OBJECTIVETo study the influence of the quorum sensing inhibitor brominated furanone on Porphyromonas gingivalis (P. gingivalis) biofilm formation.

METHODSDoubling dilution method was used to determine the minimal inhibition concentration (MIC) of brominated furanone on P. gingivalis. Absolute ethyl alcohol added in P. gingivalis bacterial suspension was used as the negative control, while P. gingivalis bacterial suspension as blank control. The influences of 1/4MIC, 1/2MIC, MIC, 2MIC of brominated furanone on P. gingivalis biofilm formation were studied by the optical density determination and scanning electron microscope (SEM).

RESULTSFour groups of brominated furanone with different concentrations were shown to inhibit P. gingivalis biofilm formation. With the increased concentration of brominated furanone, optical density of P. gingivalis suspension decreased. The biofilm structures of 1/4MIC group, 1/2MIC group and MIC group were loose. Only scattered P. gingivalis cells but no biofilm structure was seen in 2MIC group.

CONCLUSIONBrominated furanone could inhibit P. gingivalis biofilm formation without the influence on bacterial growth. The future application of this chemical compound may provide a new possibility for the antimicrobial treatment of periodontal disease.

Biofilms ; Furans ; Porphyromonas gingivalis ; Quorum Sensing

OBJECTIVETo determine the optimal method for separating neutrophils for studying neutrophil polarization.

METHODSHuman neutrophil was separated from healthy human peripheral blood by Percoll density gradient centrifugation and Dextran sedimentation. The cell polarization, purity and activity of the neutrophils were determined, and F-actin polymerization and [Ca2+]i were analyzed.

RESULTSNo significant difference was found in cell polarization, purity and activity of the human neutrophils separated by Dextran sedimentation and Percoll density gradient centrifugation (P>0.05), but F-actin polymerization was inhibited in PMNs separated by Dextran sedimentation, and the peak value of [Ca2+]i was decreased by 25% in PMNs separated by Dextran sedimentation compared to the cells separated by Percoll density gradient centrifugation.

CONCLUSIONSBoth Percoll density gradient centrifugation and Dextran sedimentation can be used for isolating human neutrophils to study cell polarization, but the former method allows better isolation. Dextran sedimentation can be considered when a large number of neutrophils need to be separated.

Actins ; Cell Polarity ; Cell Separation ; Centrifugation, Density Gradient ; methods ; Humans ; Leukocyte Count ; Neutrophils ; cytology ; Povidone ; Silicon Dioxide