Polyacrylic Acid Modifies Local and Lateral Mobilities in Lipid Membranes

Polyacrylic acid (PAA) is a promising polymer for engineering lipid-based drug-delivery vesicles. Its unique properties allow lowering drug dose and delivery the drug close to the site of its release. To design a successful delivery scheme, however, it is important to understand on the molecular scale how the polymer interacts with lipids under various conditions in the human body. Some aspects of the PAA-lipid interaction can be revealed using physical methods, such as differential scanning microscopy, nuclear magnetic resonance spectroscopy, NMR-diffusometry, and infrared spectroscopy. This work discusses the use of these techniques as well as the peculiarities of preparing vesicular and microscopically aligned PAA-lipid systems.      

Effect of Association of Curcumin with Chitosan in Presence of TX 100 on Its Degradation

The binding of curcumin with chitosan in the presence of nonionic surfactant, iso-octylphenoxy-polyethoxy-ethanol (Triton X-100) and its stability in such systems have been investigated by monitoring the changes in the absorption spectra at physiological pH (7.4). It was observed that curcumin binds to chitosan more than 10 times stronger in presence of TX 100 at the experimental condition. From spectrophotometric analysis of the kinetics of degradation of the dye, it was observed that the yield of suppression of degradation of curcumin by chitosan increases by 33.5% in the presence of TX 100 than alone. The interaction of the dye with chitosan has been found to be exothermic and driven by hydrophobic interactions, hydrogen bond formation, and electrostatic interactions.     

A Comparison Investigation of Coix Seed Oil Liposomes Prepared by Five Different Methods

The physicochemical properties of coix seed oil (CSO) liposomes prepared by five different methods were evaluated for morphology, encapsulating efficiency, particle size, storage stability, and in vitro release. The different preparation methods resulted in several types of vesicles with different properties. The type of vesicles was closely related to leakage pattern, which affected the storage stability and in vitro release profiles. Ethanol injection method was the best choice for preparing safe and stable liposomes with controlled release. The release mechanisms might account for the diffusion of CSO, and Higuchi was the most suitable model for liposomes stored at high temperature or released in simulated intestinal fluid (SIF).     

Liquid-Crystal Based Formulations for Topical Drug Delivery

Monoolein, being a biocompatible and bioadhesive penetration enhancer that can form liquid crystalline (LC) phases, possesses remarkable characteristics for addressing drug delivery systems across the biological membrane. A range of formulations based on LC phases were investigated in this study, which includes lamellar, reverse hexagonal, and bicontinuous cubic phases along with an emulsion stabilized by LC phases. Caffeine was chosen as hydophilic model drug to evaluate in vitro release performance. The different monoolein based caffeine formulations were characterized by techniques such as polarized light microscopy, nuclear magnetic resonance (NMR) and small angle x-ray scattering (SAXS). The release experiments, performed through Franz diffusion cells, revealed that the presence of a liquid crystalline (LC) phase prevented burst release in all cases. In addition, taking into consideration that all ingredients are fully biocompatible, the creamy emulsion formulation stabilized by a hexagonal lipid LC phase can be proposed as a challenging preformulation for topical drug delivery.     

Preparation and Characterization of Polymeric Nanocapsules Produced by in Situ Polymerization From Nanoemulsions Produced by Direct Emulsification

Polymeric nanoparticles constitute an important drug delivery system with controlled release profile. This article describes a new way to produce polymeric nanocapsules using a vegetable oil nanoemulsion as template. The process occurs in two steps: First, a nanoemulsion was obtained with a low-energy method based on phase inversion emulsification, using 2-ethylhexyl acrylate as lipophilic monomer. The in situ polymerization of the nanoemulsion droplets is induced by the addition of polymerization catalyzers. The mean size of the polymeric nanoparticles was evaluated by photon correlation spectroscopy and atomic force microscopy. Both techniques showed the formation of polymeric nanocapsules with a mean particle size less than 300 nm.     

Curcumin-Encapsulated Hexagonal Liquid Crystalline Formed by Brij 97/NaDC Mixtures

The phase diagram of a five-components Brij 97-NaDC/IPM-PEG 400/H₂O system was determined at 25°C. The hexagonal liquid crystalline phase (H₁) was found in this system. By use of small-angle x-ray scattering (SAXS), polarization microscopy, and rheology techniques, the influence of composition, temperature, and addition of curcumin on H₁ phase was studied. It is shown that: 1) the investigated hexagonal liquid crystals exhibit a strong shear thinning behavior and viscoelasticity and the strength of the network of H₁ phase becomes weaker with increasing oil content; 2) the frequency-dependent moduli of H₁ samples decreases as the temperature increases and the steady-state limiting viscosity of the hexagonal samples shows an Arrhenius-like dependence on temperature; and 3) samples in H₁ phase containing curcumin retained their organized hexagonal structure. The SAXS results show that the curcumin molecules may be solubilized both into the apolar core of cylinders together with IPM and in the polar domain coexisting with PEG 400 between the cylinders. When curcumin is encapsulated in samples with low oil content, there is a significant decrease in the frequency-dependent moduli. The tendency of frequency behavior for samples incorporating curcumin as a function of temperature is weakened.     

Utilization of Chitosan-Lactide Copolymer Nanoparticles as Controlled Release Pesticide Carrier for Pyraclostrobin Against Colletotrichum gossypii Southw

Low effective availability of modern pesticides places heavy burdens on both the environment and costs to farmers. Nano-augmented delivery systems seem to be more promising to address the present challenge modern pesticides are facing. In this article, biodegradable chitosan-lactide copolymer (CPLA) was prepared and characterized as hydrophobic pesticide-pyraclostrobin carrier. Nano-precipitation method was used to fabricate pyraclostrobin-loaded nanoparticles. Loading content (LC), encapsulation efficiency (EE), size, and size distribution of the resulting nanoparticles were investigated. The size of pesticide-loaded nanoparticles can be adjusted between 77 to 128 nm by varying the feed mass ratio of copolymer to pyraclostrobin from 50/1 to 5/1. Compounds contained within nanoparticles was protected from light compared with the technical material. The pyraclostrobin-loaded nanoparticles showed an initial burst, subsequent sustained and pH-controlled release profile. Compared to 25% pyraclostrobin emulsifiable concentrate (EC), the nanoparticles demonstrated better fungicidal activity against Colletotrichum gossypii Southw under long incubation time, which further exhibited sustained release characteristic.      

Equilibrium and Dynamic Surface Tension of Carboxymethylchitosan and Alkyl Trimethylammonium Bromide Mixtures

A water-soluble derivative of chitosan, carboxymethylchitosan (CMCH), was mixed with alkyltrimethylammoniumbromides (C_mTAB) and was studied on the adsorption at air/water interface using equilibrium and dynamic surface tension method. The effects of surfactant and polymer concentrations, surfactant chain length, as well as pH of solution were investigated. Addition of the surfactants remarkably promotes the polymer adsorption. Increasing any one of surfactant concentration, surfactant chain length, and pH will facilitate the adsorption of the mixture whereas little effects of polymer concentration were observed. The results are explained in terms of the interaction between CMCH and C_mTAB under different conditions.     

Investigation of Asphaltene Aggregate Size Distribution Under Aggregation and Breakage Phenomena Using Monte Carlo Simulation

In this article, the aggregation and breakage processes are simulated through Monte Carlo method for asphaltene aggregates under shear-induced petroleum mixtures. The simulation results are verified by the aggregate size distributions of two types of asphaltenes having different fractal dimensions extracted from Iranian crude oil types. The obtained aggregate size distributions are affected by shear rate, toluene to heptane ratios and the oil type. The dynamic evolution of asphaltene aggregates shows an ascendant trend with time until they reach a maximum average diameter and then descent to a steady-state size. The asphaltene fractal dimension affects the aggregation process.