Stability Of Nanocapsules Research Articles

A timescale-guided microfluidic synthesis of tannic acid-FeIII network nanocapsules of hydrophobic drugs

Many drugs are poorly water-soluble and suffer from low bioavailability. Metal-phenolic network (MPN), a hydrophilic thin layer such as tannic acid (TA)-FeIII network, has been recently used to encapsulate hydrophobic drugs to improve their bioavailability. However, it remains challenging to synthesize nanocapsules of a wide variety of hydrophobic drugs and to scale up the production in a continuous manner. Here, we present a microfluidic synthesis method to continuously produce TA-FeIII network nanocapsules of hydrophobic drugs. We hypothesize that nanocapsules can continuously be formed only when the microfluidic mixing timescale is shorter than the drug's nucleation timescale. The hypothesis was tested on three hydrophobic drugs - paclitaxel, curcumin, and vitamin D with varying solubility and nucleation timescale. The proposed mechanism was validated by successfully predicting the synthesis outcomes. The microfluidically-synthesized nanocapsules had well-controlled sizes of 100–200 nm, high drug loadings of 40–70%, and a throughput of up to 70 mg hr−1 per channel. The release kinetics, cellular uptake, and cytotoxicity were further evaluated. The effect of coating constituents on nanocapsule properties were characterized. Fe content of nanocapsules was reported. The stability of nanocapsules at different temperatures and pHs were also tested. The results suggest that the present method can provide a quantitative guideline to predictively design a continuous synthesis scheme for hydrophobic drug encapsulation via MPN nanocapsules with scaled-up capability.

Recent Advances in Nanocapsule: Types, Preparation Methods and Characterizatio

Nanocapsules are submicroscopic colloidal drug carrier systems consist of a liquid/solid core in which the drug, gene, protein, and other substances are incorporated into the interior cavity that is surrounded by a distinctive polymeric membrane. Polymers like collagen, albumin, and gelatin are mainly using polymers in nanocapsule formulations. Nanocapsules can serve as nano-sized drug carriers to achieve controlled release as well as efficient drug targeting. The process is used to improve the poor aqueous drug solubility, taste, stabilizing drugs by protecting the molecule from the environment, providing the desired pharmacokinetic profile, allowing controlled release, as well as facilitating oral administration. Capsules are generally prepared between the range of 100 and 1000 nm. Their release and degradation properties largely depend on the composition and the structure of the capsule walls. The dispersion stability of nanocapsules determined by the surfactant, nature of the outer coating. This review describes various facts of nanocapsule drug delivery systems in relation to the method of formulation, characterization, potential benefits and risks, and pharmaceutical applications in drug delivery.

The role of surfactant and costabilizer in controlling size of nanocapsules containing TEGDMA in miniemulsion

Nanocapsules with triethylene glycol dimethacrylate (TEGDMA) as core material and polyurethane as wall material used for self-healing bonding resin were prepared by interfacial polycondensation in miniemulsion. The influence of surfactant and costabilizer concentration on nanocapsules size and stability of nanocapsules was investigated. The size and its polydispersity of the nanocapsules were measured by light-scattering particle size analyzer. When the concentration of SDS were increased from 2.5wt% to 10wt%, the size decreases from 340.5 nm to 258.3 nm, PDI decreased from 0.210 to 0.111. As the concentration of HD increased, the size and PDI were both decreased, When reaching 10wt%, the size was 258.0 nm, PDI was 0.130. SDS and HD play important effect in synthesis of Nanocapsules containing TEGDMA. By changing the surfactant and costabilizer concentration it was possible to synthesize a wide variety of nanocapsules sizes. The performance and technical parameters of nanocapsules had been researched preliminarily, which built the solid foundation for the application to the self-repairing bonding resin.

Estabilização do ácido lipoico via encapsulação em nanocápsulas poliméricas planejadas para aplicação cutânea

This work reports the development of polymeric nanocapsules containing lipoic acid prepared by interfacial deposition of poli(e-caprolactona). The suspensions showed acid pH and encapsulation efficiencies from 77 to 90%. Zeta potential values were from -7.42 to -5.43 mV and particle sizes were lower than 340 nm with polidispersion lower than 0.3. The stability of nanocapsules within 28 days was evaluated in terms of pH, lipoic acid content, diameter, size distribution, zeta potential and measurements of relative light backscattering. The stability of formulations containing free lipoic acid was also evaluated. Nanoencapsulation drastically improved the physico-chemical stability of lipoic acid.

Effect of a High-Pressure-Induced Freezing Process on the Stability of Freeze-Dried Nanocapsules

The objective of this study was to develop a freeze-drying process involving high-pressure techniques during freezing in order to optimize the stability of nanocapsules. Nanocapsules prepared by the emulsion-diffusion method were frozen at − 20, − 10, and − 5°C, respectively, and dried under vacuum as a conventional freeze drying (CFd). For the high-pressure freezing process, the nanocapsules suspensions were frozen at − 20, − 10, and − 5°C at 100, 200, and 300 MPa, respectively, and then dried under vacuum conditions (abbreviated as HPFd). The size and morphological analysis of freeze-dried samples were investigated by using Mastersizer®, TEM, and SEM. From these experiments, the mean nanocapsules sizes were entirely aggregated depending on increasing pressure and decreasing freezing temperature in CFd. In HPFd, the nanocapsules frozen at − 10°C were stable depending on the increment of the pressure level. We concluded that the HPFd process was more effective for the stability of nanocapsules compared to the CFd process at freezing temperatures of − 10°C due to high supercooling of the internal phase during the high-pressure freezing process.

Anharmonic Magnetic Deformation of Self-Assembled Molecular Nanocapsules

High magnetic fields were used to deform spherical nanocapsules, self-assembled from bolaamphiphilic sexithiophene molecules. At low fields the deformation--measured through linear birefringence-scales quadratically with the capsule radius and with the magnetic field strength. These data confirm a long standing theoretical prediction [W. Helfrich, Phys. Lett. A 43, 409 (1973)10.1016/0375-9601(73)90396-4], and permit the determination of the bending rigidity of the capsules as (2.6+/-0.8) x 10(-21) J. At high fields, an enhanced rigidity is found which cannot be explained within the Helfrich model. We propose a complete form of the free energy functional that accounts for this behavior, and allows discussion of the formation and stability of nanocapsules in solution.

The effect of monomers on the formulation of polymeric nanocapsules based on polyureas and polyamides

Formulation of nanocapsules based on polyureas and polyamides have been tested using a patented process. This method based on polycondensation reaction of two complementary monomers and spontaneous formation of oil in water emulsion, is an alternative concept to the known technique based on the same type of reaction used for the formulation of microcapsules, and in which the lipophilic monomer was emulsified in the organic phase before the formation of the polymeric membrane. Nanocapsules can be prepared from different monomers. Wall based on cross-linked polymer contributes to the stability of nanocapsules during and after formulation. The permeability of the polymeric wall is related to its crystallinity and contributes to the growth of nanocapsule membrane by the diffusion of the hydrophilic monomers to get stable colloidal suspensions.

Investigation of nanocapsules stabilization by amorphous excipients during freeze-drying and storage

Freeze-drying was recently applied to improve the long-term storage stability of nanoparticles. Nanocapsules have a thin polymeric envelope that may not withstand the stresses of such process. So, cryoprotectants and lyoprotectants are usually added to the formulation to protect these vectors during freezing and desiccation steps. The aim of this paper was to investigate the importance of the vitrification of cryoprotectants on the stabilization of nanocapsules during freezing, desiccation, and storage steps. Furthermore, the effect of stabilizer crystallization on the conservation of nanocapsules properties was studied. Finally, the effect of temperature storage and relative humidity on the stability of nanocapsules was tested through an accelerated stability study. Results indicate that nanocapsules stabilization during the different steps of freeze-drying requires their dispersion within a vitrified matrix of amorphous excipient to protect them against the stress of freezing and dehydration. The crystallization of this stabilizer during the freezing, the desiccation or the storage steps can destabilize these fragile particles. Electron spectroscopy for chemical analysis revealed the adsorption of nanocapsules at the interface ice/liquid during the freezing step. Such adsorption must be avoided in the case of freeze-drying of immuno-nanoparticles to preserve the native structure of proteins attached to their surface.

The role of surfactant in controlling particle size and stability in the miniemulsion polymerization of polymeric nanocapsules

The influence of surfactant concentration on particle size and stability of nanocapsules with liquid cores, synthesized by an in situ miniemulsion polymerization process, was investigated. Although the role of surfactant in the synthesis of particles in the nanometer range has frequently been documented, the transition to structured particles, which almost consist of a 1:1 weight ratio of encapsulated liquid hydrophobe to polymeric shell, has not received much attention. Capillary hydrodynamic fractionation (CHDF) analyses were used to evaluate particle size. Results were subsequently used to stoichiometrically calculate the area which is occupied per surfactant molecule on the particle surface. These results were compared with “classical” miniemulsion data, i.e. data generated from the synthesis of polymeric latexes in the presence of a hydrophobe, but at a much lower hydrophobe:monomer ratio as was used here. The surface coverage per surfactant molecule could be related to the surface tension of the latex, thus providing a relationship between particle size and stability. CHDF was furthermore used to investigate particle size after grafting of a secondary PMMA shell. Data obtained from CHDF experiments were in all cases confirmed by TEM analysis of the synthesized particles. To conclude, the synthesis of nanocapsules with liquid cores could be successfully scaled-up, with retention of all the characteristics of the final latex.