title: Ultrastructural changes in bacterial membranes induced by nano-assemblies β-cyclodextrin chlorhexidine: SEM, AFM, and TEM evaluation.
abstract: 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.
authors.affiliation: Restorative Dentistry Department, Universidade Federal de Minas Gerais (UFMG), Belo Horizonte, Brazil.
authors.forename: Karina Imaculada Rosa
authors.initials: KI
authors.lastname: Teixeira
authors.forename: Patrícia Valente
authors.initials: PV
authors.lastname: Araújo
authors.forename: Bernardo Ruegger Almeida
authors.initials: BR
authors.lastname: Neves
authors.forename: German Arturo Bohorquez
authors.initials: GA
authors.lastname: Mahecha
authors.forename: Rubén Dario
authors.initials: RD
authors.lastname: Sinisterra
authors.forename: Maria Esperanza
authors.initials: ME
authors.lastname: Cortés
mesh_terms: D016976:Aggregatibacter actinomycetemcomitans / Q000737:chemistry / Q000648:ultrastructure; D002462:Cell Membrane / Q000187:drug effects / Q000648:ultrastructure*; D002710:Chlorhexidine / Q000008:administration & dosage / Q000138:chemical synthesis; D004353:Drug Evaluation, Preclinical / Q000379:methods; D006090:Gram-Negative Bacteria / Q000187:drug effects / Q000648:ultrastructure*; D008826:Microbial Sensitivity Tests / Q000379:methods; D018625:Microscopy, Atomic Force / Q000379:methods*; D008855:Microscopy, Electron, Scanning / Q000379:methods; D046529:Microscopy, Electron, Transmission / Q000379:methods*; D053758:Nanoparticles / Q000008:administration & dosage / Q000737:chemistry*; D010316:Particle Size; D047392:beta-Cyclodextrins / Q000008:administration & dosage / Q000138:chemical synthesis*
chemical_list: D047392:beta-Cyclodextrins; D002710:Chlorhexidine