Sanja Petrović

Sulfanilamide in solution and liposome vesicles; in vitro release and UV-stability studies

The main goal of this study was to develop a liposome formulation with sulfanilamide and to investigate the liposomes impact on its release and stability to the UV-A/UV-B and UV-C irradiation. Liposome dispersions with incorporated sulfanilamide were prepared by thin-film hydration method and liposomes role to the sulfanilamide release was investigated by using a dialysis method. Comparatively, sulfanilamide in phosphate buffer solution was subject to release study as well to the UV irradiation providing for the possibilities of kinetics analysis. In vitro drug release study demonstrated that 20% of sulfanilamide was released from liposomes within 1 h that is approximately twice as slower as in the case of dissolved sulfanilamide in phosphate buffer solution. The kinetic release process can be described by Korsmeyer–Peppas model and according to the value of diffusion release exponent it can be concluded that drug release mechanism is based on the phenomenon of diffusion. The sulfanilamide degradation in phosphate buffer solution and liposomes is related to the formation of UV-induced degradation products that are identified by UHPLC/MS analysis as: sulfanilic acid, aniline and benzidine. The UV-induced sulfanilamide degradation in the phosphate buffer solution and liposome vesicles fits the first- order kinetic model. The degradation rate constants are dependent on the involved UV photons energy input as well as sulfanilamide microenvironment. Liposome microenvironment provides better irradiation sulfanilamide stability. The obtained results suggest that liposomes might be promising carriers for delayed sulfanilamide delivery and may serve as a basis for further research.

Synthesis and Physicochemical Characterization of Anion Exchanger Based on Green Modified Bottle Gourd Shell

The structural performance and biosorption behavior of a new cationic biosorbent (CALV) prepared from bottle gourd (Lagenaria vulgaris) shell (LVS) as a potentially valuable agrowaste have been established. The biosorbent with anion exchangeable function was synthesized from a modified lignocellulosic biomass (MLV) by a quaternary ammonium agent, N-(3-chloro-2-hydroxypropyl)trimethylammonium chloride. Preparation of the appropriate MLV precursor was firstly carried out by the process of alkaline pretreatment of LVS biomass using a green carbonate solution. In this way, partial delignification, removal of extractive substances, and increased porosity of the cellulose-enriched MLV biomass, as well as the activation of available cellulosic microfibrils to alkaline-cellulose have been achieved. The optimization of synthesis conditions was carried out by direct estimation of the CALV biosorption efficiency to phosphate (using ICP-OES) and nitrate (using UV-VIS) from the aqueous solutions. The structural changes of MLV precursors during green modification and the success of synthesis and biosorbent performances before and after the removal of anions from contaminated solutions have been registered and clarified by physicochemical methods, which include elemental analysis, chemical constitution, morphological characterization, and FTIR spectroscopy. In accordance with the FTIR spectroscopic analysis and isotherm studies, a structural model of the CALV biosorbent and its ion exchange mechanism are proposed.

Thermal Energy Storage of Composite Materials Based on Clay, Stearic Acid, Paraffin and Glauber’s Salt as Phase Change Materials

Thermal protection and insulation are important problems in many fields such as industry, agriculture and medicine. New composite materials with good thermal storage capacities have become important in the last few decades. The role of these materials is reflected in their ability to store energy and allow it to be reused in some other thermal systems. The aim of this study was to create a new material based on the basically activated bentonite clay. First, the clay was basically activated, resulting in a thick gel. Afterwards, stearic acid, Glauber’s salt and active carbon were added, and a heterogeneous gel was obtained as a finished final product. In order to obtain the best heterogeneous gel with satisfactory storage properties, the amount of stearic acid and Glauber’s salt was varied. The characterization of the resulting heterogeneous gel was performed by measuring the cooling rate of the gel samples. Compared with stearic acid, Glauber’s proved to be more effective. Heterogeneous gel cooling tests have shown that there was a certain proportional dependence between the concentration of stearic acid and the Glauber salt. However, it has been noticed the reduction in the cooling rate. Namely, the increase in stearic acid and Glauber’s salt concentration lead to slowing down the cooling rate of the gel. Adding active carbon to the heterogeneous gel also reduced the cooling rate, which indicated that the presence of active carbon in the heterogeneous gel should not be excluded in the future. The advantage of this system is the improvement of the gel thermal characteristics by the presence of water and clay. The gel was reversibly cooled and heated up to 100 °C without changing the homogeneous structure. This system can be used as a heat recovery pad, due to its flexible body pillow. It can be very quickly warmed up in a microwave oven if it is packaged in polyethylene packaging.

Effect of UV irradiation on biomimetic membranes labelled with bioporphyrins

ABSTRACT Two kinds of biomimetic membranes labelled with chlorophyll a and chlorophyllide a were obtained through hydration of a phosphatidylcholine thin film. These artificial membranes were subjected to UVC irradiation (253.7 nm) for different times and were characterized by spectral methods (Vis absorption and emission spectroscopy, Dynamic Light Scattering). The stability of the samples was checked by zeta potential measurements. A photo-bleaching effect occurred depending on the exposure time. The two types of membranes exhibited different photo-responses. Both bioporphyrins proved to be excellent sensors for detection of changes occurred in artificial lipid bilayers, at molecular level.

Scaling potential of geothermal water from the well A-2 at Vranjska Banja: Serbia

Geochemical and physicochemical characteristics of geothermal water from A-2 well are investigated in order to estimate its tendency towards the formation of scale in the pipe installation. Based on the geochemiocal analysis of major elements and groups, as well as triangular plots, this geothermal water can be classified as NaAlk·SO4 type. The ternary diagram classifies it as steamheated-peripheral water. A-2 has a good utilization capacity of 1 L s-1 at the water temperature of 84 °C. Regarding this, SI values are determined as the measure of tendency to form deposits. A positive SI value of calcite (0.14) and aragonite (0.03) at the temperature of 84 °C suggests a very low tendency to form scale, as well as the possible occurrence of a minor proportion of carbonate minerals. XRD mineralogical and SEM analyses of the scale have confirmed its calcite composition. SI values for the temperature of 25 °C indicate the safe silicate minerals deposition due to the positive temperature coefficient. The obtained SI values indicate that the A-2 geothermal water in Vranjska Banja is suitable for use in piping installations because it shows poorly pronounced tendency to form deposits.