• AGNIESZKA SOBCZAK-KUPIEC

      Articles written in Bulletin of Materials Science

    • Effect of calcination conditions of pork bone sludge on behaviour of hydroxyapatite in simulated body fluid

      Agnieszka Sobczak-Kupiec Zbigniew Wzorek Regina Kijkowska Zygmunt Kowalski

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      The paper presents in vitro (in SBF) behaviour of hydroxyapatite (HAp) obtained from pork bone sludge from meat plant via two essentially different calcination methods using a stationary, electrically heated chamber oven and enlarged laboratory scale rotary kiln designed by the authors, heated by gas combustion methods enabling application of different set of physical parameters such as temperature, holding time-differing according to type of the kiln. HAp ceramic discs, after 62-days of incubation in SBF at 37 °C, characterized by X-ray diffraction (XRD), FTIR, SEM and EDS methods, underwent changes recorded by:

      1. a reduction in Ca/P molar ratio in all the investigated materials resulting from modification in phase composition and
      2. weight increase in the investigated disc-samples, resulting from a precipitation of newly formed phase as an admixture of primary HPO$^{2-}_{4}$-free HAp.

      They were: secondary (with HPO$^{2-}_{4}$ incorporated) HAp and chlorapatite in all the samples, while in addition to the listed above, 𝛽-tricalcium phosphate was formed on the discs made of HAp from stationary chamber oven, but not from rotary kiln. The new phases were formed in agglomerates on the surface of the investigated ceramic discs and in their pores. The results obtained proved that calcination conditions of pork bone sludge (temperature 750–950 °C, time and type of the applied kiln) under which hydroxyapatite (HAp) powders were obtained had an impact on its different behaviour in SBF, nevertheless, indicating a potential ability of the material to form a new biologically relevant interface with hard tissue and suitability for further investigations intended for medical grafting.

    • Physicochemical characterization of zinc-substituted calcium phosphates

      DOROTA WALCZYK DAGMARA MALINA MILENA KRÓL KLAUDIA PLUTA AGNIESZKA SOBCZAK-KUPIEC

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      Biocompatible and bioactive calcium phosphates can make chemical bonds with living bones. Improvement of their biological and physicochemical properties can be achieved by doping with various ions that are presented in natural apatites of bones. These substitutions influence lattice parameters, structure and morphology of apatites. In recent times great attention has been devoted to zinc ions that are the second most abundant trace element present in bones. Zinc embedded into calcium phosphate may enhance the bone formation and in addition exhibits antifungal and antibacterial properties. Therefore, it is rational to form structures incorporated with this ion. In this paper the incorporation of the Zn ions into natural and synthetic calcium phosphates has been reported.Natural hydroxyapatites (HAs) applied in this study were derived mainly from pork bones whereas both brushite and synthetic were formed using wet chemical methods. Ambient temperature synthesis leads to the formation ofbrushite, whereas the process performed at elevated temperature gives HA. Subsequently, attained structures were modified with Zn ions by using in situ or sorption procedures. Phase composition and morphology of obtained materials were determined by means of X-ray diffractometry, Fourier transform infrared spectroscopy and scanning electron microscopy equipped with energy-dispersive spectroscopy. Introduced XRD patterns depict changes of the crystallinity of HA with the increase in the amount of embedded zinc ions. On the contrary, no changes of the crystallinity were observed for the brushite doped with Zn ions. Morphology of attained powders, visualized using scanningelectron microscopy exemplified structural changes between calcium phosphates conjugated with zinc ions. Many authors report that the addition of small amounts of Zn ions leads to loss of crystallinity and decrease of lattice parameters. Interestingly, upon addition of Zn ions to the natural and synthetic HAp by sorption procedures no crystallographic and structural changes were observed. Notably, upon increase of zinc ions also structure of brushite formed by the in situ method remains constant, indicating no influence of added ions. Our outstanding finding promotes sorption procedure as suitable route to form structures incorporated with various ions that can be further employed as potential implants.

© 2017 Indian Academy of Sciences, Bengaluru.