Properties Of Nanocapsules Research Articles

Tailoring Properties of Hyaluronate-Based Core-Shell Nanocapsules with Encapsulation of Mixtures of Edible Oils.

Dispersions of core-shell nanocapsules (nanoemulsion) composed of liquid oil cores and polysaccharide-based shells were fabricated with emulsification using various mixtures of edible oils and amphiphilic hyaluronate derivatized with 12-carbon alkyl chains forming the shells. Such nanocapsules, with typical diameters in the 100-500 nm range, have been previously shown as promising carriers of lipophilic bioactive compounds. Here, the influence of some properties of the oil cores on the size and stability of the capsules were systematically investigated using oil binary mixtures. The results indicated that, in general, the lower the density, viscosity, and interfacial tension (IFT) between the oil and aqueous polymer solution phases, the smaller the size of the capsules. Importantly, an unexpected synergistic reduction of IFT of mixed oils was observed leading to the values below the measured for individual oils. Such a behavior may be used to tailor size but also other properties of the nanocapsules (e.g., stability, solubility of encapsulated compounds) that could not be achieved applying just a single oil. It is in high demand for applications in pharmaceutical or food industries and opens opportunities of using more complex combinations of oils with more components to achieve an even further reduction of IFT leading to even smaller nanocapsules.

Preparation and performance characteristics of spider venom peptide nanocapsules

ω-hexatoxin-Hvn1b is an insecticidal toxin produced by the Tasmanian funnel-web spider (Hadronyche venenata), that can be exploited for development of novel bioinsecticides. Due to its larger size and low membrane permeability, this toxin usually has a slower mode of action compared to conventional small molecule insecticides. Nanoscale materials have unique optical, electrical, mechanical and biological properties, and show great application prospects for pesticide delivery. The physical and chemical properties of nanocapsules were characterized using transmission electron microscopy, laser particle size analysis, Fourier transform infrared spectroscopy, contact angle testing and with a fluorescence spectrophotometer. The results indicated that the nanocapsules were spherical, with an average particle size of 197.70 nm, the encapsulation efficiency rate was 75.82% and the Zeta potential was -32.90 mV. Penetration experiments showed that the nanocapsules could promote protein passage through the intestinal tract of Spodoptera litura and reach the body fluid. Then we expressed ω-hexatoxin-Hvn1b by prokaryotic expression. Bioassay results showed that the oral toxicity of ω-hexatoxin-Hvn1b nanocapsules to S.litura was higher than that of the ω-hexatoxin-Hvn1b. In this paper, we reported a construction method of spider venom peptide nanocapsules based on polylactic-co-glycolic acid by multiple emulsion for delivery of protein to improve the insecticidal effect and oral activity of ω-hexatoxin-Hv1a. © 2022 Society of Chemical Industry.

Evaluation of antioxidant activity of nano- and microencapsulated rosemary (Rosmarinus officinalis L.) leaves extract in cress (Lepidium sativum) and basil (Ocimum basilicum) seed gums for enhancing oxidative stability of sunflower oil.

There has been interest in the use of plant extract as a natural preservative agent for improving the oxidative stability of vegetable oils. However, plant extracts have low stability against heat and environmental stress. In this study, the antioxidant potential of nano‐ and microencapsulated Rosmarinus officinalis L. extract (RE) obtained using the ultrasonication method was measured. The total phenolic and flavonoid content of the extract was 174.4 ± 25.9 mg gallic acid/g extract and 78.30 ± 3.2 mg rutin/g extract, respectively. Antioxidant activity of 50, 100, 200, and 400 ppm of RE was measured by DPPH free radical scavenging methods, ferric reduction assay, and β‐carotene/linoleic acid assay, and then compared to the 100 ppm of TBHQ as a common synthetic antioxidant. The results showed that the antioxidant activity increased with increasing the concentration of the extract in all evaluating methods. The antioxidant activity of 200 ppm of the free and encapsulated extract in cress (Lepidium sativum) and basil (Ocimum basilicum) seed gums at different ratios (1:0, 1:1, and 0:1) was compared to sunflower oil without antioxidants, and oil‐containing TBHQ which was stored at 60°C for 24 days. The oxidation indexes of oil samples include peroxide value, thiobarbituric acid value, and p‐anisidine value measured at 4‐day intervals. A lower oil oxidation was observed in oil‐containing nanoencapsulated extract followed by microencapsulated extract, free extract, and TBHQ. Since producing nanoencapsulated RE requires a higher time and speed of homogenization and due to no statistically significant difference between the antioxidant properties of nanocapsules and microcapsules in oil, the use of microcapsules of RE in basil seed gum to increase the shelf life of sunflower oil is recommended.

Preparation, Characterization, and Evaluation of Pyraclostrobin Nanocapsules by In Situ Polymerization.

In this study, pyraclostrobin nanocapsules were prepared by in situ polymerization with urea–formaldehyde resin as a wall material. The effects of different emulsifiers, emulsifier concentrations, and solvents on the physicochemical properties of pyraclostrobin nanocapsules were investigated. Solvesso™ 100 was selected as the solvent, and Emulsifier 600# was used as the emulsifier, which accounted for 5% of the aqueous phase system, to prepare pyraclostrobin nanocapsules with excellent physical and chemical properties. The particle size, ζ potential, and morphology of the nanocapsules were characterized by a particle size analyzer and transmission electron microscope. The nanocapsules were analyzed by Fourier-transform infrared spectroscopy, and the loading content and sustained release properties of the nanocapsules were measured. The results show that the size of the prepared nanocapsules was 261.87 nm, and the polydispersity index (PDI) was 0.12, presenting a uniform spherical appearance. The loading content of the pyraclostrobin nanocapsules was 14.3%, and their cumulative release rate was 70.99% at 250 h, providing better efficacy and sustainability compared with the pyraclostrobin commercial formulation.

Synthesis and Properties of Inositol Nanocapsules.

Sugar alcohols are phase-change materials with various advantages but may suffer from leakage during applications. In this study, inositol nanocapsules were synthesized at various conditions, including the amount of precursors and the time for adding the precursors. The effects of synthesis conditions on the properties of the nanocapsules were studied. The morphology, chemical composition, microstructure, phase-change characteristics and size distribution of the nanocapsules were investigated by scanning electron microscope (SEM), Fourier transform infrared spectroscopy (FT-IR), transmission electron microscope (TEM), differential scanning calorimeter (DSC) and a zeta potential analyzer. The results confirm that inositol was well-encapsulated by an SiO2 shell. The shell thickness increased, while the supercooling degree of the nanocapsules decreased with increasing time for adding the precursors. In order to obtain nanocapsules with good morphology and phase-change characteristics, the time for adding the precursors should increase with the amount of precursors. The nanocapsules with the best properties exhibited high melting enthalpy, encapsulation ratio and energy storage efficiency of 216.0 kJ/kg, 83.1% and 82.1%, respectively. The size of the nanocapsules was remarkably affected by the triethoxysilane (TES) amount.

A review on synthesis, characterization and application of nanoencapsulated phase change materials for thermal energy storage systems

Nanoencapsulated phase change materials (NEPCMs) are expected to be one of the most potential energy storage materials. After years of research and development, a mature and huge microencapsulated phase change material (MEPCM) industry has been built in terms of both synthetic technology and practical application. However, microcapsules also have its limitations, such as low heat transfer efficiency, high breakage rate and so on. In order to solve these problems, NEPCMs are being successfully developed. In this review, the research background and development process of NEPCMs were introduced. The structure, principle and function of NEPCMs, including the types and selection principles of core and shell materials were analyzed. Besides, almost all of the common nanoencapsulation methods were presented, some of the methods were emphatically introduced such as in-situ polymerization, interfacial polymerization, emulsion polymerization, miniemulsion polymerization, suspension polymerization and sol–gel method. Furthermore, the thermal properties, physical properties and chemical properties of nanocapsules were discussed and analyzed. Finally, the applications of nanocapsules in building, textile, slurry, solar energy and food industry were summarized. This study was devoted to PCM, nanoencapsulation methods, characterization and application prospects.

Intelligent modeling of rheological and thermophysical properties of nanoencapsulated PCM slurry

AbstractNanoencapsulated phase change material slurries (NPCMS) combine properties of carried fluid and phase change material (PCM). Usage of NPCMS instead of water as a working fluid has a lot of advantages in many industrial fields. The costly and time‐consuming determination of thermophysical properties of NPCMS through the experimental analysis led the current investigations to use soft computing methods like correlating, artificial neural network (ANN), and ant colony optimization (ACOR). In this study, the application of ANN, empirical correlations, and ACOR for modeling the thermophysical properties of NPCM slurry, which has been synthesized through a facile and eco‐friendly procedure, has been investigated. PCM nanocapsules have been synthesized using a miniemulsion polymerization method. Nancapsules consist of AP‐25 as core and a Styrene shell, which is modified with graphene oxide nanosheets as an extra protective screen. The morphology and thermal properties of nanocapsules were characterized and analyzed, respectively. Results revealed that minimum average particle‐size values result in a melting latent heat of 146.8 J/g. In case of NPCM slurry, the results showed that the thermal conductivity of MPCS decreased with particle concentration for the temperatures below the melting point. The NPCMS can be considered a Newtonian fluid within the test region (shear rate > 200/seconds and mass fraction < 0.25). The ANN‐ACOR model consists of two neurons in the input layer, six neurons in the hidden layer, and two neurons in the output layer. The input layer consists of two nodes (PCM concentration and temperature) that correspond to parameters found essential and sufficient for thermophysical properties prediction. Upon comparison, the results show that the presented model, which is a combination of the ACOR algorithm and an artificial neural network, is compatible with experimental work.

Synthesis and properties of nanoencapsulated D-mannitol for medium temperature thermal energy storage

Sugar alcohols with high latent heat have great potential for medium temperature thermal energy storage. Micro/nano-encapsulation can effectively improve the performance of phase change materials (PCMs), such as avoiding leakage and enhancing thermophysical properties. However, only a few work have been reported on the microencapsulation of sugar alcohol, and the reported methods showed some drawbacks such as requiring strictly controlled reactions or resulting in disability for the capsules to solidify. This paper reports for the first time the synthesis and properties of nanocapsules of a sugar alcohol D-mannitol (DM) by a facile sol-gel method. The nanoencapsulation was confirmed by various characterization using Fourier transformation infrared spectroscope (FT-IR), X-ray diffractometer (XRD), and transmission electron microscope (TEM). Uniform size distribution of the nanoencapsulated DM (NEDM) in 100–200 nm was observed by scanning electron microscope (SEM). The phase change performance of the NEDMs were investigated by differential scanning calorimeter (DSC). The results show that the NEDMs with a melting temperature of 166.2 °C, a melting enthalpy of 220.3 J/g, and an encapsulation ratio of 76.5% were obtained. The thermal reliability of the NEDMs was demonstrated by thermal cycling experiments. The thermal stability of the NEDMs was enhanced compared to DM as investigated by thermogravimetric analyzer (TGA). The NEDMs exhibited great potential for applications in medium temperature thermal energy storage and transfer.

Controlled hierarchical self-assembly of networked coordination nanocapsules via the use of molecular chaperones.

Supramolecular chaperones play an important role in directing the assembly of multiple protein subunits and redox-active metal ions into precise, complex and functional quaternary structures. Here we report that hydroxyl tailed C-alkylpyrogallol[4]arene ligands and redox-active MnII ions, with the assistance of proline chaperone molecules, can assemble into two-dimensional (2D) and/or three-dimensional (3D) networked nanocapsules. Dimensionality is controlled by coordination between the exterior of nanocapsule subunits, and endohedral functionalization within the 2D system is achieved via chaperone guest encapsulation. The tailoring of surface properties of nanocapsules via coordination chemistry is also shown as an effective method for the fine-tuning magnetic properties, and electrochemical and spectroscopic studies support that the nanocapsule is an effective homogeneous water-oxidation electrocatalyst, operating at pH 6.07 with an exceptionally low overpotential of 368 mV.

Enhancing optical functionality by co-loading NaYF4:Yb,Er and CdSe QDs in a single core-shell nanocapsule

Nonlinear optical properties of nanocapsules co-loaded with up-converting NaYF4 NPs and CdSe QD are investigated. Large two-photon absorption and low cytotoxicity determine studied nanocapsules for effective luminescence visualisation applications.

Deciphering and Controlling Structural and Functional Parameters of the Shells in Vesicle-Templated Polymer Nanocapsules.

Vesicle-templated nanocapsules are prepared by polymerization of hydrophobic acrylic monomers and cross-linkers in the hydrophobic interior of self-assembled bilayers. Understanding the mechanism of capsule formation and the influence of synthetic parameters on the structural features and functional performance of nanocapsules is critical for the rational design of functional nanodevices, an emerging trend of application of the nanocapsule platform. This study investigated the relationship between basic parameters of the formulation and synthesis of nanocapsules and structural and functional characteristics of the resulting structures. Variations in the monomer/surfactant ratio, temperature of polymerization, and the molar fraction of the free-radical initiators were investigated with a multipronged approach, including shell thickness measurements using small-angle neutron scattering, evaluation of the structural integrity of nanocapsules with scanning electron microscopy, and determination of the retention of entrapped molecules using absorbance and fluorescence spectroscopy. Surprisingly, the thickness of the shells did not correlate with the monomer/surfactant ratio, supporting the hypothesis of substantial stabilization of the surfactant bilayer with loaded monomers. Decreasing the temperature of polymerization had no effect on the spherical structure of nanocapsules but resulted in progressively lower retention of entrapped molecules, suggesting that a spherical skeleton of nanocapsule forms rapidly, followed by filling the gaps to create the structure without pinholes. Lower content of initiators resulted in slower reactions, outlining the baseline conditions for practical synthetic protocols. Taken together, these findings provide insights into the formation of nanocapsules and offer methods for controlling the properties of nanocapsules in viable synthetic methods.

Building Functional Nanodevices with Vesicle-Templated Porous Polymer Nanocapsules.

Vesicle-templated nanocapsules offer a unique combination of properties enabled by robust shells with single-nanometer thickness containing programmed uniform pores capable of fast and selective mass transfer. These capsules emerged as a versatile platform for creating functional devices, such as nanoreactors, nanosensors, and containers for the delivery of drugs and imaging agents. Nanocapsules are synthesized by a directed assembly method using self-assembled bilayers of vesicles as temporary scaffolds. In this approach, hydrophobic building blocks are loaded into the hydrophobic interior of vesicles formed from lipids or surfactants. Pore-forming templates are codissolved with the monomers and cross-linkers in the interior of the bilayer. The polymerization forms a cross-linked shell with embedded pore-forming templates. Removal of the surfactant scaffold and pore-forming templates leads to free-standing nanocapsules with shells containing uniform imprinted nanopores. Development of reliable and scalable synthetic methods for the modular construction of capsules with tunable properties has opened the opportunity to pursue practical applications of nanocapsules. In this Account, we discuss how unique properties of vesicle-templated nanocapsules translate into the creation of functional nanodevices. Specifically, we focus the conversation on applications aiming at the delivery of drugs and imaging agents, creation of fast-acting and selective nanoreactors, and fabrication of nanoprobes for sensing and imaging. We present a brief overview of the synthesis of nanocapsules with an emphasis on recent developments leading to robust synthetic methods including the synthesis under physiological conditions and creation of biodegradable nanocapsules. We then highlight unique properties of nanocapsules essential for practical applications, such as precise control of pore size and chemical environment, selective permeability, and ultrafast transport through the pores. We discuss new motifs for catch and release of small molecules with porous nanocapsules based on controlling the microenvironment inside the nanocapsules, regulating the charge on the orifice of nanopores in the shells, and reversible synergistic action of host and guest forming a supramolecular complex in nanocapsules. We demonstrate successful creation of fast-acting and selective nanoreactors by encapsulation of diverse homogeneous and nanoparticle catalysts. Due to unhindered flow of substrates and products through the nanopores, encapsulation did not compromise catalytic efficiency and, in fact, improved the stability of entrapped catalysts. We present robust nanoprobes based on nanocapsules with entrapped sensing agents and show how the encapsulation resulted in selective measurements with fast response times in challenging conditions, such as small volumes and complex mixtures. Throughout this Account, we highlight the advantages of encapsulation and discuss the opportunities for future design of nanodevices.

Influence of the surface properties of nanocapsules on their interaction with intestinal barriers

Despite the convenience of the oral route for drug administration, the existence of different physiological barriers associated with the intestinal tract greatly lowers the bioavailability of many active compounds. We have previously suggested the potential polymeric nanocapsules, consisting of an oily core surrounded by a polymer shell, as oral drug delivery carriers. Here we present a systematic study of the influence of the surface properties of these nanocapsules on their interaction with the intestinal barriers. Two different surfactants, Pluronic®F68 (PF68) and F127 (PF127), and two polymeric shells, chitosan (CS) and polyarginine (PARG) were chosen for the formulation of the nanocapsules. We analyzed nine different combinations of these polymers and surfactants, and studied the effect of each specific combination on their colloidal stability, enzymatic degradation, and mucoadhesion/mucodiffusion. Our results indicate that both, the polymer shell and the surfactants located at the oil/water interface, influence the interaction of the nanocapsules with the intestinal barriers. More interestingly, according to our observations, the shell components of the nanosystems may have either synergic or disruptive effects on their capacity to overcome the intestinal barriers.

Nanoencapsulation mechanism of fragrant oil: effect of formaldehyde − melamine molar ratio

AbstractEncapsulation of essential oils by in situ polymerization is commonly used to contain the oil and thus ensure its controlled release. Melamine resin formaldehyde is one of the most widely used shell materials due to its thermal and chemical stability. One of the factors that influences the properties of the capsules is the molar relationship between monomers. The effect of formaldehyde − melamine (F/M) molar ratios 3, 4 and 6 on the nanoencapsulation, morphology and properties of nanocapsules was investigated. The morphology and particle size were investigated by the scanning electron microscopy and atomic force microscopy techniques. The composition of the formaldehyde − melamine resins was determined by Fourier transform infrared spectroscopy, and the thermal stability of the nanocapsules was analysed by differential scanning calorimetry and thermogravimetric analysis. Increasing the formaldehyde content reduced the nanocapsules' chemical stability. The capsule sizes obtained were nanometric at all melamine − formaldehyde ratios studied, with a non‐significant variation in particle size and shape. © 2017 Society of Chemical Industry

Crystallinity Tunes Permeability of Polymer Nanocapsules

Permeability is the key property of nanocapsules because it dictates the release rate of encapsulated payloads. Herein, we engineer the crystallinity of polymers confined in the shell of nanocapsules. Nanocapsules with crystalline shells are formed from polyurea and polyphosphoester. The thermal properties, such as crystallization temperature and degree of crystallinity, are different from the bulk. The degree of crystallinity is used to control the shell permeability and, therefore, the release of encapsulated payloads, such as fluorescent dyes, typically used as model components for biomedical applications.

Capability of magnetic functional metal-organic nanocapsules for removal of mercury(II) ions

In this study, a magnetic infinite coordination polymer with the morphology of nanocapsule, as an efficient adsorbent for removal of Hg2+ ions has been introduced. This infinite coordination polymer was synthesized from Zn2+ ion and a ditopic organic ligand (1,3-bis(tetrazol-5-ylmethyl)benzene (btb)) and its efficiency as an adsorbent was studied in view of adsorption isotherms, kinetics and thermodynamics. The adsorption capacity of mercury(II) ions was impressed by pH value and adsorption time and the optimal adsorption conditions were pH value of 8, adsorption time of 75 min. The adsorption isotherm was analyzed by Freundlich and Langmuir equations and was fitted with Langmuir model better. Outcomes indicated that the adsorption was an endothermic process. Moreover, this adsorption process was fitted with pseudo-second order model kinetically. Finally, the magnetic properties of nanocapsules synthesized in high and low concentration of initial reagents were investigated. Studies showed that the saturation magnetization of nanocapsules synthesized in low concentration of initial reagent is higher.

Intracellular localisation of proteins to specific cellular areas by nanocapsule mediated delivery

Nanocapsules are promising carriers with great potential for intracellular protein transport. Although many studies have intended to improve cell uptake efficacy, there is an increasing interest in understanding of subcellular distribution of cargoes inside cells, which is essential for purposeful delivery of biomolecules into specific sites within cells. Herein, we interrogate the intracellular localisation of exogenous proteins, including fluorescein isothiocyanate (FITC)-labelled bovine serum albumin (BSA) and green fluorescent protein (GFP), mediated by specially designed nanocapsules. The results show that the designed nanocapsules can deliver the two types of fluorescent proteins into different cellular destinations (cytosol, nucleus or the whole cell), depending on the composition of nanocapsules. Meanwhile, several impact factors that influence the distribution of proteins in cells have also been investigated, and the results suggest that the localisation of capsule-mediated proteins in cells is strongly affected by the surface properties of nanocapsules, the types of stabilisers and proteins, and environmental temperatures. The rational control of intracellular localised delivery of exogenous proteins as we demonstrated in this study might open new avenues to obtain desired magnitude of drug effects for modulating cell activity.

Preparation of stimuli-responsive nano-sized capsules based on cyclodextrin polymers with redox or light switching properties

We report the preparation and encapsulation properties of stimuli-responsive nanocapsules, self-assembled by the noncovalent interactions of cyclodextrinappended polymers (host) and complementary ferrocene or azobenzene carriers (guest). The encapsulation process was significantly accelerated by applying (electro) chemical or light stimulus, enabling the easier and faster diffusion of guest molecules through the polymer layers. The nanocapsules were characterized by dynamic light scattering, confocal microscopy, ESEM, AFM, UV–visible and fluorescence spectroscopy, and electrochemical techniques. The encapsulation and release properties of the nanocapsules were reversible and could be repeated several times, indicating that the prepared nanoassemblies are very stable.

Effects of fluorinated silane compound on the repeated self- healing properties of nanocapsules

Urea-formaldehyde (UF) nanocapsules, used as self-healing materials, were prepared by in situ polymerization. Fluorinated silane compound KBM7803 was used to modify the surface of the UF nanocapsules. OM and SEM images exhibited the uniform distribution of nanocapsules without any agglomeration when the amount of KBM7803 was less than 2 %. FT-IR of nanocapsules indicated KBM7803 was easily absorbed on the surface of nanocapsules. The evaluation of thermal stability and mechanical properties revealed that addition of KBM7803 significantly improved the thermal stability, tensile strength, and elastic property. Evaluation of self-healing efficiency indicated when the amount of KBM7803 was 2 %, the material exhibited up to 58.9 and 53.6 % of the first and second self-healing efficiency. XPS indicates that F1s can self migrate to the surface of the cracks which guarantees it can be used as self-healing materials to achieve the repeated self healing property.

Nanoencapsulation of Rose-Hip Oil Prevents Oil Oxidation and Allows Obtainment of Gel and Film Topical Formulations.

The rose-hip oil holds skin regenerating properties with applications in the dermatological and cosmetic area. Its nanoencapsulation might favor the oil stability and its incorporation into hydrophilic formulations, besides increasing the contact with the skin and prolonging its effect. The aim of the present investigation was to develop suitable rose-hip-oil-loaded nanocapsules, to verify the nanocapsule effect on the UV-induced oxidation of the oil and to obtain topical formulations by the incorporation of the nanocapsules into chitosan gel and film. The rose-hip oil (500 or 600μL), polymer (Eudragit RS100®, 100 or 200mg), and acetone (50 or 100mL) contents were separately varied aiming to obtain an adequate size distribution. The results led to a combination of the factors acetone and oil. The developed formulation showed average diameter of 158 ± 6nm with low polydispersity, pH of 5.8 ± 0.9, zeta potential of +9.8 ± 1.5mV, rose-hip oil content of 54 ± 1μL/mL and tendency to reversible creaming. No differences were observed in the nanocapsules properties after storage. The nanoencapsulation of rose-hip oil decreased the UVA and UVC oxidation of the oil. The chitosan gel and film containing rose-hip-oil-loaded nanocapsules showed suitable properties for cutaneous use. In conclusion, it was possible to successfully obtain rose-hip-oil-loaded nanocapsules and to confirm the nanocapsules effect in protecting the oil from the UV rays. The chitosan gel and film were considered interesting alternatives for incorporating the nanoencapsulated rose-hip oil, combining the advantages of the nanoparticles to the advantages of chitosan.