Formation Of Microcapsules Research Articles

Synthesis and Characterization of Microcapsules as Fillers for Self-Healing Dental Composites.

This article proposes the synthesis and characterization of (triethylene glycol dimethacrylate-N,N-dihydroxyethyl-p-toluidine) TEGDMA-DHEPT self-healing microcapsules for their inclusion in dental composite formulations. The obtaining method is the in situ emulsion polymerization of the (poly urea-formaldehyde) (PUF) coatings. The microcapsules were characterized by Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), atomic force microscopy (AFM), high-performance liquid chromatography (HPLC), and low-field nuclear magnetic resonance (NMR) techniques. The optimal formation of uniform microcapsules is achieved at a stirring speed of 800 rpm and centrifugation is no longer necessary. HPLC demonstrates that the microcapsules formed at 800 rpm show a better control of liquid release than the heterogeneous ones obtained at a lower stirring speed. The centrifuged samples have rounded shapes, with dimensions between 80 and 800 nm, while the non-centrifuged samples are more uniform, with a spherical shape and dimensions of approximately 800 nm.

Comparative proteomic and genomic analysis of Lactococcus garvieae and Lactococcus petauri isolates from Turkey

Piscine lactococcosis, a bacterial disease caused by Lactococcus garvieae, L. petauri and L. formosensis, induces mass mortalities in multiple farmed fish species globally. Following the identification of L. petauri as one of the emerging etiological agents of piscine lactococcosis, it was revealed that the majority of isolates previously recognized as L. garvieae actually belong to L. petauri. In this study, a total of 134 Lactococcus sp. isolates, including L. garvieae (n = 40) and L. petauri (n = 94) were analyzed. Differential identification of L. garvieae and L. petauri isolates was performed through basic sucrose fermentation and end-point PCR analysis using species-specific primer sequences. Comparative analysis of capsule formation in both species was conducted for the first time using transmission electron microscopy, whole-cell protein profile via 1D SDS-PAGE, antigenic protein characterization using Western blot analysis, and serological profile description by slide and microagglutination assays. Moreover, comprehensive genomic comparisons were made, deciphering overall genomic relatedness indices, virulence genes, and antimicrobial resistance patterns among these closely related species.Analysis showed microcapsule formation in some isolates of L. garvieae and L. petauri for the first time. While a high similarity rate was observed in the whole-cell protein profiles of these species, significant differences were identified among antigenic proteins. Variations between species were observed in slide agglutination and quantitative agglutination tests of L. garvieae and L. petauri field isolates. Capsule-deficient L. garvieae reference and field strain antisera did not agglutinate with each other; however, L. garvieae field strain antisera agglutinated with all L. garvieae field strains and L. petauri strains. These results indicated distinct serological characteristics of capsule-deficient L. garvieae isolates from Turkey compared to previously reported serological classifications.Genomic analyses revealed that none of the investigated L. garvieae and L. petauri isolates harbored the capsule gene cluster. In addition, Turkish isolates of L. garvieae and L. petauri clustered separately from isolates of other geographical origins but together with each other. This study aims to address the problem of lactococcosis, commonly referred to as “Summer Mortality Outbreak and Vaccine-Preventable Diseases,” in a wide variety of cultured fish species through the selected L. garvieae and L. petauri isolates as potential vaccine strains.

Synthesis and microencapsulation of acylglycerols rich in omega-3 PUFAs by glycerolysis using lipase immobilized on activated carbon

This work aimed to explore the potential of immobilized lipase (Rhizomucor miehei) on activated carbon to convert the high Free Fatty Acid (FFA) content of squid waste oil into acylglycerols (Mono-diacylglycerols (MDG)) rich in n-3 PUFAs in a solvent-free system. The product was microencapsulated by complex coacervation, and stability studies were investigated. The effect of glycerolysis conditions was evaluated according to enzyme concentration, derivative (immobilized lipase) concentration, substrate molar ratio, and reaction time, with the conversion of Free Fatty Acid as the response variable. The optimal parameters were 15 mg g−1 support, 8 % of derivative (w/v of the reaction mixture), 1:5 of glycerol:oil, and 24 h. The lipid class of squid waste oil in the optimal conditions was Ethyl ester (EE) = 2.63 %, Triacylglycerol (TAG) = 17.91 %, FFA = 8.08 %, and MDG = 71.38 %. The fatty acid composition analysis confirmed that squid waste oil had a high content of omega-3 PUFAs (ω-3 = 42.28 %). The enzyme-treated oil was microencapsulated through complex coacervation to protect the oil against oxidation. Microscope and Scanning Electron Microscopy (SEM) confirmed the microcapsule formation. The microcapsules showed unexpectedly high oxidative stability (OSI = 52.35 h) compared to untreated (OSI = 0.04 h) and lipase-treated oil (OSI = 2.46 h). Therefore, immobilized lipase on activated carbon has the potential to efficiently synthesize acylglycerol without solvents, making it a fast and reusable enzyme technology for creating omega-3-rich functional ingredients. Furthermore, microencapsulation by complex coacervation can stabilize the omega-3 oil structure against oxidation for food and pharmaceutical distribution.

Plant-based flaxseed oil microcapsules fabricated from coacervation of gluten at oil droplet surface: Microstructure, oxidation stability, and oil digestion control.

This study aimed to develop microcapsules with wheat gluten-coated oil droplets to enhance the oxidation stability and control the digestibility of flaxseed oil. The microcapsules were fabricated using a three-step procedure: (i) flaxseed oil was homogenized with an alkaline gluten solution to form oil-in-water emulsions containing small gluten-coated oil droplets (320-400nm); (ii) the pH of these emulsions was then neutralized to facilitate the deposition of gluten around the oil droplets, thereby forming a thick layer; (iii) a flaxseed oil microcapsule powder was then prepared by spray drying. During the microcapsule formation, intermolecular interactions, including hydrophobic interactions and hydrogen bonds, were involved in the coacervation of gluten at the emulsion surface. The resultant microcapsules with a multiple-core structure had external diameters of 4-26µm and encapsulation efficiencies of 90%-94%. The microencapsulated oil powders contained a relatively high flaxseed oil content (60%-80%). Among them, the sample with 60% oil content demonstrated the best stability in resisting oil droplet coalescence; thus, it exhibited a higher lipolysis rate and extent during simulated gastrointestinal digestion. A 30-day accelerated storage study showed that encapsulation of the flaxseed oil improved its resistance to oxidation. These findings suggest that the pH-deposition method can successfully produce microencapsulated polyunsaturated lipids using all plant-derived ingredients, which may facilitate their use in new plant-based foods through a green and sustainable approach.

Encapsulation of Essential Oils Using Complex Coacervation: A Study on Microcapsule Formation and Efficiency

Encapsulation by Coacervation is a process used to create microcapsules. Coacervation is a process that has been used in the food and pharmaceutical industry to produce microspheres with an active ingredient, such as drugs, flavors or fragrances encapsulated by them. It is common in pharmacies, food preparation, cosmetics, and agriculture. This phase separation process is called Coacervation, where a colloidal (in this case polymer) solution will separate into two distinct liquid phases: a Polymer-rich phase, which we refer to as the coacervate, and the other is known as Polymer-poor or solvent-based. This can be accomplished by varying the temperature or pH of a non-solvent being introduced. In this study, essential oils of lemon and eucalyptus were encapsulated by the complex coacervation process using gum Arabic, gelatin, and chitosan as wall materials. Glutaraldehyde was used as a cross-linking agent in the methodology. FT-IR and GC characterized the essential oils used. The microcapsules were analyzed using a digital microscope, scanning electron microscopy (SEM), and thermogravimetric analysis. Conclusively, microcapsules were formed in spherical form. Encapsulation efficiencies were obtained between 75-78%. In conclusion, microencapsulated essential oils offer a technology that makes essential oils more effective, long-lasting, and customized. These advantages reveal their widespread impact, offering various uses for a variety of industries and applications.

Pomegranate Peel Flour as a Co-encapsulant Improves the Survival of Lactic Acid Bacteria to Thermal Treatment and Simulated Gastrointestinal Conditions

AbstractPomegranate peel flour was employed as a co-encapsulant of two lactic acid bacteria, by alginate emulsion templated microencapsulation, to enhance their resistance to thermal treatment, acidic pHs, and gastric conditions. Samples with pomegranate peel flour increased the tolerance to heat treatment, results consistent with thermal properties related to higher denaturation enthalpy of microcapsules. Co-encapsulated microcapsules also enhanced the survival to low pHs and enhanced almost 60% up the tolerance to bile salts. There was also an increase in survival rate against in vitro gastric acid conditions due to use of the co-encapsulant. In scanning electron microscopy, the incorporation of pomegranate peel flour resulted in a rough and porous structure, probably due to certain interference with the formation of spherical microcapsules, although it presented similar mean diameter, plus higher cell viability as confirmed by confocal laser microscopy. The obtained results indicate that co-encapsulation with a prebiotic ingredient represents a reinforcement of the physical microcapsule integrity to tolerate food process temperatures, besides retarding the adverse effect of acidic, bile salts, and simulated gastrointestinal conditions. The micro alginate co-encapsulation by ionic gelation with a prebiotic as pomegranate peel flour is a suitable alternative to develop thermal processed functional foods.

Facile Preparation of Silica/Tannic Acid/Zein Microcapsules Templated from Non-Aqueous Pickering Emulsions and their Application in Cargo Protection.

Microcapsules have attracted significant attention in academia and industry due to their unique properties for protecting and controlling the release of active substances. However, based on water-insoluble biopolymers, developing a straightforward approach to prepare microcapsules with improved biocompatibility and functional shells remains a great challenge. In this study, zein, a water-insoluble protein, is employed to prepare robust microcapsules facilely using oil-in-aqueous ethanol Pickering emulsions as templates. First, the emulsion template is stabilized by hydrophobic silica nanoparticles with in situ surface modification of tannic acid. The zein is then precipitated at the interface in a controlled manner using antisolvent approach to obtain silica/tannic acid/zein (STZ) microcapsules. It is found that the concentration of zein and the presence of tannic acid played a significant role in the formation of STZ microcapsules with well-defined morphology and a robust shell. The uniform deposition of zein on the surface of template droplets is facilitated by the interactions between tannic acid and zein via hydrogen bond and electrostatic force. Finally, the resulting STZ microcapsules showed super resistance to ultraviolet (UV) radiation and high temperature for the unstable, lipophilic, and active substance of β-carotene.

Interfacial Polymerization Fabricated Polydopamine Capsules as a Step Toward a Photothermal Protocell Model

AbstractPhotothermal is a significant solar energy conversion process on Earth, and photothermal‐responsive protocells are a potential model for prebiotic chemistry. Here, polydopamine microcapsules are fabricated via emulsion droplets‐templated interfacial polymerization and investigated their potential as synthetic protocell models for photothermal conversion and utilization. DNAzyme‐mediated dopamine peroxidation and polymerization occur at the water/oil interface of the emulsion droplets, facilitated by a biphasic microfluidic technique, leading to the formation of uniform polydopamine microcapsules, which retain structural integrity upon transfer into a continuous water phase. These microcapsules exhibit size‐dependent semi‐permeability and high photothermal capability due to their broad spectral absorbance. The photothermal‐mediated temperature rise within the microcapsules triggers DNA denaturation and rearrangement, and intermittent photothermal irradiation modulates reversible phase separation of DNA condensates, mimicking membrane‐less organelles. This work suggests that interfacial polymerization fabricated polydopamine capsules are a plausible photothermal protocell model that can demonstrate aspects of primitive abiotic cellularity.

Incorporation of CuS nanorods in polyelectrolyte multilayer microcapsules improved cancer cell cytotoxicity and signal intensity in ultrasound imaging

The fabrications of hollow microcapsules (MCs) with new architecture and ability to incorporate different nanomaterials have received great interest for targeted cancer therapy. Recently, CuS based nanomaterials have been demonstrated to possess the ability to mimic Fenton-like activity in tumor environment and inducing cancer cell apoptosis by generating highly reactive oxygen species (ROS). In this study, we have developed poly(allylamine) hydrochloride (PAH)/dextran sulfate (DS) polyelectrolyte MCs capable of carrying doxorubicin (DOX) for targeted cancer therapy and ultrasound imaging. The electron microscopy investigations showed the formation of polymeric MCs of 3 µm in size with incorporated CuS NRs in their interior structure. The surface modification of MCs with folic acid (FA), and encapsulation of model hydrophilic molecules in MCs was studied by UV–Visible (UV–Vis) spectroscopy, Fourier transform infra-red (FTIR) spectroscopy and confocal laser scanning microscopy. The encapsulation efficiency of DOX was found to be 56 % and the release was found to be linear at pH 5.5 and 7.4 in the absence of ultrasound exposure. The ultrasound exposure resulted in sudden rupture of MCs at 1 MHz and 1 W/cm2 and caused burst release of DOX at both pH conditions. The FA decorated PAH/DS/CuS NR MCs exhibited improved anti-cancer activity against MDA-MB-231 cancer cells due to the synergistic effects of ultrasound mediated burst release of chemotherapeutic drug (DOX), glutathione-stimulated ROS and targeted cancer therapy. Further, the capsules showed better echogenicity than that of control PAH/DS MCs when imaged under medical ultrasound-scanning system. Hence, the MCs demonstrated in this study have huge potential for targeted cancer theranostics by offering an option to image the cancer cells during the treatment period.

Formation of Microcapsules of Pullulan by Emulsion Template Mechanism: Evaluation as Vitamin C Delivery Systems.

Pullulan is a polysaccharide that has attracted the attention of scientists in recent times as a former of edible films. On the other hand, its use for the preparation of hydrogels needs more study, as well as the formation of pullulan microcapsules as active ingredient release systems for the food industry. Due to the slow gelation kinetics of pullulan with sodium trimetaphosphate (STMP), capsules cannot be formed through the conventional method of dropping into a solution of the gelling agent, as with other polysaccharides, since the pullulan chains migrate to the medium before the capsules can form by gelation. Pullulan microcapsules have been obtained by using inverse water-in-oil emulsions as templates. The emulsion that acts as a template has been characterized by monitoring its stability and by optical microscopy, and the size of the emulsion droplets has been correlated with the size of the microcapsules obtained, demonstrating that it is a good technique for their production. Although some flocs of droplets form, these remain dispersed during the gelation process and two capsule size distributions are obtained: those of the non-flocculated droplets and the flocculated droplets. The microcapsules have been evaluated as vitamin C release systems, showing zero-order release kinetics for acidic pH and Fickian mechanism for neutral pH. On the other hand, the microcapsules offer good protection of vitamin C against oxidation during an evaluation period of 14 days.

Enhancing Encapsulation Efficiency of Chavir Essential Oil via Enzymatic Hydrolysis and Ultrasonication of Whey Protein Concentrate-Maltodextrin.

This study focused on the characterization of emulsions and microparticles encapsulating Chavir essential oil (EO) by application of modified whey protein concentrate-maltodextrin (WPC-MD). Different physical, chemical, morphological, thermal, and antioxidant properties and release behavior of spray-dried microparticles were assessed. Antioxidant, solubility, emulsifying, and foaming activities of modified WPC were increased compared to those of primary material. The results indicated that the particle size distribution varied depending on the type of carriers used, with the smallest particles formed by hydrolyzed WPC (HWPC). Binary blends of modified WPC-MD led to improved particle sizes. The spray-drying yield ranged from 64.1% to 85.0%, with higher yields observed for blends of MD with sonicated WPC (UWPC). Microparticles prepared from primary WPC showed irregular and wrinkled surfaces with indentations and pores, indicating a less uniform morphology. The UWPC as a wall material led to microparticles with increased small cracks and holes on their surface. However, HWPC negatively affected the integrity of the microparticles, resulting in broken particles with irregular shapes and surface cracks, indicating poor microcapsule formation. Encapsulating EO using WPC-MD increased the thermal stability of EO significantly, enhancing the degradation temperature of EO by 2 to 2.5-fold. The application of primary WPC (alone or in combination with MD) as wall materials produced particles with the lowest antioxidant properties because the EO cannot migrate to the surface of the particles. Enzymatic hydrolysis of WPC negatively impacted microparticle integrity, potentially increasing EO release. These findings underscore the crucial role of wall materials in shaping the physical, morphological, thermal, antioxidant, and release properties of spray-dried microparticles, offering valuable insights for microencapsulation techniques.

Effect of the formation of open microcapsules with Mn3O4 walls during hydrolysis of the MnSO4 salt solution droplets deposited on the alkaline solution surface

It was shown for the first time that open microcapsules 1–5 µm in size with Mn3O4 walls and unique morphology are formed as a result of spraying an aqueous MnSO4 solution onto the surface of an alkali solution. The walls have a thickness of 80–120 nm and consist of an array of Mn3O4 nanosheets with a thickness of 2–3 nm, oriented predominantly in the radial direction towards the center of the microcapsule. There is a special rim with a height of 100–200 nm around the hole of the most microcapsules, which can be a kind of ‘ground’ when fixing such microcapsules on the surface of a substrate in the process of application by the Langmuir–Schaefer technique.

Tailoring Microemulsification Techniques for the Encapsulation of Diverse Cargo: A Systematic Analysis of Poly (Urea-Formaldehyde) Microcapsules.

Cargo encapsulation through emulsion-based methods has been pondered over the years. Although several microemulsification techniques have been employed for the microcapsule's synthesis, there are still no clear guidelines regarding the suitability of one technique over the others or the impacts on the morphological and physicochemical stability of the final particles. Therefore, in this systematic study, we investigated the influence of synthesis parameters on the fabrication of emulsion-based microcapsules concerning morphological and physicochemical properties. Using poly(urea-formaldehyde) (PUF) microcapsules as a model system, and after determining the optimal core/shell ratio, we tested three different microemulsification techniques (magnetic stirring, ultrasonication, and mechanical stirring) and two different cargo types (100% TEGDMA (Triethylene glycol dimethacrylate) and 80% TEGDMA + 20% DMAM (N,N-Dimethylacrylamide)). The resulting microcapsules were characterized via optical and scanning electron microscopies, followed by size distribution analysis. The encapsulation efficiency was obtained through the extraction method, and the percentage reaction yield was calculated. Physicochemical properties were assessed by incubating the microcapsules under different osmotic pressures for 1 day and 1, 2, or 4 weeks. The data were analyzed statistically with one-way ANOVA and Tukey's tests (α = 0.05). Overall, the mechanical stirring resulted in the most homogeneous and stable microcapsules, with an increased reaction yield from 100% to 50% in comparison with ultrasonication and magnetic methods, respectively. The average microcapsule diameter ranged from 5 to 450 µm, with the smallest ones in the ultrasonication and the largest ones in the magnetic stirring groups. The water affinities of the encapsulated cargo influenced the microcapsule formation and stability, with the incorporation of DMAM leading to more homogeneous and stable microcapsules. Environmental osmotic pressure led to cargo loss or the selective swelling of the shells. In summary, this systematic investigation provides insights and highlights commonly overlooked factors that can influence microcapsule fabrication and guide the choice based on a diligent analysis of therapeutic niche requirements.

Encapsulation of probiotic bacteria in pectin and pectin-chitosan matrices for use in confectionery products

Probiotics are live bacteria that benefit the host's health when administered in adequate quantities. However, their use may be limited due to a decrease in cell viability during production, product storage, and subsequent passage through the gastrointestinal tract. This work theoretically substantiates the use of a combined method of microcapsule formation – immobilization of probiotics into a gel and microencapsulation, which will protect microorganisms from the effects of technological and physiological factors, regulate their targeted delivery and controlled release from microcapsules at the site of deployment. Suitable carriers for coating the capsules were selected, which is crucial for ensuring adequate protection of probiotics since their properties determine the effectiveness of protecting microorganisms from harmful environmental factors and the ability to release them in the lower gastrointestinal tract. In the course of the research, microcapsules with pectin and pectin-chitosan matrices containing bifidobacteria Bifidobacterium bifidum-1 and lactobacilli Lactobacillus acidophilus Ep-317/402 were developed. The possibilities and feasibility of using the developed microcapsules with different matrices to protect cells from adverse gastrointestinal tract conditions in vitro were substantiated. The results showed that the survival rate of microencapsulated bifidobacteria in the gastric juice medium was 87 % in both matrices, in bile – in pectin 82 %, and pectin-chitosan 92 %. Survival of lactobacilli: in gastric juice – 89 % in the pectin matrix, 93 % in the pectin-chitosan matrix, in bile – 94 and 88 %, respectively. The obtained pectin and pectin-chitosan microcapsules can potentially be used as a means of delivering viable probiotic microorganisms to their location – the human large intestine and can be used in confectionery technology as ingredients to provide.

Self-healing epoxy coatings via microencapsulation of aromatic diisocyanate in lignin stabilized Pickering emulsions

Isocyanate-filled microcapsules are gaining increased attention for their role in developing self-healing materials, thereby reducing maintenance costs and increasing polymer durability. Nevertheless, microencapsulating highly reactive -NCO groups remains a challenging task in the literature. Likewise, considerable efforts have been directed towards developing polymers from renewable and biobased sources, which could also be applied to microcapsule synthesis. In this work, lignin, an abundant biopolymer, was used as a solid stabilizer for oil-in-water (O/W) interfaces, enabling the encapsulation of highly reactive isocyanate. Hybrid polyurethane/polyurea microcapsules containing reactive methylenediphenyl diisocyanate (MDI) were obtained via optimized O/W Pickering emulsions using lignin for system stabilization. This optimized process facilitated shell formation via the reaction of diisocyanate with lignin and water, eliminating the need for additional chain extenders. Scanning electron microscopy revealed the formation of spherical and rough microcapsules, while infrared spectroscopy confirmed the presence of residual free -NCO groups, indicating effective encapsulation of MDI. Additionally, a core -NCO concentration of 11 wt% was confirmed by titration. The microcapsules were further assessed as components in self-healing epoxy coatings. Their incorporation resulted in the retardation of corrosion on a low carbon steel panel after 72 h of submersion in a saline solution. Electrochemical impedance spectroscopy (EIS) confirmed a significant increase of approximated 620% in impedance modulus after 83 days of immersion in a 3.5 wt% NaCl solution, compared to the neat epoxy coating. These findings suggest a promising technological application of this material for the advancement of self-healing epoxy-based coatings and composites.

Enzymatically produced acylglycerol and glycerin monostearate additives improved the characteristics of gelatin-stabilized omega-3 emulsions and microcapsules

The impacts of enzymatically produced acylglycerol and glycerin monostearate on the characteristics of gelatin-stabilized omega-3 emulsions and microcapsules were investigated. Tuna oil was enzymatically produced and the resulting acylglycerol was mixed with tuna oil at 12.5% (w/w) to prepare a novel oil phase. This oil phase was stabilized by gelatin to prepare oil-in-water emulsions and subsequent microcapsules via complex coacervation. The tuna oil with glycerin monostearate (GMS) at 1 and 2% (w/w) were used as controls. Results showed that both acylglycerol and GMS significantly reduced the emulsion droplet size and zeta potential, while increasing the viscoelasticity and stability. The diacylglycerol/monoacylglycerol were involved in the oil/water interfacial layer formation by lowering interfacial tension and increasing droplet surface hydrophobicity. Overall, the changed emulsion properties promoted the complex coacervation and contributed to the formation of microcapsules with improved oxidative stability. Therefore, enzymatically produced acylglycerol can develop high-quality stable omega-3 microencapsulated novel food ingredients.

Preparation and thermal properties of nano-microcapsule and simulation heat storage application

The prevention of material leakage and improvement of thermal conductivity are very important for thermal energy storage application. In this work, nano-TiO2@n-docosane microcapsules were synthesized by the fine emulsion interface polymerization method using tetra-n-butyl titanate (TBT). This approach enhances the encapsulation rate and efficiency of phase change microcapsules. The microcapsules formation process was observed using a biological microscope. The diameter of the microcapsules decreased significantly with the increase of stirring rate. The phase transition temperature of the optimal microcapsules is 42.4 °C. The encapsulation rate and efficiency reach up to 90.7% and 91.0%, respectively. The average thermal conductivity of nano-TiO2@n-docosane microcapsules is 215% higher than that of n-docosane. SEM and infrared spectroscopy testing results confirm the successful coating of n-docosane by TiO2. Thermogravimetric analysis presents that TiO2 forms a shell, which reduces the leakage of n-docosane. The melting and solidification processes of n-docosane and nano-TiO2@n-docosane microcapsules were simulated numerically. In comparison to n-docosane, nano-TiO2@n-docosane microcapsules exhibit a 14.89% increase in peak storage power and a 12.47% increase in heat transfer coefficient during charging. Additionally, during discharging, these values rise by 3.23% and 6.46%, respectively. Nano-TiO2@n-docosane microcapsules enhance heat transfer and the charging/discharging process of phase change materials.

Development of chitosan microparticles via interfacial polymeric crosslinking method utilizing sodium trimetaphosphate

Chitosan derived from the alkaline deacetylation of chitin found in crustacean exoskeletons, is a natural biopolymer. It has been employed as a matrix for microparticles and crosslinked systems, facilitating the immobilization and controlled release of drugs, ensuring stability, safety, and efficacy. Microencapsulation, a technique involving the coating of active products in polymeric layers, allows for their release under specific conditions and controlled rates, achieved through the formation of microspheres or microcapsules. The distinctive features of chitosan, such as its non-toxicity, biodegradability, and cost-effectiveness, make it advantageous over other polysaccharides. This study aimed to produce chitosan microparticles through the interfacial polymeric crosslinking method, utilizing sodium trimetaphosphate as the crosslinking agent. A pre-formulation study, involving varying concentrations of polymer, crosslinking agent, and two stirring speeds, was conducted to assess their direct correlation with microparticle size. The interfacial polymeric crosslinking method successfully yielded spherical microparticles, maintaining a wrinkled surface aspect, with size variations according to the formulation. Parameters such as crosslinking agent concentration and stirring speed were identified as influencing factors on microparticle size. In conclusion, interfacial polymeric crosslinking using sodium trimetaphosphate proves effective in obtaining chitosan microparticles.

Formation mechanism of n-octadecane @ calcium fluoride microencapsulated phase change material

Microencapsulating phase change materials (PCMs) with CaF2 as shell could obtain not only novel microencapsulated PCMs (MPCMs) but also potential luminescence materials with self-thermal regulation property. Prior to the preparation of good luminescent MPCMs with doped CaF2 as shell, the formation mechanism of the MPCMs should be well understood. In this work, n-octadecane (ODE) was selected as core to prepare CaF2 MPCMs and the formation mechanism was comprehensively investigated. The results revealed that the concentrations of the Ca2+ and the F− in the solution, which could be adjusted by the coordination equilibrium of Ca-citrate complex and the hydrolysis balance of NaBF4, played key roles in formation of the MPCMs. Moreover, the formation of the MPCMs was composed of five periods, including: formation of emulsion; formation of Ca-citrate intermediate microcapsules; induction of CaF2 shell; growth and aggregation of CaF2 shell and overgrowth of CaF2. Meanwhile, the results also revealed that prolonging the overgrowth period of CaF2 had significant effects on the morphology and properties of the prepared MPCMs. In addition, with the increase of the reaction temperature, the nucleation, growth and aggregation of CaF2 crystals could be accelerated, and the formation and growth periods of the CaF2 shell were shortened. This work is not only significant for the preparation and optimization of MPCMs with CaF2 as shell, but also can guide and promote the development of luminescent MPCMs.

Controlling the Synthesis of Polyurea Microcapsules and the Encapsulation of Active Diisocyanate Compounds.

The encapsulation of active components is currently used as common methodology for the insertion of additional functions like self-healing properties on a polymeric matrix. Among the different approaches, polyurea microcapsules are used in different applications. The design of polyurea microcapsules (MCs) containing active diisocyanate compounds, namely isophorone diisocyanate (IPDI) or hexamethylene diisocyanate (HDI), is explored in the present work. The polyurea shell of MCs is formed through the interfacial polymerization of oil-in-water emulsions between the highly active methylene diphenyl diisocyanate (MDI) and diethylenetriamine (DETA), while the cores of MCs contain, apart from IPDI or HDI, a liquid Novolac resin. The hydroxyl functionalities of the resin were either unprotected (Novolac resin), partially protected (Benzyl Novolac resin) or fully protected (Acetyl Novolac resin). It has been found that the formation of MCs is controlled by the MDI/DETA ratio, while the shape and size of MCs depends on the homogenization rate applied for emulsification. The encapsulated active compound, as determined through the titration of isocyanate (NCO) groups, was found to decrease with the hydroxyl functionality content of the Novolac resin used, indicating a reaction between NCO and the hydroxyl groups. Through the thorough investigation of the organic phase, the rapid reaction (within a few minutes) of MDI with the unprotected Novolac resin was revealed, while a gradual decrease in the NCO groups (within two months) has been observed through the evolution of the Attenuated Total Reflectance-Fourier-Transform Infrared (ATR-FTIR) spectroscopy and titration, due to the reaction of these groups with the hydroxyl functionalities of unprotected and partially protected Novolac resin. Over longer times (above two months), the reaction of the remaining NCO groups with humidity was evidenced, especially when the fully protected Acetyl Novolac resin was used. HDI was found to be more susceptible to reactions, as compared with IPDI.