Iain Allan

Antibacterial activity of particulate Bioglass® against supra- and subgingival bacteria

Particulate Bioglass is a bioactive material used in the repair of periodontal defects. This material undergoes a series of surface reactions in an aqueous environment which lead to osseointegration. The aim of this study was to determine whether these reactions exerted an antibacterial effect on a range of oral bacteria. Streptococcus sanguis, Streptococcus mutans and Actinomyces viscosus were suspended in nutrient broth (NB), artificial saliva (AS) or Dulbeccos modified eagle medium plus 10% foetal calf serum (DMEM + 10%FCS), with or without particulate Bioglass. All bacteria showed reduced viability following exposure to Bioglass in all the media after 1 h. This antibacterial effect increased after 3 h. Porphyromonas gingivalis, Fusobacterium nucleatum, Prevotella intermedia and Actinobacillus actinomycetemcomitans were suspended in either BM broth or 40% horse serum (HS) in RPMI. A considerable reduction in viability was observed with all bacteria tested, in both media, compared to inert glass controls. In further experiments it was found that the viability of S. sanguis was significantly reduced following exposure to NB pre-incubated with Bioglass. Additionally, it was found that neutralisation of this highly alkaline solution eliminated the antibacterial effect. Moreover, a solution of NB and NaOH (of equivalent pH) exerted an antibacterial effect of similar magnitude to that of the solution pre-incubated with Bioglass. Thus, particulate Bioglass exerts an antibacterial effect on certain oral bacteria, possibly by virtue of the alkaline nature of its surface reactions. This may reduce bacterial colonisation of its surface in vivo.

Gelatin-fibrinogen cryogel dermal matrices for wound repair: Preparation, optimisation and in vitro study.

Macroporous sponge-like gelatin-fibrinogen (Gl-Fg) scaffolds cross-linked with different concentrations (0.05-0.5%) of glutaraldehyde (GA) were produced using cryogelation technology, which allows for the preparation of highly porous scaffolds without compromising their mechanical properties, and is a more cost-efficient process than freeze-drying. The produced Gl-Fg-GA(X) scaffolds had a uniform interconnected open porous structure with a porosity of up to 90-92% and a pore size distribution of 10-120 microm. All of the obtained cryogels were elastic and mechanically stable, except for the Gl-Fg-GA(0.05) scaffolds. Swelling kinetics and degradation rate, but not the porous structure of the cryogels, were strongly dependent on the degree of cross-linking. A ten-fold increase in the degree of cross-linking resulted in an almost 80-fold decrease in the rate of degradation in a solution of protease. Cryogels were seeded with primary dermal fibroblasts and the densities observed on the surface, plus the expression levels of collagen types I and III observed 5 days post-seeding, were similar to those observed on a control dermal substitute material, Integra. Fibroblast proliferation and migration within the scaffolds were relative to the GA content. Glucose consumption rate was 3-fold higher on Gl-Fg-GA(0.1) than on Gl-Fg-GA(0.5) cryogels 10 days post-seeding. An enhanced cell motility on cryogels with reducing GA crosslinking was obtained after long time culture. Particularly marked cell infiltration was seen in gels using 0.1% GA as a crosslinker. The scaffold started to disintegrate after 42 days of in vitro culturing. The described in vitro studies demonstrated good potential of Gl-Fg-GA(0.1) scaffolds as matrices for wound healing.

THE USE OF CONFOCAL LASER SCANNING MICROSCOPY TO ASSESS THE POTENTIAL SUITABILITY OF 3D SCAFFOLDS FOR TISSUE REGENERATION, BY MONITORING EXTRA‐CELLULAR MATRIX DEPOSITION AND BY QUANTIFYING CELLULAR INFILTRATION AND PROLIFERATION

The great many varieties of dermal regeneration materials currently being developed requires that sound in vitro assessments of their potential to be infiltrated with host cells are needed prior to any in vivo studies. The biocompatibility of scaffolds is conventionally determined by indirect biochemical assays as measures of cell number/viability within these materials. A disadvantage of these methods is the failure to provide information pertaining to the spatial distribution of cells in situ. In the case of dermal regeneration, if cells are only present in appreciable numbers on the outer portion of a scaffold, then critical aspects such as extra‐cellular matrix (ECM) production and vascularization will be limited, and the likelihood of successful tissue regeneration low. Thus, direct enumeration of cells within scaffolds, with respect to spatial distribution and time, is required to adequately assess the potential biocompatibility. In this article we demonstrate a systematic approach to the quantification of infiltration and proliferation of primary human dermal fibroblasts into the dermal regeneration scaffold, Integra® (the most frequently used dermal regeneration template in burns patients), using confocal laser scanning microscopy (CLSM). Scaffold samples were placed on top of confluent cell layers and infiltrated by cells migrating from the culture dish against gravity. Cells were then enumerated (by nuclear staining) with respect to their location within the scaffold and over a time period of up to 28 days. Large increases in cell numbers were observed on the surface of the scaffolds, together with measurable increases in cell numbers within their interiors. We also describe the immunofluorescent staining of fibroblasts and ECM components as well as the subsequent use of CLSM to qualitatively assess the potential for scaffold re‐modeling. Of particular note was the cellular deposition of a “front” of fibronectin matching the maximum extent of cell infiltration at each time point. We suggest that this key ECM component is a useful indicator of the extent of cellular re‐modeling of a biomaterial.

A Comprehensive Review of Topical Odor-Controlling Treatment Options for Chronic Wounds.

The process of wound healing is often accompanied by bacterial infection or critical colonization, resulting in protracted inflammation, delayed reepithelization, and production of pungent odors. The malodor produced by these wounds may lower health-related quality of life and produce psychological discomfort and social isolation. Current management focuses on reducing bacterial activity within the wound site and absorbing malodorous gases. For example, charcoal-based materials have been incorporated into dressing for direct adsorption of the responsible gases. In addition, multiple topical agents, including silver, iodine, honey, sugar, and essential oils, have been suggested for incorporation into dressings in an attempt to control the underlying bacterial infection. This review describes options for controlling malodor in chronic wounds, the benefits and drawbacks of each topical agent, and their mode of action. We also discuss the use of subjective odor evaluation techniques to assess the efficacy of odor-controlling therapies. The perspectives of employing novel biomaterials and technologies for wound odor management are also presented.

An in vitro evaluation of fibrinogen and gelatin containing cryogels as dermal regeneration scaffolds

Macroporous cryogels containing mixtures of two key components of the dermal extracellular matrix, fibrinogen and collagen-derived gelatin, were evaluated for use as dermal tissue regeneration scaffolds. The infiltration of human dermal fibroblasts into these matrices was quantitatively assessed in vitro using a combination of cell culture and confocal laser scanning microscopy. The extent of cellular infiltration, as measured by the number of cells per distance travelled versus time, was found to be positively correlated with the fibrinogen concentration of the cryogel scaffolds; a known potentiator of cell migration and angiogenesis within regenerating tissue. An analysis of the proteins expressed by infiltrating fibroblasts revealed that the cells that had migrated into the interior portion of the scaffolds expressed predominantly F-actin along their cytoplasmic stress fibres, whereas those present on the periphery of the scaffolds expressed predominantly α-smooth muscle actin, indicative of a nonmotile, myofibroblast phenotype associated with wound contraction. In conclusion, the cryogels produced in this study were found to be biocompatible and, by alteration of the fibrinogen content, could be rendered more amenable to cellular infiltration.

Metal chelation by a plant lignan, secoisolariciresinol diglucoside

Abstract Secoisolariciresinol diglucoside (SDG) is a polyphenolic phytoestrogen which is particularly abundant in flaxseed. As a diphenolic compound, SDG is expected to function as a metal chelating ligand. The affinity of SDG for metal cations was determined using a mass spectrometric approach. Experiments yielded equilibrium constants in aqueous solution for SDG·Ca2+, SDG·Cu2+, SDG·Pb2+, SDG·Ni2+, SDG·Fe2+ and SDG·Ag+ of 20.34, 5.99, 4.26, 2.77, 2.46 and 1.90, respectively. These values are consistent with those determined for plant phenolics. Semiempirical calculations for the SDG metal complexes yield an insight into their likely structures.Graphical Abstract.

Susceptibility of microcosm subgingival dental plaques to lethal photosensitization

Photodynamic therapy (PDT) offers potential as a non-invasive treatment of periodontal disease. In this study, microcosm biofilmswere grown in vitro under conditions designed to mimic subgingival plaques typically found in patients with periodontitis. To investigate potential PDT modalities, biofilms were exposed to light from a helium/neon laser in conjunction with a photosensitizer, toluidine blue O (TBO), at varying output and concentration, respectively. To determine cytotoxic effects, viability profiling was undertaken on whole biofilms using standard plating methods, and on horizontal cross-sections of biofilms using confocal laser-scanning microscopy (CLSM) in conjunction with a differential viability stain. A light energy dose of 94.5 J in combination with 81.7 µM TBO was found to be optimal, achieving significant kills of over 97%. CLSM enabled visualization of the effects of PDT in three dimensions. Viability profiling of the CLSM images revealed that lethal photosensitization was most effective in the upper layers of biofilm. PDT was found to reduce the viability of subgingivally modelled plaques in vitro by a magnitude similar to that of chlorhexidine digluconate, which is commonly used to treat periodontal disease. The findings of this study indicate that PDT may be an effective alternative to conventional modalities in the treatment of periodontal disease.

Activated carbon-plasticised agarose composite films for the adsorption of thiol as a model of wound malodour

Conditions such as diabetes, cardiovascular disease and long-term immobilisation can precipitate the development of chronic dermal ulcers. Such wounds are associated with inflammation and bacterial contamination which in turn can lead to the liberation of offensive odours that cause patient embarrassment and, in some instances, social isolation. Activated carbon-containing dressings have been used to manage the odours from such wounds. However, these can be bulky and can become fouled by wound exudate. Agarose is a natural polysaccharide derived from seaweed that forms brittle free-standing films that can be made pliable by addition of a plasticiser. In this study, activated carbon-containing plasticised agarose films were evaluated for their ability to sequester thiol-containing molecules from solution and the gaseous phase. The water vapour transmission rate was also evaluated to determine the potential breathability of these films should they be considered for application to the skin. It was found that the adsorption of thiols was directly proportional to the activated carbon content of the films. Water vapour was found to pass relatively freely through the films indicating that sweat-induced tissue maceration would be unlikely to occur if applied clinically. In conclusion, activated carbon-containing plasticised agarose films have some potential in the sequestration of malodourous molecules such as those liberated from chronic dermal wounds.Graphical abstract

Does flax Linum usitatissimum positively impact populations of declining farmland birds

Capsule Skylarks and Yellowhammers generally did not preferentially establish territories in flax relative to autumn-sown crops on lowland farmland. Aims To investigate the biodiversity value of flax using farmland birds as indicator species. Methods Field surveys took place annually between 2009 and 2011 in Northern France, during the breeding season. Fifteen 1 km grid squares were surveyed using a grid-transect method during the periods of greatest avian activity. Territories were identified by the presence of singing males, which were assigned to crop types. Pairwise habitat comparisons were performed. Results Our results suggest that flax is not universally beneficial for Yellowhammers and Skylarks in our study area. However there were inter-specific differences in its use: Skylarks established more territories in flax than in oilseed rape, ploughed fields or improved grassland, whereas Yellowhammers mostly avoided flax fields in preference for grassland, ploughed fields and barley. Conclusion Overall, Skylarks and Yellowhammers did not preferentially establish territories in flax relative to autumn-sown crops, although some selection for flax by Skylarks was evident. Further work is required to: (a) quantify breeding success in flax relative to other crops and (b) investigate the effect of flax on territory densities of other species.