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    Lipsome encapsulated antimicrobial metal ions and essential oils

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    Authors
    Low, Wan Li
    Advisors
    Kenward, M.A. Dr, Martin Claire Dr, Hill D. J. Dr
    Issue Date
    2012-01
    
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    Abstract
    Abstract This study investigates the feasibility of using TTO and Ag+ alone and in combination either as free or liposome encapsulated agents. Based on the minimum lethal concentration (MLC), the fractional lethal concentration index (FLCI) showed that treatment with unencapsulated combinations of TTO and Ag+ exerted a synergistic effect against P. aeruginosa (FLCI = 0.263) and indifferent effects against S. aureus and C. albicans (0.663 and 0.880, respectively). Using polyvinyl alcohol (PVA) emulsified agents in combination, showed synergistic effects against P. aeruginosa and S. aureus (FLCI = 0.325 and 0.375, respectively), but C. albicans remained indifferent (FLCI = 0.733). Time kill experiments revealed that the combined agent concentrations and elimination time (to the lowest limit of detection, LOD) are as follows: C. albicans: 0.12%v/vTTO:2.5x10-4Ag+:1.5hrs, P. aeruginosa: 1%v/vTTO:3.2x10-4Ag+:15mins and S. aureus: 1.2%v/vTTO:3.2x10-4Ag+:30mins. Repeating these experiments with emulsified TTO encapsulated in liposomes (lipo-TTO:PVA30-70kDa) against P. aeruginosa and S. aureus reduced the effective amount of TTO required (compared to free TTO). However, this was not observed in C. albicans. The required effective concentration of Ag+ from liposome encapsulated Ag+ (lipo-Ag+) was shown to remain the same as free Ag+. The effective concentration and elimination time of liposomal agents in combination are as follows: C. albicans: 0.05%v/vTTO:PVA:8.9x10-5Ag:PVA:2.0hrs, P. aeruginosa: 0.25%v/vTTO:PVA:3.2x10-4Ag:PVA:30mins and S. aureus: 0.05%v/vTTO:PVA:6.0x10-4Ag:PVA:1.5hrs. These results showed the potential of using TTO and Ag+ in combination, along with liposome delivery systems to effectively lower the MLC. Scanning electron micrographs of microorganisms exposed to Ag+ showed a reduction in cell size when compared to untreated cells. Transmission electron micrograph of C. albicans showed the cell surface damaging potential of Ag+. Furthermore, this investigation also demonstrated the feasibility of using chitosan hydrogels as an alternative delivery system for TTO and/or Ag+. The development of these controlled release systems to deliver alternative antimicrobial agents may allow sustained targeted delivery at microbiocidal concentrations.
    Publisher
    University of Wolverhampton
    URI
    http://hdl.handle.net/2436/219012
    Type
    Thesis or dissertation
    Language
    en
    Description
    Thesis submitted for the Degree of Doctor of Philosophy
    Collections
    Theses and Dissertations

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