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Nanoengineered polymer architectures for antimicrobial medical applications: Novel additives

Isaacs, Mark 2014. Nanoengineered polymer architectures for antimicrobial medical applications: Novel additives. PhD Thesis, Cardiff University.
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Silver is a clinically important, broad spectrum antibacterial, whose use extends back over several millennia. Its potent antibacterial activity, range of susceptible microorganisms, and lack of developed resistances, elevate silver as an exciting weapon in the fight against hospital acquired infections and so-called ‘superbugs’. The active, ionic form is efficacious at very low concentrations, thus controlling release rates offers potential durable, non-specific, antibacterial medical devices. This thesis examines a number of inorganic systems as potential slow-release, antibacterial silver nanocomposites for incorporation into polyurethane foam wound dressings. A range of silver core-silica shell nanocomposites were synthesised with tuneable dimensions, with porosity introduced into the silica shells, via base-etching or surfactant-templating producing disordered or ordered architectures respectively. An alternative system based on mesoporous SBA-15 silica was also investigated, which was employed as a scaffold for subsequent multilayer titania functionalisation, onto which mixed silver/silver carbonate nanoparticles were subsequently deposited. Detailed characterisation allowed fundamental structural-function relationships for silver dissolution kinetics and their associated impact upon antibacterial activity towards Gram-positive and Gram-negative bacteria including methicillin-resistant Staphylococcus aureus. Silver ion release rates are inversely proportional to silver crystallite size, with further governance via shell thickness and mesoporosity achievable in core shell systems. The intrinsic antibacterial activity of titania coated SBA-15 further enhances performance, independent of silver, whilst support macropore introduction increases silver particle dispersion. Antibacterial prowess of all materials demonstrates a strong activity correlation with dissolution kinetics, evidencing up to seven-fold logarithmic reductions in the bacterial concentrations within four hours. Materials were potent for > 24 hours, with the reverse micelle core-shell formulation showing continuous activity over a 14 day period. Comparative benchmarking indicates mesoporous silver core-silica shell architectures as promising candidates due to antibacterial longevity, manufacturing simplicity and cost, with their hydrophilic nature and small dimensions rendering them amenable to incorporation into compatible polyurethane foams.

Item Type: Thesis (PhD)
Status: Unpublished
Schools: Chemistry
Subjects: Q Science > QD Chemistry
Date of First Compliant Deposit: 30 March 2016
Last Modified: 19 Mar 2017 02:30

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