Robocasting of 3D printed and sintered ceria scaffold structures with hierarchical porosity for solar thermochemical fuel production from the splitting of CO2.

We report the first ever robocast (additive manufacturing/3D printing) sintered ceria scaffolds, and explore their use for the production of renewable fuels via solar thermochemical fuel production (STFP, water and carbon dioxide splitting using concentrated solar energy). CeO2 catalyst scaffolds were fabricated as 50 mm diameter discs (struts and voids ∼500 µm), sintered at 1450 °C, with specific surface area of 1.58 m2 g-1. These scaffolds have hierarchical porosity, consisting of the macroporous scaffold structure combined with nanoscale porosity within the ceria struts, with mesopores <75 Å and an average pore size of ∼4 nm, and microporosity <2 nm with a microporous surface area of 0.29 m2 g-1. The ceria grains were ≤500 nm in diameter after sintering. STFP testing was carried out via thermogravimetric analysis (TGA) with reduction between 1050-1400 °C under argon, and oxidation at 1050 °C with 50% CO2, gave rapid CO production during oxidation, with high peak CO production rates (0.436 µmol g-1 s-1, 0.586 ml g-1 min-1), for total CO yield of 78 µmol g-1 (1.747 ml g-1). 90% CO was obtained after just 10 min of oxidation, comparing well to reticulated ceria foams, this CO production rate being an order of magnitude greater than that for ceria powders when tested at similar temperatures.

Cytotoxicity and bioactivity assessments for Cu2+ and La3+ doped high-silica sol-gel derived bioglasses: The complex interplay between additive ions revealed.

We show the influence of two functional ions (Cu2+ and La3+ ), incorporated into a quaternary (Si, Ca, Na, P) sol-gel derived bioactive glass system, on its particle size, cytotoxicity, and bioactivity. By doping the parent glass with the two ions in singular or combined forms, 15 doped glasses were prepared by a rapid sol-gel technique. The influence of the combined doping on the particle size and cell viability was successfully evaluated by the aid of signal-to-noise-ratio (S/N), using Taguchi analysis. This allowed us to analyze the complex interplay of effects between these ions, and the marked differences in biocompatibility between the three cell types studied. Cu addition had a significant effect on reducing the glass particle size, while both increased density. Cell viability was significantly improved for some doping combinations, demonstrating that while combined Cu-La doping was beneficial for biocompatibility with lymphoblasts, individual high-Cu or low-La doping was better with fibroblasts, and either high-Cu or low-La doping, or certain combined Cu-La combinations, were the optimum for osteoblasts. However, the bioactivity of doped samples was generally similar to that of the parent glass, although both La, and particularly Cu, did appear to aid dissolution of ions when immersed in SBF, act as glass modifiers, and encourage HAp crystallization. The results reveal that potential synergistic benefits can be obtained by combining the effects on the mean particle size, density, cytotoxicity, and bioactivity of the glasses. The greatly improved biocompatibility of some of the doped glasses makes them promising candidates for biomedical applications.

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.

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.

Synthesis and bioactivity assessment of high silica content quaternary glasses with Ca: P ratios of 1.5 and 1.67, made by a rapid sol-gel process.

Sol-gel glasses in quaternary silica-sodium-calcium-phosphorous systems have been synthesized using a rotary evaporator for rapid drying without ageing. This novel fast drying method drastically decreases the total drying and ageing time from several weeks to only 1 hour, thus overcoming a serious drawback in sol-gel preparation procedures for bioglasses. This work investigates the bioactivity behavior of two glasses synthesized by this fast method, with Ca:P ratios of 1.5, and 1.67. X-ray diffraction (XRD), Inductive coupled plasma, Fourier-transform infrared, and Raman spectroscopy were used to confirm the bioactivity of the synthesized powders. MAS-NMR was also used to assess the degree of silica polymerization. The composition with a higher Ca:P = 1.67 ratio showed better bioactivity in comparison to the one with Ca:P = 1.5, which exhibited little bio-response with up to 4 weeks of immersion in SBF (simulated body fluid). It was also found that an orbital agitation rate of 120 rpm favors the interfacial bio-mineralization reactions, promoting the formation of a crystalline hydroxyapatite (HAp) layer at the surface of the (Ca:P = 1.67) composition after 2 weeks immersion in SBF. © 2017 Wiley Periodicals, Inc. J Biomed Mater Res Part A: 106A: 510-520, 2018.

Novel route for rapid sol-gel synthesis of hydroxyapatite, avoiding ageing and using fast drying with a 50-fold to 200-fold reduction in process time.

We have developed an innovative, rapid sol-gel method of producing hydroxyapatite nanopowders that avoids the conventional lengthy ageing and drying processes (over a week), being 200 times quicker in comparison to conventional aqueous sol-gel preparation, and 50 times quicker than ethanol based sol-gel synthesis. Two different sets of experimental conditions, in terms of pH value (5.5 and 7.5), synthesis temperature (45 and 90°C), drying temperature (60 and 80°C) and calcination temperature (400 and 700°C) were explored. The products were characterised by X-ray diffraction (XRD) Fourier-transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM) and specific surface area (SSA) measurements. Pure hydroxyapatite (Ca10(PO4)6(OH)2, HAp) was obtained for the powders synthesised at pH7.5 and calcined at 400°C, while biphasic mixtures of HAp/ß-tricalcium phosphate (ß-Ca3(PO4)2, TCP) were produced at pH5.5 and (pH7.5 at elevated temperature). The novel rapid drying was up to 200 times faster than conventional drying, only needing 1h with no prior ageing step, and favoured the formation of smaller/finer nanopowders, while producing pure HAp or phase mixtures virtually identical to those obtained from the slow conventional drying method, despite the absence of a slow ageing process. The products of this novel rapid process were actually shown to have smaller crystallite sizes and larger SSA, which should result in increased bioactivity.

Effect of embolisation on endoscopic resection of angiofibroma.

OBJECTIVE: To determine the effect of embolisation on endoscopic resection of angiofibroma. SUBJECTS AND METHOD: A partially blinded trial was undertaken. Twenty-three patients with angiofibroma (nine embolised and 14 not embolised) underwent endoscopic resection between January 2007 and August 2008 in two tertiary referral centres. Demographic data were collected, the pre-operative tumour extent was assessed by computed tomography, and tumours were staged according to their computed tomography appearance (Radkowski scale). In addition, we evaluated the duration of surgery, amount of haemorrhage, blood pressure during surgery, duration of hospitalisation, complications of surgery and embolisation, cost of treatment, and number of post-operative recurrences, as well as the angiographic characteristics in the embolisation group. RESULTS: There was no significant difference between the general characteristics of both groups. At the end of the study period, we could find no significant difference between the two groups regarding haemorrhage, number of recurrences or complications. The only significant difference was cost of treatment, which was significantly higher in the embolisation group. CONCLUSION: Endoscopic resection is a feasible and safe method for angiofibroma surgery. The current evidence does not support obligatory embolisation in every case of endoscopic angiofibroma resection.

Infratemporal hydatid cyst: a case presenting with blindness.

OBJECTIVE: We report a very rare case of a hydatid cyst in the infratemporal fossa, causing visual loss over a 10-day period, which disappeared with rapid surgical and medical treatment. CASE REPORT: A 14-year-old girl presented with right exophthalmos and visual loss. Over a 10-day period, her visual acuity had decreased to detection of hand motion only, due to pressure on the optic nerve caused by a parapharyngeal cyst pressing through a inferior orbital fissure on the right side. A craniotomy had previously been performed for a right frontoparietal hydatid cyst. The patient had been treated intermittently with albendazole. The patient was primarily diagnosed with hydatid cyst, on the basis of her previous medical history and radiological findings, and underwent surgery. Three cysts were carefully removed from the right maxillary sinus, via a standard Caldwell-Luc approach, and the surgical area was irrigated with hypertonic saline. CONCLUSION: Infratemporal hydatidosis is very rarely reported in the world literature, although hydatid cysts are endemic in many countries, including Iran. We discuss the common presenting features, investigation and treatment options for infratemporal hydatosis. Constant evaluation of adjacent organs is necessary, with treatment as required, due to the propensity of hydatidosis to recur in essential organs. Immediate surgery is recommended, both to prevent the development of disease and to improve the prognosis.