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6 results on '"Veljović, Đorđe"'

1. Processing and properties of scaffolds based on calcium phosphate doped with magnesium, copper and zinc-ions coated with gelatin

Author

Dragutinović Olivera Z., Dimitrijević-Branković Suzana I., and Veljović Đorđe N.

Subjects
macroporosity, calcium phosphate, doping, gelatin, mechanical properties, Engineering (General). Civil engineering (General), TA1-2040
Abstract

The main goal of this study was to examine the possibility for obtaining macroporous scaffolds with defined properties based on calcium phosphate doped with magnesium, copper and zinc ions, coated with gelatin, which would potentially provide controlled conditions for the formation of new bone tissue after implantation. As a first, multi-doped nanoparticles of hydroxyapatite (HAp), which represents the main component of the inorganic part of bone tissue, was synthesized by autoclaving the precursor solution obtained at a Ca/P molar ratio of 1.52. Calcium in the initial solution was partially replaced by ions of magnesium (5 mol.%), copper (0.4 mol.%) and zinc (0.4 mol.%). Obtained powder was further calcinated, the changes in the morphology of the powders during calcination at 1000 ̊ C were reflected in the transition of spherically agglomerated needle-like nanoparticles of the multi-doped hydroxy-apatite powder to a spherical grained morphology. Macroporous bioceramic structures were obtained using the sponge replica method, green macroporous samples made of calcinated multi-doped powder, polyvinyl alcohol and water were sintered at 1.370°Ϲ and 1.430°Ϲ. X-ray diffraction analysis deter-mined that the presence of magnesium in the structure of hydroxyapatite favors the phase transformation of HAp into b-tricalcium-phosphate (b-TCP), which contributed to the formation of the biphasic HAp/b-TCP system during the calcination of the powders, but also during the sintering of macroporous beads. Examination of the antimicrobial activity of the obtained macroporous supports against E. coli showed a more effective degree of inhibition compared to S. aureus. A significant increase in the compressive strength of sintered macroporous scaffolds was obtained after the formation of coating based on 7.5% gelatin solution.

Published
2023
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2. Mechanical properties of UHMWPE/EVA hybrid composite reinforced with fibers obtained by electrospinning

Author

Zec Jelena R., Tomić Nataša Z., Vuksanović Marija M., Veljović Đorđe N., Stojanović Dušica B., and Jančić-Heinemann Radmila M.

Subjects
Electrospinning, Al2O3 fibers, mechanical properties, EVA matrix, UHMWPE, Engineering (General). Civil engineering (General), TA1-2040
Abstract

Alumina (Al2O3) nano fibers are prepared from an aqueous solution of aluminum hydroxy chloride/poly (vinyl alcohol) (PVA)/water using the electrospinning technique. The weight ratio of aluminum hydroxy chloride/PVA was 5: 1. After calcification of fibers at 1100 ° C, continuous aluminum oxide fibers were obtained from 200 to 800 nm. The fiber morphology is characterized by a scanning electron microscope (SEM). Image analysis software (Image Pro Plus) was used to measure the diameter of the obtained aluminum oxide (Al2O3) fibers. The aim of this paper is to examine the mechanical properties of the hybrid composite, consisting of a polymer matrix (ethylene and vinyl acetate copolymer (EVA)), ultrahigh molecular weight polyethylene fibers (UHMWPE) and Al2O3 fibers obtained by electrospinning. Al2O3 fibers were added in an amount of 1 wt. % as shown by the improvement of the mechanical properties of the matrix and the hybrid composite.

Published
2018

3. Synthesis and properties of nano-hydroxyapatite/poly (methacrylic acid) composite hydrogels

Author

Ugrinović Vukašin Đ., Panić Vesna V., Veljović Đorđe N., Spasojević Pavle M., Šešlija Sanja I., and Janaćković Đorđe T.

Subjects
composites, hydrogel, hydroxyapatite, poly (methacrylic acid), Engineering (General). Civil engineering (General), TA1-2040
Abstract

Goals. The goal of this study was a development of biocompatible composite hydrogels, structurally similar to native bone tissue, by incorporation of ~60 wt % of calcium hydroxyapatite (HA) into a matrix of hydrogels. Also, a possibility to control swelling kinetic and equilibrium swelling degree (SDeq) of hydrogels, by altering the degree of neutralization of the precursor (DN) was examined. Methods. Composite hydrogels, based on HA and poly(methacrylic acid) (PMAA), were synthesized by free-radical polymerization with different DN. Theoretical content of HA in synthesized composites was 60 wt %. Composites were synthesized by methods of dynamic mechanical analysis and scanning electron microscopy. SDeq and swelling kinetic were examined in distilled water and simulated body fluid. Results. Morphological observations revealed uniform distribution and strong bond of spherical HA particles within the polymer matrix. Swelling analyses demonstrated that SDeq is directly proportional to DN, while rheological examinations indicated inverse proportion between DN and storage modulus, but due to the HA particles inclusion, mechanical properties of composites were significantly better compared to monophasic PMAA hydrogels. Significance. Simple method of synthesis of composite hydrogels with high content of filler nanoparticles is presented. Incorporation of HA nanoparticles significantly improved mechanical properties of hydrogels, while at the same time was demonstrated a possibility to control swelling kinetic by influencing the DN.

Published
2018

4. Mechanical properties of UHMWPE/EVA hybrid composite reinforced with fibers obtained by electrospinning

Author

Zec, Jelena, Tomić, Nataša, Vuksanović, Marija M., Veljović, Đorđe, Stojanović, Dušica, Jančić-Heinemann, Radmila, Zec, Jelena, Tomić, Nataša, Vuksanović, Marija M., Veljović, Đorđe, Stojanović, Dušica, and Jančić-Heinemann, Radmila

Abstract

Alumina (Al2O3) nano fibers are prepared from an aqueous solution of aluminum hydroxy chloride/poly (vinyl alcohol) (PVA)/water using the electrospinning technique. The weight ratio of aluminum hydroxy chloride/PVA was 5: 1. After calcification of fibers at 1100 ° C, continuous aluminum oxide fibers were obtained from 200 to 800 nm. The fiber morphology is characterized by a scanning electron microscope (SEM). Image analysis software (Image Pro Plus) was used to measure the diameter of the obtained aluminum oxide (Al2O3) fibers. The aim of this paper is to examine the mechanical properties of the hybrid composite, consisting of a polymer matrix (ethylene and vinyl acetate copolymer (EVA)), ultrahigh molecular weight polyethylene fibers (UHMWPE) and Al2O3 fibers obtained by electrospinning. Al2O3 fibers were added in an amount of 1 wt. % as shown by the improvement of the mechanical properties of the matrix and the hybrid composite., Aluminijum oksidna (Al2O3) nanovlakna pripremljena su iz vodenog rastvora aluminijum hlorohidrata/poli(vinil alkohola) (PVA) korišćenjem tehnike elektropredenja. Maseni odnos aluminijum hlorohidrata/PVA bio je 5:1. Nakon kalcinacije vlakana na 1100 °C, dobijena su kratka aluminijum oksidna vlakna prečnika od 200 do 800 nm. Morfologija vlakana je karakterisana pomoću skenirajućeg elektronskog mikroskopa sa emisijom polja (FE-SEM). Softver za analizu slike Image ProPlus korišćen je za merenje prečnika dobijenih Al2O3 vlakana. Cilj ovog rada bio je ispitivanje mehaničkih svojstava hibridnog kompozita, koji se sastoji od polimerne matrice (kopolimer etilena i vinil-acetata (EVA)), polietilenskih vlakana ultra-visoke molarne mase (UHMWPE) i Al2O3 vlakana dobijenih elektropredenjem. Al2O3 vlakna su dodavana u količini od 1 mas. % što je pokazalo poboljšanje mehaničkih svojstava matrice i hibridnog kompozita.

Published
2018

5. Synthesis and properties of nano-hydroxyapatite/poly (methacrylic acid) composite hydrogels

Author

Ugrinović, Vukašin, Panić, Vesna, Veljović, Đorđe, Spasojević, Pavle, Šešlija, Sanja I., Janaćković, Đorđe, Ugrinović, Vukašin, Panić, Vesna, Veljović, Đorđe, Spasojević, Pavle, Šešlija, Sanja I., and Janaćković, Đorđe

Abstract

Goals. The goal of this study was a development of biocompatible composite hydrogels, structurally similar to native bone tissue, by incorporation of ~60 wt % of calcium hydroxyapatite (HA) into a matrix of hydrogels. Also, a possibility to control swelling kinetic and equilibrium swelling degree (SDeq) of hydrogels, by altering the degree of neutralization of the precursor (DN) was examined. Methods. Composite hydrogels, based on HA and poly(methacrylic acid) (PMAA), were synthesized by free-radical polymerization with different DN. Theoretical content of HA in synthesized composites was 60 wt %. Composites were synthesized by methods of dynamic mechanical analysis and scanning electron microscopy. SDeq and swelling kinetic were examined in distilled water and simulated body fluid. Results. Morphological observations revealed uniform distribution and strong bond of spherical HA particles within the polymer matrix. Swelling analyses demonstrated that SDeq is directly proportional to DN, while rheological examinations indicated inverse proportion between DN and storage modulus, but due to the HA particles inclusion, mechanical properties of composites were significantly better compared to monophasic PMAA hydrogels. Significance. Simple method of synthesis of composite hydrogels with high content of filler nanoparticles is presented. Incorporation of HA nanoparticles significantly improved mechanical properties of hydrogels, while at the same time was demonstrated a possibility to control swelling kinetic by influencing the DN., Ciljevi - Cilj ove studije bio je razvoj biokompatibilnih kompozitnih hidrogelova, koji su slične strukture kao prirodno koštano tkivo, inkorporacijom ∼60 mas % kalcijum-hidroksiapatita (HA) u matricu hidro-gela. Takođe, ispitan je uticaj neutralizacije prekursora polimerne mreže na kinetiku bubrenja i ravnotežni stepen bubrenja (SDeq).Metode - Kompozitni hidrogelovi, sastavljeni od HA i poli(metakrilne kiseline) (PMAA), sintetisani su slobodno-radikalskom polimerizacijom, pri različitim stepenima neutralizacije prekursora (SN). Svi sintetisani kompoziti sadrže visok maseni udeo HA (~60 mas %). Kompoziti su okarakterisani metodama skenirajuće elektronske mikroskopije (SEM) i dinamičko-mehaničke analize (DMA). SDeq i kinetika bubrenja ispitivani su u destilovanoj vodi i simuliranoj telesnoj tečnosti (SBF). Rezultati - Morfološka ispitivanja pokazala su uniformnu raspodelu i dobru povezanost sferičnih čestica apatita sa polimernom matricom. Analiza procesa bubrenja pokazala je proporcionalnu zavisnost SN i SDeq kompozita. Reološka ispitivanja ukazala su na obrnuto proporcionalnu zavisnost između SN i vrednosti modula sačuvane energije, koji su iznosili 55130 Pa u slučaju potpune neutralizacije i 77480 Pa u slučaju 0% neutralizacije. Značaj - Predstavljena je jednostavna metoda za sintezu kompozitnih hidrogelova sa visokim masenim udelom nanočestica punioca. Inkorporacijom nanočestica HA postignuto je značajno poboljšanje mehaničkih svojstava hidrogelova, dok je istovremeno pokazano da je promenom SN moguće kontrolisati kinetiku bubrenja hidrogelova. .

Published
2018

6. Mehanička svojstva hibridnog kompozita UHMWPE/EVA ojačanog vlaknima dobijenim elektropredenjem

Author

Zec, Jelena, Tomić, Nataša, Vuksanović, Marija M., Veljović, Đorđe, Stojanović, Dušica, Jančić-Heinemann, Radmila, Zec, Jelena, Tomić, Nataša, Vuksanović, Marija M., Veljović, Đorđe, Stojanović, Dušica, and Jančić-Heinemann, Radmila

Abstract

Aluminijum oksidna (Al2O3) nanovlakna pripremljena su iz vodenog rastvora aluminijum hlorohidrata/poli(vinil alkohola) (PVA) korišćenjem tehnike elektropredenja. Maseni odnos aluminijum hlorohidrata/PVA bio je 5:1. Nakon kalcinacije vlakana na 1100 °C, dobijena su kratka aluminijum oksidna vlakna prečnika od 200 do 800 nm. Morfologija vlakana je karakterisana pomoću skenirajućeg elektronskog mikroskopa sa emisijom polja (FE-SEM). Softver za analizu slike Image ProPlus korišćen je za merenje prečnika dobijenih Al2O3 vlakana. Cilj ovog rada bio je ispitivanje mehaničkih svojstava hibridnog kompozita, koji se sastoji od polimerne matrice (kopolimer etilena i vinil-acetata (EVA)), polietilenskih vlakana ultra-visoke molarne mase (UHMWPE) i Al2O3 vlakana dobijenih elektropredenjem. Al2O3 vlakna su dodavana u količini od 1 mas. % što je pokazalo poboljšanje mehaničkih svojstava matrice i hibridnog kompozita., Alumina (Al2O3) nano fibers are prepared from an aqueous solution of aluminum hydroxy chloride/poly (vinyl alcohol) (PVA)/water using the electrospinning technique. The weight ratio of aluminum hydroxy chloride/PVA was 5: 1. After calcification of fibers at 1100 ° C, continuous aluminum oxide fibers were obtained from 200 to 800 nm. The fiber morphology is characterized by a scanning electron microscope (SEM). Image analysis software (Image Pro Plus) was used to measure the diameter of the obtained aluminum oxide (Al2O3) fibers. The aim of this paper is to examine the mechanical properties of the hybrid composite, consisting of a polymer matrix (ethylene and vinyl acetate copolymer (EVA)), ultrahigh molecular weight polyethylene fibers (UHMWPE) and Al2O3 fibers obtained by electrospinning. Al2O3 fibers were added in an amount of 1 wt. % as shown by the improvement of the mechanical properties of the matrix and the hybrid composite.

Published
2018

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