Microencapsulation of oil droplets using freezing-induced gelatin–acacia complex coacervation

Biodegradable Polymers for Microencapsulation Systems

Environmentally friendly alternatives have become sought after upon the development of scientific research and industrial processes. Recent trends suggest biodegradable polymers as the most promising solution for synthetic microcapsule systems. Safety, efficiency, biocompatibility, and biodegradability are some of the properties that biodegradable systems in microencapsulation can provide for a broad spectrum of applications. The controlled release of encapsulated active agents is a research field that, over the years, has been constantly innovating due to the promising applications in the areas of pharmaceutical, cosmetic, textile industry, among others. This article presents an overview of different polymers with potential for microcapsule synthesis, namely, biodegradable polymers. First, natural polymers are discussed, which are divided into two categories: polysaccharide-based polymers (cellulose, starch, chitosan, and alginate) and protein polymers (gelatin). Second, synthetic polymers are described, where biodegradable polymers such as polyesters, polyamides, among others appear as examples. For each polymer, this review presents its origin, relevant properties, applications, and examples found in the literature regarding its use in biodegradable microencapsulation systems.

Freeze vs. Spray Drying for Dry Wild Thyme (Thymus serpyllum L.) Extract Formulations: The Impact of Gelatin as a Coating Material

Freeze drying was compared with spray drying regarding feasibility to process wild thyme drugs in order to obtain dry formulations at laboratory scale starting from liquid extracts produced by different extraction methods: maceration and heat-, ultrasound-, and microwave-assisted extractions. Higher total powder yield (based on the dry weight prior to extraction) was achieved by freeze than spray drying and lower loss of total polyphenol content (TPC) and total flavonoid content (TFC) due to the drying process. Gelatin as a coating agent (5% w/w) provided better TPC recovery by 70% in case of lyophilization and higher total powder yield in case of spray drying by diminishing material deposition on the wall of the drying chamber. The resulting gelatin-free and gelatin-containing powders carried polyphenols in amount ~190 and 53–75 mg gallic acid equivalents GAE/g of powder, respectively. Microwave-assisted extract formulation was distinguished from the others by a higher content of polyphenols, proteins and sugars, higher bulk density and lower solubility. The type of the drying process mainly affected the position of the gelatin-derived -OH and amide bands in FTIR spectra. Spray-dried formulations compared to freeze-dried expressed higher thermal stability as confirmed by differential scanning calorimetry analysis and a higher diffusion coefficient; the last feature can be associated with the lower specific surface area of irregularly shaped freeze-dried particles (151–223 µm) compared to small microspheres (~8 µm) in spray-dried powder.

Microencapsulation of vitamin D3 by complex coacervation using carboxymethyl tara gum (Caesalpinia spinosa) and gelatin A

Vitamin D₃ plays a fundamental role in human health; however, it is highly susceptible to environmental conditions and the gastrointestinal tract. In this study, complex coacervates obtained from gelatin A and carboxymethyl tara gum (CMTG) were used as wall materials for the encapsulation of vitamin D₃ (VD₃). Zeta potential and turbidity measurements were employed to optimize the pH and ratio (gelatin A:CMTG), and the results showed that the ideal conditions for the complex coacervation were pH 4.0 and a 6:1 ratio. The encapsulation efficiency (EE) was determined as a function of the total concentration of biopolymers (TC%) and the core-to-wall ratio, and the greatest EE (80%) was achieved at a TC of 1% and a ratio of 1:2; spherical particles with an average size of 0.25 µm were obtained. The microencapsulation increased the thermal stability of VD₃, and FTIR confirmed the presence of the biopolymers and VD₃ in the capsules. An in vitro simulation showed a more pronounced release in the small intestine with a vitamin bioaccessibility of 56%. The encapsulation of bioactive lipophilic compounds by complex coacervates of gelatin A and CMTG resulted in improved stability and prolonged release during digestion.

Effects of microencapsulated abamectin on the mechanical, cross-linking, and release properties of PBS

Herein, nanocomposite microencapsulated abamectin (A-G-G) have been prepared by composite coacervation method with gelatin and gum arabic as the wall materials and abamectin (A-W) as core material. The formation mechanism of A-G-G was determined by fourier-transform infrared spectroscopy, scanning electron microscopy, and other characterization methods. Then, polybutylene succinate (PBS)/A-G-G composite films with different contents of A-G-G microcapsules were prepared. The effects of adding A-G-G microcapsules on the mechanical and sustained-release properties of the composite films were studied. Results show that there is a strong interaction between the CO groups in PBS and free OH of the A-G-G microcapsules. With an increase in the A-G-G microcapsule content, the elongation at the break of composite films increases significantly. When the A-G-G content is 15 %, the elongation at break of the composite films reaches 178.6 ± 6.26 %. The maximum water absorption is 329 ± 5.84 %. Overall, the PBS/A-G-G composite films exhibit good slow-release performance.

Gum-based nanocarriers for the protection and delivery of food bioactive compounds

Gums, which for the most part are water-soluble polysaccharides, can interact with water to form viscous solutions, emulsions or gels. Their desirable properties, such as flexibility, biocompatibility, biodegradability, availability of reactive sites for molecular interactions and ease of use have led to their extremely large and broad applications in formation of nanostructures (nanoemulsions, nanoparticles, nanocomplexes, and nanofibers) and have already served as important wall materials for a variety of nano encapsulated food ingredients including flavoring agents, vitamins, minerals and essential fatty acids. The most common gums used in nano encapsulation systems include Arabic gum, carrageenan, xanthan, tragacanth plus some new sources of non-traditional gums, such as cress seed gum and Persian/or Angum gum identified as potential building blocks for nanostructured systems. New preparation techniques and sources of non-traditional gums are still being examined for commercialization in the food nanotechnology area as low-cost and reproducible sources. In this study, different nanostructures of gums and their preparation methods have been discussed along with a review of gum nanostructure applications for various food bioactive ingredients.

Vehiculation of Active Principles as a Way to Create Smart and Biofunctional Textiles

In some specific fields of application (e.g., cosmetics, pharmacy), textile substrates need to incorporate sensible molecules (active principles) that can be affected if they are sprayed freely on the surface of fabrics. The effect is not controlled and sometimes this application is consequently neglected. Microencapsulation and functionalization using biocompatible vehicles and polymers has recently been demonstrated as an interesting way to avoid these problems. The use of defined structures (polymers) that protect the active principle allows controlled drug delivery and regulation of the dosing in every specific case. Many authors have studied the use of three different methodologies to incorporate active principles into textile substrates, and assessed their quantitative behavior. Citronella oil, as a natural insect repellent, has been vehicularized with two different protective substances; cyclodextrine (CD), which forms complexes with it, and microcapsules of gelatin-arabic gum. The retention capability of the complexes and microcapsules has been assessed using an in vitro experiment. Structural characteristics have been evaluated using thermogravimetric methods and microscopy. The results show very interesting long-term capability of dosing and promising applications for home use and on clothes in environmental conditions with the need to fight against insects. Ethyl hexyl methoxycinnamate (EHMC) and gallic acid (GA) have both been vehicularized using two liposomic-based structures: Internal wool lipids (IWL) and phosphatidylcholine (PC). They were applied on polyamide and cotton substrates and the delivery assessed. The amount of active principle in the different layers of skin was determined in vitro using a Franz-cell diffusion chamber. The results show many new possibilities for application in skin therapeutics. Biofunctional devices with controlled functionality can be built using textile substrates and vehicles. As has been demonstrated, their behavior can be assessed using in vitro methods that make extrapolation to their final applications possible.

Phoxim Microcapsules Prepared with Polyurea and Urea-Formaldehyde Resins Differ in Photostability and Insecticidal Activity

The application of pesticide microcapsules (MCs) in agriculture is becoming more and more popular. In this study, the effects of different wall materials on the stomach toxicity, contact toxicity, length of efficacy, and photolysis characteristics of pesticide microcapsules were investigated. The results showed that microencapsulation reduced the stomach and contact toxicities of phoxim and prolonged the efficacy of this light-sensitive chemical in the greenhouse test. Neither of the degradation curves for microencapsulated phoxim under ultraviolet light fit a first-order model, although the emulsifiable concentrate (EC) degradation curve fit it well. The phoxim-loaded polyurea microcapsules (PUA-MCs) showed significantly increased UV-resistance ability, stomach toxicity, and contact toxicity compared with the phoxim-loaded urea-formaldehyde microcapsules (UF-MCs). These experiments indicated that it is crucial to select the appropriate wall materials for pesticide microcapsules on the basis of application sites and physicochemical properties of pesticide active ingredients.