PEGylated systems in pharmaceutics

This review addresses the use of poly(ethylene glycol) (PEG) and PEG conjugation for the design of novel dosage forms and the modification of biomolecules. The peculiarities of PEGylated nanoparticles, liposomes, proteins, enzymes, and small drug and polyelectrolyte molecules and their influence on systemic drug delivery, including overcoming of various biological barriers and adhesion to mucosal tissues (mucoadhesion), are considered

Application of the method of phase portraits to the analysis of the kinetics of redistribution of metal ion concentrations in the polyelectrolyte hydrogel-multicomponent solution system

International audienceThe kinetics of redistribution of metal ion concentrations in a system based on a polyelectrolyte hydrogel and a multicomponent salt solution (CuSO 4 and Na 2SO 4) were experimentally examined and theoretically treated. Independently of the mixture composition, the hydrogel swelling-contraction behavior and the sorption-desorption of metal ions are determined by the reactivity of metal ions: the hydrogel sorbs copper ions from solution and collapses; as a result, sodium ions (counterions) are released into the solution. The presence of sodium ions in the mixture decreases the amount of absorbed copper ions and slows down their sorption rate. The method of phase portraits made it possible to obtain a phenomenological equation describing the kinetics of redistribution of metal ion concentrations in the hydrogel-solution system at each hydrogel swelling step (disappearance of dry phase, swelling, and collapse). Experimental data were treated using the frequency filtration technique, which is based on the numerical simulation of a low-pass filter used in radio engineering. With increasing filtration period, the difference between various hydrogel swelling steps is shown to vanish. Comparison of the phase portraits of various mixtures shows that an increase in the amount of any component in the mixture decreases the differences between swelling steps and, thus, substantially simplifies the theoretical description of the process kinetics

A generalized form of the Fuoss law for viscosity of polyelectrolytes in salt solutions of complex composition

International audienceThe viscosity of dilute solutions of flexible-chain and semirigid-chain polyelectrolytes containing high- and low-molecular-mass electrolytes was studied as a function of solute concentration. A generalized relationship was derived, which includes the Fuoss law as the limiting case. A theoretical proof of the validity of the generalized form of the Fuoss law was given on the basis of direct analysis of the set of differential equations describing the concentration distribution of mobile ions inside and outside the macromolecular coil. The obtained generalized expression of the reduced viscosity describes the experimental data well over the entire concentration range in which the polyelectrolyte swelling of polymers is observed