X-Ray Diffraction and Multifrequency EPR Study of Radiation-Induced Room Temperature Stable Radicals in Octacalcium Phosphate

Octacalcium phosphate (OCP) {Ca8H2(PO4)6×5H2O] has attracted increasing attention over the last decade as a transient intermediate to the biogenic apatite for bone engineering and in studies involving the processes of pathological calcification. In this work, OCP powders obtained by hydrolysis of dicalcium phosphate dehydrate were subjected to X- and γ-ray irradiation and studied by means of stationary and pulsed electron paramagnetic resonance at 9, 36 and 94 GHz microwave frequencies. Several types of paramagnetic centers were observed in the investigated samples. Their spectroscopic parameters (components of the g and hyperfine tensors) were determined. Based on the extracted parameters, the induced centers were ascribed to H0, CO33-, CO2- and nitrogen-centered (presumably NO32-) radicals. The spectroscopic parameters of the nitrogen-centered stable radical in OCP powders were found to be markedly different from those in hydroxyapatite. According to X-ray diffraction data, γ-ray irradiation allowed the phase composition of calcium phosphates to change; all minor phases with the exception of OCP and hydroxyapatite disappeared, while the OCP crystal lattice parameters changed after irradiation. The obtained results could be used for the tracing of mineralization processes from their initiation to completion of the final product, identification of the OCP phase, and to follow the influence of radiation processes on phase composition of calcium phosphates.

[The impact of octacalcium phosphate on the dynamics of bone matrix formation in experimental bone defects]

The aim of the study was to assess the interaction of of octacalcium phosphate (OCP) with bone matrix and cells and its impact on the process of bone generation. The survey was conducted on animal model: critical hipbone defect was created in 12 230-250 g Wister rats. The animals were then divided in two groups. In group 1 (6 animals) defect was left to heal under blood clot and in group 2 (6 animals) it was filled with OCP. Three animals with no defect served as a control group. It was showed significant (p<0.05) increase of the area of the newly formed bone tissue and its direct correlation with duration of observation.

Silver-Doped Calcium Phosphate Bone Cements with Antibacterial Properties

Calcium phosphate bone cements (CPCs) with antibacterial properties are demanded for clinical applications. In this study, we demonstrated the use of a relatively simple processing route based on preparation of silver-doped CPCs (CPCs-Ag) through the preparation of solid dispersed active powder phase. Real-time monitoring of structural transformations and kinetics of several CPCs-Ag formulations (Ag = 0 wt %, 0.6 wt % and 1.0 wt %) was performed by the Energy Dispersive X-ray Diffraction technique. The partial conversion of β-tricalcium phosphate (TCP) phase into the dicalcium phosphate dihydrate (DCPD) took place in all the investigated cement systems. In the pristine cement powders, Ag in its metallic form was found, whereas for CPC-Ag 0.6 wt % and CPC-Ag 1.0 wt % cements, CaAg(PO₃)₃ was detected and Ag (met.) was no longer present. The CPC-Ag 0 wt % cement exhibited a compressive strength of 6.5 ± 1.0 MPa, whereas for the doped cements (CPC-Ag 0.6 wt % and CPC-Ag 1.0 wt %) the reduced values of the compressive strength 4.0 ± 1.0 and 1.5 ± 1.0 MPa, respectively, were detected. Silver-ion release from CPC-Ag 0.6 wt % and CPC-Ag 1.0 wt % cements, measured by the Atomic Emission Spectroscopy, corresponds to the average values of 25 µg/L and 43 µg/L, respectively, rising a plateau after 15 days. The results of the antibacterial test proved the inhibitory effect towards pathogenic Escherichia coli for both CPC-Ag 0.6 wt % and CPC-Ag 1.0 wt % cements, better performances being observed for the cement with a higher Ag-content.

[A PERSPECTIVE CULTURAL MODEL FOR CONTROL OF BIOLOGICAL ACTIVITY OF HUMAN INTERFERONS]

AIM

Study species specificity of human lymphocyte interferon alpha in vitro in cell cultures of swine origin for expansion of cell line spectrum for interferon titration and control of newly created interferons and interferon-like preparations in vivo in mini-pig model.

MATERIALS AND METHODS

Cell cultures of various species origin were used: Vero (monkey kidney), MDBK (bull kidney), HEK 293T (human embryo kidney), PK-15 (swine kidney), SPEV(swine embryo kidney), PTP (swine testicles), MDCK (canine kidney), RK-13 (rabbit kidney). Human lymphocyte interferon alpha (hINF-alpha) from Biomed company (1000 IU/ml), established in MDBK cells, was tested. Vesicular stomatitis virus (Indiana strain) was used. Human plasma was obtained from heparin-treated venous blood in the process of human peripheral blood lymphocyte isolation in medium for lymphocyte separation (Ficoll with a density of 1.077 g/cm3).

RESULTS

Vesicular stomatitis virus, adapted to Vero cells, was established to have the least active reproduction in Vero and MDBK and reproduces more actively in cell of swine origin by 0.25 - 0.75 lg TCD50. At the same time, virus, adapted to cells of swine origin, reproduces more actively by 2 - 3 lg TCD50 in both cells of swine origin and Vero and MDBK.

CONCLUSION

A possibility of titration of hINF-alpha in cells of swine origin was shown for both 100 doses of the indicator virus and low virus doses (5 and 10). This allows to determine low titers of hINF-alpha in blood plasma as one of the important indicators of interferon status--sera hINF-alpha.

[The priority directions of improvement of specialized oncologic out-patient care]

The article presents the priority directions of development and improvement of organization of specialized out-patient care of oncologic patients with propose to enhance quality of their life.