Chlorhexidine-loaded hydroxyapatite microspheres as an antimicrobial delivery system and its effect on in vivo osteo-conductive properties.

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.

Evaluation of metronidazole-loaded poly(3-hydroxybutyrate) membranes to potential application in periodontitis treatment.

Guided tissue regeneration is a technique used for periodontium reconstruction. This technique uses barrier membranes, which prevent epithelial growth in the wound site and may also be used to release antibiotics, to protect the wound against opportunistic infections. Periodontal poly(3-hydroxybutyrate) membranes containing metronidazole (a drug used to help in infection control) were produced and characterized. The kinetic mechanism of the metronidazole delivery of leached and nonleached membrane as well as its cytotoxicity and structural integrity were evaluated. Poly(3-hydroxybutyrate) membranes containing 0.5-2 wt % of the drug and 20 wt % of the plasticizer were manufactured via compression molding. Based on morphological analysis, membranes loaded with 2% metronidazole were considered for detailed studies. The results revealed that metronidazole delivery by the leached membranes seemed to follow the Fick's law. Membranes were noncytotoxic. The amount of metronidazole delivered was in the range of the minimal inhibitory concentration for Porphyromonas gingivalis, and the membranes inhibited the proliferation of these bacteria. Besides, they maintained their mechanical resistance after 30 days of immersion in phosphate buffer at pH 7.4.

Avaliação funcional de implantes por mineralização óssea in vitro / Functional evaluation of implants by bone mineralization in vitrot

A evolução do projeto dos implantes osseointegráveis é resultado do desenvolvimento de diferentes tipos de estruturas em sua superfície. No entanto, ainda existe a necessidade de estudos para definir o tipo de superfície ideal. Esse trabalho discute métodos de avaliação da superfície de implantes que mostram o potencial de determinadas superfícies para induzir mineralização óssea in vitro, partir do uso de células mesenquimais progenitoras. Foram realizadas análises comparativas entre a topografia de implantes com e sem rugosidades nanométricas e o tipo de interação entre pré-osteoblastos semeados diretamente nesses implantes. Características distintas foram observadas em cada superfície.

Improvements in dental implants structure is the result of development of different types of geometrically intelligent surfaces, provided by the emergence of companies interested in innovation of these materials, however, there is still a need for studies to define the type of ideal surface. This work addresses an unprecedented discussion regarding implant surface evaluation methods, able to show the potential of certain areas to induce bone mineralization in vitro. From the use of mesenchymal progenitor cells, which have the capacity to respond to stimuli surface, comparative tests were performed between the topography implants with and without nano-roughness and the type of functional interaction between pre-osteoblasts seeded directly into these implants. Different characteristics of coating cells and mineralization niches on different surfaces were found.