title: Adsorption of chlorhexidine on synthetic hydroxyapatite and in vitro biological activity.
abstract: The kinetic of chlorhexidine digluconate (CHXDG) uptake from aqueous solution by hydroxyapatite (HA) was investigated by ultraviolet (UV) analysis performed in HA powder (UV-solid) after the CHX adsorption. Adsorption isotherm of chlorhexidine (CHX) uptake was modeled by a combination of Languimir and Langmuir-Freundlich mechanisms. Strong molecule-molecule interactions and positive cooperativity predominated in the surface when CHX concentration was above 8.6 μg(CHX)/mg(HA). UV-solid spectra (shape, intensity and band position) of CHX bound to HA revealed that long-range molecular structures, such as aggregates or micelles, started to be formed at low CHX concentrations (1.52 μg(CHX)/mg(HA)) and predominated at high concentrations. Grazing-incidence X-ray diffraction (GIXRD) analysis from synchrotron radiation discarded the formation of crystalline structures on HA surface or precipitation of CHX crystalline salts, as suggested in previous works. The effect of the HA/CHX association on HA in vitro bioactivity, cytotoxicity and CHX antimicrobial activity was evaluated. It was shown that CHX did not inhibit the precipitation of a poorly crystalline apatite at HA/CHX surface after soaking in simulating body fluid (SBF). Cell viability studies after exposure to extracts of HA and HA/CHX showed that both biomaterials did not present significant in vitro toxicity. Moreover, HA/CHX inhibited Enterococcus faecalis growth for up to 6 days, revealing that binding to HA did not affect antimicrobial activity of CHX and reduced bacterial adhesion. These results suggested that HA/CHX association could result in a potential adjuvant antimicrobial system for clinical use.
authors.affiliation: Department of Applied Physics, Brazilian Center for Physics Research, Rio de Janeiro, RJ, Brazil. soriano@cbpf.br
authors.forename: Carlos A Soriano
authors.initials: CA
authors.lastname: de Souza
authors.forename: Ana Paula V
authors.initials: AP
authors.lastname: Colombo
authors.forename: Renata M
authors.initials: RM
authors.lastname: Souto
authors.forename: Carina M
authors.initials: CM
authors.lastname: Silva-Boghossian
authors.forename: Jose M
authors.initials: JM
authors.lastname: Granjeiro
authors.forename: Gutemberg G
authors.initials: GG
authors.lastname: Alves
authors.forename: Alexandre M
authors.initials: AM
authors.lastname: Rossi
authors.forename: Maria Helena M
authors.initials: MH
authors.lastname: Rocha-Leão
mesh_terms: D000327:Adsorption; D000818:Animals; D000891:Anti-Infective Agents, Local / Q000032:analysis / Q000737:chemistry* / Q000494:pharmacology; D041702:BALB 3T3 Cells; D001672:Biocompatible Materials / Q000032:analysis / Q000737:chemistry*; D018441:Biofilms / Q000187:drug effects / Q000254:growth & development; D001826:Body Fluids / Q000737:chemistry; D002710:Chlorhexidine / Q000032:analysis / Q000737:chemistry* / Q000494:pharmacology; D003692:Delayed-Action Preparations / Q000032:analysis / Q000737:chemistry* / Q000494:pharmacology; D017886:Durapatite / Q000032:analysis / Q000737:chemistry*; D013293:Enterococcus faecalis / Q000187:drug effects*; D016908:Gram-Positive Bacterial Infections / Q000188:drug therapy / Q000382:microbiology; D006801:Humans; D051379:Mice; D008855:Microscopy, Electron, Scanning; D008863:Microspheres; D018716:Molecular Mimicry; D009055:Mouth / Q000187:drug effects / Q000382:microbiology; D056951:Photoelectron Spectroscopy; D013499:Surface Properties; D014961:X-Ray Diffraction
chemical_list: D000891:Anti-Infective Agents, Local; D001672:Biocompatible Materials; D003692:Delayed-Action Preparations; D017886:Durapatite; D002710:Chlorhexidine