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Title: Lifecycle of the antibacterial Triclosan
Author: Shackleford, Marie Anna
ISNI:       0000 0004 5994 7709
Awarding Body: Durham University
Current Institution: Durham University
Date of Award: 2016
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With the rise of liquid soaps, and consumers becoming more environmentally conscious, manufacturers have two duties of care; one being to ensure adequate bug inhibition and the other to ensure that an excessive burden is not placed on the environment by any benefit agent. Recently there have been concerns about the excessive use of certain benefit agents. It is key to deliver the right amount of Triclosan (TC) to the right place at the right time so that at least the Minimum Inhibitory Concentration is delivered but not to over deliver which causes waste. The antibacterial TC has been studied as a model active ingredient in surfactant systems and on its own to contribute to the understanding of the lifecycle of active ingredients when used in soap formulations. The effect of TC in sodium dodecyl sulphate (SDS) and sodium laurate (SL) systems has been investigated using a range of physical chemistry techniques including UV-Vis and NMR to determine the increased solubility of TC in surfactant micelles. The effect of TC on the size and shape of SDS micelles has been examined using small angle neutron scattering. The surface tension of TC/ surfactant mixtures was studied to find the effects of TC on the critical micelle concentration (CMC) of the surfactant solutions: TC decreases the CMC of SDS and the effect is pH dependant. The partitioning of the poorly water soluble TC is dependent on pH as well as the concentration of surfactant. It is important to understand the partitioning in these soap system to understand factors such as bioavailability and deposition. I have proposed a model for partitioning between free TC and TC in micelles, and between anionic and neutral forms based on an NMR study. The phenol form of TC partitions much more strongly into micelles than the phenolate: when there is 1% SDS, there is 700 times more phenol in the micelles than in the bulk, whereas the proportion of phenolate in bulk and micelles is nearly the same. The partitioning of TC into supported lipid bilayers as models for cell membranes has been investigated by Total Internal Reflection Raman spectroscopy. In these experiments, TC was inserted into the bilayer at high pH and rinsed with low pH buffer. In these conditions TC is very resistant to rinsing from the bilayer. When bilayers with mixtures of lipids close to those found in bacterial cells were treated with TC, the bilayers were removed from the surface. The work described in this thesis has contributed to the investigation of surfactant systems in combination with TC and can be applied to other active ingredients in similar formulations as part of product development. I have investigated the state of the active ingredient TC in surfactant formulations through dilution and to delivery to one of the sites of action using appropriate physical chemistry techniques for each stage of the investigation.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available