No abstract

BACKGROUND: The mass transfer of model drugs Lidocaine hydrochloride and Dihydroquercetin from hydrogels (the usual carriers for topical drugs), and hydrogels containing liposomes, as novel drug vehicles, was studied. Diffusion experiments were performed using a Franz diffusion cell. Experimental data were used to calculate drug diffusion coefficients across membranes, and their effective diffusion coefficients from hydrogels and liposome containing hydrogels. For the first time the diffusion resistance of all drug carriers was determined from corresponding diffusion coefficients.The main aim of this work was the study of drug diffusion coefficients from liposomes and their comparison with related diffusion coefficients from hydrogels to find how liposomes contribute to prolonged and controlled drug release.

This study evaluated the water absorption, solubility, kinetics of water diffusion and residual monomer content of commercial poly(methyl methacrylate) (PMMA) denture base material modified with dimethyl itaconate (DMI) and di‐n‐butyl itaconate (DBI). Water absorption and solubility were measured gravimetrically while the residual monomer content was analysed using high‐performance liquid chromatography with ultraviolet detection. It was found that the addition of di‐n‐alkyl itaconates significantly decreases the residual methyl methacrylate (MMA) content in the polymerized material. Maximum uptake (M∞) and loss (M′∞), and diffusion coefficients for absorption (Da) and desorption (Dd) of water through all materials were established. M∞ shows a linear decrease with increasing amount of itaconate in the system while Da shows a linear increase with increasing amount of itaconate, both of these effects being more pronounced when DBI is present compared to DMI. M∞ is a linear function of the value of Hoy's solubility parameter. The reduction in residual MMA promoted by addition of a small amount of di‐n‐alkyl itaconates can improve the applicative properties and biocompatibility of the PMMA denture base material. Also, it is shown that modification of the denture base material with di‐n‐alkyl itaconates can enable precise control of water absorption in the system. Copyright © 2012 Society of Chemical Industry

pH sensitive, nontoxic, and biocompatible poly(methacrylic) acid (PMAA) based soft networks have been extensively used in the design of systems for targeted drug delivery. Still, their highly hydrophilic nature limits their potential to be used as a carrier of poorly water-soluble substances. With the aim to overcome this limitation, the present study details a new approach for modification of PMAA based carriers using two amphiphilic components: casein and liposomes. The FTIR analysis revealed structural features of each component as well as the synergetic effect that originated from the formation of specific interactions. Namely, hydrophobic interactions between the poorly watersoluble model drug (caffeine) and casein enabled caffeine encapsulation and controlled release, while addition of liposomes ensured better control of the release rate. The morphological properties of the carriers, swelling behavior, and release kinetics of caffeine were investigated depending on the variable synthesis parameters (neutralization degree of methacrylic acid, concentration of caffeine, presence/absence of liposomes) in two different media simulating the pH environment of human intestines and stomach. The data obtained from in vitro caffeine release were correlated and analyzed in detail using several mathematical models, indicating significant potential of investigated carriers for targeted delivery and controlled release of poorly water-soluble substances.

Ethyl cinnamate, an ester known as flavor and fragrance compound, has been synthesized using two immobilized bioreactor systems, batch and fluidized bed bioreactors. The enzyme used for this synthesis is a commercial lipase B preparation, Novozyme 435. Initial kinetic studies were conducted in both employed bioreactor configurations, and kinetic constants were obtained. Several models were tried for fitting of experimental data, but the best fit, for both bioreactors, was obtained when the ping-pong bi-bi mechanism was used. Interestingly enough, ethanol inhibition occurred in batch bioreactor, but it did not exist in the fluidized bed bioreactor. Solid−liquid mass transfer coefficients were calculated for both bioreactors to determine whether mass transfer limitations existed in either of these systems. The calculation of Damkoḧler numbers and Thiele modulus confirmed that mass transfer limitations had no effect on the overall reaction in both bioreactors.