Enhanced bioactivity of a rapidly-dried sol-gel derived quaternary bioglass

Novel quaternary (67Si-24Ca-10Na-8P) glass powders were successfully synthesised by sol-gel followed by two alternative drying schedules, conventional drying (CD) and an innovative fast drying (FD) process (200 times quicker). The glasses were thermally stabilised at 550 °C, and then characterised by different complementary techniques. The samples showed very similar silica network structures, with the FD one having slightly lower degree of polymerisation than the CD sample. This less polymerised, more open, network structure exhibited an improved bioactivity in simulated body fluid (SBF), probably also due to the apparent presence of poorly crystalline HAp in the stabilised glass powder. In contrast, the CD glass exhibited an unwanted secondary crystalline silica phase. Both glasses showed excellent biomineralisation upon immersion in SBF, being more pronounced in the case of FD with clear evidence of HAp formation after 4 h, while equivalent signs in the CD samples were only noticed after longer immersion periods between 8 h and 1 week.publishe

The role of calcium (source & content) on the in vitro behaviour of sol–gel quaternary glass series

To highlight the effect of salt precursors on the final properties, bioactivity and biocompatibility, five quaternary (Si–Ca–P–Na) glass compositions were successfully prepared through two distinct rapid sol–gel routes; one using acetate salt precursors (A) catalysed by nitric acid, and the other using nitrate salts (N) and citric acid as a catalyst. The sols dried rapidly, and stabilised at 550 & 800 °C to be characterised by X–ray diffraction (XRD), Magic angle spinning–Nuclear magnetic resonance (29Si MAS–NMR) and Fourier transform infra–red spectroscopy (FTIR). Upon immersion in simulated body fluid (SBF), hydroxyapatite (HAp) formation was initially enhanced by increasing Ca–content up to 40 mol%, but the formation of calcite was favoured with further increments of Ca to 45 and 48 mol%. The A–glasses exhibited lower density and lower network connectivity compared with N–glasses. The chemical surface modifications after 4 h in SBF were more evident for N–glasses in comparison to A–glasses. The biocompatibility is favoured for the samples treated at 800 °C and for the samples of the higher silica contents

Late Holocene palynology and palaeovegetation of tephra-bearing mires at Papamoa and Waihi Beach, western Bay of Plenty, North Island, New Zealand.

The vegetation history of two mires associated with Holocene dunes near the western Bay of Plenty coast, North Island, New Zealand, is deduced from pollen analysis of two cores. Correlation of airfall tephra layers in the peats, and radiocarbon dates, indicate that the mires at Papamoa and Waihi Beach are c. 4600 and c. 2900 conventional radiocarbon years old, respectively. Tephras used to constrain the chronology of the pollen record include Rotomahana (1886 AD), Kaharoa (700 yr B.P.), Taupo (Unit Y; 1850 yr B.P.), Whakaipo (Unit V; 2700 yr B.P.), Stent (Unit Q; 4000 yr B.P.), Hinemaiaia (Unit K; 4600 yr B.P.), and reworked Whakatane (c. 4800 yr B.P.) at Papamoa, and Kaharoa and Taupo at Waihi Beach. Peat accumulation rates at Papamoa from 4600 - 1850 yr B.P. range from 0.94 to 2.64 mm/yr (mean 1.37 mm/yr). At Waihi Beach, from 2900 yr B.P. - present day, they range from 0.11 to 0.21 mm/yr (mean 0.20 mm/yr). Peat accumulation at both sites was slowest from 1850 to 700 yr B.P., suggesting a drier overall climate during this interval. At both sites, the earliest organic sediments, which are underlain by marine or estuarine sands, yield pollen spectra indicating salt marsh or estuarine environments. Coastal vegetation communities declined at both sites, as sea level gradually fell or the coast prograded, and were eventually superseded by a low moor bog at Papamoa, and a mesotrophic swamp forest at Waihi Beach. These differences, and the marked variation in peat accumulation rates, probably reflect local hydrology and are unlikely to have been climatically controlled. The main regional vegetation during this period was mixed northern conifer-angiosperm forest. Kauri (Agathis australis) formed a minor component of these forests, but populations of this tree have apparently not expanded during the late Holocene at these sites, which are near its present southern limit. Occasional shortlived forest disturbances are detectable in these records, in particular immediately following the deposition of Taupo Tephra. However, evidence for forest clearance during the human era is blurred by the downward dislocation of modern adventi ve pollen at these sites, preventing the clear differentiation of the Polynesian and European eras

Robocasting of Cu2+ & La3+ doped sol-gel glass scaffolds with greatly enhanced mechanical properties: compressive strength up to 14 MPa

This research details the successful fabrication of scaffolds by robocasting from high silica sol-gel glass doped with Cu2+ or La3+. The parent HSSGG composition within the system SiO2-CaO-Na2O-P2O5 [67% Si - 24% Ca - 5% Na - 4% P (mol%)] was doped with 5 wt% Cu2+ or La3+ (Cu5 and La5). The paper sheds light on the importance of copper and lanthanum in improving the mechanical properties of the 3-D printed scaffolds. 1 h wet milling was sufficient to obtain a bioglass powder ready to be used in the preparation of a 40 vol% solid loading paste suitable for printing. Moreover, Cu addition showed a small reduction in the mean particle size, while La exhibited a greater reduction, compared with the parent glass. Scaffolds with macroporosity between 300 and 500 µm were successfully printed by robocasting, and then sintered at 800 °C. A small improvement in the compressive strength (7-18%) over the parent glass accompanied the addition of La. However, a much greater improvement in the compressive strength was observed with Cu addition, up to 221% greater than the parent glass, with compressive strength values of up to ∼14 MPa. This enhancement in compressive strength, around the upper limit registered for human cancellous bones, supports the potential use of this material in biomedical applications. STATEMENT OF SIGNIFICANCE: 3D porous bioactive glass scaffolds with greatly improved compressive strength were fabricated by robocasting from a high silica sol-gel glasses doped with Cu2+ or La3+. In comparison to the parent glass, the mechanical performance of scaffolds was greatly improved by copper-doping (>220%), while a modest increase of ∼9% was registered for lanthanum-doping. Doping ions (particularly La3+) acted as glass modifiers leading to less extents of silica polymerisation. This favoured the milling of the glass powders and the obtaining of smaller mean particle sizes. Pastes with a high solid loading (40 vol%) and with suitable rheological properties for robocasting were prepared from all glass powders. Scaffolds with dimensions of 3 × 3 × 4 mm and macro-pore sizes between 300 and 500 µm were fabricated.publishe

Re-identification of c. 15 700 cal yr BP tephra bed at Kaipo Bog, eastern North Island: implications for dispersal of Rotorua and Puketarata tephra beds.

A 10 mm thick, c. 15 700 calendar yr BP (c. 13 100 14C yr BP) rhyolitic tephra bed in the well-studied montane Kaipo Bog sequence of eastern North Island was previously correlated with Maroa-derived Puketarata Tephra. We revise this correlation to Okataina-derived Rotorua Tephra based on new compositional data from biotite phenocrysts and glass. The new correlation limits the known dispersal of Puketarata Tephra (sensu stricto, c. 16 800 cal yr BP) and eliminates requirements to either reassess its age or to invoke dual Puketarata eruptive events. Our data show that Rotorua Tephra comprises two glass-shard types: an early-erupted low-K2O type that was dispersed mostly to the northwest, and a high-K2O type dispersed mostly to the south and southeast, contemporary with late-stage lava extrusion. Late-stage Rotorua eruptives contain biotite that is enriched in FeO compared with biotite from Puketarata pyroclastics. The occurrence of Rotorua Tephra in Kaipo Bog (100 km from the source) substantially extends its known distribution to the southeast. Our analyses demonstrate that unrecognised syn-eruption compositional and dispersal changes can cause errors in fingerprinting tephra deposits. However, the compositional complexity, once recognised, provides additional fingerprinting criteria, and also documents magmatic and dispersal processes

Robocasting: Prediction of ink printability in solgel bioactive glass

Bioactive glass powders synthesized by solgel are usually porous and exhibit high specific surface areas, conferring them poor ability for scaffolds fabrication using colloidal processing approaches. The difficulties associated with colloidal processing of solgel glass have hindered so far the processing of 3-D scaffolds by robocasting. This research paper investigates the importance of calcination temperature (CT) and balls to powder ratio (BPR) used upon wet milling on the maximum achievable solid loading in aqueous media. The effects of CT, BPR, and solid loading on the flow behavior and viscoelastic properties of the suspensions/pastes were evaluated in this preliminary work. The aim is to disclose the sets of experimental variables that are most promising for the formulation of printable inks, and open the way for the future fabrication of porous scaffolds by robocasting and other 3-D additive manufacturing techniques

Robocasting of Cu 2+ & La 3+ doped sol–gel glass scaffolds with greatly enhanced mechanical properties: Compressive strength up to 14 MPa

This research details the successful fabrication of scaffolds by robocasting from high silica sol–gel glass doped with Cu 2+ or La 3+ . The parent HSSGG composition within the system SiO 2 –CaO–Na 2 O–P 2 O 5 [67% Si – 24% Ca – 5% Na – 4% P (mol%)] was doped with 5 wt% Cu 2+ or La 3+ (Cu5 and La5). The paper sheds light on the importance of copper and lanthanum in improving the mechanical properties of the 3–D printed scaffolds. 1 h wet milling was sufficient to obtain a bioglass powder ready to be used in the preparation of a 40 vol% solid loading paste suitable for printing. Moreover, Cu addition showed a small reduction in the mean particle size, while La exhibited a greater reduction, compared with the parent glass. Scaffolds with macroporosity between 300 and 500 µm were successfully printed by robocasting, and then sintered at 800 °C. A small improvement in the compressive strength (7–18%) over the parent glass accompanied the addition of La. However, a much greater improvement in the compressive strength was observed with Cu addition, up to 221% greater than the parent glass, with compressive strength values of up to ∼14 MPa. This enhancement in compressive strength, around the upper limit registered for human cancellous bones, supports the potential use of this material in biomedical applications. Statement of Significance: 3D porous bioactive glass scaffolds with greatly improved compressive strength were fabricated by robocasting from a high silica sol–gel glasses doped with Cu 2+ or La 3+ . In comparison to the parent glass, the mechanical performance of scaffolds was greatly improved by copper-doping (>220%), while a modest increase of ∼9% was registered for lanthanum-doping. Doping ions (particularly La 3+ ) acted as glass modifiers leading to less extents of silica polymerisation. This favoured the milling of the glass powders and the obtaining of smaller mean particle sizes. Pastes with a high solid loading (40 vol%) and with suitable rheological properties for robocasting were prepared from all glass powders. Scaffolds with dimensions of 3 × 3 × 4 mm and macro-pore sizes between 300 and 500 µm were fabricated

BIONANOSCULP, an ongoing project in biotechnology applications for preventive conservation of outdoor sculptures

The objective of this paper is the presentation of the research strategies adopted and results of the ongoing BIONANOSCULP research project that is aiming to develop solutions in the area of sustainable nanomaterials, which are non-invasive and high-performance in their preventive conservation approach. An integrated methodology was designed as a holistic strategy to the characterisation of the microbiota present on the surface of public outdoor sculptures. Gathering objective data in the characterization of the surface microbiota of public outdoor sculptures is important, in order to design strategies for the preventive conservation of these objects that make use of biotechnology innovative coatings. Such is one of the objectives of the project BIONANOSCULP. Methodologies applied include conservation reports, surface sampling methodologies using gels, 3D modeling, SEM, flow cytometry and metagenomics. The project is already significantly contributing to create a bridge between the experts from different areas: the skills of biotechnologists, microbiologists, materials scientists, art historians and conservators-restorers to assess the state of conservation, biodeterioration and biocontamination of a selected number of sculptures, and to design the appropriate materials to pursue preventive conservation through coatings with anti-microbial activities

Robocasting of ceramic glass scaffolds: Sol–gel glass, new horizons

This article reports the first robocasting of a sol–gel based glass ceramic scaffold. Sol–gel bioactive glass powders usually exhibit high volume fractions of meso– and micro–porosities, bad for colloidal processing as this adsorbs significant portion of the dispersing medium, affecting dispersion and flow. We circumvent these practical difficulties, to achieve pastes with particle size distributions, high solids loading and appropriate rheological properties for extrusion through fine nozzles for robocasting. Scaffolds with different macro-pore sizes (300–500 μm) with solid loadings up to 40 vol.% were robocast. The sintered (800 °C, 2 h) scaffolds exhibited compressive strength of 2.5–4.8 MPa, formed hydroxyapatite after 72 h in SBF, and had no cytotoxicity and a considerable MG63 cells viability rate. These features make the scaffolds promising candidates for tissue engineering applications and worthy for further in vivo investigations