Research Trends in Contemporary Materials Science

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Authors: B. Obradović, A. Osmokrović, B. Bugarski, D. Bugarski, G. Vunjak-Novaković
Abstract: Alginate was shown to be a suitable support for entrapment and cultivation of chondrocytes and bone marrow stromal cells, which under appropriate in vitro conditions synthesized cartilaginous components. The main limitation in these cultures may be low rates of mass transport through the alginate matrix governed by diffusion. In this study, we have designed and utilized a bioreactor system based on a packed bed of alginate beads with immobilized chondrogenic cells. Continuous medium perfusion provided convective mass transport through the packed bed, while small diameters of beads (2.5 mm and down to 500 μm) ensured short diffusion distances to the immobilized cells. During up to 5 weeks of cultivation, the cells synthesized extracellular matrix components merging beads together and indicating potentials of this system for precise regulation of the cellular microenvironment in cartilage tissue engineering.
Authors: Nenad R. Filipović, Tamara R. Todorović, D.M. Sladić, Irena T. Novaković, D.A. Jeremić, K.K. Andjelković
Abstract: New complexes of Pt(II) with condensation derivatives of ethyl hydrazinoacetate and either 2-acetylpyridine or 2-quinolinecarboxaldehyde, and of Pd(II) with the condensation derivative of ethyl hydrazinoacetate and 2-quinolinecarboxaldehyde were synthesized and characterized by elemental analysis, IR, 1H- and 13C-NMR spectroscopy, and molar conductivity measurements. The complexes have a square planar geometry, ligands binding as bidentates in the neutral form, and the remaining two coordination sites being occupied by chloride ions. Biological activity of new complexes, and of previously synthesized Pd(II), Cd(II), Co(III) and Zn(II) complexes with this ligand type was evaluated by the brine shrimp test. All the complexes showed a moderate activity.
Authors: Marko Rakin, Lj. Mojović, Suzana Dimitrijević, K. Mihajlovski, S. Siler Marinković
Abstract: Antimicrobial activity of essential oils obtained from many plants has been known for a long time. However, the use of essential oils as active components of biomedical textile have recently gained popularity and aroused scientific interest. The antimicrobial activity of two essential oils, Rosmarinus officinalis and Abies sibirica, respectively, was detected using two indicator strains: Staphylococcus aureus ATCC 25923 and Escherichia coli ATCC 25922, respectively. To achieve a controlled release of antimicrobial activity and to enable utilization of higher concentrations of active ingredient, the essential oils were first encapsulated in beads based on alginate, gelatin and yeast cells, and then bounded to medical textile. The maximum oil content (85.4%) was achieved in alginate capsules. The release of essential oils was followed by determination of viable bacterial cells during a seven-day incubation of beads in saline. Rosmarinus officinalis and Abies sibirica immobilized in the beads showed a significantly prolonged activity, with some gel-dependent variation.
Authors: B.J. Drakulić, S.P. Sovilj
Abstract: In silico model of title drugs mode of interaction with Cu2+ ion was proposed. A hundred conformations of each drug are used in this study. Examination of drugs interactions with Cu2+ ion were conducted using GRID package. The Cu2+ probe was used. The two favorable regions of interactions were detected: a) the nitro group and terminal imino nitrogen in a γ position from it, as proposed from the experimental data, b) the region of heterocyclic ring (tiazoline and furan from Nizatidine and Ranitidine, respectively) as the most favorable one. Therefore, the present study identifies the second region of the molecule that is able to strongly interact with the Cu2+ ion. The position and energies of obtained molecular interaction fields (MIF) are discussed. The results support the fact that the properties, which express recognition forces of the molecules, are strongly dependent on 3D geometry.
Authors: M.M. Mićić, S.Lj. Tomić, J.M. Filipović, E. Suljovrujić
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.
Authors: Magdalena Stevanović, Branka Jordović, Zoran Nedić, Dejan Miličević
Abstract: Copolymer poly(D,L-lactide-co-glycolide) is used for obtaining the systems for controlled delivery of medicaments. Its specific characteristics make it suitable for various researches where its synthesis is performed in different ways. Using the system for controlled delivery of medicaments, an equal concentration of the medicament is achieved in the body throughout an extended period of time and it has advantages over the conventional methods. In this paper we present a new solvent/non-solvent chemical method for obtaining DLPLG nanospheres. In the experiment various stabilizers were used in order to examine their influence on morphological characteristics of DLPLG particles. The samples were characterized by Infrared Spectroscopy (IR), Differential Scanning Calorimetry (DSC), Scanning Electron Microscopy (SEM) and Stereological analysis.
Authors: Ivana Jovanović, Magdalena Stevanović, B. Nedeljković, N. Ignjatović
Abstract: Biodegradable micro- and nanospheres made of poly-l-lactide (PLLA) are very potent drug or antigen delivery systems with inherent potential for drug and antigen targeting. The objective of this study is to formulate modified PLLA microparticles with defined size and shape that can efficiently bind bioactive component. The effects of some process variables on the size distribution of particles prepared by precipitation method are examined. The main focus is to study the effect of co-solvent selection and poly(vinyl alcohol) PVA concentration on the shape and size of the particles. Chlorophorm is used as a solvent. Methanol (MeOH) and ethanol (EtOH) are selected as co-solvents. Motivation for replacing MeOH with EtOH in pharmaceutical applications is explained by less harmful nature of EtOH. Scanning electron microscopy (SEM) and X-ray diffraction (XRD) are used to characterize the particles. Optimal particles are achieved in ethanol and at higher PVA concentration
Authors: Z.S. Petrović, I. Javni, X. Jing, D.P. Hong, A. Guo
Abstract: Molded polyurethane foams for car seats are based on petrochemical polyols of molecular weight 4000-6000 and copolymer polyols containing micron size polymeric particles. Copolymer polyols (CPP) typically constitute 30% of the mixture with the base polyol. They help cell opening, increase load bearing and tear strength of the foams, but they are relatively expensive. Hyperbranched polyols of petrochemical origin were used in molded foams.[1] They are solid in the pure form and due to high crosslinking density could be incorporated at low concentration in conjunction with copolymer polyols. Instead, we have made hyperbranched polyols which could be a total replacement for CPP in molded foams. Six hyperbranched polyols with primary and secondary hydroxyl groups and different hydroxyl numbers were prepared from soybean oil and tested in flexible foams. Novel polyols were liquid even at very high molecular weights and could completely replace copolymer polyols. Functionality of these polyols increased linearly with molecular weight to very high values, resulting eventually in their high crosslinking power. The effects of the type of hydroxyl groups (primary vs. secondary), hydroxyl number (from 85 to 135 mg KOH/g), and concentration (7.5-30%) in the mixture with the base polyol on foam properties were analyzed. It was found that hyperbranched polyols could replace copolymer polyols completely but their effect on cell morphology and mechanical properties varied with the type of polyol and concentration.
Authors: M.B. Plavšić, Iva Pajić-Lijaković
Abstract: Scaling of the real and the imaginary part of dynamic moduli with frequency, for fully cured elastomer materials as gum and active carbon black filled butyl rubbers, is considered experimentally and theoretically. For gum rubber in different ranges of frequency complete agreement with G''-scaling predicted by the Rouse theory is obtained. Obtained slopes for all G' and G'' of filled rubber are much lower.
Authors: N.L. Lazić, J. Budinski-Simendić, S. Ostojić, M. Kićanović, M.B. Plavšić
Abstract: Properties of four materials based on styrene-butadiene rubber (SBR), one without filler and the other three with the same amount but different types of silica fillers, are investigated. The fillers used are Vulkasil S and two new fillers, differing in nano-structures: specific surface area and particle aggregate morphology. All other components in the material formulations are the same as well as the procedures of material preparation. Thermal and thermo-mechanical properties of all four materials are investigated by modulated differential scanning calorimetry (MDSC) and dynamic mechanical analysis (DMA). Morphology of the materials is studied using scanning electron microscopy (SEM). The results for glass transition temperature (Tg ) of gum rubber and three filled rubbers, obtained by MDSC are for all four materials Tg = -50±1 0C, and by DMA loss tangent measurements also for all of them Tg = -29±1 0C. It indicates no significant influence of active silica fillers on the rubber network segment dynamics, in the temperature range close to Tg of SBR. But, at higher temperatures MDSC gives insights into dynamic transitions that are under the influence of filler interactions and sensitive to filler structure. The difference in Tg results obtained for the same material by MDSC and DMA can be understood in terms of different sensitivity of network segment dynamics to conditions provided by those two measuring methods.

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