Božana Čolović

Relationship between activity of silica thin films and density of cells occupation

The SiO2 thin films (STFs) were deposited on the surfaces of stainless steel tapes and their activity was particularly investigated from the aspect of the number density of hydroxyl groups on their surfaces. The calculation procedure of density of active OH groups includes determination of average length of silica chains that constitute silica sol particles with almost uniform size, on the base of thermogravimetric analysis. The size of SiO2 particles is analyzed by transmission electron microscopy and dynamic light scattering method. Fibroblast (L929) cell densities on the surfaces of these films were investigated using phase contrast microcopy. It was shown that there is a relationship between OH group densities and density of attached cells. Besides, the cytotoxicity effect was studied and compared for various thermally treated STFs.

Multiscale study of the influence of cationic surfactants on amorphous calcium phosphate precipitation

The influence of monomeric and micellar concentrations of the cationic monomeric, dodecyltrimethylammonium bromide (DTAB), and the corresponding dimeric, bis(N,N-dimethyl-N-dodecyl)ethylene-1,2-diammonium dibromide (12-2-12), surfactants on the formation and transformation of amorphous calcium phosphate (ACP) was investigated. The combination of microscopy (AFM and TEM) and light scattering techniques (size and zeta potential measurements) enabled, for the first time, the simultaneous monitoring of the effect that additives exert on different length scales during CaP formation in solution – from prenucleation clusters and ACP particles to the crystalline phase. Depending on their aggregation state (monomers or micelles) and the geometry of the aggregate (spherical or elongated micelles), DTAB and 12-2-12 have exhibited different effects on the rate of ACP transformation, as well as on the morphology of the amorphous and crystalline phases. It was shown that the effect of surfactants on the precipitation process observed on the microscale could be a result of different pathways on the nanoscale. The obtained results may have implications for the understanding of the general mechanism of inorganic–organic interactions underlying the biomineralization processes, as well as for materials science.

A new approach to the drug release kinetics of a discrete system: SiO2 system obtained by ultrasonic dry spraying

Mesoporous silica materials have already proved to be non-toxic and biocompatible, and also to have large pore volume and very high specific surface area suitable for loading of small molecules. Having this in mind and the fact that silicon dioxide (SiO(2)) powders can be so designed to obtain particle structures organized at multi levels, SiO(2) was chosen as a potential carrier for metronidazole, an antibiotic drug. SiO(2) powder was synthesized in two stages: first silica sol was prepared by hydrothermal synthesis and second the sol was converted into powder by dry spraying with simultaneous incorporation of the antibiotic into its structure. Scanning and transmission electron microscopy study revealed very complex structure and sub-structure of SiO(2) particles. Cell viability tests were used for estimation of cytotoxicity of so synthesized SiO(2). The drug release data showed that the system can provide drug release for a long time. Also, the device behavior is fully predictable, according to our theoretical model of multilevel structure design, and gives many opportunities for model investigations of drug release and its kinetics. The pore sizes and their distribution were observed as a limiting factor of drug release kinetics. Therefore, as the pore sizes are given as a set of discrete values, the kinetics of drug release might also be given as a set of corresponding discrete values.

Mineral trioxide aggregate as material of choice in endodontic therapy

Mineral trioxide aggregate (MTA) is a material with broad indications in endodontics. Currently, this material is used for pulp capping, pulpotomy, as apical barrier in teeth with necrotic pulp and open apex, and in the treatment of various root canal perforations. By comparing the biological response of pulp tissue capped with calcium hydroxide and MTA, the superiority of MTA has been indicated. The bridge of hard tissue formed under MTA prevented the irritation of pulp. Histological studies of pulpotomy in dog teeth have shown after 120 days a hard tissue without necrosis formed under MTA. MTA is also the material of choice for retrograde root canal obturation and lateral perforation. Meta analysis of published papers on MTA in recent years indicated the great clinical success of this material which ensured a good canal seal and superior biocompatibility. It is the only material for retrograde root canal obturation that encourages tissue regeneration. Studies have also shown that MTA has inductive and conductive properties for hard tissue as well as the ability to release ions in a liquid medium. The main disadvantage of MTA is related to its color, the presence of iron and mangan ions, the difficulties in maintaining the characteristics of material during time, absence of solvent for this material and the difficulty for its removal after crosslinking.

In Vitro Biocompatibility of Nanostructured Endodontic Materials Using SCAP Cells

Summary Background/Aim: Lately, fully innovative sol-gel method with high-temperature self-propagating reaction was used for the synthesis of new nanostructured endodontic materials, in combination with different radiopacifiers: bismuth (ALBO-MPCA1) and barium (ALBO-MPCA2). The aim of this study was to investigate the biocompatibility of nanostructured endodontic materials based on highly active calcium silicates and mixed with different radiopacifiers in comparison to MTA+ using human stem cells from the apical papilla- SCAP cells. Material and Methods: Morphology of the samples was studied by SEM. The tested materials were mixed with distilled water in a ratio 2:1 (m/m). Fifteen minutes fter the preparation, samples were used in the experiment. The biocompatibility of fresh materials, after 3h and 7 days, was tested using 3-(4,5-dimethylthiazol-2-yl)-2,5- diphenyltetrazolium bromide- MTT test. Results: Samples mostly consisted of spherical and rode-like. The relative viability of cells increased following the exposure time. Conclusion: The biocompatibility of synthesized materials is comparable to the control material MTA+, and therefore these materials can be recommended for for further clinical stuadies.

Structural characteristics and mechanisms of fluorapatite mechanochemical synthesis

Abstract This paper analyzes mechanisms of fluorapatite mechanochemical synthesis and its structural characteristics. Several studies of Jokanovic et al. published in appropriate journals and the book “Nanomedicine, the biggest challenge of the 21st century” are the base for this article. Characteristics of obtained materials show numerous biological advantages associated with the specific structural design of material during the process of synthesis. X-ray diffraction (XRD) and infrared spectroscopy with Fourier transform (FTIR) were used for studying the processes of fluorapatite synthesis.

In Vivo Investigation of ALBO-OS Scaffold Based on Hydroxyapatite and PLGA

A synthetic bone substitute based on calcium hydroxyapatite CHA and polylactic-co-glycolic acid PLGA, described in this paper, was synthesized to fulfill specific requirements like biodegradability, satisfying mechanical properties, optimal porosity and nanotopology, osteoinductive and osteoconductive properties, and so forth. Structural and morphological properties of the new scaffold were analyzed by micro computed tomography and scanning electron microscopy, while its physicochemical properties were investigated by X-ray diffraction and infrared spectroscopy. In vivo biological investigations of the synthesized scaffold were conducted over the cutaneous irritation and biofunctionality assays on rabbits and the test of acute systemic toxicity on mice. The results showed that the scaffold is not irritant and that it does not exhibit any symptoms of acute toxicity. Biofunctionality assays which include evaluation of the presence of various cells of immune response, the presence of neoangiogenesis, percentage of mineralization of newly formed bone, and fibroplasia in the tissue indicated that the new scaffold is suitable for the application in maxillofacial and dental surgery as a bone substitute. Also, it showed significant advantages over commercial product Geistlich Bio-Oss® from the aspect of some parameters of immunological response.

Ultra-High and Near-Zero Refractive Indices of Magnetron Sputtered Thin-Film Metamaterials Based on TixOy

Metamaterials based on with ultra-high and near-zero refractive indices were obtained by DC magnetron sputtering. The data on refractive indices, extinction coefficients, film thickness, and band gaps, obtained by spectroscopic ellipsometry, showed very high potential of these materials as metamaterials. Phase analysis performed by XRD revealed the presence of titanium phases with lower titanium oxidation states resulting from high concentration of oxygen vacancies, which are crucial for such extraordinary jumps and drops of refractive indices. Numerous band gaps for direct and indirect electron transitions additionally confirmed unique properties of these materials.

Subchronic Systemic Toxicity of New Endodontic Material Based on Calcium Hydroxyapatite and Calcium Silicates

As an alternative to MTA, a new endodontic material based on hydroxyapatite and calcium silicates (ALBO-MPSA) has been synthesized, and its biocompatibility has been studied in many in vitro and in vivo studies. The current study aims to evaluate a subchronic systemic toxicity of ALBO-MPSA on the rat animal model, as a continuation of the previous studies. Biochemical parameters of blood and histological parameters of the liver, kidneys, and spleen of the rats were analyzed after 120 days of consumption of the aqueous extract of ALBO-MPSA. The results showed no myelotoxic effect or autoimmune effect on peripheral blood cells and no pathological effect on the liver, kidney, and spleen tissues. Besides, no changes in the skin and hair of the rats, neither the change in the consumption of food and water, nor the change in their usual behavior were noticed during the experiment.

Informative article. Scaffold in bone tissue engineering

Summary Treatment of bone tissue injuries and diseases is still a great challenge for surgeons, but also for researchers who work with materials. Today stem cells are commonly used in bone tissue engineering. However, advances in biocompatible materials design, especially biodegradable porous structure (scaffold) is gaining an important role in the treatment of diseased bone tissue. The basic advantage of these carriers is specifically designed scaffold with defined porosity and pore structure that is favourable for cells settlement. Scaffolds are most commonly used as ceramic brackets because they have excellent characteristics in biodegradation and bioactivity. The process of scaffold production is important because the appropriate technology must ensure control of liquids and reproducibility of scaffold production through standardized process. The aim of this study was to present some of different procedures of scaffold production in bone tissue engineering and point out the advantages and disadvantages of these methods.