Arita Dubnika

Impact of sintering temperature on the phase composition and antibacterial properties of silver-doped hydroxyapatite

In the present study, the impact of sintering temperature on the phase composition and antibacterial properties of silver-doped hydroxyapatite (HAp/Ag) samples was investigated. HAp/Ag containing 0.2 and 1.2 % silver was prepared using a modified wet chemical precipitation method. The surface morphology and inner structure of the sintered samples were discussed. X-ray powder diffraction (XRD) and scanning electron microscopy (SEM) studies showed that, after the sintering process, HAp/Ag contained a silver oxide phase, which was not observed in raw materials. Phase composition changes at different sintering temperatures were studied, and it was found that silver oxide undergoes phase changes during the sintering process. In vitro antibacterial properties approved the excellent antimicrobial activity of HAp/Ag against the bacterial strains Staphylococcus epidermidis and Pseudomonas aeruginosa. The HAp/Ag sample with 1.2 % silver content, sintered at 1150 °C, showed the highest antibacterial activity.

Porous hydroxyapatite for drug delivery

The disadvantages of systemic drug therapy are that only a small fraction of any given dose actually reaches the surgical site, producing low-therapeutic tissue levels. An alternative approach is based on the use of implantable delivery tools, able to release the active substance in a controlled way. Biocompatibility, bioactivity, and osteoconductivity are the main driving forces of calcium phosphate biomaterials, promoting their application as bone substitutes. At the same time, multimodal porous structure and interconnectivity of pores make them promising candidates for site-specific drug delivery. The use of porous hydroxyapatite as a drug delivery system could result in a dual effect: the ability to interact with the bone tissues at the same time ensuring increased drug efficiency, controlled release, and site-specific delivery.

In Vitro Evaluation of Osteoblast Cell Behavior and Antimicrobial Properties of Biphasic Calcium Phosphate Ceramics

Calcium phosphate ceramic materials in form of hydroxylapatite (HAp) and β-tricalcium phosphate (TCP) are good candidates for bone substitution and regeneration. Majority of methods used for biphasic calcium phosphate (mixture of HAp and TCP) preparation includes synthesis of calcium deficient apatite, not so often mechanical mixing of HAp and TCP is applied. The aim of this work was to evaluate the effect of HAp/TCP ratio as well as the impact of biphasic calcium phosphate (BCP) preparation technique on osteoblast cell behavior and ceramic antimicrobial properties. Results showed that BCP composite samples supported much higher proliferation rate of osteoblast cells as those of pure HAp or TCP. The best result was observed for BCP samples with HAp/TCP ratio 60/40. BCP preparation technique significantly does not affect the cell attachment on the surface of BCP samples, while influence on colonization intensity of bacteria was observed. Results indicated that the use of pure HAp or BCP ceramics as implant materials can cause less inflammatory risks compared to the pure TCP ceramics.

Effect of Various Additives and Aeration on the Properties of Lightweight Concrete

In the present study the effect of various additives (silica sand, silica fume, zeolite and cenospheres) as well as the aeration on the properties (consistency, density, compressive and bending strength) of lightweight concrete was studied. Density, compressive and bending strength of the lightweight concrete were substantially reduced by replacing silica sand with censopheres or by adding air entraining agent to the grout used for the preparation of the samples. Silica fume and zeolite admixture improved mechanical properties of the samples. Specific compressive strength of the cenospheres containing samples is comparable or even higher than the ones made of the mixes without the cenospheres.

Recent Developments in Diffusion Tensor Imaging of Brain

Magnetic resonance imaging (MRI) has come to be known as a unique radiological imaging modality because of its ability to perform tomographic imaging of body without the use of any harmful ionizing radiation. The radiologists use MRI to gain insight into the anatomy of organs, including the brain, while biomedical researchers explore the modality to gain better understanding of the brain structure and function. However, due to limited resolution and contrast, the conventional MRI fails to show the brain microstructure. Diffusion tensor imaging (DTI) harnesses the power of conventional MRI to deduce the diffusion dynamics of water molecules within the tissue and indirectly create a three-dimensional sketch of the brain anatomy. DTI enables visualization of brain tissue microstructure, which is extremely helpful in understanding various neuropathologies and neurodegenerative disorders. In this review, we briefly discuss the background and operating principles of DTI, followed by current trends in DTI applications for biomedical and clinical investigation of various brain diseases and disorders.

Evaluation of Silver Ion Bioavailability from Silver Doped Hydroxyapatite

The in vitro behavior of silver doped hydroxyapatite (HAp/Ag) prepared by two wet precipitation routes were studied in water and simulated body fluid (SBF). In order to evaluate the silver ion bioavailability from HAp/Ag, the samples were soaked in SBF or water and kept at 37°C for fixed periods of time up to one year. After fixed periods of time, analyses of SBF and water solutions were performed and silver ion concentration within the solutions determined. According to silver release data from dense and porous HAp/Ag ceramic scaffolds, release rate of silver ions were reduced in water as the ion exchange there was slower compared to SBF solution. X-ray diffraction and scanning electron microscopy analysis approved the formation of hydroxyapatite type layer on the surfaces of scaffolds after one year soaking in SBF.

Bioactivity of Silver Doped Hydroxyapatite Scaffolds in Simulated Body Fluids

In the present study, the in vitro bioactivity of silver-doped hydroxyapatite (HAp/Ag) scaffolds was investigated. HAp/Ag was prepared using two different modified wet precipitation methods. The X-ray powder diffraction (XRD) results showed, that sintered HAp/Ag samples prepared using method (I) contain two phases HAp and Ag, but samples prepared by method (II) contain three different phases - HAp, Ag and AgO. After 2 month incubation period in simulated body fluid (SBF), surface of HAp/Ag scaffolds was coated with bone-like apatite. Thickness of bone-like apatite layer increased from 2 μm up to 32 μm, increasing the incubation period.

Phase Transitions of Ipidacrine Hydrochloride Polymorphs and Hydrates

Ipidacrine hydrochloride is pharmaceutically active compound that forms variety of crystalline modifications which differs by solvent type and content in crystalline structure. These crystalline forms analyzed by powder x-ray diffraction, differential thermal analysis, thermogravimetry and Karl Fisher titration. Obtained crystalline forms include two monohydrates, two hemihydrates, two anhydrous forms, two non-stoichiometric hydrates and mixed solvates with octanol and water and methanol and water, solvate with chloroform and dimethylformamide.