Papers by Author: E. Suljovrujić

Abstract: Hydroxyapatite/poly L-lactide (HAp/PLLA) is a composite biomaterial which has been widely utilized for substitution and reparation of the hard bone tissue. It is well known that gamma irradiation has been successfully employed in the modification/sterilization of such porous composites and that it has advantages over other procedures. In this study, differential scanning calorimetry (DSC) measurements were made to investigate the influence of the radiation on glass transition behavior and structural relaxation, as well as to estimate the activation energy for this process. The apparent activation energy ΔH* for structural relaxation in the glass transition region was determined on the basis of the heating rate dependence of the glass transition temperature Tg. Furthermore, the results were correlated with those obtained by gel permeation chromatography (GPC). Our findings support the fact that the radiation-induced chain scission in the PLLA phase is the main reason for the decrease of the glass transition temperature and/or activation energy with the absorbed dose.

Abstract: Controlled release studies of drugs (theophylline (TH), fenethylline hydrochloride (FE) and gentamicin sulphate (GS)) from pH sensitive poly(2-hydroxyethyl methacrylate/itaconic acid) (P(HEMA/IA)) hydrogels obtained by gamma irradiation were carried out to investigate transport phenomena. Drug behavior and release profiles were analyzed using the restriction coefficient combining the influence of network structure and the size of the drug on release and transport properties. The results demonstrated that the ratio of drug radius to polymer pore size and drugpolymer interactions were dominant factors in hindering the diffusion process. The diffusivity of a drug through the hydrogels decreases with the size of the drug molecules and with the decrease in gel pore size. The diffusion equations for used drugs explain drug transport in hydrogels.

Abstract: A numerical procedure for the calculation of space distribution of the thermal field in thermally inhomogeneous solids with thermal memory induced by a harmonically modulated surface heat source is presented. The procedure is based on the division of the complex hyperbolic heat conduction equation into four real first-order differential equations, followed by employment of the Bulirsch-Stoer method with adoptive stepsize. The applicability of the procedure is then demonstrated in few issues, important for the understanding of thermal signal distribution.