Modification of poly(methyl methacrylate) denture base materilas with diesters of itaconic acid

Cilj ovog rada je ispitivanje mogućnosti modifikacije komercijalnih dvokomponentnih sistema za dobijanje materijala za bazu proteza dodavanjem estara itakonske kiseline u tečnu komponentu sistema, radi dobijanja materijala većeg stepena biokompatibilnosti. U prvom delu ovog rada izvršena je karakterizacija tri sistema za dobijanje baza proteze (Biocryl, Poli Hot i Futura Basic Hot) i ispitan je uticaj veličine zrna i raspodele veličina zrna čvrste komponente sistema koja se sastoji od PMMA praha. Komercijalni sistem za bazu proteza se sastoji od čvrste i tečne komponente. Tečna komponenta sadrži monomer metil metakrilat i umreživač nejčešće etilenglikol-dimetakrilat (EGDM) dok se čvrsta komponenta sastoji od praha PMMA i inicijatora, najčešće dibenzoil peroksida (DBO). Proteze sa dobijaju mešanjem čvrste i tečne komponente u odnosu 2:1 i polimerizacijom pri odabranom temperaturnom režimu. Ispitan je uticaj veličine zrna i raspodele veličina zrna čvrste komponente sistema na apsorpciju vode i mehaničke karakteristike gotovog proizvoda radi određivanja najpovoljnijeg komercijalnog sistema. Kao optimalni komercijalni sistem pokazao se Byocril koji poseduje najužu raspodelu veličina zrna čvrste komponente i srednju prečnik zrna od 55 μm. U drugom delu ovog rada izvršena je modifikacija komercijalnog sistema za bazu proteza dimetil itakonatom, dibutil itakonatom i ditetrahidrofurfuril itakonatom (2,5 - 10 masenih % itakonata). Ispitan je uticaj tipa i količine itakonata na: apsorpciju tečnosti (voda i smeša etanol/voda), količinu zaostalog monomera, termičke, dinamičko-mehaničke i mehaničke karakteristike (tvrdoća, žilavost, napon pri kidanju) sintetisanih materijala. Takođe je ispitan i uticaj ubrzanog starenja na mehanička svojstva sintetisanih materijala. Utvrđeno je da dodatak itakonata u sastav komercijalnih sistema za dobijanje baze proteza značajno smanjuje količinu zaostalog metil metakrilata što materijal čini niže toksičnim i biokompatibilnijim. Kao najoptimalniji uzorak pokazao se materijal modifikovan sa 2,5 masena % dimetil itakonata. Činjenica II da za dobijanje itakonske kiseline nije potrebno koristiti petrohemijske izvore sirovina predstavlja veliku prednost u odnosu na akrilnu i metakrilnu kiselinu i njihove derivate.The aim of this work is to examine the possibility of modification of commercial denture base materials with itaconic acid esters, in order to obtain a higher degree of material biokompatibility. In the first part of this work characterization of three commercial materials was carried out. The effect of bead size and bead size distribution of prepolymer powder onto water absorption and mechanical characteristics of the end product in order to determine the optimal commercial material for the further course of study. The Byocril that has the narrowest bead size distribution and mean bead diameter of 55 μm is found to be the optimal commercial material. In the second part of this work modification of commercial PMMA denture base material with dimethyl itaconate, di-n-butyl itaconate and ditetrahydrofurfuryl itaconate (2.5 to 10 wt%) was carried out. The effect of the itaconate content on the absorption of fluids (water and a mixture of ethanol/water), the residual monomer content, thermal, dynamic-mechanical and mechanical properties (hardness, toughness, stress at break) was investigated. The effect of the accelerated aging on the mechanical properties of synthesized materials was also investigated. It was found that the addition of itaconate in the denture base materials formulation significantly reduces the amount of residual methyl methacrylate, which makes the material less toxic. The optimal sample was found to be the material modified with 2.5 wt% of dimethyl itaconate. In the third part of this work, the influence of isothermal microwave polymerization on the applicative properties of denture base materials was investigated. It was found that the samples synthesized under isothermal microwave field have better application properties compared to the samples synthesized by conventional polymerization

Dual responsive hybrid hydrogels for controlled release of local anesthetic

Inteligentni hidrogelovi, kao što su pH osetljivi hidrogelovi na bazi poli(metakrilne kiseline) (PMAA), imaju veliku primenu u ciljanoj dostavi lekova. Međutim, slaba mehanička svojstva često ograničavaju primenu PMAA. Kako bi se prevazišlo navedeno ograničenje, nanoceluloza (NC) je prvo ekstrakovana iz drvnog otpadnog materijala, a zatim dodata u PMAA, zato što je NC biokompatibilna, netoksična i ima odlična mehanička svojstva. Zatim je dodata karboskimetil celuloza (CMC) (celulozni derivat koji se često koristi za kontrolisano otpuštanje lekova). CMC može da stabilizuje nanočestice magnetita (MN) koje su takođe dodate. MN mogu značajno da poboljšaju mehanička svojstva hidrogelova i takođe poseduju magnetna svojstva zbog čega imaju primenu za ciljano otpuštanje lekova. Ovako dobijeni materijal bi mogao da zaštiti lek, dostavi ga do mesta delovanja, kontroliše brzinu njegovog otpuštanja i na taj način omogući efikasno dejstvo leka sa smanjenim neželjenim efektima. Lokalni anestetik – lidokain hidrohlorid (LH) se često u tretmanima injektira što može imati ozbiljne neželjene efekte. Inkapsulacijom LH u hidrogelove na bazi PMAA, NC, CMC i MN (PMNC/MN-L) rešen je navedeni problem. Karakterizacija PMNC/MN-L hidrogelova je izvedena primenom FTIR i SEM spektroskopija i kompresionim testovima, a zatim je analizirano bubrenje hidrogelova i otpuštanje LH. U ovom radu predstavljen je jedinstveni način „zelene” sinteze hibridnih hidrogelova osetljivih na spoljne stimulanse unapređenih svojstava i njihove primene za kontrolisano otpuštanje lokalnog anestetika sa smanjenim neželjnim efektima

Supplementary data for article : Panic, V. V.; Seslija, S. I.; Popovic, I. G.; Spasojevic, V. D.; Popovic, A. R.; Nikolic, V. B.; Spasojevic, P. M. Simple One-Pot Synthesis of Fully Biobased Unsaturated Polyester Resins Based on Itaconic Acid. Biomacromolecules 2017, 18 (12), 3881–3891. https://doi.org/10.1021/acs.biomac.7b00840

Supporting information for: [https://doi.org/10.1021/acs.biomac.7b00840]Related to published version: [http://cherry.chem.bg.ac.rs/handle/123456789/2568]Related to accepted version: [http://cherry.chem.bg.ac.rs/handle/123456789/3058

Supplementary data for article : Panic, V. V.; Seslija, S. I.; Popovic, I. G.; Spasojevic, V. D.; Popovic, A. R.; Nikolic, V. B.; Spasojevic, P. M. Simple One-Pot Synthesis of Fully Biobased Unsaturated Polyester Resins Based on Itaconic Acid. Biomacromolecules 2017, 18 (12), 3881–3891. https://doi.org/10.1021/acs.biomac.7b00840

Supporting information for: [https://doi.org/10.1021/acs.biomac.7b00840]Related to published version: [http://cherry.chem.bg.ac.rs/handle/123456789/2568]Related to accepted version: [http://cherry.chem.bg.ac.rs/handle/123456789/3058

Biohidrogelovi poli(metakrilne kiseline): bubrenje i kontrolisano otpuštanje kofeina

Modern society are faced with lot of challenges in the treatment of many diseases, especiallywith serious ones such as cancer. Safer and more efficient treatment of the cancer patients are maingoals which researchers are aiming. One of the good approaches can be drug delivery systems.Still, a lot of anticancer drugs are poorly water-soluble and their encapsulation and controlled releasecan be quite challenging. Present study is focused to improve drug delivery system based onhydrophilic poly(methacrylic acid) and amphiphilic casein with encapsulated poorly water-solublecaffeine, which has been developed through our previous research. The hydrogels with 1.6mol% ofcrosslinker and 100% of neutralization degree of methacrylic acid are synthetized (PMAC-100N-4M). The swelling process of the PMAC-100N-4M hydrogels and caffeine release are analyzed intwo environments which simulate human stomach and intestines. It is also investigated how thechange in the encapsulated caffeine weight and the addition of liposomes with encapsulated caffeine,affect swelling degree of the PMAC-100N-4M hydrogels and release of caffeine. The resultsshow that controlled release of caffeine is improved, therefore overall therapy can be enhanced.Savremeno društvo je suočeno sa mnogim izazovima u tretamanu raznih bolesti, naročito ozbiljnih oboljenja kao što je rak. Glavni ciljevi naučnika su da se postigne bezbednija i efikasnija terapija pacijenata koji se leče od raka. Jedan od dobrih načina da se to postigne su sistemi za dostavu lekova. Ipak, mnogi antikancerogeni lekovi su slabovodorastvorni, pa bi veliki izazov mogao da bude inakpsulacija i njihovo kontorlisano otpuštanje iz sistema za dostavu lekova. Cilj ovog rada je da se unapredi sistem za dostavu lekova na bazi hidrofilne poli(metakrilne kiseline) i amfifilnog kazeina sa inkapsuliarnim slabo vodorastvornim kofeinom, koji je razvijen tokom našeg prethodnog istraživanja. U ovom radu sintetisani su hidrogelovi sa 1,6mol% umreživača i 100% neutralisanom metakrilnom kiselinom (PMAC-100N-4M). Procesi bubrenja PMAC-100N-4M hidrogelova i kontrolisanog otpuštanja kofeina su ispitivani u dve sredine koje simuliraju želudac i tanko crevo čoveka. Takođe je ispitano kako promena količine inkapsuliranog kofeina i dodatak lipozomne suspenzije sa inkapsuliranim kofeinom utiče na procese bubrenja PMAC-100N-4M hidorgelova i otpuštanje kofeina. Rezultati pokazuju da je proces kontrolisanog otpuštanje kofeina unapređen, a samim tim je moguće unaprediti i celokupnu terapiju

Synthesis, Structure and Properties of Nickel-Iron-Tungsten Alloy Electrodeposits PART I: Effect of Synthesis Parameters on Chemical Composition, Microstructure and Morphology

Kinetic and operational electrolysis parameters determine the polarization characteristics, electrodeposition current efficiency, morphology, chemical composition and microstructure of nickel/iron/tungsten alloy deposits. The alloys electrodeposited at a current density of 50 mA cm(-2) to 1000 mA cm(-2) contain an amorphous phase and nanocrystals of an FCC solid solution of iron and tungsten in nickel. During annealing at temperatures above 500 degrees C, amorphous phase crystallization, crystalline grain growth of the FCC phase and a reduction in both internal microstrain and minimum density of chaotically distributed dislocations take place in the alloy. Milling the spongy deposit of the alloy causes amorphous phase crystallization, FCC-phase crystalline grain growth, and size reduction and rounding of powder particles

Microstructure of new composite electrocatalyst and its anodic behavior for chlorine and oxygen evolution

The first layer of active coating made from a rutile-structured solid solution of ruthenium and titanium dioxides having an average crystal grain size of 30 nm was thermally deposited on an adequately prepared titanium metal substrate. Then, at a temperature of 500 degrees C, the second layer was formed on the first layer from a mixture of amorphous particles of metallic platinum and rutile-structured iridium dioxide nanocrystals having an average crystal grain size of 26 nm. Rutile phase nanocrystals are characterized by a high density of chaotically distributed dislocations and high internal microstrain values. The coatings exhibit a compact granular morphology without cracks on the surface. Their catalytic activity is similar to that of conventional DSAs for the anodic oxidation of chloride ions from both concentrated and dilute sodium chloride solutions. The anodic current efficiency both during chlorate formation and active chlorine production was several percentage points higher in electrolyzers containing these anodes than in those containing DSAs. The catalytic activity of anodes having these coatings is about 50 mV lower than that of DSAs and about 350 mV higher than that of lead/antimony alloy electrodes, for oxygen evolution from acid sulfate solutions (0.5 mol dm(-3) H2SO4) characteristic of processes for the production of some metals. An accelerated corrosion test showed that the stability of the double-layer anodes is about twelve-fold higher than that of conventional DSAs

Structure and magnetic properties of electrodeposited Ni87.3Fe11.3W1.4 alloy

A dark gray nanostructured coating of an alloy composed of 87.3 wt.% Ni, 11.3 wt.% Fe and 1.4 wt.% W (Ni87.3Fe11.3W1.4) was electrodeposited from an ammonia citrate bath on a titanium cathode at a current density of 500 mA cm(-2). A cathodic polarization curve was recorded and dependence of the current efficiency of alloy deposition on current density was determined. Partial polarization curves for alloy deposition and hydrogen evolution were also measured. Alloy deposition at current densities of up to 300 mA cm(-2) is an activation-controlled process which turns into a diffusion-controlled process at higher current densities. At potentials more positive than -960 mV, hydrogen is evolved from NH4+ and (HCit)(3-) ions (where (HCit)(3-) denotes triply deprotonated citric acid, C6H5O73-). At potentials more negative than -960 mV, hydrogen evolution from water is the dominating reaction. SEM images show that the surface of the deposit obtained at 500 mA cm(-2) has a globular structure containing a large number of craters, mostly located between the globules. XRD analysis revealed that the alloy contains an amorphous matrix with embedded nanocrystals of the FCC-structured solid solution of Fe and Win Ni with a mean particle size of 8.8 nm. The deposit has a high internal microstrain value and a high density of chaotically distributed dislocations. Heating and milling the alloy cause structural changes involving changes in the magnetic properties of the alloy. Structural relaxation takes place in the temperature interval of 80 degrees C to 420 degrees C. In this temperature range, magnetization of both as-deposited and milled alloy samples increases with increasing temperature, reaching maximum at a certain temperature, but decreases thereafter with further heating. During structural relaxation, short-term structural arrangement facilitates the expansion and orientation of magnetic domains, leading to increased magnetization of the alloy. The abrupt decline in magnetization at higher temperatures is the result of a heatinduced change in magnetic domain orientation. Annealing the alloy at temperatures above 420 degrees C causes amorphous phase crystallization and growth of crystal grains of the FCC-structured solid solution of Fe and W in Ni, as well as a simultaneous decrease in internal microstrain and mean density of chaotically distributed dislocations. The same structural changes, somewhat lower in intensity, are also caused by alloy milling. The new state of the microstructure achieved through annealing and milling is best illustrated by the mean crystal size. The increase in mean crystal size results in a shift of the Curie temperature towards lower temperatures, whereas magnetization increases at first, reaching maximum at a certain mean crystal size, but decreases, thereafter, with a further increase in mean crystal size

The effect of annealing temperatures on magnetic and electric properties of electrodeposited Ni85,3Fe10,6W1,4Cu2,2 alloy

Ni-85,Ni-8 Fe-10,Fe-6 W-1,W-4 Cu-2,Cu-2 alloy powder consisting of an amorphous matrix and nanocrystals of an FCC solid solution of Fe, W and Cu in nickel was produced by electrodeposition. Heating the pressed powder sample over the temperature range of 20 to 600 degrees C permitted structural changes to take place in the alloy, causing changes in its electrical resistivity and magnetic permeability. The alloy exhibits structural stability up to 150 degrees C. In the temperature interval 150-360 degrees C, the alloy undergoes intensive structural relaxation resulting in an increase in electrical conductivity and magnetic permeability. Less intensive structural relaxation occurs at temperatures between 360 degrees C and 460 degrees C. In this interval, under heat treatment, magnetic domain arrangement decreases and, hence, the interaction between magnons and conduction electrons is reduced, leading to a decrease in the temperature coefficient of electrical resistivity (TCER). Amorphous matrix crystallization and FCC crystal growth take place in the temperature interval 460-520 degrees C, causing a decline in electrical resistivity and magnetic permeability

Effect of Electrodeposition Current Density on the Microstructure and Magnetic Properties of Nickel-cobalt-molybdenum Alloy Powders

Nanostructured nickel-cobalt-molybdenum alloy powders were electrodeposited from an ammonium sulfate bath. The powders mostly consist of an amorphous phase and a very small amount of nanocrystals with an mean size of less than 3 nm. An increase in deposition current density increases the amorphous phase percentage, the density of chaotically distributed dislocations and internal microstrains in the powders, while decreasing the mean nanocrystal size. The temperature range over which the structural relaxation of the powders deposited at higher current densities occurs is shifted towards lower temperatures. A change in relative magnetic permeability during structural relaxation is higher in powders deposited at higher current densities. Powder crystallization takes place at temperatures above 700 degrees C. The formation of the stable crystal structure causes a decrease in relative magnetic permeability