The effect of the source and the concentration of polymers on the release of chlorhexidine from mucoadhesive buccal tablets.

In the current work, two groups of chlorhexidine mucoadhesive buccal tablets were prepared, using either rod or irregularly-shaped spherical particles of hydroxypropyl methylcellulose and different ratios of poloxamer 407 (P407). The tablets were designed to release the drug over two hours. Their physicochemical properties and drug release profiles were investigated. The impact on dry granulation, the ex-vivo mucoadhesion, the swelling index, the morphology of swollen tablets and the drug release kinetic were investigated. Drug-polymers chemical interaction was studied using Fourier Transforms Infrared Spectroscopy (FTIR) and differential scanning calorimetry (DSC). Due to different particle shapes, the preparation of dry granules required a 40 KN force for rod-shaped particles compared to 10 KN for the irregularly-shaped spherical particles. All formulations showed at least two-hours residence time using ex-vivo mucoadhesion. Statistically, there was no significant difference in the swelling index, drug release nor its kinetic for both groups. However, the microscopical morphology of the swollen tablet and the size of the pores were affected by particle shape. Increasing the ratio of P407 to 62.5% resulted in a pronounced increase in drug release from around 60% to >90% after two hours. Following the FTIR and DSC analyses, no chemical interaction was noted apart from the steric hindrance effect of P407, which was observed even with the physical mixtures.

Essential oils and metal ions as alternative antimicrobial agents: a focus on tea tree oil and silver.

The increasing occurrence of hospital-acquired infections and the emerging problems posed by antibiotic-resistant microbial strains have both contributed to the escalating cost of treatment. The presence of infection at the wound site can potentially stall the healing process at the inflammatory stage, leading to the development of a chronic wound. Traditional wound treatment regimes can no longer cope with the complications posed by antibiotic-resistant strains; hence, there is a need to explore the use of alternative antimicrobial agents. Pre-antibiotic compounds, including heavy metal ions and essential oils, have been re-investigated for their potential use as effective antimicrobial agents. Essential oils have potent antimicrobial, antifungal, antiviral, anti-inflammatory, antioxidant and other beneficial therapeutic properties. Similarly, heavy metal ions have also been used as disinfecting agents because of their broad spectrum activities. Both of these alternative antimicrobials interact with many different intracellular components, thereby resulting in the disruption of vital cell functions and eventually cell death. This review will discuss the application of essential oils and heavy metal ions, particularly tea tree oil and silver ions, as alternative antimicrobial agents for the treatment of chronic, infected wounds.

Characterisation and in vitro antimicrobial activity of biosynthetic silver-loaded bacterial cellulose hydrogels.

Wounds that remain in the inflammatory phase for a prolonged period of time are likely to be colonised and infected by a range of commensal and pathogenic microorganisms. Treatment associated with these types of wounds mainly focuses on controlling infection and providing an optimum environment capable of facilitating re-epithelialisation, thus promoting wound healing. Hydrogels have attracted vast interest as moist wound-responsive dressing materials. In the current study, biosynthetic bacterial cellulose hydrogels synthesised by Gluconacetobacter xylinus and subsequently loaded with silver were characterised and investigated for their antimicrobial activity against two representative wound infecting pathogens, namely S. aureus and P. aeruginosa. Silver nitrate and silver zeolite provided the source of silver and loading parameters were optimised based on experimental findings. The results indicate that both AgNO3 and AgZ loaded biosynthetic hydrogels possess antimicrobial activity (p < .05) against both S. aureus and P. aeruginosa and may therefore be suitable for wound management applications.

Strategies for antimicrobial drug delivery to biofilm.

Biofilms are formed by the attachment of single or mixed microbial communities to a variety of biological and/or synthetic surfaces. Biofilm micro-organisms benefit from many advantages of the polymicrobial environment including increased resistance against antimicrobials and protection against the host organism's defence mechanisms. These benefits stem from a number of structural and physiological differences between planktonic and biofilm-resident microbes, but two main factors are the presence of extracellular polymeric substances (EPS) and quorum sensing communication. Once formed, biofilms begin to synthesise EPS, a complex viscous matrix composed of a variety of macromolecules including proteins, lipids and polysaccharides. In terms of drug delivery strategies, it is the EPS that presents the greatest barrier to diffusion for drug delivery systems and free antimicrobial agents alike. In addition to EPS synthesis, biofilm-based micro-organisms can also produce small, diffusible signalling molecules involved in cell density-dependent intercellular communication, or quorum sensing. Not only does quorum sensing allow microbes to detect critical cell density numbers, but it also permits co-ordinated behaviour within the biofilm, such as iron chelation and defensive antibiotic activities. Against this backdrop of microbial defence and cell density-specific communication, a variety of drug delivery systems have been developed to deliver antimicrobial agents and antibiotics to extracellular and/or intracellular targets, or more recently, to interfere with the specific mechanisms of quorum sensing. Successful delivery strategies have employed lipidic and polymeric-based formulations such as liposomes and cyclodextrins respectively, in addition to inorganic carriers e.g. metal nanoparticles. This review will examine a range of drug delivery systems and their application to biofilm delivery, as well as pharmaceutical formulations with innate antimicrobial properties such as silver nanoparticles and microemulsions.

Sensitivity and specificity of the empirical lymphocyte genome sensitivity (LGS) assay: implications for improving cancer diagnostics.

Lymphocyte responses from 208 individuals: 20 with melanoma, 34 with colon cancer, and 4 with lung cancer (58), 18 with suspected melanoma, 28 with polyposis, and 10 with COPD (56), and 94 healthy volunteers were examined. The natural logarithm of the Olive tail moment (OTM) was plotted for exposure to UVA through 5 different agar depths (100 cell measurements/depth) and analyzed using a repeated measures regression model. Responses of patients with cancer plateaued after treatment with different UVA intensities, but returned toward control values for healthy volunteers. For precancerous conditions and suspected cancers, intermediate responses occurred. ROC analysis of mean log OTMs, for cancers plus precancerous/suspect conditions vs. controls, cancer vs. precancerous/suspect conditions plus controls, and cancer vs. controls, gave areas under the curve of 0.87, 0.89, and 0.93, respectively (P<0.001). Optimization allowed test sensitivity or specificity to approach 100% with acceptable complementary measures. This modified comet assay could represent a stand-alone test or an adjunct to other investigative procedures for detecting cancer.

Greenbottle (Lucilia sericata) larval secretions delivered from a prototype hydrogel wound dressing accelerate the closure of model wounds.

The resurgence of larval biotherapy as a debridement tool in wound management has been accompanied by several clinical reports highlighting concomitant tissue regeneration. Studies employing in vitro cell motility assays have found that purified excretory/secretory (ES) products from Greenbottle larvae (blowfly, Lucilia sericata) are motogenic for human dermal fibroblasts when used as a supplement in culture media. The objective of the present study was to determine whether ES delivered using a prototype hydrogel wound dressing induced similar motogenic effects on fibroblastic (3T3) and epithelial cells (HaCaTs) comprising a scratched-monolayer wound model. Quantitative analysis by MTT assay failed to detect significant mitogenic effects of ES on either cell type. Quantitative image analysis revealed that ES exposure markedly accelerated wound closure through a motogenic effect on both fibroblasts and keratinocytes. Quantitative histochemical analysis detected significantly higher phosphotyrosine (pTyr) expression in ES-exposed cell cultures than in controls; moreover immunocytochemistry revealed conspicuously raised levels of pTyr expression in cells located at the wound margin. By attenuation with a panel of enzyme inhibitors these effects were attributed to the protease components of ES. The present results suggest that controlled delivery of ES as a follow-up to maggot debridement therapy may be an effective therapeutic option for stimulation of tissue regeneration in wound management.

Microengineered surface topography facilitates cell grafting from a prototype hydrogel wound dressing with antibacterial capability.

Skin wounds derive therapeutic benefit from redeployment of dermal tissues, whether as split-thickness allo- and autografts or as biological dressings comprising cultured cells. However, the clinical outcome is strongly influenced by the techniques used for cell/tissue grafting and also the microbiological status of the wound. Here we report that microtopography incorporated into the surface of a novel polymeric material, derivatized with fibronectin to promote attachment and encourage motility, improved the efficiency of cell transfer onto de-epithelialized human skin ex vivo. The microtopography had two functions, first as a conduit for migrating cells to cross between the vehicle and recipient surface and second to shield adherent cells from destruction by mechanical shearing during handling and application. Quantitative analysis showed that topographic projections (columns) rather than recesses (pits) in the hydrogel surface achieved the highest efficiency of cell transfer. In order to address the crucial relevance of microbiological contamination to the success of wound grafting, the effect of iodine on several common bacterial pathogens was examined using an XTT+C(Q10) kinetic cell viability assay. Increasing concentrations of iodine initially stressed and after 0.5% v/v were subsequently bacteriocidal for Gram-negative Pseudomonas aeruginosa and Escherichia coli and Gram-positive Bacillus subtillis and Staphylococcus aureus. Slightly higher doses of iodine (approx 1-1.5% v/v) were required to kill HaCaT cells outright, but for both pro- and eukaryotes the major determinant of cytotoxicity was absolute dose rather than duration of exposure. Iodine delivered by the hydrogel at low concentration was bacteriostatic but not apparently cytotoxic to epithelial cells as measured by MTT end-point cell viability assay. Zone of inhibition studies confirmed that bacteriocidal quantities of neomycin, phenol red, and silver could also be delivered using the same hydrogel. This research suggests that grafting cell-based biological dressings to wounds using a topographically modified hydrogel dressing capable of simultaneous reducing the microbiological threat to a successful outcome may be a realistic clinical proposition.

Acute and remitting painful diabetic polyneuropathy: a comparison of peripheral nerve fibre pathology.

The cause of the neuropathic pain that is experienced by some patients with diabetic neuropathy remains to be established. Early neuropathological reports, based on comparisons between diabetic patients and non-diabetic control subjects, emphasised associations between pathological changes in specific classes of peripheral nerve fibre and the presence of pain. By making comparisons with more appropriate control subjects, namely diabetic patients without neuropathic pain, more recent studies have found that there are few clear morphological correlates for this type of pain. To investigate this further, we have conducted a detailed morphometric study of sural nerve biopsies from six diabetic patients, four with active acute painful neuropathy and two with recent remission from the same condition. Normal values for the neuropathological parameters were obtained from six non-diabetic control subjects. Teased fibre analysis showed that similar axonal and Schwann cell abnormalities were present in both groups of diabetic patients. Electron microscopical studies revealed that evidence of both myelinated and unmyelinated fibre degeneration and regeneration was also present in the nerves of all diabetic patients, irrespective of whether they had pain. Within the constraints of interpreting results from small numbers of patients, our observations suggested that remission from pain might be associated with a less abnormal axon/Schwann cell calibre ratio, more successful myelinated fibre regeneration and less active unmyelinated fibre regeneration. However, the inescapable finding of this study was, in fact, the similarity in the nerve fibre pathology in diabetic patients with active and remitting painful neuropathy. We conclude that the occurrence of nerve fibre degeneration and regeneration is in itself unlikely to be sufficient to account fully for diabetic neuropathic pain. However, it is conceivable that events occurring during certain stages in the pathological cycle of degeneration and regeneration create the necessary circumstances which lead to pain.