeric Capsules and Cyclodextrins Inclusion Complexes: An Update

Flavours and fragrances are volatile compounds of large interest for different applications. Due to their high tendency of evaporation and, in most cases, poor chemical stability, these compounds need to be encapsulated for handling and industrial processing. Encapsulation, indeed, resulted in being effective at overcoming the main concerns related to volatile compound manipulation, and several industrial products contain flavours and fragrances in an encapsulated form for the final usage of customers. Although several organic or inorganic materials have been investigated for the production of coated micro- or nanosystems intended for the encapsulation of fragrances and flavours, polymeric coating, leading to the formation of micro- or nanocapsules with a core-shell architecture, as well as a molecular inclusion complexation with cyclodextrins, are still the most used. The present review aims to summarise the recent literature about the encapsulation of fragrances and flavours into polymeric micro- or nanocapsules or inclusion complexes with cyclodextrins, with a focus on methods for micro/nanoencapsulation and applications in the different technological fields, including the textile, cosmetic, food and paper industries.

Gum arabic and collagen hydrolysate extracted from hide fleshing wastes as novel wall materials for microencapsulation of Origanum onites L. essential oil through complex coacervation

Renewable resource-based biodegradable materials attract more attention than petroleum-based biodegradable materials to support the sustainable development of ecology. Obtaining collagen hydrolysate (CH) from hide fleshing wastes of leather industry is an environmentally friendly way to develop multifunctional materials that can contribute to technological advances in different industries. In this study, 2:1, 1:1, and 1 2 ratios of gum arabic (GA) and CH extracted from hide fleshing waste were used as wall materials to encapsulate Origanum onites L. essential oil (OOEO) using the complex coacervation method. The encapsulation yield and efficiency, functional group composition, particle size, morphology, and thermal stability of the obtained OOEO microcapsules were characterized. The results showed that the obtained microcapsules had high encapsulation yield and efficiency, as well as good functional properties such as uniform morphology and low water activity. The best mass ratio for the biopolymers (GA:CH) was 1:1. Scanning electron microscopy analysis showed that OOEO microcapsule samples had a spherical shape. FTIR analysis was performed on obtained microcapsules, confirming the molecular interactions between GA and CH. These findings can be useful in designing an ideal wall material using GA and CH for microencapsulation of essential oils by the complex coacervation method.

Biofunctionalization of Natural Fiber-Reinforced Biocomposites for Biomedical Applications

In the last ten years, environmental consciousness has increased worldwide, leading to the development of eco-friendly materials to replace synthetic ones. Natural fibers are extracted from renewable resources at low cost. Their combination with synthetic polymers as reinforcement materials has been an important step forward in that direction. The sustainability and excellent physical and biological (e.g., biocompatibility, antimicrobial activity) properties of these biocomposites have extended their application to the biomedical field. This paper offers a detailed overview of the extraction and separation processes applied to natural fibers and their posterior chemical and physical modifications for biocomposite fabrication. Because of the requirements for biomedical device production, specialized biomolecules are currently being incorporated onto these biocomposites. From antibiotics to peptides and plant extracts, to name a few, this review explores their impact on the final biocomposite product, in light of their individual or combined effect, and analyzes the most recurrent strategies for biomolecule immobilization.

In-Situ Direct Synthesis of HKUST-1 in Wool Fabric for the Improvement of Antibacterial Properties

The use of Metal-Organic Frameworks (MOF) such as HKUST-1 in textiles is an alternative with regard to the development of technologies that are increasingly seeking for functionalities, mainly in the fields of health and hygiene, named biofunctional fabrics. However, the application of the MOF under the surface of the wool fiber can lead to a low durability finish due to its low fixation. Thus, this project aims to perform the direct synthesis of HKUST in the wool fiber, so that a product with good washing durability can be obtained. The purpose of this study was to incorporate metal-organic frameworks, composed of copper and trimesic acid, into woolen fabrics, to improve the antibacterial properties. The synthesis was performed directly in the wool fabric, at time intervals of 24 and 48 h. The resulting fabrics were characterized by Scanning Electron Microscopy (SEM), Energy Dispersive Spectroscopy (EDS), X-Ray Diffractometry (XRD), Fourier Transform Spectroscopy Infrared-Attenuated Total Reflectance (FTIR-ATR), and colorimetric analysis (CIElab), and the Antimicrobial Activity Test (American Association of Textile Chemist and Colourists - AATCC Test Method 61-2007-2A) was performed. The results suggested that the application produced textiles with antibacterial properties, showing activity against Escherichia coli.