New selenium antimicrobials and material coating against bacteria and bacterial biofilms
This Dissertation discusses the development of covalent selenium containing antimicrobials which targets a bacterium and the development of a cellulose bandage material that contains selenium and blocks biofilm formation. Both the antimicrobials and the cellulose bandage employ the redox property of selenium that produces O2• − (superoxide). Phase I: Selenium containing antimicrobials Purpose: To produce selenium labeled peptides and phage that can selectively bind to the surface of the pathogenic bacteria Yersinia pestis and inactivate it through the generation of superoxide radicals on its surface. Results: 1. Specific phage and peptides for a given bacterium can be obtained from peptide displayed phage library. 2. Selenium was covalently attached phage and peptides that target a specific site on a bacterial without affecting their binding ability. 3. These selenium labeled phage and peptides at micromolar concentration killed targeted bacteria that are resistant to the phage and peptides without selenium, at 10 ìM concentration. 4. These selenium labeled phage and peptides do not kill non-targeted bacteria. These results suggest a novel approach for the development of an antibacterial agent that can target a specific bacterial pathogen for destruction. Phase 2: Selenium containing antimicrobial bandage Purpose: To develop a selenium-based antimicrobial coating for cellulose materials that will prevent bacterial attachment and colonization, that could lead to bacterial biofilm formation and related infections. Results: 1. Selenium can be covalently attached to cellulose. 2. Di-(Se-AAEMA) coated cellulose, at 0.1% and 0.2% selenium concentrations, completely inhibited Staphylococcus aureus and Pseudomonas aeruginosa biofilm formation respectively. After soaking in Phosphate Buffered Saline for a week, these selenium labeled cellulose discs still retained their antibacterial activity. A toxicology study on these same discs showed no indication of toxicity as exhibited by mammalian cell cultures exposed to the soaking solutions of 0.2% and 0.1% selenium coated cellulose discs. Moreover, selenium treated discs reduced already established P. aeruginosa biofilms. In contrast to the parent strain, colony biofilms formed by a P. aeruginosa sodA (a superoxide dismutase) mutant was significantly reduced at 0.05% selenium indicating that the effect depends on oxygen radicals. This study demonstrates the ability to produce a new wound dressing using selenium that resists biofilm formation.