Bacterial morphotypes and early cellular responses in clinically infected and non-infected sites after combination therapy of guided tissue regeneration and allograft

Antimicrobial and Immunomodulatory Surface-Functionalized Electrospun Membranes for Bone Regeneration

Guided bone regeneration (GBR) is a surgical procedure utilizing occlusive membranes for providing space maintenance and enabling selective repopulation of the damaged area. While this technique is effective in regenerating bone, bacterial infiltration occurs frequently and can compromise the regenerative outcome. In this study, the authors describe the development and characterization of a GBR membrane made of medical grade polycaprolactone (mPCL) electrospun fibers with antibacterial and immunomodulatory properties. This is achieved by the immobilization of the antibiotic azithromycin into the membrane via a solvent evaporation technique leading to a sustained release of the drug over 14 d. In vitro testing shows that this controlled release of azithromycin is proficient at inhibiting the growth of Staphylococcus aureus for 14 d. Implantation of azithromycin loaded mPCL membrane in a rodent calvarial defect induces macrophage polarization toward the M2 phenotype after one week and results in significantly more bone regeneration eight weeks post-surgery. The results suggest that this antibacterial membrane should be effective at preventing infection and also impacts on the macrophage polarization enhancing bone regeneration. The drug loading technique developed in this study is simple, effective with a strong potential for clinical translation and can be applied to different types of scaffolds and implants for applications in craniofacial and orthopedics applications.

Antibacterial activity of chitosan-based matrices on oral pathogens

Chitosan is a well sought-after polysaccharide in biomedical applications due to its biocompatibility, biodegradability to non-toxic substances, and ease of fabrication into various configurations. However, alterations in the anti-bacterial properties of chitosan in various forms is not completely understood. The objective of this study was to evaluate the anti-bacterial properties of chitosan matrices in different configurations against two pathogens-Gram-positive Streptococcus mutans and Gram-negative Actinobacillus actinomycetemcomitans. Two-dimensional (2-D) membranes and three-dimensional (3-D) porous scaffolds were synthesized by air drying and controlled-rate freeze drying. Matrices were suspended in bacterial broths with or without lysozyme (enzyme that degrades chitosan). Influences of pore size, blending with Polycaprolactone (PCL, a synthetic polymer), and neutralization process on bacterial proliferation were studied. Transient changes in optical density of the broth, adhesion characteristics, viability, and contact-dependent bacterial activity were assessed. 3-D porous scaffolds were more effective in reducing the proliferation of S. mutans in suspension than 2-D membranes. However, no significant differences were observed on the proliferation of A. actinomycetemcomitans. Presence of lysozyme significantly increased the antibacterial activity of chitosan against A. actinomycetemcomitans. Pore size did not affect the proliferation kinetics of either species, with or without lysozyme. NaOH neutralization of chitosan increased bacterial adhesion whereas ethanol neutralization inhibited adhesion without lowering proliferation. Mat culture tests indicated that chitosan does not allow proliferation on its surface and it loses antibacterial activity upon blending with PCL. Results suggest that the chemical and structural characteristics of chitosan-based matrices can be manipulated to influence the interaction of different bacterial species.

Characterization and Antibacterial Effect of a Novel Nanocomposite Membrane

In this experiment, un-dried silver-hydroxyapatite-titania nanoparticles slurry was used to make membrane with Polyamide-66 by co-polymerization method. The morphology, chemical components and structures of the membrane were characterized by AAS, XRD, SEM and EDX. S. aureus, E. eoli, P.gingivalis, F.nucleatum and S.mutans were utilized to test the antibacterial effect. XRD results demonstrated that the membrane have characteristic diffraction peaks of pure HA. A homogeneous distribution of the Ca, P, Ti, and Ag element in the membrane was confirmed by EDX. Both surface and section showed porous structure which was confirmed by SEM and the holes size was average 20-30μm. The bacteria assay reflects to the antibacterial effect, 56.31 % of S. aureus and 50.10 % of E. eoli were killed after 24 hours incubation. However, 91.84 % of P. gingivalis, 90.64 % of F. nucleatum and 90.49 % of S. mutans were killed and pictures of SEM showed obviously fewer cells on the surface. So the nanocomposite membrane could be one of the bioactive materials with antibacterial properties for oral GBR technique.

Efficacy of controlled-release subgingival chlorhexidine to enhance periodontal regeneration

BACKGROUND

Periodontal regeneration success may be limited by placing bone grafts and membranes in infected sites. The objective of this study was to test the hypothesis that adjunctive subgingival administration of chlorhexidine gelatin bioresorbable chips enhances bone gain when used in conjunction with guided tissue regeneration.

METHODS

This was a single center, blinded, 2-arm parallel design study of 44 subjects with one or more sites with probing depth and clinical attachment loss > or = 5 mm following initial therapy and radiographic evidence of bone loss. The patients were randomly assigned to receive either chlorhexidine (CHX) chip or sham chip placement one week prior to regenerative therapy that included graft placement and site coverage with guided tissue membranes. Patients also received CHX or sham chip placement, per their randomization, adjunctively to scaling and root planing or maintenance procedures. Periodontal examinations were completed at baseline (8 weeks prior to surgery); 1 week prior to surgery; and at 3, 6, and 9 months postsurgery. The major outcomes for the study were changes in bone height and bone mass as measured from standardized radiographs used for quantitative digital subtraction radiography over the 11-month study period.

RESULTS

Subjects receiving sham chip placement gained a mean bone height of 1.49 +/- 0.22 mm, while patients receiving the CHX chips gained significantly more bone height (3.54 +/- 0.45 mm; P<0.001). Similarly, subjects receiving CHX chips as an adjunct gained significantly more bone mass (5.57 +/- 0.69 mg; P<0.001) than the standard therapy (2.59 +/- 0.34 mg).

CONCLUSIONS

These pilot results indicate that locally delivered, controlled-release antimicrobial treatment may improve the amount of bone gain during guided tissue regeneration procedures. These data support the evidence that infection control is an important variable in successful regeneration.