Zivile Stankeviciute

Study of Eu3+ and Tm3+ substitution effects in sol–gel fabricated calcium hydroxyapatite

In this study, an aqueous sol–gel chemistry route based on phosphoric acid as the phosphorus precursor, calcium acetate monohydrate and lanthanide (III) oxides as source of calcium and lanthanide ions, respectively, have been used to prepare europium- and thulium-substituted calcium hydroxyapatite (CHAp:Ln3+) powders. The ethylenediaminetetraacetic acid was used as complexing agent in the sol–gel processing. The final products were obtained by calcination of the dry precursor gels for 5 h at 1000 °C. The phase transformations, composition, and structural changes in the polycrystalline samples were studied by infrared spectroscopy, X-ray powder diffraction analysis, scanning electron microscopy and photoluminescence measurements. It was demonstrated, however, that the substitution of calcium by Eu or Tm proceeds in the CHAp at low concentration of lanthanide ion.Graphical abstractExcitation and emission of Tm3+ in CHAp:Tm3+ spectra.

Fabrication of a composite of nanocrystalline carbonated hydroxyapatite (cHAP) with polylactic acid (PLA) and its surface topographical structuring with direct laser writing (DLW)

Correction for ‘Fabrication of a composite of nanocrystalline carbonated hydroxyapatite (cHAP) with polylactic acid (PLA) and its surface topographical structuring with direct laser writing (DLW)’ by E. Garskaite et al., RSC Adv., 2016, 6, 72733–72743.The fabrication of polylactic acid (PLA)-carbonated hydroxyapatite (cHAP) composite material from synthesised phase pure nano-cHAP and melted PLA by mechanical mixing at 220-235{\deg}C has been developed in this study. Topographical structuring of PLA-cHAP composite surfaces was performed by direct laser writing (DLW). Microstructured surfaces and the apatite distribution within the composite and formed grooves were evaluated by optical and scanning electron microscopies. The influence of the dopant concentration as well as the laser power and translation velocity on the composite surface morphology is discussed. The synthesis of carbonated hydroxyapatite (cHAP) nanocrystalline powders via wet chemistry approach from calcium acetate and diammonium hydrogen phosphate precursors together with crosslinking and complexing agents of polyethylene glycol, poly(vinyl alcohol) and triethanolamine is also reported. Thermal decomposition of the gels and formation of nanocrystalline cHAP were evaluated by thermal analysis, mass spectrometry and dilatometry measurements. The effect of organic additives on the formation and morphological features of cHAP was investigated. The phase purity and crystallinity of the carbonated apatite powders were evaluated by X-ray diffraction analysis and FT-IR spectroscopy.

Environmentally benign fabrication of calcium hydroxyapatite using seashells collected in Baltic Sea countries: A comparative study

GRAPHICAL ABSTRACT ABSTRACT In this study, high purity crystalline calcium hydroxyapatite (Ca10(PO4)6(OH)2; CHAp) was fabricated from seashells collected in different regions of the Baltic Sea using an environment-friendly water-based sol-gel synthesis route. The phase composition of the synthesized CHAp powders was studied by X-ray diffraction analysis and Fourier transform infrared spectroscopy. The surface morphologies of the precursors and synthesized samples were examined by scanning electron microscopy. A single shell type, Macoma balthica (L.), was collected from various locations around the Baltic Sea. Nevertheless, the resulting CHAp powders had surprisingly large variations in the surface morphology of sol-gel-derived CHAp bioceramics.

The Antimicrobial Action of Silver Halides in Calcium Phosphate

Silver halides represent a yet unexplored avenue for imparting antimicrobial activity in calcium phosphates. Silver halide colloids were added to calcium phosphate. Concurrent melting of silver halides and crystallization of carbonated apatite was achieved by heating to increase the silver halide surface area available to bacteria.Pseudomonas aeruginosa were more sensitive to silver iodide and silver bromide than Staphylococcus aureus. Silver iodide demonstrated greater activity than silver bromide. Silver chloride did not produce an antibacterial response. Both amorphous calcium phosphate and carbonated apatite displayed similar antibacterial activity when accompanied by silver halides. It is thought that amorphous calcium phosphate dissolves more readily and increases the bioavailability of the silver halide particles. Silver iodide displays a greater antibacterial response of all silver halides, with a response that is improved in a more resorbable matrix.

Fabrication and investigation of high-quality glass-ceramic (GC)–polymethyl methacrylate (PMMA) composite for regenerative medicine

The preparation of a glass-ceramic (GC)–polymethyl methacrylate (PMMA) composite material is reported. Precursor GC powders were synthesised via sol–gel method at 600 °C. XRD analysis revealed the formation of sodium calcium silicate (Na6Ca3Si6O18) as a main constituent phase of GC powders. The cylindrical-shaped GC–PMMA composite samples with fractional GC content ranging from 75 to 95% were prepared via photopolymerization reaction. The largest compressive strength for the composites containing 90% of GC has been determined. The growth of ceramic layer on the surface of composites immersed into simulated body fluid (SBF) under static conditions was studied by ICP-OES, FE-SEM/EDX, FTIR and XRD techniques. The changes in the concentrations of Ca, Si and P after the dissolution indicate the degradation process of GC–PMMA composites. The structures of the resultant surface confirmed the formation of new ceramic layer on the surface of composite materials. FTIR and XRD analyses revealed the deposition of low-crystallinity calcium phosphate layer with the composition similar to that of the carbonated hydroxyapatite (cHAP) after the soaking in SBF.

Sol–gel processing of calcium hydroxyapatite thin films on silicon nitride (Si 3 N 4 ) substrate

Calcium hydroxyapatite (Ca10(PO4)6(OH)2, CHAp) films were obtained on silicon nitride (Si3N4) substrate by a sol–gel method using a dip-coating technique. In the sol–gel process, ethylendiamintetraacetic acid and 1,2-ethandiol, triethanolamine, and polyvinyl alcohol were used as complexing agents and gel network forming agents, respectively. Calcium acetate monohydrate was used as Ca source. The samples were annealed at 650 °C for 5 h in air after each dip-coating procedure which was repeated 10, 20, and 30 times. The coatings were characterized using X-ray diffraction, scanning electron microscopy, atomic force microscopy, Raman spectroscopy, and contact angle measurements. Monophasic CHAp layers on silicon nitride (Si3N4) substrate were fabricated and characterized for the first time to the best our knowledge.Graphical Abstract