Papers by Author: Uwe Gbureck

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Authors: Peih Jeng Jiang, Sarika Patel, Uwe Gbureck, Liam M. Grover
Abstract: There is a current need for the localized delivery of antibiotics in order to treat implant based infections. In this study, the efficacy of hydroxyapatite (HA) gels, HA cements, and silica gels in the delivery of vancomycin have been investigated and compared. Vancomycin release was monitored at set time points using a UV/VIS spectrophotometer (288 nm). The activity of the vancomycin released from the cements and gels was assessed using an agar diffusion test with Staphylococcus aureus. Vancomycin was released rapidly from both HA matrices, and the silica gel in the first day of the experiment, but the release rate was slowed considerably after 3 days for the HA gels. Following ten days of aging, 70% of the vancomycin remained in the HA gel matrix and the quantity released from the gel was shown to retain its effectiveness against Staphylococcus aureus.
Authors: Liam M. Grover, Uwe Gbureck, David Farrar, J.E. Barralet
Abstract: In this study, we have shown that by incorporating pyrophosphoric acid into a brushite cement system, it is possible to produce a cement that exhibits adhesive tensile strengths with cortical bone, alumina, sintered hydroxyapatite and 316L stainless steel of 700 kPa. To our knowledge, this is the first report of a calcium phosphate cement formulation that exhibits such adhesive properties without the addition of an organic additive. The production of a bond between medical prostheses and bone may further widen the field of application of calcium phosphate cements, additionally the adhesive nature of the calcium phosphate cement may be a desirable ‘handling characteristic’ during reconstructive surgery.
Authors: K.J. Lilley, Uwe Gbureck, David Farrar, C. Ansell, J.E. Barralet
Authors: S. Mahmood, W.M. Palin, Uwe Gbureck, O. Addison, M.P. Hofmann
Abstract: The effect of mechanical mixing on compressive strength, relative porosity and reliability of strength data of a brushite forming cement at different powder to liquid ratios (PLRs) was investigated. Mean compressive strengths were measured, associated reliability (Weibull moduli) and survival probability distributions of the data sets were analysed. Relative porosities were determined using helium pycnometry. For low PLR (2.2g/ml), no significant differences in compressive strength were observed for either mechanical or hand mixed samples, although reliability of the former was significantly increased. At high PLR (3.4g/ml), mechanically mixed cements exhibited approximately twice the mean compressive strength compared with hand mixing, although Weibull moduli remained statistically similar. At medium PLR (2.8g/ml) strength and reliability of cements were similar and independent of mixing regime. For all PLRs, a significant decrease in porosity of mechanical- compared with hand-mixed cements was observed. Mechanical mixing of a brushite cement can provide lower porosity, increased reliability and higher strength.
Authors: K.J. Lilley, Uwe Gbureck, Adrian J. Wright, David Farrar, J.E. Barralet
Abstract: Bajpai et al. originally reported the formation of cements by the mixture of carboxylic acids and β-tricalcium phosphate (β-TCP). In the current study, we report and contrast four such cement systems formed from mixing citric, malic, 2-oxoglutaric or phosphoric acid with β-TCP. Cements formed from malic or 2-oxoglutaric appeared to contain crystalline phases and were determined to contain brushite, β-TCP and unreacted acid. In contrast, cement formed with citric acid was poorly crystalline, containing little evidence of brushite formation and was unstable in water and therefore does not appear to be a feasible cement system.
Authors: Liam M. Grover, Uwe Gbureck, A. Hutton, David Farrar, C. Ansell, J.E. Barralet
Authors: J.E. Barralet, Uwe Gbureck, Liam M. Grover, R. Thull
Authors: Liam M. Grover, Sarika Patel, Y. Hu, Uwe Gbureck, J.E. Barralet
Abstract: The hydrolysis of brushite in calcium phosphate cements to form hydroxyapatite is known to result in the long term stability of the material in the body. It has previously been established that this hydrolysis reaction can be influenced by implant volume, media refreshment rate and media composition. In this study, the effect of macroporosity on the rate of degradation of the material is investigated. Macroporosity was incorporated into the material using calcium alginate beads mixed into the cement paste. The inclusion of the calcium alginate beads did not influence the degree of conversion of the material and allowed the incorporation of porosity at up to maximum of 57%. The macroporosity weakened the cement matrix (from 46.5 to 3.2 MPa). When aged the brushite in the macroporous cement dissolved completely from the matrix resulting in a weight loss of 60wt% in a period of 28 days. This suggests that the controlled incorporation of calcium alginate beads into brushite cements in vivo can be used to control implant degradation rate.
Authors: M.P. Hofmann, A.M. Young, Showan N. Nazhat, Uwe Gbureck, J.E. Barralet
Abstract: Time resolved infrared spectroscopy (FTIR) and isothermal differential scanning calorimetry (DSC) were used for the first time to monitor the chemical reaction in a fast setting brushite forming calcium phosphate cement. It was found that the reaction percentage at a given time was dependent on temperature and not powder to liquid (P/L) ratio. Both methods showed that there was, within the temperature range investigated, a single autocatalytic like setting reaction within the cement paste. Final conversion of the reactants was found to be unaffected by temperature and P/L ratio.
Authors: M.P. Hofmann, Uwe Gbureck, Liam M. Grover, J.E. Barralet
Abstract: This study sought to examine the efficiency of coating cement powder reactants in order to reduce the solubility rate of reactants and thereby increase setting times of cement systems. In this investigation magnesium and sodium stearate salts were used to coat the highly soluble monocalcium phosphate monohydrate (MCPM) powder component of a hydraulic brushite forming calcium phosphate cement system with b-tricalcium phosphate (b-TCP) as other component. The results showed that stearate coating of the MCPM reactant could lead to a 100% increase in setting and working times without affecting compressive strength of the set cement when applied with the appropriate P/L-ratio.
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