title: Chlorhexidine-loaded hydroxyapatite microspheres as an antimicrobial delivery system and its effect on in vivo osteo-conductive properties.
abstract: Hydroxyapatite (HA) has been investigated as a delivery system for antimicrobial and antibacterial agents to simultaneously stimulate bone regeneration and prevent infection. Despite evidence supporting the bactericidal efficiency of these HA carriers, few studies have focused on the effect of this association on bone regeneration. In this work, we evaluated the physico-chemical properties of hydroxyapatite microspheres loaded with chlorhexidine (CHX) at two different concentrations, 0.9 and 9.1 μgCHX/cm2 HA, and characterized their effects on in vitro osteoblast viability and bone regeneration. Ultraviolet-visible spectroscopy, scanning and transmission electron microscopy associated with energy-dispersive X-ray spectroscopy and electron energy loss spectroscopy were used to characterize the association of CHX and HA nanoparticles. The high CHX loading dose induced formation of organic CHX plate-like aggregates on the HA surface, whereas a Langmuir film was formed at the low CHX surface concentration. Quantitative evaluation of murine osteoblast viability parameters, including adhesion, mitochondrial activity and membrane integrity of cells exposed to HA/CHX extracts, revealed a cytotoxic effect for both loading concentrations. Histomorphological analysis upon implantation into the dorsal connective tissues and calvaria of rats for 7 and 42 days showed that the high CHX concentration induced the infiltration of inflammatory cells, resulting in retarded bone growth. Despite a strong decrease in in vitro cell viability, the low CHX loading dose did not impair the biocompatibility and osteoconductivity of HA during bone repair. These results indicate that high antimicrobial doses may activate a strong local inflammatory response and disrupt the long-term osteoconductive properties of CHX-HA delivery systems.
authors: Department of Applied Physics, Brazilian Center for Physics Research, Rua Dr. Xavier Sigaud, 150, Lab 203, Urca, 22290-180, Rio de Janeiro, RJ, Brazil, sorianososo@gmail.com.
authors: Carlos Alberto
authors: CA
authors: Soriano-Souza
authors: Andre L
authors: AL
authors: Rossi
authors: Elena
authors: E
authors: Mavropoulos
authors: Moema A
authors: MA
authors: Hausen
authors: Marcelo N
authors: MN
authors: Tanaka
authors: Mônica D
authors: MD
authors: Calasans-Maia
authors: Jose M
authors: JM
authors: Granjeiro
authors: Maria Helena M
authors: MH
authors: Rocha-Leão
authors: Alexandre M
authors: AM
authors: Rossi
mesh_terms: D016475:3T3 Cells; D000818:Animals; D000900:Anti-Bacterial Agents / Q000008:administration & dosage / Q000737:chemistry; D018407:Bacterial Physiological Phenomena / Q000187:drug effects*; D018786:Bone Substitutes / Q000008:administration & dosage* / Q000138:chemical synthesis; D002214:Capsules / Q000008:administration & dosage / Q000138:chemical synthesis; D002460:Cell Line; D049109:Cell Proliferation / Q000187:drug effects / Q000502:physiology; D002710:Chlorhexidine / Q000008:administration & dosage* / Q000737:chemistry; D003131:Combined Modality Therapy; D004058:Diffusion; D004343:Drug Implants / Q000008:administration & dosage* / Q000737:chemistry; D017886:Durapatite / Q000008:administration & dosage / Q000737:chemistry; D008297:Male; D051379:Mice; D010006:Osteoblasts / Q000166:cytology / Q000502:physiology*; D010012:Osteogenesis / Q000187:drug effects / Q000502:physiology*; D051381:Rats; D017208:Rats, Wistar
chemical_list: D000900:Anti-Bacterial Agents; D018786:Bone Substitutes; D002214:Capsules; D004343:Drug Implants; D017886:Durapatite; D002710:Chlorhexidine