A.L. Iordanskii

Modeling of percutaneous drug transport in vitro using skin-imitating Carbosil membrane.

A comparative study of the barrier function of human skin and polydimethylsiloxane-polycarbonate block copolymer Carbosil membrane was performed in vitro using 14 drugs spanning a wide range of structures and therapeutic classes. The drug permeability coefficients across the skin and the Carbosil membrane wee examined as an explicit dependence of permeant molecular weight, melting point, solubility in aqueous solution in aqueous solution and octanol-water partition coefficient. Owing to heterophase and heteropolar structure, Carbosil membranes and human skin epidermis share a common solubility-diffusion mechanism of drug transport. This synthetic membrane is shown to provide a mechanistically substantiated model for percutaneous drug absorption. Carbosil membrane can be used both foe quantitative prediction for transdermal drug delivery rate and as a skin-imitating standard membrane in the course of in vitro drug delivery kinetics evaluation.

Water transport phenomena in ‘green’ and ‘petrochemical’ polymers. Differences and similarities

Abstract The paper is devoted to the description of specific differences of water transport between petroleum-based (‘petro’ polymers) and environmentally friendly polymers (‘green’ polymers). The differences in water transport mechanisms are presented for poly-R-(3-hydroxybutyrate) and its blends with low density polyethylene (68–100 wt%) on the chemical and crystalline levels. The water diffusion coefficients and permeabilities were obtained using vacuum quartz spring microbalance techniques and permeability cells at 25°C. Spectral characteristics were obtained with FTIR procedure (IFS-48 Brucker IR spectrometer). ESR spectra for Tempol spin probe (sensitive to polar sites in polymer) are presented using Radiopan spectrometer within the temperature range of 20–75°C. As a result of polymer manufacture process, the accumulation of hydrophilic embedded groups is observed in petropolymers (PELD, PP, synthetic rubbers, etc.) which results in the water sorption increase and the effective diffusivity decrease. The immobilization of water both on polar polymeric groups and on impurities leads to an essential decrease in water molecule mobility. Due to their soft natural origin, this situation is less typical for green polymers. The effect of hydrophilic groups on water permeability was demonstrated for PHB/LDPE blends. Narrow MW distribution, stereo regularity and rigid order of polymeric fragments make for a more perfect crystalline structure as compared with petro polymers. The crystalline structure perfection leads to the decrease of water diffusivities as was shown for PHB. ESR data elucidate the relationship between the isotropic/textured PHB crystalline structure and spin probe rotating mobility. The study of the transport features in petro and green polymers is the necessary stage of investigation of such basic processes as physical aging at high humidity and corrosive stability of polymer membranes. The results may promote the design of novel environmentally friendly membranes for desalination and separation processes.

Modification via preparation for poly(3‐hydroxybutyrate) films: Water‐transport phenomena and sorption

The effect of the preparation technique on the sorption-diffusion parameters of poly(3-hydroxybutyrate) (PHB) films was studied. The films formed by a single-stage technique have an axial texture of the crystalline phase, with the polymer chain oriented predominantly perpendicularly to the film plane. Moreover, the crystallites in PHB are preferably ordered in stacks in the course of diffusion; the alignment of the crystallites noticeably decreases the sites of PHB (polar groups) which are accessible to water molecules. As a result, the sorption capacity decreases but the rate of diffusion increases. On the contrary, PHB films prepared by a two-stage technique are characterized by a poor ordering of crystallites without texture organization. Here, the sorption/immobilization on the polar groups of PHB is increased, but diffusivities are decreased. Concentration dependencies of the water-diffusion coefficient are discussed. Additional information on the existence of protein impurities in the PHB samples obtained by the above two preparation techniques was obtained by FTIR spectroscopy and H-D exchange methods.

Transport water and molecular mobility in novel barrier membranes with different morphology features

Abstract Bacterial poly(3-hydroxybutyrate) (PHB) — a new biopolymer and its derivatives are being extensively applied in medicine, biotechnology and membrane technologies. The relationship between structure-transport parameters and molecular mobility of PHB was investigated by quartz McBains microbalance, X-ray diffraction and ESR method. Two types of the PHB membranes with different structural organisation-isotropic and textured-were studied. The specific features of the sorption and diffusion characteristics of PHB are related to the structural organisation. The polymer matrixes are characterised by significantly microstructural heterogeneity as it was shown by the spin probe (TEMPO/TEMPOL) measurements. A non-crystalline phase of PHB includes two kinds of microfields with different molecular mobility. Moisture is found to change both the velocity of molecular motion and the mole content of such microfields. The diffusion behaviour of the membranes has been explained in accordance with dynamic information based on the ESR method.

Poly(3-hydroxybutyrate)-chitosan: a new biodegradable composition for prolonged delivery of biologically active substances

A new polymer composition based on bacterial poly-3-hydroxybutyrate and chitosan encapsulating the wide-spectrum antibiotic rifampicin was developed. Both biopolymers are biocompatible and can undergo enzymatic and hydrolytic degradation. Variations in the ratio of poly-3-hydroxybutyrate and chitosan in the mixture, altering the ratio of hydrophilic and hydrophobic components, influenced not only the sorption capacities for water and drug but also the controlled release profile of the drug. Analysis of kinetic curves for rifampicin release showed that drug release was determined by the superimposition of two processes: drug desorption by a diffusional mechanism and hydrolytic degradation of poly-3-hydroxybutyrate, which was most marked after the initial diffusional stage. Kinetic parameters (the constant of hydrolysis of poly-3-hydroxybutyrate k and the coefficient of diffusion of rifampicin D) were required for a full description of the poly-3-hydroxybutyrate-chitosan-rifampicin system. The fact that the kinetic curves had a prolonged linear region suggests that this composition may have value as a biodegradable therapeutic system for local controlled drug release.

Immobilization influence on the water sorption and diffusion in poly(3-hydroxybutyrate)

The temperature dependency of water vapor sorption and diffusion in poly(3-hydroxybutyrate) (PHB) was studied for the first time. Equilibrium sorption and diffusion kinetics were determined by a quartz McBains vacuum microbalance technique in the temperature range of 303–333 K. A probability of water molecule interaction with the polymer matrix was analyzed for wet PHB films by FTIR spectroscopy technique. Sorption isotherms are interpreted as the solution of free water molecules estimated by the Flory–Huggins equation and the sorption of water molecules immobilized on the carbonyl groups of PHB. The immobilization effect was described by a Langmuir-type equation. The dependency of diffusivity on water concentration was described in the frames of Fujitas immobilization model in which the growing function Dw versus Cw characterized the filling degree of carbonyl groups as sites of immobilization in the polymer. Enthalpy of free water sorption (12 kJ/mol) and water immobilization (42 kJ/mol), as well as the activation energy of water diffusion coefficients (71 kJ/mol), in noncrystalline areas of PHB were determined.

Desorption of human serum albumin and human fibrinogen from the poly(3‐hydroxybutyrate) surface

The protein desorption of human serum albumin and human fibrinogen from the surface of poly(3-hydroxybutyrate) films was studied using ATR–FTIR spectroscopy. The diffusion model for reversible and irreversible sandwiched layers was confirmed. The reversible ratio (ratio of reversible adsorbed concentration to irreversible adsorbed concentration as a function of time allows for a suggestion as to a kinetic model of the initial stage of thromb formation. The parameters of adsorption/desorption for both proteins are compared. The reversible ratio of plasma protein adsorption is proposed as a quantitative criterion of thromb-resistance behavior for polymers in biomedicine; namely, controlled drug release vehicles, artificial vessels, magistrals, reservoirs for blood storage, and surgical threads, especially. The mechanism of interaction of protein molecules with poly(3hydroxybutyrate (PHB) macromolecules is discussed.

Diffusion-activation laws for drug release from polymer matrices

Abstract This paper deals with investigations of simultaneous solvent and drug transport in three component systems (copolymers of N-vinylpyrrolidone-water-drug). A proposed mathematical model of transport processes in such systems has been confirmed by the experimental results. It has been shown that the water sorption velocity and the drug release mechanism depend on the hydrophilic/hydrophobic balance in the copolymer. For each investigated system, physicochemical parameters for the release process have been determined that enable the behaviour of these systems in practice to be predicted.

Performance of Poly(lactic acid) Surface Modified Films for Food Packaging Application

Five Poly(lactic acid) (PLA) film samples were analyzed to study the gas barrier behavior, thermal stability and mechanical performance for food packaging application. O2, CO2, N2, N2O, and C2H4 pure gases; Air; and Modified Atmosphere (MA, 79% N2O/21% O2) were used to analyze the influence of the chemical structure, storage temperature and crystalline phase on the gas barrier behavior. The kinetic of the permeation process was investigated at different temperatures, ranging from 5 °C to 40 °C. Annealing thermal treatment on the samples led to the crystalline percentage, influencing especially the gas solubility process. Thermal properties such as Tg and χc, and mechanical properties such as tensile strength and modulus were remarkably improved with surface PLA modification. A more pronounced reinforcing effect was noted in the case of metallization, as well as improved gas barrier performance. Tensile testing and tensile cycling tests confirmed the rigidity of the films, with about a 20% loss of elasticity after 25 cycles loading.

Prosthetic Devices with Nanostructurated Surfaces for Increased Resistance to Microbial Colonization

This review highlights and discusses the impact of nanotechnology on the inhibition of microbial colonization and biofilm development on modified surface prosthetic devices. In the first part of the paper the current status of infections related to prosthetic devices and the inquiries resulting from the increased number of patients with these infections are briefly reviewed. Next we discuss several aspects about the implication of nanotechnology in prosthetic devices surface modification and its impact on the prevention of infections. The main aspects regarding the biocompatibility and the application of these nanomodified prosthetic devices in tissue engineering are also highlighted.