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Copolymeric hydrogels of poly(N-isopropylmethacrylamide-co-N-isopropylacrylamide), p(NIPMAM/NIPAM), are synthesized by radical polymerization of N-isopropylmethacryl-amide (NIPMAM) and N-isopropylacrylamide (NIPAM) monomers by using the cross-linker ethylen glycol dimethacrylate (EGDM). The synthesized copolymeric p(NIPMAM/NIPAM) hydrogels, starting monomers and the cross-linker were structurally characterized by using Fourier transform infrared spectroscopy (FTIR). The amounts of residual reactants in the synthesized hydrogels were determined by high-pressure liquid chromatography (HPLC). Swelling of p(NIPMAM/NIPAM) hydrogels was investigated in relation to the temperature and pH value of the solution. The obtained values of residual monomer quantities are within acceptable limits and in the range from 2.69 to 5.25 mg g-1 for NIPMAM and 14.55 to 30.80 mg g-1 for NIPAM. The synthesized p(NIPMAM/NIPAM) hydrogels are negatively thermosensitive. The most common mechanisms of transport of a swelling solution in p(NIPMAM/NIPAM) hydrogels are polymer chain relaxation, (Case III), and the anomalous type of diffusion (non-Fickian diffusion). The maximal equilibrium swelling degree of 51.19 was reached by the p(NIPMAM/NIPAM) hydrogel with 1.5 mol% of EGDM at the temperature of 25°C and pH 4, whereas the lowest one of 0.98 was exhibited by the hydrogel with 3 mol% of EGDM at the temperature of 80°C and pH 7. Due to their low content of residual reactants and a satisfactory degree of swelling at various pH values, synthesized p(NIPMAM/NIPAM) hydrogels can be applied as carriers for the controlled release of pharmaceutically active substances.

Acrylic restorations in the mouth are exposed to strong occlusal forces. Their mechanical properties depend on the type and method of their polymerization. The aim of this study is a comparative analysis of mechanical properties (flexural strength and modulus of elasticity) of acrylic materials before and after the post-polymerization treatments (water boiling, microwave irradiation and water storage). The study included denture base resins, as well as an acrylate for orthodontic appliances impregnated with aesthetic beads. Flexural strength, modulus of elasticity and the deflection were measured immediately after polymerization, after a hot and microwave post-polymerization and after immersion in a water bath at the temperature of 37°C. The applied post-polymerization methods resulted in an increase in flexural strength and modulus of elasticity relative to the initial values for all tested materials. Being aware of the reduction in fracture risk of dental prosthesis after a proposed post-polymerization procedure, it could be used in all clinical situations where there is an increased risk of damage to dentures.

Hydrogels are synthesized by the method of radical polymerization of monomers: N-isopropylacrylamide (NIPAM) and acrylic acid (AA). Characterization of poly(N-isopropylacrylamide- co-acrylic acid) hydrogels, p(NIPAM/AA), has been performed by Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD) and by determination of the swelling behaviour in aqueous solutions at different temperatures (25, 31 and 37°C) and pH values (2.2, 4.5, 6 and 6.8). After lyophilisation in the solution at pH 6 and temperature of 25°C, p(NIPAM/AA) hydrogels have rapidly reached equilibrium degree of swelling, αe, in comparison to non-lyophilized samples. The mechanism of solvent transport within matrix in lyophilized samples corresponds to less Fickian diffusion, whereas Super case II diffusion is characteristic for non-lyophilized samples. p(NIPAM/AA) hydrogel with 1.5 mol% of ethylene glycol dimethacrylate (EGDM) at the temperature of 25°C and pH 6.8, has reached the highest swelling equilibrium degree, αe = 259.8. The results of swelling studies have shown that p(NIPAM/AA) hydrogels can be classified as superabsorbent polymers (SAPs). For the evaluation of pH and temperature influences on synthesized hydrogels swelling, a full three-level experimental design has been used. Two-factor interaction model (2FI) is the most optimal model of a full three-level experimental design for representing the swelling equilibrium degree of p(NIPAM/AA) hydrogels as a function of investigated parameters, i.e., temperature and pH. [Project of the Serbian Ministry of Education, Science and Technological Development, Grant no. TR-34012]

New, simple, cost effective, accurate and reproducible RP-HPLC method was developed and validated for the quantification of trans-resveratrol in the extracts of grape exocarp and seeds. The method has proved to be simpler and faster than available methods. Methanol was used as a mobile phase with a flow rate of 1.0 cm3 min-1, while the quantification was effected at 306 nm. The separation was performed at 35°C using a C18 column. The results showed that the peak area response was linear in the concentration range of 1-40 μg cm-3. The values of LOD and LOQ were found to be 0.125 and 0.413 μg cm-3, respectively. The antioxidant activity of the extracts was determined using DPPH assay. The ability of DPPH radicals inhibition decreases in the following order: the extract of grape exocarp > trans-resveratrol standard > the extract of grape seeds. [Projekat Ministarstva nauke Republike Srbije, br. TRp-34012]

The aim of this work was the preparation of the inclusion complex of naproxen with 2-hydroxypropyl-β-cyclodextrin (HP-β-CD) in order to improve the physical and chemical properties of naproxen. The molecular inclusion complexes of naproxen with HP-β-CD were prepared by using the co-precipitation method in the solid state with the molar ratio of 1:1. The structure of the obtained complex was characterized by using FTIR, 1H NMR, UV-Vis and XRD methods. The testing of naproxen photostability by the UV-Vis method indicated the degradation to aromatic ketone, 2-acetyl-6-methoxynaphthalene. FTIR analysis showed that the degradation started 15 days after the exposure of naproxen to daylight while the inclusion complex of naproxen: 2-hydroxypropyl-β-cyclodextrin was photostable for a period of 30 days. [Projekat Ministarstva nauke Republike Srbije, br. TR 34012]

In this study the qualitative, quantitative and microbial determination of the aqueous extract of comfrey root was done. The qualitative and quantitative analyses were done by the UHPLC-DAD-HESI-MS method. As major bioactive compounds, allantoin, rosmarinic acid and ellagic acid were identified and their quantification was also done. The obtained results showed a high content of allantoin, ellagic acid and rosmarinic acid (8.91, 7.4 and 12.8%, respectively) which indicated that the comfrey root can be used as a source for the isolation of these three compounds. The results obtained by the determination of the antimicrobial activity showed that Escherichia coli ATCC8739 and Salmonela typhimirium ATCC6538 were most sensitive to the aqueous extract of comfrey root. The results showed that allantoin did not express the antimicrobial activity on all the investigated bacteria species, and based on this it can be concluded that allantoin is not responsible for the antimicrobial activity of the aqueous extract of comfrey root. [Projekat Ministrstva nauke Republike Srbije, br TR-34012]

In the last decade, exploration of transition alumina phases with good adsorption properties has attracted a great research interest from both a fundamental and a practical point of view. The transition phases of alumina are metastable polymorphs of aluminum oxide formed through the thermal dehydration of aluminum trihydroxide and aluminum oxyhydroxide. Powder X-ray diffraction (XRD), Fourier-transformed infrared spectroscopy (FT-IR), scanning electron microscopy (SEM) and low-temperature nitrogen absorption studies were employed to trace the formation of the transition phases of alumina. In this work transition alumina powders were synthesized starting from sodium aluminate solution prepared from Bayer liquor. The neutralization of sodium aluminate solution was performed with the use of sulphuric acid, while glucose was added in the starting solution. In this way, the single phase nanocrystalline boehmite was obtained. As-synthesized boehmite powders have high surface area (above 360 m2/g) and the average crystallite size less than 5 nm. The results showed that the properties of the powders (structure, morphology) are strongly influenced by the initial pH value of sodium aluminate solution, as well as by the duration of neutralization step. [Projekat Ministarstva nauke Republike Srbije, br. III 45021]

The aim of this work is the protection of piroxicam from photodegradation by forming inclusion complex with 2-hydroxypropyl-β-cyclodextrin. Piroxicam:2-hydroxypropyl-β-cyclodextrin molecular inclusion complex was prepared by coprecipitation method with molar ratio of 1:1. Structural characterization of the complex, the corresponding physical mixture and complexing agents of piroxicam and 2-hydroxypropyl-β-cyclodextrin was carried out by X-ray diffraction (XRD), proton nuclear magnetic resonance (1H NMR) and Fourier transform infrared spectroscopy (FTIR). Photosensitivity to daylight for piroxicam and piroxicam:2-hydroxypropyl-β-cyclodextrin inclusion complex was investigated by Fourier-transform infrared spectroscopy. The investigations show that higher photostability of piroxicam was achieved in complex than in non-complexed piroxicam.

A comprehensive analysis of physicochemical parameters in geothermal waters from the sites in Sijarinska spa (drill hole B-4) and Vranjska spa (drill hole VG-2) in order to investigate their tendency to form deposits in the pipe installation is presented. Drill holes B-4/VG-2 posses utilization capacity of 30/27 L s-1 with water temperatures 75/90 oC. VG-2 water does not show any tendency to (or shows very small) sedimentation compared to the B4 water. The behaviour of the geothermal water from the B-4 hole was examined in real condition in Sijarinska spa, by letting it flow through the pipe installation. The results of geochemical analysis of water B-4 show that aragonite is the predominant mineral in the sediment (98 %) with lesser amount of calcite, vaterite and anhydrite. [Projekat Ministarstva nauke Republike Srbije, br. TR 33034]

In order to investigate the influence of sodium-polyacrylate polymer as a co-builder in addition to the carbonate/zeolite builders in detergent builder system, secondary washing performances of powder laundry detergent containing equal percentage of sodium polyacrylate with the different weight average molar mass, Mw, have been examined. The value of the degree of whiteness, elongation at break, and total residue content are the most important secondary washing performances that significantly depend on sodium polyacrylates efficiency used as crystal inhibitors, stabilizers for suspended soil, and agents for soil redisposition prevention on fabric surface. The values of the whiteness and elongation at break for cotton fabrics increase with the increase of average weight molecular mass, Mw, up to the value of 70000 g/mol, while in the case of further increase of weight average molar mass up to the 250000 g/mol value of these characteristics begin to decline. The values of the total residue content after combustion indicate an increase in its content with the increase of weight average molar mass of 3000 to 70000 g/mol, while the highest value has been reached in the sample of detergent containing sodiumpolyacrilic with the weight average molar mass of 250000 g/mol. All detergent samples show no significant dependence of the secondary washing characteristics on the number of washing cycles.

The yield of extractive substances, antioxidant activity, as well as total phenolic and total flavonoid contents of aqueous-ethanolic extracts obtained from aerial parts of Galium mollugo L. by different extraction techniques (maceration, reflux and ultrasonic extraction) were reported. The antioxidant activity of extracts was tested by measuring their ability to scavenge a stable DPPH free radical, while the total phenolic and total flavonoid contents were determined according to the Folin-Ciocalteu procedure and a colorimetric method, respectively. The Duncan’s multiple range tests were used to evaluate if there were significant differences among yields of extractive substances, total phenolics, total flavonoids and EC50 values for the extracts obtained by different extraction techniques. The extracts obtained by the reflux extraction contained higher amounts of extractive substances, as well as phenolic and flavonoid compounds, and showed a better antioxidant activity than those obtained by the two other recovering techniques.

The aim of this paper was to model and optimize the process of total flavonoid extraction from the green tea using the artificial neural network and response surface methodology, as well as the comparation of these optimization techniques. The extraction time, ethanol concentration and solid-to-liquid ratio were identified as the independent variables, while the yield of total flavonoid was selected as the dependent variable. Central composite design (CCD), using second-order polynomial model and multilayer perceptron (MLP) were used for fitting the obtained experimental data. The values of root mean square error, cross-validated correlation coefficient and normal correlation coefficient for both models indicate that the artificial neural network is better in prediction of total flavonoid yield than CCD. The optimal conditions using the desirability function at CCD model was achieved for the extraction time of 32.5 min, ethanol concentration of 100% (v/v) and solid-to-liquid ratio of 1:32.5 (m/v). The predicted yield at these conditions was 2.11 g/100 g of the dried extract (d.e.), while the experimentally obtained was 2.39 g/100 g d.e. The extraction process was optimized by the use of simplex method at MLP model. The optimal value of total flavonoid yield (2.80 g/100 g d.e.) was achieved after the extraction time of 27.2 min using ethanol concentration of 100% (v/v) at solid-to-liquid ratio of 1:20.7 (m/v). The predicted value of response under optimal conditions for MLP model was also experimentally confirmed (2.71 g/100 g d.e.).

The method of the synthesis of poly(N-isopropylacrylamide-co-2-hydroxypropyl methacrylate) hydrogels obtained by radical polymerization is described. Their characterization was carried out by the determination of the quantity of residual monomers and by investigating their structure using the FTIR. Three glass transitions were detected by DSC method. The porous surfaces of hydrogels with incorporated ibuprofen were shown in SEM micrographs. The swelling ratio of hydrogels decreased with the temperature increase and the swelling transport mechanism was changed from non-Fickian to Fickian. Ibuprofen was incorporated in hydrogel as a drug carrier and released quantity was monitored by HPLC method depending on the temperature. Hydrogel with the lower cross-linker content had the highest swelling degree (α = 34.72) at 10°C and released the largest amount of ibuprofen (64.21 mg/gxerogel) at 40°C. [Projekat Ministarstva nauke Republike Srbije, br. TR-34012]

Over the past years, many scientific researches have been focused on thermo-sensitive hydrogels containing N-isopropylacrylamide (NIPAM) as a monomer. The NIPAM based hydrogels with 20 mol% 2-hydroxypropyl methacrylate (HPMet) were synthesized using ethylene glycol dimethacrylate as a cross-linker. The characterization of xerogel and phenacetin using FTIR spectra and SEM micrographs confirm the performed synthesis with satisfactory purity as well as loading of phenacetin into hydrogel. The swelling transport mechanism at simulated physiological conditions (pH 2.20 and 7.40 at 37°C) is described by the time-independent kinetics. The potential application of synthesized hydrogels for the controlled release of phenacetin as a model drug was investigated at simulated physiological conditions by HPLC method. [Acknowledgement. This work is part of the project MNTR TR-34012 financed by the Ministry of Education and Science of the Republic of Serbia. The authors are grateful for the support provided by the Ministry.]

Transition (active) phases of alumina were synthesized starting from sodium aluminate solution prepared out of Bayer liquor. The neutralisation of sodium aluminate solution was performed by sulphuric acid. Powder X-ray diffraction (XRD), Fourier-transformed infrared spectroscopy (FT-IR), scanning electron microscopy (SEM) and low-temperature nitrogen absorption studies were employed to trace the formation of the transition phases of alumina. The results show that the properties of the powders (phase composition, morphology and specific surface area) are strongly influenced by the initial pH value of the system, as well as by the duration of neutralisation step. It is possible to obtain powders with heterogeneous structure with dominant phase of bayerite, gibbsite or boehmit by tuning the pH and concentration of the starting sodium aluminate solution. The transition (active) phases of alumina (η- and γ-alumina) with high specific surface area (264-373 m2/g) are formed through the thermal dehydratation of aluminium hydroxide (bayerite and gibbsite) and aluminium oxyhydroxide (boehmite or pseudoboehmite) at the temperature of 500°C. Namely, bayerite and pseudoboehmite transforms to η-phase of alumina upon heating, while gibbsite transforms to γ-phase, maintaining the parent morphology.

The oral tissue conditioners are applied temporarily to the gingival surface of a denture for the purpose of reconditioning the abused denture supporting tissues, allowing them to return to a normal, healthy state. According to chemical composition they can be classified into methacrylic and silicon conditioners. The objective of this research was to examine the potential toxicity of one, seven and thirty day extracts of different concentrations. Different effective concentrations (5, 12.5, 25 and 50%) of two silicone and four methacrylic conditioners extracts were used after extraction period of one, seven and thirty days. Amount of toxic substances and dynamics of their release were monitored by high-pressure liquid chromatography (HPLC). HPLC analysis could not be applied to the silicone conditioners because they consist of polymeric and inorganic 19 substances. Evaluation of cell proliferation, as cytotoxic parameters, was done by Mosmann’s MTT assay based on reduction of yellow tetrazole (3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide - MTT) to purple formazan by mitochondrial succinate dehydrogenase of metabolic active cells. With increasing of extraction period, the amount of released potential toxic substances increased. The cytotoxicity of tested materials significantly increased with extract concentration increase and duration of extraction period. To improve the biological characteristics of mobile dentures relined by soft materials, soaking in water the day before insertion into patient’s mouth was recommended. Silicone conditioners showed less cytotoxicity compared to the methacrylic conditioners, so they are more appropriate for daily dental practice.

Poly (methyl methacrylate) (PMMA) is material widely used in dentistry. Despite the various methods used to initiate the polymerization of acrylic resins, the conversion of monomer to polymer is not complete thus leaving some unreacted methyl methacrylate (MMA), known as residual monomer (RM), in denture structure. RM in dental acrylic resins has deleterious effects on their mechanical properties and their biocompatibility. The objective of the work was to test the residual monomer reduction possibility by applying the appropriate postpolymerization treatment as well as to determine the effects of this reduction on pressure yields stress and surface structure characteristics of the acrylic resins. Postpolymerization treatments and water storage induced reduction of RM amount in cold-polymerized acrylic resins improved their mechanical properties and the homogenized surface structure. After the polymerization of heat-polymerized acrylic resins the post-polymerization treatments for improving the quality of this material type are not necessary.

The essential oils from flowers of Lavandula officinalis L. (L. officinalis L. = L. angustifolia Mill.) were obtained by two hydrodistillation techniques: standard (technique I) and modified (technique II) Clevenger hydrodistillation. The yield, hydrodistillation kinetics, composition and antimicrobial activity of essential oils were investigated. The higher yield of oil was obtained by hydrodistillation technique II. The new analytical hydrodistillation kinetics model of essential oil from Lavandulae flowers was defined. The essential oil composition was analyzed by gas chromatography-mass spectroscopy (GC-MS). There are differences in chemical compositions of the oils obtained by different techniques. Antimicrobial activity of essential oil obtained by technique I and II against Salmonella enteritidis, Klebsiella pneumoniae, Staphylococcus aureus, Enterococcus faecalis, Candida albicans and Aspergillus niger is the same, while the activity against Escherichia coli and Pseudomonas aeruginosa is slightly different.

The main carriers of the pharmacological activity of garlic (Allium sativum L.) are organic sulfur compounds, the most important among them being allicin, a sulfenic acid thioester, or allylthiosulfonate. In this paper, the identification of synthesized and purified allicin was determined by using various spectroscopic methods (UV/VIS, FTIR, NMR). A HPLC method was developed for the detection and determination of the allicin content. The thermal degradation of allicin by using FTIR method was monitored. The method for the production of allicin gel based on Carbopol 940 (poly(acrylic acid)) was elaborated. The antimicrobial activity of pure allicin and allicin incorporated into gel by using a disk diffusion method was determined. In order to determine the antioxidant activity of allicin DPPH test was done and it was proved that with low concentrations (1 mgcm-3) a high DPPH radicals scavenging capacity (90%) was achieved.

The application of polymers for controlled drug delivery is influenced by no toxicity and solubility in different pH mediums. There already are existing pharmaceutical medicaments based on aqueous dispersion of an anionic copolymer methyl acrylate, methyl methacrylate and methacrylic acid. The aim of this work was to synthesise copolymers of methyl methacrylate and methacrylic acid and to estimate the effects of monomers ratio (1:1 and 1:2) on the molecular mass, polydispersity index, and solubility of obtained polymers. Acetone was used as a solvent because both monomers and the initiator azobisisobutyronitrile are soluble in it. FTIR method was used for functional group characterization, the gel permeation chromatography method for average molecular weights and the distribution of molecular weights determinations. High pressure liquid chromatography (HPLC) was applied for the estimation of residual monomers in obtained copolymers. The titration with ethanol solution of NaOH was used for assessing of monomer units in copolymers. The copolymer with the molar ratio of monomers 1:1 was soluble in water bufer with pH values higher then 6, while the copolymer with the molar ratio of monomers 1:2 was soluble in bufer with pH higher then 9.

The optimal operational extraction conditions were determined by investigating the influence of the methanol concentration, solvomodule and temperature of the maceration extraction on the yield and kinetics of total extractive matter, chlorogenic acid, umbelliferone and apigenin-7-O-glucoside from Hieracium pilosella L. Based on the results of Soxhlet and Tillepape extraction kinetics investigations of the total extractive matter and the components under the optimal maceration operation conditions it was found that the highest yields of the extractive matter and investigated bioactive components extracted from the dry plant material were obtained by using the Soxhlet extraction method. The contents of chlorogenic acid, umbelliferone and apigenin-7-O-glucoside in the extracts were determined by HPLC method. Chlorogenic acid is the component with the highest share in all the extracts.

The characteristics of two types of porous polymers: poly(methyl methacrylate) and copolymers of methyl methacrylate and acrylamide were investigated in this study. Poly(methyl methacrylate) was synthesized in suspension, using ethylene glycol dimethacrylate as the cross-linking agent, poly(vinyl pyrrolidone) as the protective colloid, and benzoyl peroxide as the initiator. The synthesis of poly(methyl methacrylate-co-acrylamide) was initiated in emulsion in the presence of dioctyl sulfosuccinate sodium salt, followed by a sol-gel process, and completely reacted to the solid state. Potassium persulfate was used as the initiator, and tetramethylol glycoluril as the cross-linking agent. Both types of syntheses were carried out in the presence of ethyl acetate. The porosity, specific surface and distribution of the pore sizes of the obtained polymers were determined by mercury porosimetry. The polymers were used as inert carriers for the immobilization of enzymes and whole cells of Saccharomyces cerevisiae yeast.

Garlic powder, essential oil and aqueous extracts from raw garlic and garlic powder prepared in accordance with the corresponding procedures were tested for antimicrobial activity on Staphylococcus aureus ATCC 6538, Escherichia coli ATCC 25922, Bacillus subtilis 6633, Sarcina lutea ATCC 4391, Pseudomonas aeruginosa ATCC 9027, Salmonella enteritidis, Klebsiel la pneumoniae, Proteus vulgaris, Candida albicans ATCC 10231 and Aspergillus niger ATCC 16404; and, three pathogen microorganisms isolated from human material were also used: Staphylococcus aureus, Escherichia coli and Candida albicans. The antimicrobial activities of the preparations were compared with that of commercial antibiotics and four commercial preparation based on garlic powder and essential oil. Aqueous extracts from raw garlic, from freshly prepared powder and powder stored for 18 months at +4°had the greatest antibacterial and antimycotic activities on all the microorganisms tested. The essential oil obtained by hydro distillation and commercial preparations based on garlic essential oil showed no antimicrobial activity on the microorganisms tested. Thermal oils showed a bacteriostatic or very weak bacteriostatic effect on all the microorganisms except Pseudomonas aeruginosa. The garlic powder and commercial preparations based on the powder have a strong antimicrobial effect on all the microbes except on Pseudomonas aeruginosa.

The influence of different working parameters (vibration intensity superficial gas and liquid rate and content of the solid phase) on liquid flow in a multiphase (gas-liquid: RPC-II and gas-liquid-solid: RPC-III) reciprocating plate column was analyzed using step-response methods and sorbic acid as a tracer. The liquid flow was determined using a model of N-tanks in series followed by back mixing of the liquid phase between the tanks. The parameters of this model N, a and x were calculated by applying several methods: calculation of the moments of the residence time distribution function for a constant number of tanks in series (N=const) analysis of a set of linear equations for N *const and determination of the minimum of defined goal function using the optimization technique leastsq.m of MATLAB software.