Edita Garskaite

Effect of processing conditions on the crystallinity and structure of carbonated calcium hydroxyapatite (CHAp)

Previous synthesis routes created apatites in low crystallinity and high crystallinity states, but a wider range will extend the design capabilities of apatites for hard tissue replacements. While high crystallinity apatites are more conventional, this work investigated lower crystallinity variations from an amorphous state to low crystallinity apatite. Carbonated hydroxyapatite was prepared by precipitating an amorphous phase followed by crystallization at 650 °C at slow (5 °C min−1) and fast heating rates (60 °C min−1). The effect of processing conditions on crystallinity and structural changes was evaluated by thermal analysis, X-ray diffraction, transmission electron microscopy, Fourier transform infrared and Raman spectroscopy. Furthermore, peak deconvolution of IR and Raman spectra resolved the carbonate and phosphate bands and revealed the carbonate and crystalline phase content in CHAp. Similar to precipitation of crystalline apatites, the crystallization at elevated temperature led to carbonate in both the phosphate and hydroxyl positions. Heating at 650 °C provided a nanosized spherical hydroxyapatite containing carbonate controlled by the heating rate. This creates a mechanism for creating a large range in crystallinity with a greater resorption capability for regenerative medicine.

Synthesis and evolution of crystalline garnet phases in Y3Sc5-xGaxO12

Mixed-metal oxides with the composition Y3Sc x Ga5− x O12 (x = 2.0, 2.1, 2.2, 2.25, 2.3, 2.4, 2.5, and 3.0) have been prepared by an aqueous sol–gel method. The effects of scandium substitution on the garnet phase formation were studied by IR spectroscopy and X-ray powder diffraction (XRD). The XRD data indicate that single-phase Y3Sc x Ga5− x O12 ceramic samples were obtained for x = 2.0, 2.1, 2.2, 2.25, 2.3, and 2.4. The results also show that the formation of Y3Sc x Ga5− x O12 garnets depends on the molar ratio of scandium and gallium in the investigated composition, and consequently on the mean cationic radius at the Al3+ sites. The variation of lattice parameters for the Y3Sc x Ga5− x O12 phases with different x is reported.

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.

Structural, morphological, and magnetic characterization of bulk and thin films Y3Al5–xFexO12 (YAIG): From the perspective of aqueous sol–gel processing

ABSTRACT An aqueous sol–gel method was used for the preparation of bulk Y3Al5–xFexO12 (yttrium aluminum–iron garnet, YAIG) with the composition of x = 0.0, 1.0, 2.0, 2.5, 3.0, 4.0, 5.0 and thin films with the composition of x = 0, 3.0, 4.0, 5.0. The dip-coating technique was used for the preparation of Y3Al5–xFexO12 films on a silicon (Si) substrate. The phase composition and surface morphology of both bulk and coatings were determined and compared. The synthesized powder samples were investigated by X-ray diffraction analysis, infrared spectroscopy, scanning electron microscopy, and Mössbauer spectroscopy. The data provide evidence that some sol–gel-derived powder specimens consist of magnetically ordered component, while others show paramagnetic behavior depending on the composition of the product. It was also shown that sol–gel processing route could be successfully used for the preparation of mixed-metal YAIG thin films.

Feasibility evaluation of low-crystallinity β-tricalcium phosphate blocks as a bone substitute fabricated by a dissolution–precipitation reaction from α-tricalcium phosphate blocks

Although sintered β-tricalcium phosphate blocks have been used clinically as artificial bone substitutes, the crystallinity of β-tricalcium phosphate, which might dominate biocompatibility, is extremely high. The objective of this study is to evaluate the feasibility of fabricating low-crystallinity β-tricalcium phosphate blocks, which are expected to exhibit good biocompatibility via a dissolution–precipitation reaction of α-tricalcium phosphate blocks as a precursor under hydrothermal conditions at 200°C for 24 h. Although β-tricalcium phosphate is a metastable phase, the presence of Mg2+ in the reaction solution inhibits the formation of its corresponding stable phase and induces β-tricalcium phosphate formation under acidic conditions. It was found that low-crystallinity β-tricalcium phosphate blocks could be fabricated from α-tricalcium phosphate blocks immersed in 1.0 mol/L MgCl2 + 0.1 mol/L NaH2PO4 solution while maintaining the shape of the α-tricalcium phosphate blocks. The crystallite size of the fabricated β-tricalcium phosphate blocks was 42 nm, which was substantially smaller than that of the sintered β-tricalcium phosphate blocks. When the fabricated β-tricalcium phosphate blocks were implanted into bone defects in rabbit femurs, they exhibited excellent tissue responses. In particular, the initial osteoconductivity (two and four weeks) was substantially greater than that of sintered β-tricalcium phosphate blocks.

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.