pH-sensitive membranes with crosslinked poly(acrylic acid) hydrogel for controlled delivery

Polymeric pH-sensitive membranes and hydrogels are interesting materials for the controlled delivery of chemical agents triggered by external stimuli. In this contribution, we present a novel membrane design consisting of a polyethersulfone polymeric base and a crosslinked poly(acrylic acid) hydrogel containing pH-responsive carboxyl groups. Membranes were prepared using the modified traditional liquid phase inversion process. Solutions containing all membrane precursors were cast on a glass plate and cured by UV irradiation. UV curing was followed by immersion into the water bath to achieve phase separation and solidification. Obtained membranes exhibited high ion-exchange capacity and a moderate swelling degree dependent on the crosslinker properties. Studies of membrane loading with methylene blue and subsequent release of methylene blue from the membrane into the alkaline and acidic buffered solutions demonstrated pH-dependent delivery kinetics

The influence of silver, copper and zinc ions on the properties of bioceramic materials based on calcium phosphate

Kalcijum-fosfati čine neorganski deo kostiju i zuba sisara. Ova dobro poznata činjenica je ohrabrila istraživače da tokom prethodnih godina primene sintetisani kalcijum-hidroksiapatit (HAp, Ca10(PO4)6(OH)2) i kalcijum-fosfat (TCP, Ca3(PO4)2), α- i β-TCP faze, kao implantne materijale. Njihova sličnost sa neorganskim delom kostiju je potvrđena, a posebno je istaknuta njihova biokompatibilnost i osteokonduktivnost i dodatno bioaktivnost HAp-a i bioresorpcija TCP-a. Dvofazne forme (BCP): HAp/β-TCP i HAp/α-TCP, kao i trifazna forma HAp/β-TCP/α-TCP, pokazale su se kao bolji biomaterijali nego pojedinačne faze i posebno su interesantne za dalja istraživanja. U cilju dobijanja biomaterijala sa antimikrobnim efektom, prahovi HAp-a dopirani jonima Ag+, Cu2+ ili Zn2+ su sintetisani hidrotermalnom metodom pri čemu je odnos Ca/P iznosio 1,67. U sintezama molski udeo dopanata iznosio je 0,2, odnosno 0,4 mol% sa ciljem da se dobiju prahovi sa dobrom antimikrobnom aktivnošću uz očuvanje biokompatibilnosti. Dopirani prahovi HAp-a su kalcinisani na 1200 °C tokom 2 h sa namerom da se ispita uticaj dopiranja na stvaranje dvofaznih prahova HAp/α-TCP, kao i antimikrobna aktivnost i biokompatibilnost tako dobijenih prahova. Za analizu svih prahova, nedopiranih i dopiranih HAp i HAp/α-TCP, korišćeni su visokorezolucioni skenirajući elektronski mikroskop (FESEM), rendgenska difrakcija (XRD), infracrvena spektroskopija sa Furijeovom transformacijom (FTIR), atomska apsorpciona spektroskopija (AAS) i energetska disperziona spektroskopija (EDS). Termička analiza sintetisanih prahova je sprovedena u cilju određivanja faznih transformacija tokom zagrevanja do 1200 °C. Antibakterijska aktivnost prahova ispitana je u in vitro uslovima u odnosu na mikroorganizme: Staphylococcus aureus (S. aureus), Escherichia coli (E. coli), Pseudomonas aeruginosa (P. aeruginosa) i Candida albicans (C. albicans). Svi prahovi su pokazali dobru antimikrobnu aktivnost, s tim da su prahovi dopiranih HAp/α-TCP dali malo bolje rezultate u odnosu na sve patogene mikroorganizme nego dopirani HAp prahovi. In vitro testovi biokompatibilnosti, kolorimetrijski test sa tetrazolijum solima (MTT) i test odbacivanja boje (DET), su korišćeni da bi se procenila biokompatibilnost dopiranih HAp/α-TCP prahova sa MRC-5 humanim fibroblastnim ćelijama. Ovi testovi su potvrdili da dati prahovi nemaju citotoksični efekat. Posebno dobru biokompatibilnost su pokazali prahovi HAp/α-TCP dopirani nižim udelom jona Ag+, Cu2+ i Zn2+. Na osnovu testova antimikrobne aktivnosti i biokompatibilnosti zaključeno je da su dopirani HAp/α-TCP prahovi obećavajući materijal za korišćenje u rekonstruktivnoj hirurgiji kostiju...Calcium phosphates constitute the inorganic part of bones and teeth of mammals. This fact is well known and has encouraged researchers to apply hydroxyapatite (HAp, Ca10(PO4)6(OH)2) and tricalcium phosphate (TCP, Ca3(PO4)2), both α- and β-TCP, over the past years as implant materials. Their similarity to the inorganic part of hard tissues has been confirmed, highlighting their biocompatibility and osteoconductivity and, in addition, the bioactivity of HAp and the bioresorbability of TCP. The biphasic forms (BCP): HAp/β-TCP and HAp/α-TCP and the triphasic form HAp/β-TCP/α-TCP, which were proved to be even better biomaterial than single phases, are of particular interest. Hydroxyapatite (HAp) powders doped with Ag+, Cu2+ or Zn2+ were synthesized by a hydrothermal method, at a Ca/P ratio of 1.67, in order to obtain biomaterial with an antimicrobial effect. The synthesis was performed with two contents of dopant (0.2 or 0.4 mol %) by considering both the antimicrobial activities and biocompatibility of the powders. The doped HAp was annealed at 1200 °C for 2 h with the intention of investigating the influence of doping on the creation of biphasic HAp/α-TCP and determining the antimicrobial activity and biocompatibility of the obtained biphasic powders. Analyses of all powders, undoped and doped HAp and HAp/α-TCP, were performed by Field emission scanning electron microscopy (FESEM), X-Ray diffraction (XRD), Atomic absorption spectroscopy (AAS) and Energy-dispersive X-Ray spectroscopy (EDS). Thermal analysis of the synthesized powders was performed to evaluate the phase transformations during heating up to 1200 °C. The in vitro antibacterial activities of the powders were evaluated against the pathogenic microorganisms: Staphylococcus aureus, Escherichia coli, Pseudomonas aeruginosa and Candida albicans. All powders showed good antimicrobial activity but generally the powders of doped HAp/α-TCP demonstrated better results against all pathogenic microorganisms than the powders of doped HAp. In vitro biocompatibility tests, MTT and DET, were used to evaluate the biocompatibility of doped HAp/α-TCP with MRC-5 human fibroblast cells. These tests confirmed that the powders did not have a cytotoxic effect. The HAp/α-TCP powders doped with the lower content of Ag+, Cu2+ and Zn2+ ions showed especially good biocompatibility. The antimicrobial and biocompatibility tests recommend the doped HAp/α-TCP as promising material for use in reconstructive surgery of bones..

Policijski aspekti forenzičkih metoda studije procenta sadržaja vode kod određivanja starosti fresaka

The novels of the Criminal Procedure Code (CPC) Republic of Serbia have introduced the concept of prosecutorial investigation in relation to that of evidence, special evidentiary actions and other software for the operation of the criminal prosecution. The meaning of novels is to conduct harmonization of standards with solutions of modern criminal law practice, particularly with regard to EU standards Serbia applying for membership in the Union. Preventing the most serious forms of crime is the focus of authorized bodies Serbia and in this context combating and preventing all forms of forgery, as is the case with forgeries frescoes and selling them on the world market. In exposed paper the method determining age of the frescoes is proposed. It is based on the use of closed Markov's graphs with three cells. The measurements of contents of water molecules in surrounding area can be done only for the space in which the frescoes is located. This means that followed exposed method is non destructive.Novele o krivičnom postupku (ZKP) Republike Srbije imaju uvodni koncept tužilačke istrage u vezi sa ovim dokazima, posebne dokazne radnje i drugi softver za funkcionisanje krivičnog gonjenja. Značenje novela je da sprovede usklađivanje standarda sa rešenjima savremenog krivičnog zakona u praksi, posebno u vezi sa standardima EU Srbije, koja se prijavljuje za članstvo u Uniji. Sprečavanje najozbiljnijih oblika kriminala je fokus nadležnih organa Srbije i u tom kontekstu je sprečavanje i borba protiv svih oblika falsifikata, kao što je slučaj sa falsifikatima fresaka i umetničkih slika i njihova prodaja na svetskom tržištu. U izloženom radu je predložen metod određivanja starosti fresaka. On se zasniva na korišćenju zatvorenih Markovljevih grafova sa tri ćelije. Merenja sadržaja molekula vode u okolini može se uraditi samo za prostor u kome se nalaze freske. To znači da je sledeći izloženi metod koji se koristi - nedestruktivan

Analysis of the change in structural parameters of mechanically alloyed Cu composite materials using different milling methods

In this study, the Cu-Zr-B ternary system was investigated as it has proven to be a promising composite material used in various industries, including aerospace, automotive, electronics, nuclear and tooling, among others. Owing to its versatility and a combination of desirable properties such as high strength and hardness, corrosion and wear resistance, and thermal stability, making it suitable for a wide range of applications. The effects of mechanical alloying (MA) parameters on the Cu-Zr-B properties, including ball-to-powder ratio, rotation speed, milling time, and milling atmosphere, were examined using the X-ray analysis, scanning electron microscopy, stereological analysis, and the Williamson-Hall analysis. Different mills, namely Atritor Mill and Turbula Shaker, were used in order to determine the effect that the type of mill has on the final structural parameters of the Cu-Zr-B. All results are given after 20 hours of mechanical alloying of the composite material. The rotation speed was around 300 rpm for both devices, and the ball-to-powder ratio was 10:1 for all the cases. It was shown that the ball size also plays a significant role in the final microstructural and morphological properties of the MA powders of the Cu-Zr-B. A comprehensive analysis showed that the powders produced in the Atritor mill (Powder 1, with a uniform ball size), as well as the powders produced in the Turbula where there was a range of different ball sizes used (Powder 2), showed lower values of dislocation density and crystalline size values compared to the powders produced in the Turbula with a uniform ball size (Powder 3). It is important to state that, with time, due to the plastic deformation mechanisms present, crystallite size decreases in all cases, with the lowest value again being powder 3.Twenty-First Young Researchers’ Conference - Materials Science and Engineering: Program and the Book of Abstracts; November 29 – December 1, 2023, Belgrade, Serbi

Biodegradable polymer/hydrogel composite for controlled delivery of cationic formulations

Composites of biodegradable polymers and hydrogels are promising materials for controlled delivery systems with prolonged drug release. In this contribution, we present an innovative implant design comprising poly(DL-lactide-co-ε-caprolactone) copolymer base and a crosslinked poly(acrylic acid) hydrogel. Implants were prepared in the form of disks using the modified traditional liquid phase inversion process. Solutions containing all implant precursors were dispensed into transparent non-stick molds and cured by UV irradiation. UV curing was followed by immersion into the phosphate buffer solution bath to achieve phase separation and solidification. Structure and composition of the implant were characterized using SEM and FTIR. Obtained implants exhibited high loading capacity for cationic formulations and a moderate degree of swelling. Studies of implant loading and subsequent release of methylene blue into the phosphate-buffered saline demonstrated diffusioncontrolled delivery kinetics over a period of several weeks. To assess biocompatibility of implants as possible materials for drug delivery systems in mammals, we evaluated their effects on viability (Trypan blue exclusion assay), metabolic activity, proliferation (MTT assay) and priming (nitric oxide/NO production) of freshly isolated rat splenocytes during 24 h and 48 h of cultivation. The viability was unaltered, metabolic activity/proliferation was increased after 48 h and the decrease of NO production, as well as drop in responsiveness to cell mitogen concanavalin A (ConA) in cells on implants were observed. These results suggest that implants could be used as a suitable material for drug delivery systems, but their capacity to stimulate cell proliferation and their immunosuppressive potential deserve further investigations

Comparative properties of composite poly(lactic-co-glycolic acid)/poly(acrylic acid) implants synthesized using ultraviolet and gamma irradiation

Composite implants comprising a biodegradable hydrophobic polymer matrix and crosslinked hydrogel with fixed ion exchange groups are promising materials for the construction of controlled drug delivery systems. Poly(lactic-co-glycolic acid)/poly(acrylic acid) (PLGA/PAA) composite implants in our study were synthesized using the sequential application of irradiation and immersion precipitation. Precursor solutions with all functional components were dispensed into a disc-shaped non-stick mold and cured either by ultraviolet (UV) or gamma irradiation. Cured disks were subsequently immersed in the phosphate buffer saline bath to finalize phase separation and solidification of the implants. The synthesized implants were characterized by FTIR-ATR and DSC, and their basic properties such as ion exchange capacity, swelling degree, and swelling kinetics were examined. Synthesis using gamma irradiation resulted in implants with similar ion exchange capacity, but the greater swelling degree and faster swelling kinetics compared to the implants prepared with UV irradiation. Gamma irradiation also resulted in altered and less homogeneous chemical composition compared to the implants synthesized with UV irradiation. Further investigations are required to determine the differences in drug release kinetics and degradation behavior of the synthesized implants

Immobilization of nickel ions into stable crystal structures as a promising way for their removal from wastewater

Environmental pollution is increasing day by day due to industrial activities. Heavy metals are pollutants of special concern due to their toxicity, persistence, and bioaccumulation in nature. Nickel is a heavy metal that is mostly used in industries because of its anticorrosion behavior. As a consequence, nickel ions are present in the wastewater from mining, electroplating, battery manufacturing and metal finishing industries. Nickel ions are nonbiodegradable, and as such, they are present in surface water. Their high concentrations can have a dangerous impact on human health and aquatic life. In this work, a promising method for the removal of Ni ions from wastewater and their incorporation into a stable crystal structure was described. Ni-exchanged form of LTA zeolite was prepared by the standard procedure of ion exchange. After the ion exchange, powder samples were heated at temperatures of 900 to 1300 ºC in order to obtain a stable crystal structure of Ni-spinel, NiAl2O4. XRF analysis was used to study ion exchange efficiency. Characterization of raw as well as thermally treated powder samples of Ni-exchanged LTA zeolite was conducted by XRPD, DTA/TG, FT-IR and SEM analysisTwenty-First Young Researchers’ Conference - Materials Science and Engineering: Program and the Book of Abstracts; November 29 – December 1, 2023, Belgrade, Serbi

Prilog teorijsko-metodološkim koncepcijama klimatske regionalizacije

According to the recommendation of the World Meteorological Organization (WMO), examination of the climatic characteristics of any given area should cover a 30-year period (for instance, the years 1931 to 1960, or, 1961 to 1990, etc). In time, changes and oscillations happen in climate, so that the climatic regions will also change, in time and in space. Such alterations are a frequent subject of scientific studies, concerned with cyclical nature and fluctuations of climate. Research of meteorological and climatic elements is, in fact, the precondition of knowing what the climate is, and without this knowledge it would be pointless to discuss any kind of concrete climatic regionalization. Depending on aims that we wish to accomplish, there is practically a limitless possibility of studying regions in one way or another. Essentially, though, the main starting assumption is that it would be desirable to perform a general climatic regionalization of the world, or of any territorial unit, and, starting from that, to proceed with subdivision into smaller climatic zones. A quite opposite approach perhaps more appropriate in certain cases, would be to start research from the other end, by examining each station in detail, so that maximum-quality data could then serve to give us an idea about the spatial presence of various indicators.Prema preporuci Svetske meteorološke organizacije (WMO), ispitivanje klimatskih karakteristika bilo kog prostora, bi trebalo da se odnosi na vremenski period od 30 godina (npr. od 1931-1960, odnosno od 1961-1990.g). Vremenom se javljaju promene, odnosno kolebanja klimata, tako da se i klimatske regije menjaju i u vremenu i u prostoru. Takve promene su često predmet proučavanja, koja se odnose na cikličnost i fluktuacije klimata. Istraživanje meteoroloških, odnosno klimatskih elemenata, predstavlja zapravo, uslov spoznaje samog klimata, bez čega bi bilo bespredmetno razmatrati bilo koji vid konkretne klimatske regionalizacije. U zavisnosti od ciljeva koji se žele postići, mogući vidovi izučavanja regija, praktično su neograničeni. U suštini, osnovna pretpostavka je, da bi bilo poželjno izvesti opšteklimatsku regionalizaciju, bilo koje prostorne celine, a na osnovu nje, kao polazne osnove, razrađivati detaljnije podele. Nasuprot tome, u određenim slučajevima, možda bi bilo korektnije, započeti istraživanje na suprotan način, odnosno od detaljnog ispitivanja svake stanice, kako bi se na osnovu što kvalitetnijih podataka, stekla predstava o prostornoj zastupljenosti određenih pokazatelja

Manganese-pyromellitate complex as a precursor for preparation of spinel Mn3O4

In recent years, thermal decomposition studies of transition metal complexes with benzenepolycarboxylate ligands have become an area of a great importance due to the possibility of obtaining useful metal oxides with desirable electrical, magnetic and catalytic properties [1]. As a contrast to conventional methods for the preparation of metal oxides, such as hydrothermal or sol– gel treatment, thermolysis is faster, more efficient and environmentally friendly. Mn(II)–dipya (dipya = 2,2’-dipyridylamine) complex with tetraanion of 1,2,4,5-benzenetetracarboxylic (pyromellitic, H4pyr) acid, [Mn2(dipya)2(pyr)(H2O)2], has been prepared and characterized by elemental, spectral and microscopy analyses. Direct thermolysis of the complex up to 1200 °C in an air atmosphere yielded spinel Mn3O4 oxide material. The obtained Mn3O4 has been characterized for its structural, spectroscopic, morphological and optical properties. The possibilities of using this oxide as photocatalyst or co-photocatalyst for removing textile organic dyes, as well as inorganic pigmentary material, were also investigated and discussed

Mechanical properties of mullite investigated by nanoindentation

The mechanical behavior of sintered mullite material was studied using nanoindentation tests. Mullite compact was obtained by cold pressing sol-gel synthesized mullite precursor powder and sintering at 1550 °C. Analysis of the microstructural parameters and phase composition was done by XRD (X-ray diffraction) and SEM-EDS (scanning electron microscopy with energy dispersive X-ray spectrometry). A Berkovich indenter was employed for nanoindentation measurements at various loads (1000-9000 µN). After each test, in situ SPM (scanning probe microscopy) imaging was performed. The XRD pattern of sintered mullite displayed peaks of mullite (93.3%) and corundum (6.7%). Results revealed average values of hardness and elastic modulus of sintered mullite as 15.55 GPa and 174.37 GPa, respectively. Moreover, nanoindentation results indicated that mullite follows the Hall-Petch hardening relation due to the presence of grains with a size range of 0.2-2 µm. Indentation in areas with smaller grains exhibits higher hardness values. Post-test SPM images disclosed the presence of pile-ups around the indents, which were formed under loads higher than 3000 µN.Volume: Ceramic Materials for Advanced Applicatio