Optimization of Rifapentine-Loaded Lipid Nanoparticles Using a Quality-by-Design Strategy

This work aims to optimize and assess the potential use of lipid nanoparticles, namely nanostructured lipid carriers (NLCs), as drug delivery systems of rifapentine (RPT) for the treatment of tuberculosis (TB). A Box–Behnken design was used to increase drug encapsulation efficiency (EE) and loading capacity (LC) of RPT-loaded NLCs. The optimized nanoparticles were fully characterized, and their effect on cell viability was assessed. The quality-by-design approach allowed the optimization of RPT-loaded NLCs with improved EE and LC using the minimum of experiments. Analyses of variance were indicative of the validity of this model to optimize this nanodelivery system. The optimized NLCs had a mean diameter of 242 ± 9 nm, polydispersity index <0.2, and a highly negative zeta potential. EE values were higher than 80%, and differential scanning calorimetry analysis enabled the confirmation of the efficient encapsulation of RPT. Transmission electron microscopy analysis showed spherical nanoparticles, uniform in shape and diameter, with no visible aggregation. Stability studies indicated that NLCs were stable over time. No toxicity was observed in primary human macrophage viability for nanoparticles up to 1000 μg mL⁻¹. Overall, the optimized NLCs are efficient carriers of RPT and should be considered for further testing as promising drug delivery systems to be used in TB treatment.

Polishing after debracketing: its influence upon enamel surface

The effect of different time periods of polishing, after debonding orthodontic brackets, upon enamel surface was investigated. Nine brackets were bonded onto nine healthy human teeth, extracted for severe periodontal disease. The brackets were removed after twenty-four hours and the composite was removed from the dental surface with a tungsten carbide bur. Three of these teeth were polished with a rubber cup, pumice and water for 30 seconds. Three others had the same procedure for 10 seconds and the last group did not received any polishing. The three groups were examined at the Scanning Electron Microscope and compared with the sound enamel of the same teeth. The results showed that pumicing is necessary after debracketing, although, even after 30 seconds of polishing, composite is still found on the enamel surface. The three procedures did not provide a surface equal to the sound enamel, but better results were obtained by increasing polishing time.