Ultrastructural changes in bacterial membranes induced by nano-assemblies ß-cyclodextrin chlorhexidine: SEM, AFM, and TEM evaluation.

Chemical hosts bind their guests by the same physical mechanisms as biomolecules and often display similarly subtle structure activity relationships. The cyclodextrins have found increasing application as inert, nontoxic carriers of active compounds in drug formulations. The present study was conducted to prepare inclusion complexes of chlorhexidine:ß-cyclodextrin (Cx:ß-cd), and evaluate their interactions with bacterial membrane through: scanning electron microscopy (SEM) and transmission electron microscopy (TEM); and measuring morphology alterations, roughness values, and cell weights by atomic force microscopy (AFM). It was found that the antimicrobial activity was significantly enhanced by cyclodextrin encapsulation. SEM analysis images demonstrated recognizable cell membrane structural changes and ultrastructural membrane swelling. By TEM, cellular alterations such as vacuolization, cellular leakage, and membrane defects were observed; these effects were enhanced at 1:3 and 1:4 Cx:ß-cd. In addition, AFM analysis at these ratios showed substantially more membrane disruption and large aggregates mixing with microorganism remains. In conclusion, nanoaggregates formed by cyclodextrin inclusion compounds create cluster-like structures with the cell membrane, possibly due to a hydrogen rich bonding interaction system with increasing surface roughness and possibly increasing the electrostatic interaction between cationic chlorhexidine with the lipopolysaccharides of Gram negative bacteria.

Antimicrobial activity of a propolis adhesive formulation on different oral pathogens

Recent studies have shown that propolis has appreciable antibacterial, antifungal and antiviral actions, as well as cytostatic and antitumoral activity. In light of these studies, the antimicrobial activity of a new adhesive formulation containing propolis was evaluated in this in vitro study. Susceptibility of the oral strains tested (Candida albicans, Candida tropicalis, Streptococcus mutans, Staphylococcus aureus, Enterococcus faecalis, Actinomyces israelli, Actinobacillus actinomycetemcomitans) was evaluated using the agar diffusion method with different concentrations of propolis (5, 10, 15 and 20%). All of the assayed bacteria and fungi species were susceptible to propolis, with minimum inhibitory concentrations (MIC) ranging from 1.75 to 14.0 ãfg/ml. The positive results suggest that propolis in this sustained release formulation should be further tested as an alternative therapy of infectious conditions of the oral cavity, such as denture stomatitis and periodontitis. However, in vivo studies of the effect of this new adhesive formulation of propolis are needed to determine its possible effects on the oral mucosa.