Anomalous Transport Kinetics Research Articles

Preparation and Physicochemical Properties of a Thermosensitive Hydrogel-based Lipopeptide Biosurfactant

Background: Temperature-sensitive (thermo-sensitive) formulations are a novel drug delivery dosage form that shows bio-inspired behavior in various applications. The structure and properties of a thermosensitive polymer are critical in designing an intelligent biometric polymer that contains lipopeptide biosurfactants. Objectives: In this study, thermo-sensitive hydrogels with lipopeptide biosurfactants as a potential wound dressing dosage form were formulated and examined regarding physicochemical properties. Methods: The lipopeptide biosurfactants were isolated from the Acinetobacter junni B6 bacterial strain and loaded on a formulation of poloxamer 407® and carboxymethyl cellulose as a gelling agent. Numerous experiments were carried out to evaluate the physicochemical properties of these formulations, such as the stability, spreadability, release profile, and kinetic. Results: The formulation (Poloxamer 407® (19% w/v), carboxymethyl cellulose (2% w/v), lipopeptide biosurfactants (5mg/mL), benzyl alcohol (1% v/v), and 0.1mL polyethylene glycol 400) was select as the optimum formulation. The selected formulation released 26.9% of the lipopeptide biosurfactants with anomalous transport kinetics after 10 hours. Conclusions: The results showed that a thermo-sensitive formulation could help achieve a sustained release of lipopeptide biosurfactants and potentially be used as a dressing formulation for wounds in future studies.

Encapsulation of two fermentation agents, Lactobacillus sakei and calcium ions in microspheres

Alginate microspheres loaded with two fermentation active agents, calcium cations and strain LS0296 identified as Lactobacillus sakei, have been prepared and characterized. The role of calcium cation is twofold, it acts as gelling cation and as fermentation active agent. Encapsulation and the presence of calcium ions in the same compartment do not inhibit the activity of LS0296. Molecular interactions in microspheres are complex, including mainly hydrogen bonds and electrostatic interactions.In vitro calcium cations and strain LS0296 release profiles were fitted to the Korsmeyer–Peppas empirical model. The calcium cation release process is driven at first by Fickian diffusion through microspheres and then by anomalous transport kinetics. The in vitro LS0296 release process is driven by Fickian diffusion through microspheres showing a much slower releasing rate than calcium cations. The release of LS0296 strain is followed by a decrease in the pH value.Results obtained give us a new insight into complex interactions between bacterial cultures and microsphere constituents. Prepared formulations of calcium alginate microspheres loaded with LS0296 could be used as a new promising tool and a model for different starter cultures encapsulation and use in the production of fermented foods.

Physicochemical properties and release characteristics of calcium alginate microspheres loaded with Trichoderma viride spores

Novel agroformulations for simultaneous delivery of chemical and biologically active agents to the plants were prepared by encapsulation of Trichoderma viride spores in calcium alginate microspheres. The impact of calcium ions concentration on the viability and sporulation of T. viride spores as well as on the microsphere important physicochemical properties were investigated. Intermolecular interactions in microspheres are complex including mainly hydrogen bonds and electrostatic interactions. T. viride germination inside matrix and germ tubes penetration out of microspheres revealed calcium alginate microspheres provide a supportive environment for T. viride growth. Differences in physicochemical properties and bioactive agents release behaviour from microspheres were ascribed to the changes in microsphere structure. Fitting to Korsmeyer-Peppas empirical model revealed the underlying T. viride release mechanism as anomalous transport kinetics (a combination of two diffusion mechanisms and the Type II transport (polymer swelling and relaxation of the polymeric matrix)). The increasing amount of T. viride spores in the surrounding medium is closely related to the release from microspheres and germination. The rate controlling mechanism of calcium release is Fickian diffusion. A decrease in the release rate with increasing calcium ion concentrations is in accordance with the calcium ions effect on the strength of the alginate network structure. T. viride germination inside microsphere diminished the amount of released calcium ions and slowed release kinetics in comparison with microspheres prepared without T. viride. The results indicated investigated agroformulations have a great potential to be used for plant protection and nutrition.

Influence of surface morphology and structure of alginate microparticles on the bioactive agents release behavior

The structure-property relationship in alginate microparticles (microspheres and microcapsules prepared with or without Trichoderma viride spores (Tv) was investigated. Surface morphology, structure and release behavior from alginate microparticles strongly depend on calcium concentration and presence of Tv and chitosan layer. All microparticles exhibited a granular surface structure with substructures consisting of abundant smaller particles. In vitro active agents release study revealed that the increase in calcium cation concentration reduced the release rate of Tv (˜84% for microspheres; ˜57% for microcapsules) and calcium cations (˜20% for microspheres; ˜23% for microcapsules). The average decrease in k values due to chitosan layer addition is 41% for Tv and 93% for calcium ions, respectively. The underlying Tv release mechanism from microspheres is anomalous transport kinetics, whereas from microcapsules is controlled by Type II transport. The differences in microparticle surface properties did not affect the mechanism controlling calcium ions release detected as diffusion through microparticles.

Encapsulation of Biological and Chemical Agents for Plant Nutrition and Protection: Chitosan/Alginate Microcapsules Loaded with Copper Cations and Trichoderma viride.

Novel chitosan/alginate microcapsules simultaneously loaded with copper cations and Trichoderma viride have been prepared and characterized. Information about the intermolecular interactions between biopolymers and bioactive agents was obtained by Fourier transform infrared spectroscopy. Encapsulation of T.viride spores and the presence of copper cations in the same compartment does not inhibit their activity. Microcapsule loading capacity and efficiency as well as swelling behavior and release depend on both the size of the microcapsule and bioactive agents. The in vitro copper cation release profile was fitted to a Korsmeyer-Peppas empirical model. Fickian diffusion was found to be a rate-controlling mechanism of release from smaller microcapsules, whereas anomalous transport kinetics controlled release from larger microcapsules. The T.viride spore release profile exhibited exponential release over the initial lag time. The results obtained opened perspectives for the future use of chitosan/alginate microcapsules simultaneously loaded with biological and chemical agents in plant nutrition and protection.

Impact of anomalous transport kinetics on the progress of wound healing

This work focuses on the transport kinetics of chemical and cellular species during wound healing. Anomalous transport kinetics, coupling sub- and superdiffusion with chemotaxis, and fractional viscoelasticity of soft tissues are analyzed from a modeling point of view. The paper presents a generalization of well stablished mechano-chemical models of wound contraction (Murphy et al., 2012; Valero et al., 2014) to include the previously mentioned anomalous effects by means of partial differential equations of fractional order. Results show the effect that anomalous dynamics have on the contraction rate and extension and on the distribution of biological species, and indicators of fibroproliferative disorders are identified.

Encapsulation of colour from peels of eggplant in calcium alginate matrix

Microencapsulation of a natural food colourant (enriched in anthocyanins) extracted from peels of eggplants (Solanum melongena L.) was carried out in a calcium alginate matrix to improve its shelf life and portability. Encapsulation parameters were optimised using response surface methodology. Stable beads with a maximum encapsulation efficiency of 73.56% and the best combination of phytochemical properties were obtained using 43.50 g/l sodium alginate, 20.0 g/l calcium chloride and 12.50 g/l colour concentration. The morphology of the encapsulated beads was determined from scanning electron microscopy photographs, while their physicochemical properties such as antioxidant activity, total anthocyanin content and total phenolic content were determined by biochemical assays. A storage study established that encapsulation of colour extract enhanced its shelf-life 16-fold, compared to the un-encapsulated colour extract. The release profiles of the colour from encapsulated beads were found to follow first-order anomalous transport kinetics. Food application in jelly crystals was also designed wherein these encapsulated beads were successfully used as a natural colourant.

Effects of organobentonites on imidacloprid release from alginate-based formulation

To provide effective delay in release, organobentonites with different loading levels of dodecyltrimethylammonium chloride (DTMA) and hexadecyltrimethylammonium chloride (HTMA) were used as modifying agents in the alginate-based controlled release formulation (CRF) containing imidacloprid. The structure of organobentonites was characterized by FTIR and XRD, and adsorption toward imidacloprid was investigated. The results were utilized to reveal the effects of organobentonites on the release of imidacloprid as well as its mechanism, and to evaluate the potential use of organobentonites to modulate the release of imidacloprid. The results showed that organobentonites could reduce the release of imidacloprid from alginate-based granules, different from the natural bentonite that accelerated the release of imidacloprid. The time taken for 50% of the active ingredient to be released, T50, for CRF incorporating organobentonites with DTMA at loading level of 50, 75, 100 and 125% of the clay's cation exchange capacity was 2.12, 1.59, 1.55 and 1.38 times of the value for the formulation without modifying agent, respectively. The values for those incorporating organobentonites with HTMA at the same loading level were 2.61, 2.20, 1.89 and 1.88 times. It was suggested that imidacloprid released via an anomalous transport kinetics predominated by Fickian diffusion and was influenced by the addition of bentonite and organobentonites due to the change of matrix permeability and the interaction with organobentonites. The enhancement of matrix permeability and imidacloprid release resulting from the addition of natural bentonite might be attributed to the lamellar structure and swellability of bentonite in water. In contrast, the matrix permeability and imidacloprid release decreased when organobentonites were used as modifier agents, as a consequence of the hydrophobicity of organobentonite. The results also suggested the feasibility of regulating imidacloprid release via controlling the structure of the organobentonites. An increase in loading level of quaternary ammonium ions could result in an enhancement of the release, while the extension of the alkyl chain slowed down the release of imidacloprid.

Spray Dried Extract of Phormidium valderianum as a Promising Source of Natural Antioxidant.

Microencapsulation of antioxidant-rich fraction obtained by supercritical carbon dioxide extraction (at 50°C, 500 bar with extraction time of 90 min, and flow rate of CO2 at 2 L/min) of lyophilized biomass of Phormidium valderianum was carried out in a spray dryer using maltodextrin and gum arabic. Microencapsulation conditions that provided the best combination of phytochemical properties such as antioxidant activity, phenolic content, and reducing power with reasonable powder yield were an inlet temperature of 130°C and wall material composition as maltodextrin: gum arabic = 70 : 30. Toxicological study reported that the Anatoxin-a content of this encapsulated powder was below the limit of detection of HPLC. Storage study established that encapsulation of this antioxidant-rich algal extract resulted in eight times enhancement of half-life (T 1/2) values. The release profile of microencapsulated antioxidant-rich fraction from the encapsulated powder was found to follow first order anomalous transport kinetics. Therefore, this microencapsulated algal extract with minimum toxicity is a source of natural antioxidant and could have promising use as novel dietary supplement.

Anomalous transport kinetics and the glucose carrier hypothesis

In recent years several observations of glucose transport in human erythrocytes have been difficult to explain by the carrier model. Three new models have been described as candidates to supplant the carrier hypothesis. In this paper, some of the anomalous findings of Miller ((1968) Biophys. J. 8, 1329–1338) and of Stein's group ((1972) Biochim. Biophys. Acta 266, 161–173; (1966) Biochim. Biophys. Acta 127, 179–193) are discussed in terms of the carrier model with and without unstirred layers (unstirred layers being diffusion barriers between the carrier and the bulk aqueous phases inside and outside the cell). The carrier model with no simplifying assumptions (Regen, D. M. and Morgan, H. E. (1964) Biochim. Biophys. Acta 79, 151–166) with the addition of unstirred layers suggested by Miller, accommodates virtually all the data which have been considered grounds for its rejection. All transport constants for glucose and galactose are evaluated, including the diffusion constants in the unstirred layers. Some novel ways of interpreting kinetics data are described. The asymmetric features of the carrier described by Geck are confirmed ((1971) Biochim. Biophys. Acta 241, 462–472).