Cyclodextrin modulates the cytotoxic effects of chlorhexidine on microrganisms and cells in vitro.

Although several studies have shown that chlorhexidine (Cx) has bactericidal activity and exerts toxic effects on periodontal tissues a few studies evaluated mechanisms to reduce its adverse effects maintaining the antimicrobial properties. Therefore, the aim of the present study was to investigate the in vitro antimicrobial activity and cellular cytotoxicity of Cx included on cyclodextrins (Cd), α, ß or Hp-ß-cyclodextrins (Hp-ß-Cd). The influence of Cds was determined by increasing its molar rate 1:1 to 1:4 in relation with free Cx. The minimal inhibitory concentrations (MICs) for Candida albicans, Aggregatibacter actinomycetemcomitans actinomycemcomitans and Streptococcus mutans were determined. An ergosterol solubilization assay was carried out using the C. albicans model and osteoblasts, fibroblasts and tumoral Caco-2 cells for cytotoxicity assay. The antimicrobial activity results in a significant growth inhibition of C. albicans when it was treated with Cx:α-Cd complexes, whereas Cx:ß-Cd was more effective for A. actinomycetemcomitans, and Cx:Hp-ß-Cd complexes was for S. mutans when compared to the other complexes. The cytotoxicity for fibroblasts and osteoblasts decreased in relation with each kind of Cd been ß-Cd ≤ Hp-ß-Cd ≤ α-Cd. Although the Hp-ß-Cd inclusion complexes had more severe effects on Caco-2 cells, all complexes exhibited less cytotoxicity than free Cx. The α-Cd, ß-Cd and Hp-ß-Cd increase the antimicrobial activity of Cx, but decrease its cytotoxic effects on mammalian cells. Taken together these findings suggest that cyclodextrins are a tool for modulation of effects of Cx. It could be useful to design Cx/Cd delivery systems with high efficacy and minimum cytotoxic effects.

Chlorhexidine: beta-cyclodextrin inhibits yeast growth by extraction of ergosterol

Chlorhexidine (Cx) augmented with beta-cyclodextrin (β-cd) inclusion compounds, termed Cx:β-cd complexes, have been developed for use as antiseptic agents. The aim of this study was to examine the interactions of Cx:β-cd complexes, prepared at different molecular ratios, with sterol and yeast membranes. The Minimal Inhibitory Concentration (MIC) against the yeast Candida albicans (C.a.) was determined for each complex; the MICs were found to range from 0.5 to 2 µg/mL. To confirm the MIC data, quantitative analysis of viable cells was performed using trypan blue staining. Mechanistic characterization of the interactions that the Cx:β-cd complexes have with the yeast membrane and assessment of membrane morphology following exposure to Cx:β-cd complexes were performed using Sterol Quantification Method analysis (SQM) and scanning electron microscopy (SEM). SQM revealed that sterol extraction increased with increasing β-cd concentrations (1.71 × 10³; 1.4 × 10³; 3.45 × 10³, and 3.74 × 10³ CFU for 1:1, 1:2, 1:3, and 1:4, respectively), likely as a consequence of membrane ergosterol solubilization. SEM images demonstrated that cell membrane damage is a visible and significant mechanism that contributes to the antimicrobial effects of Cx:β-cd complexes. Cell disorganization increased significantly as the proportion of β-cyclodextrin present in the complex increased. Morphology of cells exposed to complexes with 1:3 and 1:4 molar ratios of Cx:β-cd were observed to have large aggregates mixed with yeast remains, representing more membrane disruption than that observed in cells treated with Cx alone. In conclusion, nanoaggregates of Cx:β-cd complexes block yeast growth via ergosterol extraction, permeabilizing the membrane by creating cluster-like structures within the cell membrane, possibly due to high amounts of hydrogen bonding.

Chlorhexidine: beta-cyclodextrin inhibits yeast growth by extraction of ergosterol.

Chlorhexidine (Cx) augmented with beta-cyclodextrin (ß-cd) inclusion compounds, termed Cx:ß-cd complexes, have been developed for use as antiseptic agents. The aim of this study was to examine the interactions of Cx:ß-cd complexes, prepared at different molecular ratios, with sterol and yeast membranes. The Minimal Inhibitory Concentration (MIC) against the yeast Candida albicans (C.a.) was determined for each complex; the MICs were found to range from 0.5 to 2 µg/mL. To confirm the MIC data, quantitative analysis of viable cells was performed using trypan blue staining. Mechanistic characterization of the interactions that the Cx:ß-cd complexes have with the yeast membrane and assessment of membrane morphology following exposure to Cx:ß-cd complexes were performed using Sterol Quantification Method analysis (SQM) and scanning electron microscopy (SEM). SQM revealed that sterol extraction increased with increasing ß-cd concentrations (1.71 ×10(3); 1.4 ×10(3); 3.45 ×10(3), and 3.74 ×10(3) CFU for 1:1, 1:2, 1:3, and 1:4, respectively), likely as a consequence of membrane ergosterol solubilization. SEM images demonstrated that cell membrane damage is a visible and significant mechanism that contributes to the antimicrobial effects of Cx:ß-cd complexes. Cell disorganization increased significantly as the proportion of ß-cyclodextrin present in the complex increased. Morphology of cells exposed to complexes with 1:3 and 1:4 molar ratios of Cx:ß-cd were observed to have large aggregates mixed with yeast remains, representing more membrane disruption than that observed in cells treated with Cx alone. In conclusion, nanoaggregates of Cx:ß-cd complexes block yeast growth via ergosterol extraction, permeabilizing the membrane by creating cluster-like structures within the cell membrane, possibly due to high amounts of hydrogen bonding.

Assessment of the antimicrobial activity of Casearia sylvestris extract against oral pathogenic microorganisms

An ethanolic extract of leaves from the tree Casearia sylvestris, known as guaçatonga in Brazil, was tested for in vitro activity against oral pathogenic bacteria and fungi. The results showed susceptibility of all the microorganisms tested. This study suggests a potential use of ethanolic extract of C. sylvestris as a novel treatment of oral infectious conditions, such as denture stomatitis, periodontitis and dental caries.