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

• Published in: Pharmaceutical development and technology 2013-06, Vol.18 (3), p.600-608
• Main Authors: Rosa Teixeira, Karina Imaculada, Araújo, Patrícia Valente, Almeida Neves, Bernardo Ruegger, Bohorquez Mahecha, German Arturo, Sinisterra, Rubén Dario, Cortés, Maria Esperanza
• Format: Article
• Language: English
• Subjects: Aggregatibacter actinomycetemcomitans - chemistry; Aggregatibacter actinomycetemcomitans - ultrastructure; bacterial effects; beta-Cyclodextrins - administration & dosage; beta-Cyclodextrins - chemical synthesis; Cell Membrane - drug effects; Cell Membrane - ultrastructure; Chlorhexidine; Chlorhexidine - administration & dosage; Chlorhexidine - chemical synthesis; cyclodextrin; Drug Evaluation, Preclinical - methods; Gram-Negative Bacteria - drug effects; Gram-Negative Bacteria - ultrastructure; Microbial Sensitivity Tests - methods; Microscopy, Atomic Force - methods; Microscopy, Electron, Scanning - methods; Microscopy, Electron, Transmission - methods; Nanoparticles - administration & dosage; Nanoparticles - chemistry; Particle Size; slow delivery
• ISSN: 1083-7450; 1097-9867
• DOI: 10.3109/10837450.2011.649853

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:β-cyclodextrin (Cx:β-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:β-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.