Developing formulations designed to deliver antiseptic agents to target sites within the skin

Healthcare associated infections (HCAI) are a major concern due there their impact on morbidity and associated costs. To prevent subsequent infection, the use of an effective antiseptic agent is necessary before an incision is performed. However, there are two important issues that may restrict effective antisepsis; the first of these is that the penetration of most antimicrobial agents is very poor, and the antiseptic may not reach the deep layers of the skin; therefore microorganisms located in these layers are likely to survive. The second issue is the lack of miscibility between the antiseptic agent and the sebum which prevents the delivery to the target site within the hair follicle. Nanoemulsions are a promising drug delivery system which can potentially facilitate the penetration of an antiseptic agent to the deeper layers of the skin.

In this thesis, the capability of nanoemulsion formulations in the delivery of antiseptic agents to target sites within the skin was assessed. Triclosan nanoemulsions were prepared using two different techniques, a high-pressure homogenisation and high-shear homogenisation followed by ultrasonication. The parameters of the triclosan nanoemulsion were evaluated; these include various types and concentrations of surfactants (Tween/Span) and various oil concentrations (eucalyptus oil). The detection of the amount of triclosan retained within the skin was also investigated both quantitatively and qualitatively using tape-stripping technique followed by hplc and micro CT scanning respectively. The lowest concentration of the surfactant mixture (0.34%W/W) (Tween 80 / Span 80) produced the highest skin retention of the antiseptic agent, this was detected quantitatively in the tape-stripping method and confirmed qualitatively in the novel approach using micro CT scans.

Hansen solubility parameters (HSPs) were used to predict the miscibility of nano-formulations with artificial sebum, the HSP for artificial sebum was calculated using three different methods: contribution group method (Van Krevelen method), Y-MB method using HSPiP software and the third using the solubility and miscibility of known HSPs and regression statistics. HSPs were successfully used as a prediction tool in estimating the miscibility of nanoemulsion in artificial sebum using the three stated methods.