Emulsions are widely used as topical formulations in the pharmaceutical and cosmetic industry.
They are thermodynamically unstable and require emulsifiers to stabilize them physically. A
literature survey has revealed that emulsifiers could have an effect on topical delivery.
Therefore, the overall aim of this research project was to investigate and to understand the
various effects of biopolymers, chosen for this study as emulsifiers, on the release and the
topical delivery of an active ingredient from emulsion-based delivery systems. Emulsions were
stabilized by either whey protein alone or in combination with chitosan or carrageenan. Salicylic
acid was chosen as a model drug. Furthermore, the emulsions were prepared at three different
pH values (pH 4, 5 and 6) in order to introduce different charges to the polymeric emulsifiers
and subsequently determine the effect of pH on release as well as on dermal and transdermal
delivery. Emulsion characteristics, such as droplet size, zeta potential, viscosity and stability
against creaming and coalescence were ascertained. In addition, turbidity was determined to
evaluate the degree of insoluble complex formation in the aqueous phase of the emulsions. A
high pressure liquid chromatographic (HPLC) method was validated for the quantitative
determination of salicylic acid in the release, skin and transdermal perfusate samples. Nine
emulsions were formulated, utilizing the layer-by-layer (LbL) self-assembly technique, from
which the release of salicylic acid was determined. These release studies were conducted,
utilizing nitrocellulose membranes (0.2 μm pore size) with the use of Franz-type diffusion cells in
four replicates per formulation over a time period of 8 hours. Based on the emulsion
characterization and release data, six formulations, including the oil solution, were chosen to
determine dermal and transdermal delivery of salicylic acid. During the diffusion studies, the
effect of different pH (whey protein pH 4.00, 5.00 and 6.00), different polymers and different
polymer combinations were investigated. These diffusion studies were conducted with the use
of dermatomed (thickness ~400 μm), human abdominal skin and Franz-type diffusion cells over
a period of 24 hours. The characterization of the emulsions revealed no significant differences
in the droplet size and viscosity between the various formulations. All emulsions showed
stability towards coalescence over a time period of 7 days; however, not all the emulsions
showed stability towards creaming and flocculation. The results of the release studies indicated
that an increase in emulsion droplet charge could have a negative effect on the release of
salicylic acid from these formulations. In contrast, positively charged emulsion droplets could
enhance the dermal and transdermal delivery of salicylic acid from emulsions. It was
hypothesized that electrostatic complex formation between the emulsifier and salicylic acid
could affect the release, whereas electrostatic interaction between emulsion droplets and skin
could influence dermal/transdermal delivery of the active. Furthermore, the degree of ionization
of salicylic acid played an important role in the dermal and transdermal delivery of salicylic acid
from the various emulsions. / MSc (Pharmaceutics), North-West University, Potchefstroom Campus, 2014
| Identifer | oai:union.ndltd.org:netd.ac.za/oai:union.ndltd.org:nwu/oai:dspace.nwu.ac.za:10394/10719 |
| Date | January 2014 |
| Creators | Combrinck, Johann |
| Source Sets | South African National ETD Portal |
| Language | English |
| Detected Language | English |
| Type | Thesis |
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