Epoxide opening versus silica condensation during sol-gel hybrid biomaterial synthesis.

Hybrid organic-inorganic solids represent an important class of engineering materials, usually prepared by sol-gel processes by cross-reaction between organic and inorganic precursors. The choice of the two components and control of the reaction conditions (especially pH value) allow the synthesis of hybrid materials with novel properties and functionalities. 3-Glycidoxypropyltrimethoxysilane (GPTMS) is one of the most commonly used organic silanes for hybrid-material fabrication. Herein, the reactivity of GPTMS in water at different pH values (pH 2-11) was deeply investigated for the first time by solution-state multinuclear NMR spectroscopic and mass spectrometric analysis. The extent of the different and competing reactions that take place as a function of the pH value was elucidated. The NMR spectroscopic and mass spectrometric data clearly indicate that the pH value determines the kinetics of epoxide hydrolysis versus silicon condensation. Under slighly acidic conditions, the epoxy-ring hydrolysis is kinetically more favourable than the formation of the silica network. In contrast, under basic conditions, silicon condensation is the main reaction that takes place. Full characterisation of the formed intermediates was carried out by using NMR spectroscopic and mass spectrometric analysis. These results indicate that strict control of the pH values allows tuning of the reactivity of the organic and inorganic moities, thus laying the foundations for the design and synthesis of sol-gel hybrid biomaterials with tuneable properties.

Assessing confidence in the understanding and management of oral cancer among medical and dental undergraduates at a UK university.

Introduction Oral cancer is the eighth most common cancer in the world and associated with a high rate of morbidity and mortality. Appropriate and early diagnosis of the condition is associated with improved patient outcomes, and an improvement in five-year survival rates.Aims We aim to ascertain if dental and medical students have similar amounts of self-confidence in the understanding and management of oral cancer within a large UK university.Methods We invited 65 final-year dental students and 101 final-year medical students to undertake our study, with 50 dental students and 59 medical students opting to participate.Results We found final-year dental students to feel significantly more confident in their understanding and management of oral cancer when compared to their medical counterparts.Conclusions Medical students may benefit from additional teaching on oral cancer. Additionally, they should be encouraged to briefly screen the oral cavity of individuals who are at high-risk of the disease.

Production of Galacto-oligosaccharides by the ß-Galactosidase from Kluyveromyces lactis : comparative analysis of permeabilized cells versus soluble enzyme.

The transgalactosylation activity of Kluyveromyces lactis cells was studied in detail. Cells were permeabilized with ethanol and further lyophilized to facilitate the transit of substrates and products. The resulting biocatalyst was assayed for the synthesis of galacto-oligosaccharides (GOS) and compared with two soluble ß-galactosidases from K. lactis (Lactozym 3000 L HP G and Maxilact LGX 5000). Using 400 g/L lactose, the maximum GOS yield, measured by HPAEC-PAD analysis, was 177 g/L (44% w/w of total carbohydrates). The major products synthesized were the disaccharides 6-galactobiose [Gal-ß(1→6)-Gal] and allolactose [Gal-ß(1→6)-Glc], as well as the trisaccharide 6-galactosyl-lactose [Gal-ß(1→6)-Gal-ß(1→4)-Glc], which was characterized by MS and 2D NMR. Structural characterization of another synthesized disaccharide, Gal-ß(1→3)-Glc, was carried out. GOS yield obtained with soluble ß-galactosidases was slightly lower (160 g/L for Lactozym 3000 L HP G and 154 g/L for Maxilact LGX 5000); however, the typical profile with a maximum GOS concentration followed by partial hydrolysis of the newly formed oligosaccharides was not observed with the soluble enzymes. Results were correlated with the higher stability of ß-galactosidase when permeabilized whole cells were used.