Citotoxidade de diferentes concentrações de hipoclorito de sódio sobre osteoblastos humanos / Citotoxicity of different amounts of sodium hypochlorite on human cultured osteoblasts

Objetivo: Avaliar o efeito citotóxico de diferentes concentrações de hipoclorito de sódio sobre uma cultura de células de osteoblastos humanos (linhagem HOB). Métodos: Culturas confluentes de osteoblastos humanos (linhagem HOB) foram obtidas em meio de Dulbecco modificado, suplementado com 10% de soro fetal bovino e submetidas a incubações com hipoclorito de sódio (concentrações de 0,5; 1,0; 2,5 e 5,25%) durante trinta segundos. O grupo controle foi representado por células incubadas em fosfato de potássio. A avaliação da viabilidade celular foi realizada através do teste de exclusão com azul de Trypan, em triplicata. Durante o período de incubação, imagens foram registradas através de um microscópio óptico invertido, para avaliação da morfologia celular. Resultados: Verificou-se que no grupo controle havia 98,7% de células viáveis, morfologicamente normais, enquanto que nos grupos experimentais, células viáveis não foram observadas. A cinética de citotoxidade seguiu tendência dependente da concentração. Conclusão: O hipoclorito de sódio nas concentrações 0,5; 1,0; 2,5; 5,25%, incubado por trinta segundos em cultura de osteoblastos humanos é citotóxico.

Objective: To evaluate the cytotoxic effect of different amounts of sodium hypochlorite, on a culture of human osteoblastos (HOB) cells. Method: Cultures of human osteoblasts (HOB) in Dulbecco's modified Eagle's medium (DMEM) supplemented with 10% of bovine fetal serum were incubated in sodium hypochlorite (concentrations of 0.5; 1.0; 2.5 and 5.25%) for thirty seconds. The control group was represented by cells incubated in phosphate buffered saline (PBS). Cell viability was assessed by means of 0.4% trypan blue dye exclusion test, in triplicate. During the incubation period, images were recorded through an inverted optic microscope to evaluate the cellular morphology. Results: In the control group 98.7% of viable cells were verified, without morphology alterations, while no viable cells were observed in the experimental groups. The kinetics of cytotoxity was concentration-dependent. Conclusion: It was concluded that there was a cytotoxic effect on cultures of human osteoblasts incubated for thirty seconds in sodium hypochlorite in all concentrations (0.5; 1.0; 2.5 and 5.25%).

The redox potential interferes with the expression of laminin binding molecules in Bacteroides fragilis

The Bacteroides fragilis ATCC strain was grown in a synthetic media with contrasting redox potential (Eh) levels [reduced (-60 mV) or oxidised (+100mV)] and their adhesion capacity to extracellular matrix components was evaluated. The strain was capable of adhering to laminin, fibronectin, fibronectin + heparan sulphate and heparan sulphate. A stronger adherence to laminin after growing the strain under oxidising conditions was verified. Electron microscopy using ruthenium red showed a heterogeneous population under this condition. Dot-blotting analyses confirmed stronger laminin recognition by outer membrane proteins of cells cultured at a higher Eh. Using a laminin affinity column, several putative laminin binding proteins obtained from the cultures kept under oxidising (60 kDa, 36 kDa, 25 kDa and 15 kDa) and reducing (60 kDa) conditions could be detected. Our results show that the expression of B. fragilis surface components that recognise laminin are influenced by Eh variations.