The aim of this study was to investigate the structure of intact oral biofilms using confocal laser scanning microscopy (CLSM). Mixed-species biofilms were grown on enamel discs in a constant depth film fermentor. The biofilms were fed with a mucin-containing artificial saliva with or without sucrose supplementation. Biofilms were examined using a Wild-Leitz CLSM, operating in reflected light mode. The microstructure of non-supplemented biofilms was revealed to be complex, with stacks of bacteria developing over time, separated by clear channels. Sucrose-supplemented biofilms appeared to colonise the substratum more rapidly. The results of this study have shown that using CLSM it is possible to examine the structure of oral biofilms grown under conditions similar to those which would exist in vivo.
The use of microthermal analysis as a means of differentiating between amorphous and crystalline forms of a model low molecular weight solid has been investigated, with a view to establishing the strengths and limitations of the technique as a means of identifying different physical forms of the same substance within a single sample. Samples of the drug indometacin were prepared in amorphous, crystalline, and partially crystalline forms and the samples studied using microthermal analysis (MTA) and modulated temperature differential scanning calorimetry (MTDSC). MTDSC studies revealed a simple melting process for the crystalline material corresponding to the ? form of the drug, while a glass transition, recrystallization and subsequent melting was seen for the amorphous indometacin; in addition, the sample demonstrated a shift in the phase angle at approximately 65 °C which has been previously associated with flow of the sample in the DSC pan. MTA studies indicated that the thermal conductivity is dominated by the surface topology and no clear differentiation between amorphous and crystalline regions was obtained in this mode. A discontinuity was seen in the localized thermal analysis (LTA) profile for the crystalline sample at 152 °C corresponding to the melting of the material. Similarly, the amorphous material showed a shift in probe position at 64 °C, these responses being ascribed to sample softening. Topographical examination of the sample following LTA studies indicated the presence of a “crater” approximately 10-20 µm in diameter, giving an indication of the scale of scrutiny of the experiment. Studies using different scanning rates (2 to 20 °C/s) did not demonstrate significant changes to the temperatures of transition and crater size. Studies on partially crystalline samples clearly showed that the technique was able to differentiate between the two physical regions in LTA mode. The technique may therefore have considerable potential as a means of identifying distinct physical regions in a single sample. However, consideration needs to be given to the experimental and interpretative issues raised in this investigation
Micro-thermal analysis is a recently introduced thermoanalytical technique that combines the principles of scanning probe microscopy (SPM) with thermal analysis via replacement of the probe tip with a thermistor. This allows samples to be spatially scanned in terms of both topography and thermal conductivity, while by placing the probe on a specific region of a sample and heating it is possible to perform localised thermal analysis (LTA) experiments on those regions. In this minireview the principles of the technique are outlined and the current uses within the polymer sciences described. Current pharmaceutical applications are then discussed; these include the identification of components in compressed tablets, the characterisation of drug-loaded polylactic acid microspheres, the analysis of tablet coats and the identification of amorphous and crystalline regions in semicrystalline samples. The current strengths and weaknesses of the technique are outlined, along with a discussion of the future directions in which the approach may be taken.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.