Browsing by Author "Barbé, CJ"

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    Biodegradability of sol-gel silica microparticles for drug delivery
    (Springer, 2009-01) Finnie, KS; Waller, DJ; Perret, FL; Krause-Heuer, AM; Lin, HQ; Hanna, JV; Barbé, CJ
    The biodegradability of porous sol–gel silica microparticles in physiological buffers has been investigated using a USP4 flow-through dissolution tester. In the open configuration, which most closely models in-vivo conditions, the particles dissolved rapidly at pH 7.4, with a rate dependent on the surface area and media flow rate. In the closed configuration, the fastest dissolving 4 mg silica sample was almost completely dissolved in 100 mL of buffer after 36 h. The initial dissolution rates appeared relatively linear but dropped off as dissolved SiO2 concentrations approached 20–25 ppm. Addition of serum proteins acted to slow dissolution by 20–30%, suggesting a slower degradation in vivo. Silica microparticles administered for controlled release drug delivery would therefore be expected to be eliminated relatively rapidly from the body, depending on the sample size and local fluid flow conditions. © 2009, Springer. The original publication is available at www.springerlink.com
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    Crystallization of TiO2 powders and thin films prepared from modified titanium alkoxide precursors
    (Wiley-Blackwell, 2008-06) Karatchevtseva, I; Cassidy, DJ; Zhang, Z; Triani, G; Finnie, KS; Cram, SL; Barbé, CJ
    The modification of titanium alkoxides by chemical reactions with ligands yields complexes or molecular clusters that are substantially different from those of the parent alkoxides. In this study, we investigate the structural evolution of powders and thin films prepared from two titanium oxo-alkoxyacylate clusters with different oxo-core structures [Ti6(μ3-O)2(μ2-O)2](CH3COO)8(μ2-OiPr)2(OiPr)6 and [Ti6(μ3-O)6](μ-RCOO)6(OiPr)6 ([6,4] and [6,6], respectively) as a function of annealing temperature. The structural evolution of powders and thin films prepared from the corresponding parent alkoxide Ti(OiPr)4 (TiP) were also investigated for comparison. In all powders, the amorphous-to-anatase transformation occurred upon heating to 400°C. In sharp contrast, the anatase-to-rutile transformation of the powder prepared from the [6,6] cluster was significantly inhibited compared with the conventionally derived powder, with no rutile being detected even after annealing at 800°C for 1 h. This was attributed to the small crystallite size in the [6,6]-derived powder, which is lower than the critical size previously reported for the anatase-to-rutile transformation in similar sol–gel-derived materials. In thin films, the amorphous-to-anatase phase transition also occurred at temperatures as low as 400°C for coatings deposited from conventional TiP precursor and [6,4] cluster solutions. However, in contrast to the corresponding powders no rutile nucleation occurred even at 800°C in either film. © 2008, Wiley-Blackwell.
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    Mechanical properties and adhesion characteristics of hybrid sol–gel thin films
    (Elsevier, 2004-07-28) Atanacio, AJ; Latella, BA; Barbé, CJ; Swain, MV
    The hardness and Young's modulus of organic–inorganic hybrid coatings, synthesised using sol–gel technology, deposited on silicon and copper were determined using indentations at low forces with a spherical tipped indenter and found to depend strongly on the size of the organic substituent. The indentation creep response of the coating systems was compared based on fast loading rates and for different times at maximum load. The adhesion characteristics of the coatings on copper were examined to ascertain the influence of the organic substituents on the film cracking behaviour and debond tendencies. For this purpose, coated tensile test specimens were strained uniaxially in a universal testing machine while the surface was examined using an optical microscope. The mechanical response was analysed from the multiple cracking patterns observed and the extent of film delamination from the underlying substrate. The results indicate that the interfacial adhesion and film toughness are dramatically affected by the nature of the organic substituent. © 2004 Elsevier B.V
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    Mechanical stability of a Ti02 coating deposited on a polycarbonate substrate
    (Routledge, 2005) Ignat, M; Getin, S; Latella, BA; Barbé, CJ; Triani, G
    The demands imposed on mechanical durability of film-substrate systems in many leading technologies (particularly microelectronics, photonics and biomaterials) are becoming more stringent and, thus, associated problems have to be understood and solved. Film-substrate systems are subjected to internal stresses, caused by thermoelastic mismatch, or to external mechanical stresses applied monotonically or cyclically. When reaching critical levels, these stresses may activate damage mechanisms such as cracking and de-adhesion of the film. Identifying these failures and understanding the critical conditions which cause them is essential, prior to any technological application of the system. © 2005 CRC Press
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    Sol-gel microspheres and nanospheres for controlled release applications
    (Australian Nuclear Science and Technology Organisation, 2002-04-29) Barbé, CJ; Beyer, R; Kong, L; Blackford, MG; Trautman, RL; Bartlett, JR
    We present a novel approach to the synthesis of inorganic sol-gel microspheres for encapsulating organic and bioactive molecules, and controlling their subsequent release kinetics.The bioactive species are incorporated, at ambient temperature, into the inorganic particles using an emulsion gelation process, Independent control of the release rate (by adapting the nanostructure of the internal pore network to the physico-chemical properties of the bioactive molecules) and particle size (by tailoring the emulsion chemistry) is demonstrated.