Controlling the plaque biofilm

AIM

To examine the effect of supragingival plaque removal in conjunction with different periodontal therapies on subgingival plaque composition in different subject populations.

METHOD

Four different studies are presented which examined the effect of repeated removal of supragingival plaque performed by professionals or by tooth brushing on subgingival plaque composition. The studies were performed in different populations including chronic periodontitis, periodontal maintenance and refractory subjects. For all studies, each subject was examined for clinical parameters at up to 168 sites and subgingival plaque samples were taken from the mesial aspect of each tooth and examined for their content of specific bacterial species using checkerboard DNA-DNA hybridisation techniques.

RESULTS

Repeated supragingival plaque removal used in conjunction with scaling and root planing only or combined with other periodontal therapies resulted in improvements in clinical parameters as well as significant decreases in the counts of subgingival species, including those associated with periodontal disease aetiology. Meticulous tooth brushing provided similar clinical and microbial improvements.

CONCLUSIONS

Meticulous removal of supragingival plaque has beneficial effects on clinical parameters of periodontal disease and on the nature of the microbiota that colonises both above and below the gingival margin and appropriately has been a major focus in the prevention and control of dental diseases, particularly periodontal disease.

Purification and characterization of human cell--cell adhesion molecule 1 (C-CAM1) expressed in insect cells

The cell--cell adhesion molecule 1 (C-CAM1) plays an important role as a tumor suppressor for prostate cancer. Decreased expression of C-CAM1 was detected in prostate, breast, and colon carcinoma. Reexpression of C-CAM1 in prostate and breast cancer cell lines was able to suppress tumorigenicity in vivo. These observations suggest that C-CAM1 may be used as a marker for cancer detection or diagnosis. To generate monoclonal antibodies specific to C-CAM1, we have overexpressed full-length human C-CAM1 in Sf9 cells using a baculovirus expression system. The protein was purified 104-fold using nickel affinity chromatography. About 0.4 mg purified C-CAM1 was obtained from 200 mg of infected cells. When the purified protein was digested with peptidyl-N-glycosidase, the apparent mobility of the protein on SDS--PAGE changed from 90 to 58 kDa, which is close to the molecular weight predicted from the cloned cDNA sequence. This observation suggests that C-CAM1 was glycosylated on asparagine residues when expressed in Sf9 cells. Western blotting and internal protein sequencing analysis confirmed that the purified protein is human C-CAM1. Biochemical and functional assays indicate that this protein expressed in Sf9 cells displays characteristics similar to those of native protein, including adhesion function and glycosylation modification. Using this protocol, sufficient quantity of this protein can be produced with purity suitable for monoclonal antibody generation and biochemical study.

Targeted antimicrobial photochemotherapy

This study explores a new approach for antimicrobial therapy with light activation of targeted poly-L-lysine (pL)-chlorin e6 (ce6) conjugates. The goal was to test the hypothesis that these conjugates between pL and ce6 would efficiently target photodestruction towards gram-positive (Actinomyces viscosus) and gram-negative (Porphyromonas gingivalis) oral species while sparing an oral epithelial cell line (HCPC-1). Conjugates of ce6 with pL (average molecular weight, 2,000) having a positive, neutral, or negative charge were prepared. Illumination with red light (lambdamax = 671 nm) from a diode array produced a dose-dependent loss of CFU from the bacteria, under conditions that did not affect the viability of the epithelial cells. For P. gingivalis, the cationic conjugate produced 99% killing, while the neutral conjugate killed 91% and the anionic conjugate killed 76% after 1 min of incubation and exposure to red light for 10 min. For A. viscosus, the cationic conjugate produced >99.99% killing while HCPC-1 cells remained intact. The importance of the positive charge was shown by the effectiveness of ce6-monoethylenediamine monoamide (a monocationic derivative of ce6) in killing both bacteria. The clinically employed benzoporphyrin derivative under the same conditions killed epithelial cells while leaving P. gingivalis relatively unharmed. A mixture of ce6 with pL did not show phototoxicity comparable with that of the cationic conjugate. These results were explained by the selective uptake of the conjugates by bacteria (20- to 100-fold) compared to that by mammalian cells, while free ce6 showed much less selectivity for bacteria (5- to 20-fold). The data suggest that the cationic pL-ce6 conjugate may have an application for the photodynamic therapy of periodontal disease.