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Biomedical subjects

R E Burrell

Publications and source records attributed to R E Burrell.

12 recordsLinked to original sources
PubMed2005

Impact of heat on nanocrystalline silver dressings. Part I: Chemical and biological properties.

Thermal stability of heat-treated nanocrystalline silver dressings was investigated using chemical techniques and biological assays. Dressings were heat-treated for 24h at temperatures from 23 to 110 degrees C. Bactericidal efficacy of heat-treated dressings was measured using a log reduction assay, while antibacterial longevity was determined via plate-to-plate transfer corrected zone of inhibition assays. Over the temperature range tested, biological activity dropped from excellent to negligible. Biological longevity results showed that controlled release properties of the dressings were significantly reduced by heat treatments above 75 degrees C. These data illustrate nanocrystalline silver sensitivity to heat. Further, it was clear that dressing efficacy is determined by total available soluble silver, not total silver in the dressing. It was determined that the quantity of soluble silver decreased significantly with increased heat treatment temperatures. These results should be considered in developing new nanocrystalline drug delivery systems.

Anti-Bacterial Agents↗
PubMed2005

Impact of heat on nanocrystalline silver dressings. Part II: Physical properties.

This work explores the effects of elevated temperature on the physical and chemical properties of nanocrystalline silver, and relates it to previously observed thermally induced changes in biological activity [Taylor PL et al. Biomaterials, in press, doi:10.1016/j.biomaterials.2005.05.040]. Microstructural evolution of nanocrystalline silver dressings, heat-treated for 24 h at temperatures from 23 to 110 degrees C, was studied in detail using X-ray diffraction (XRD), scanning electron microscopy (SEM), and X-ray photoelectron spectroscopy (XPS). These analyses indicated that silver nanocrystalline coatings undergo significant changes in structure when exposed to elevated temperature. XRD analysis showed a rapid increase in crystallite size above 75 degrees C along with decomposition of crystalline silver oxide (Ag2O) at the onset of crystallite growth. SEM imaging showed a loss of fine features and sintering of the structure at elevated temperatures. The XPS data indicated that silver-oxygen bonds disappeared completely, with the initial decomposition occurring between 23 and 37 degrees C, and total oxygen in the coating decreased from 16-17% to 6.5% over the temperature range of 75-110 degrees C. A comparison of these results to the data of Taylor et al. [Biomaterials, in press, doi:10.1016/j.biomaterials.2005.05.040] indicates that the unique biological properties of nanocrystalline silver are related to its nanostructure. This should guide future development of therapeutic nanocrystalline silver delivery systems.

Anti-Bacterial Agents↗
PubMed2000

Healing of porcine donor sites covered with silver-coated dressings.

OBJECTIVE: To compare rates of healing of donor sites in pigs between those dressed with silver-coated dressings and those dressed with petrolatum-impregnated absorbent gauze. DESIGN: Open study with each animal acting as its own control. SETTING: University research facility, Canada. ANIMALS: 6 young specific-pathogen-free domestic pigs. INTERVENTIONS: A total of 72 wounds about 1 cm x 2 cm x 0.4 mm were made in rows of eight on each pig with a dermatome. They were divided into three groups of 24, and dressed with petrolatum gauze, or silver-coated dressings moistened with sterile water either once only or daily for 10 days. All dressings were secured in place with an elastic bandage. MAIN OUTCOME MEASURES: Erythema, infection, epidermal migration, and healing. RESULTS: Wounds dressed with moistened silver-coated dressings re-epithelialised significantly more quickly. This resulted in complete re-epithelialisation within 70% of the time taken by those wounds dressed with petrolatum gauze. CONCLUSION: Silver-coated dressings provide a moist environment for the healing wound combined with an effective antimicrobial agent, and this significantly accelerates healing compared with wounds dressed with traditional petrolatum gauze dressings.

Animals↗
PubMed1999

Efficacy of topical silver against fungal burn wound pathogens.

BACKGROUND: Fungal infections of burn wounds have become an important cause of burn-associated morbidity and mortality. The nature of fungal infections dictates aggressive treatment to minimize the morbidity associated with these infections. Persons with large total body surface area burns are particularly susceptible to fungal infections and are treated in such a manner as to minimize their risk of infection. METHODS: This study examined the in vitro fungicidal efficacy of a variety of different topical agents. By placing fungal inocula in contact with mafenide acetate, silver nitrate, silver sulfadiazine, and a nanocrystalline silver-coated dressing, we determined the kill kinetics of these topical agents against a spectrum of common burn wound fungal pathogens. RESULTS: The topical antimicrobials that were tested demonstrated varying degrees of efficacy against these pathogens. CONCLUSION: The nanocrystalline silver-based dressing provided the fastest and broadest-spectrum fungicidal activity and may make it a good candidate for use to minimize the potential of fungal infection, thereby reducing complications that delay wound healing.

Antifungal Agents↗
PubMed1998

Visual detection of protein adsorption onto electrochemically oxidized aluminum surfaces.

Adsorption of proteins onto electrochemically oxidized aluminum surfaces by a simple visual observation was investigated. For this purpose, Ta and then A1 were sputtered onto glass slides (Al/Ta/glass slides). Al/Ta/glass slides were electrochemically oxidized in 0.4 M H3PO4 under the potentiostatic conditions. After the application of aqueous solutions of bovine, rabbit or human immunoglobulin onto the solid Al2O3 surfaces, a change in colour was monitored visually. It was found that all investigated proteins could successfully be adsorbed onto oxidized Al surfaces. This was manifested by a change in colour of the surface from tan to a purple or blue, depending on the concentration of proteins, coating time and degree of oxidation of the Al layer. Most importantly, when an aqueous solution of human IgG was applied on an anti-human IgG coated surface, a change in colour was also observed indicating that the adsorption process did not denature the molecular recognition sites. This type of antibody-antigen reaction was confirmed on the example of anti-human prothrombin--human prothrombin. It is believed that this technology may be useful in developing immunosensors for a variety of applications.

Adsorption↗
PubMed1998

Wound management in an era of increasing bacterial antibiotic resistance: a role for topical silver treatment.

BACKGROUND: Antibiotic-resistant bacteria represent an increasing concern in wound infections. Wound colonization with these organisms normally results in aggressive management of the wound complicated by a greatly limited choice of therapeutic antibiotics. Silver and other noble metals are recognized as potential allies in combating these organisms in wounds. METHODS: Three types of topical silver applications were tested to determine their bactericidal efficacies against clinical isolates of antibiotic-resistant organisms. The silver-based applications represent 3 methods of applying silver to wounds: as a liquid (silver nitrate), incorporated in a cream (silver sulfadiazine) and as a dressing coating (silver-coated dressings). The reduction in the viable bacterial population recovered from test articles after exposure to silver provided a comparative measure of the bactericidal efficacies of these silver applications. RESULTS: All of the products demonstrated an ability to reduce the number of viable bacteria. However, the methods varied in their efficacy against antibiotic-resistant bacteria, with the silver-coated dressing being the most efficacious and silver nitrate the least efficacious. CONCLUSIONS: Silver was demonstrated to be effective at killing the antibiotic-resistant strains tested. The silver-coated dressing was particularly rapid at killing the tested bacteria and was effective against a broader range of bacteria. Silver may be a useful prophylactic or therapeutic agent for the prevention of wound colonization by organisms that impede healing, including antibiotic-resistant bacteria.

Administration, Cutaneous↗
PubMedDate not supplied

Comparative evaluation of the antimicrobial activity of ACTICOAT antimicrobial barrier dressing.

This study evaluated the antimicrobial activity of ACTICOAT Antimicrobial Barrier Dressing (Westaim Biomedical Corp, Fort Saskatchewan, Alberta, Canada), a silver-coated wound dressing, and compared it with silver nitrate, silver sulfadiazine, and mafenide acetate. The minimum inhibitory concentrations (MIC), minimum bactericidal concentrations (MBC), zone of inhibition, and killing curves were determined with 5 clinically relevant bacteria. The data indicate that ACTICOAT silver had the lowest MIC and MBC and generated similar zones of inhibition to silver nitrate and silver sulfadiazine. Viable bacteria were undetectable 30 minutes after inoculation with the dressing, whereas it took 2 to 4 hours for silver nitrate and silver sulfadazine to achieve the same result. Mafenide acetate generated the biggest zones of inhibition, but it had the highest MICs and MBCs, and a significant number of bacteria still survived after 6 hours of treatment. The results suggest that ACTICOAT Antimicrobial Barrier Dressing has better antimicrobial performance than either of the existing silver-based products. ACTICOAT dressing killed the bacteria that were tested much faster, which is a very important characteristic for a wound dressing acting as a barrier to invasive infection to have. The study also suggests that a single susceptibility test such as a MIC or zone of inhibition test does not provide a comprehensive profile of antimicrobial activity of a topical antimicrobial agent or dressing. A combination of tests is desirable.

Anti-Infective Agents, Local↗