Biodegradation of different synthetic hydrogels made of polyethylene glycol hydrogel/RGD-peptide modifications: an immunohistochemical study in rats

Aim: The aim of the present study was to investigate the pattern of biodegradation of different polyethylene glycol (PEG) hydrogel/RGD-peptide modifications in rats. Material and methods: Two different hydrogels were employed: (i) a combination of four-arm PEG-thiol, M(n)=2.3 kDa, and eight-arm PEG-acrylate, M(n)=2.3 kDa (PEG1); and (ii) a combination of four-arm PEG-thiol, M(n)=2.3 kDa, and four-arm PEG-acrylate, M(n)=15 kDa (PEG2). Both PEG1 and PEG2 were either used alone or combined with a nine amino acid cys-RGD peptide (RGD). A non-cross-linked porcine type I and III collagen membrane [BioGide((R)) (BG)] served as control. Specimens were randomly allocated in unconnected subcutaneous pouches separated surgically on the back of 60 wistar rats, which were divided into six groups (1, 2, 4, 8, 16, and 24 weeks). Specimens were prepared for histological (tissue integration, foreign body reactions, biodegradation) and immunohistochemical (angiogenesis) analysis. Results: All materials investigated revealed unimpeded and comparable tissue integration without any signs of foreign body reactions. While BG exhibited transmembraneous blood vessel formation at 1 week, all PEG specimens were just surrounded by a well-vascularized connective tissue. The hydrolytic disruption of PEG1 and PEG1/RGD specimens was associated with an ingrowth of blood vessels at 4 weeks. Biodegradation times were highest for PEG1 (24 weeks)>PEG1/RGD (16 weeks)>BG (4 weeks)>PEG2=PEG2/RGD (2 weeks). Conclusion: Within the limits of the present study, it was concluded that (i) all materials investigated revealed a high biocompatibility and tissue integration, and (ii) hydrogel biodegradation was dependent on PEG composition. To cite this article: Herten M, Jung RE, Ferrari D, Rothamel D, Golubovic V, Molenberg A, Hämmerle CHF, Becker J, Schwarz F. Biodegradation of different synthetic hydrogels made of polyethylene glycol hydrogel/RGD-peptide modifications: an immunohistochemical study in rats

Selective medium for the isolation of Haemophilus aphrophilus from the human periodontium and other oral sites and the low proportion of the organism in the oral flora

We developed a medium for the selective recovery of Haemophilus aphrophilus. The medium, designated TSBVF, was composed of 4% tryptic soy agar, 10% heat-inactivated horse serum, 75 micrograms of bacitracin per ml, 5 micrograms of vancomycin per ml, and 50 micrograms of sodium fluoride per ml. TSBVF yielded a threefold higher recovery of oral H. aphrophilus than did chocolate agar with 75 micrograms of bacitracin per ml, which is a medium routinely used to diagnose human Haemophilus infections. H. aphrophilus and the few contaminating organisms on TSBVF were readily distinguished on the basis of colony morphology. The H. aphrophilus isolates exhibited variable fermentation of raffinose and dextrin but otherwise were biochemically similar. In a clinical study, H. aphrophilus was frequently recovered from supragingival plaque and saliva and occasionally from buccal mucosa and the tonsils. It was also isolated from 29 of 56 subgingival sites in 11 of 14 subjects. Its proportion of the subgingival microflora averaged 0.13% for healthy periodontal sites, 0.05% for adult periodontitis lesions, and 0.03% for localized juvenile periodontitis lesions. We concluded that H. aphrophilus is an indigenous bacterium of the human oral cavity. It occurs in low proportions in subgingival plaque and plays no apparent role in advanced periodontal disease in humans.</jats:p

Use of adhesin-specific monoclonal antibodies to identify and localize an adhesin on the surface of Capnocytophaga gingivalis DR2001

Monoclonal antibodies capable of inhibiting coaggregation between Capnocytophaga gingivalis DR2001 and Actinomyces israelii PK16 were used to identify the adhesin on C. gingivalis that mediates the interaction. The monoclonal antibodies were used to demonstrate that a 140-kilodalton polypeptide found in the outer membrane of C. gingivalis was the adhesin responsible for coaggregation. A coaggregation-defective mutant that was unable to coaggregate with A. israelii lacked this large polypeptide. The monoclonal antibodies were also used to estimate the number of binding sites on the surfaces of individual cells and show how the adhesin molecules were arranged on the outer membrane. Values of between 220 and 280 were obtained for the number of adhesin molecules per cell. Immunoelectron microscopy performed with the monoclonal antibodies revealed that the adhesin molecules were arranged nonuniformly on the bacterial surface and occurred singly, in pairs, and in small clusters.</jats:p

Prostaglandin E release from human monocytes treated with lipopolysaccharides isolated from Bacteroides intermedius and Salmonella typhimurium: potentiation by gamma interferon

The purpose of this investigation was to examine gamma interferon potentiation of lipopolysaccharide (LPS) responses in human monocytes by using phenol-water-extracted (unfractionated) and highly purified LPS preparations isolated from Bacteroides intermedius and Salmonella typhimurium. Phenol-water-extracted LPS preparations from these bacteria were further purified by chromatography over Sepharose-CL-4B. LPS enrichment in pooled column fractions was assessed by sodium dodecyl sulfate-polyacrylamide gel electrophoresis and quantitation of hydroxy-fatty acid and 2-keto-3-deoxyoctulosonic acid content, protein contamination, and anthrone-reactive material. Monocyte stimulation by LPS, measured as prostaglandin E (PGE) release, was assessed with and without gamma interferon treatment. Cells were either treated simultaneously with gamma interferon and LPS or pretreated with gamma interferon prior to LPS stimulation. PGE release from counterflow-isolated monocytes was quantitated during the 0- to 24-h and 24- to 48-h culture intervals. Contrary to previous results from this laboratory, phenol-water-extracted LPS preparations from B. intermedius and S. typhimurium were similar in their capacities to stimulate PGE release from monocytes. Molecular sieve chromatography was found to remove substantial amounts of high-molecular-weight polysaccharide contaminants only from the B. intermedius LPS but did not significantly alter the potency of either B. intermedius or S. typhimurium LPS. Gamma interferon cotreatment did not potentiate the release of PGE with any of the LPS preparations tested. However, 24-h pretreatment of monocytes with gamma interferon followed by a 24-h exposure to LPS resulted in significant potentiation of PGE release over LPS alone. In addition, B. intermedium preparations were approximately threefold more potent than similarly prepared LPS isolates from S. typhimurium following gamma interferon pretreatment. These results indicate that gamma interferon can selectively potentiate the effects of B. intermedius LPS in human monocyte isolates.</jats:p