The aim of this study was to investigate the effect of different penetration enhancers containing essential fatty acids (EFAs) on the transdermal delivery of flurbiprofen. Flurbiprofen was used as a marker / model compound. Fatty acids were chosen as penetration enhancers for their ability to reversibly increase skin permeability through entering the lipid bilayers and disrupting their ordered domains. Fatty acids are natural, non-toxic compounds (Karande & Mitragotri, 2009:2364). Evening primrose oil, vitamin F and Pheroid™ technology all contain fatty acids and were compared using a cream based-formulation. This selection was to ascertain whether EFAs exclusively, or EFAs in a delivery system, would have a significant increase in the transdermal delivery of a compound. For an active pharmaceutical ingredient (API) to be effectively delivered transdermally, it has to be soluble in lipophilic, as well as hydrophilic mediums (Naik et al., 2000:319; Swart et al., 2005:72). This is due to the intricate structure of the skin, where the stratum corneum (outermost layer) is the primary barrier, which regulates skin transport (Barry, 2001:102; Moser et al., 2001:103; Venus et al., 2010:469). Flurbiprofen is highly lipophilic (log P = 4.24) with poor aqueous solubility. It has a molecular weight lower than 500 g/mol indicating that skin permeation may be possible, though the high log P indicates that some difficulty is to be expected (Dollery, 1999:F126; Hadgraft, 2004:292; Swart et al., 2005:72; Karande & Mitragotri, 2009:2363; Drugbank, 2012). In vitro transdermal diffusion studies (utilising vertical Franz diffusion cells) were conducted, using donated abdominal skin from Caucasian females. The studies were conducted over 12 h with extractions of the receptor phase every 2 h to ensure sink conditions. Prior to skin diffusion studies, membrane release studies were performed to determine whether the API was released from the formulation. Membrane release studies were conducted over 6 h and extractions done hourly. Tape stripping experiments were performed on the skin circles after 12 h diffusion studies to determine the concentration flurbiprofen present in the stratum corneum and dermisepidermis. The flurbiprofen concentrations present in the samples were determined using high performance chromatography and a validated method. Membrane release results indicated the following rank order for flurbiprofen from the different formulations: vitamin F > control > evening primrose oil (EPO) >> Pheroid™. The control formulation contained only flurbiprofen and no penetration enhancers. Skin diffusion results on the other hand, indicated that flurbiprofen was present in the stratum corneum and the dermisepidermis. The concentration flurbiprofen present in the receptor phase of the Franz cells (representing human blood) followed the subsequent rank order: EPO > control > vitamin F >> Pheroid™. All the formulations stipulated a lag time shorter than that of the control formulation (1.74 h), with the EPO formulation depicting the shortest (1.36 h). The control formulation presented the highest flux (8.41 μg/cm2.h), with the EPO formulation following the closest (8.12 μg/cm2.h). It could thus be concluded that fatty acids exclusively, rather than in a delivery system, had a significant increase in the transdermal delivery of flurbiprofen. / Thesis (MSc (Pharmaceutics))--North-West University, Potchefstroom Campus, 2013.

The aim of this study was to investigate the effect of different penetration enhancers containing essential fatty acids (EFAs) on the transdermal delivery of flurbiprofen. Flurbiprofen was used as a marker / model compound. Fatty acids were chosen as penetration enhancers for their ability to reversibly increase skin permeability through entering the lipid bilayers and disrupting their ordered domains. Fatty acids are natural, non-toxic compounds (Karande & Mitragotri, 2009:2364). Evening primrose oil, vitamin F and Pheroid™ technology all contain fatty acids and were compared using a cream based-formulation. This selection was to ascertain whether EFAs exclusively, or EFAs in a delivery system, would have a significant increase in the transdermal delivery of a compound. For an active pharmaceutical ingredient (API) to be effectively delivered transdermally, it has to be soluble in lipophilic, as well as hydrophilic mediums (Naik et al., 2000:319; Swart et al., 2005:72). This is due to the intricate structure of the skin, where the stratum corneum (outermost layer) is the primary barrier, which regulates skin transport (Barry, 2001:102; Moser et al., 2001:103; Venus et al., 2010:469). Flurbiprofen is highly lipophilic (log P = 4.24) with poor aqueous solubility. It has a molecular weight lower than 500 g/mol indicating that skin permeation may be possible, though the high log P indicates that some difficulty is to be expected (Dollery, 1999:F126; Hadgraft, 2004:292; Swart et al., 2005:72; Karande & Mitragotri, 2009:2363; Drugbank, 2012). In vitro transdermal diffusion studies (utilising vertical Franz diffusion cells) were conducted, using donated abdominal skin from Caucasian females. The studies were conducted over 12 h with extractions of the receptor phase every 2 h to ensure sink conditions. Prior to skin diffusion studies, membrane release studies were performed to determine whether the API was released from the formulation. Membrane release studies were conducted over 6 h and extractions done hourly. Tape stripping experiments were performed on the skin circles after 12 h diffusion studies to determine the concentration flurbiprofen present in the stratum corneum and dermisepidermis. The flurbiprofen concentrations present in the samples were determined using high performance chromatography and a validated method. Membrane release results indicated the following rank order for flurbiprofen from the different formulations: vitamin F > control > evening primrose oil (EPO) >> Pheroid™. The control formulation contained only flurbiprofen and no penetration enhancers. Skin diffusion results on the other hand, indicated that flurbiprofen was present in the stratum corneum and the dermisepidermis. The concentration flurbiprofen present in the receptor phase of the Franz cells (representing human blood) followed the subsequent rank order: EPO > control > vitamin F >> Pheroid™. All the formulations stipulated a lag time shorter than that of the control formulation (1.74 h), with the EPO formulation depicting the shortest (1.36 h). The control formulation presented the highest flux (8.41 μg/cm2.h), with the EPO formulation following the closest (8.12 μg/cm2.h). It could thus be concluded that fatty acids exclusively, rather than in a delivery system, had a significant increase in the transdermal delivery of flurbiprofen. / Thesis (MSc (Pharmaceutics))--North-West University, Potchefstroom Campus, 2013.

Caffeine is frequently used in cosmetics due to its well-characterised skin permeation properties and is widely incorporated in cosmetic-related products intended for skin (Samah & Heard, 2013:631). Despite its polar characteristics (Dias et al., 1999:41), caffeine is an important biologically and cosmetically active compound (Herman & Herman, 2012:13). This active pharmaceutical ingredient (API) has a broad range of advantages in the world of cosmetics, including the improvement of microcirculation in the capillaries (Lupi et al., 2007:107), showing anti-cellulite activity in the fatty tissue (Velasco et al., 2008:24), anti-oxidation activity in sunscreens & anti-ageing products (Koo et al., 2007:964) and the stimulation of hair growth (Fisher et al., 2007:27). Caffeine has also shown significant decreases in UV-induced skin tumour multiplicity (Lu et al., 2001:5003, 5008) and has been proven to prevent photo-damaged skin, which includes the formation of wrinkles and histological alterations (Mitani et al., 2007:86). It is therefore clear that the challenge for the dermal delivery of the hydrophilic caffeine is for it to be retained in the specific skin layers (dermal delivery) where it can exert its action, rather than to permeate through the skin and into the hydrophilic systemic circulation (transdermal delivery) (Wiechers et al., 2008:10). In this study the calculated skin delivery gap (SDG) values, and the transdermal and dermal delivery of caffeine from three different semi-solid topical formulations were compared. The SDG theory was developed to evaluate the effectiveness of dermal delivery of API from topical formulations and is known as the ratio between the concentration required to achieve minimum effect relative to the concentration obtained at the target site (JW Solutions, 2011). During this study the principle of the SDG was investigated by using the formulating strategy, Formulating for Efficacy (FFE™), which aims to optimise skin delivery of APIs from different formulations. The SDG was therefore implemented and in vitro transdermal studies were utilised to ultimately prove or disprove the hypothesis of SDG on the prediction of the topical delivery of caffeine. The human skin consists of two distinctive layers namely the epidermis (including the stratum corneum (SC) and viable dermis) and the dermis (Menon, 2002:S3). The main barrier to dermal and transdermal permeation is the outermost layer of the skin, the SC (Fang et al., 2007:343). The difference between the target site for dermal and transdermal delivery of APIs is crucial to be mentioned. Dermal delivery includes the delivery of an API to the skin surface, SC, viable epidermis or dermis, whereas transdermal delivery requires the API to permeate all the way through the various skin layers and into the systemic circulation (Wiechers, 2000:42). Since this study involves the optimisation of the topical delivery of caffeine, the physicochemical properties of this API as well as those of the skin should be considered. As mentioned before, caffeine is a rather polar molecule (Dias et al., 1999:41), whereas the SC (lipophilic) provides the rate-limiting barrier to the percutaneous absorption of polar (hydrophilic) molecules, such as caffeine (Barry, 1983:105). Caffeine was incorporated into three different formulations: a gel and two creams (differing only in the ratio of the primary and secondary emollient). The three topical formulations each had different polarities, where the Gel represented the hydrophilic formulation (more polar than the skin), whereas the first cream, Cream 1 (containing 5% DMI and 9% glycerine), served as the intermediate formulation (similar polarity as the SC), and the second cream, Cream 2 (10% DMI and 4% glycerine), was the formulation less polar (therefore more lipophilic) than the SC. Franz cell type transdermal diffusion studies were performed on the three semi-solid formulations (Gel, Cream 1 and Cream 2). The diffusion studies were conducted over a period of 12 h, followed by the tape stripping of the skin directly after each diffusion study. Caucasian female abdominal skin was obtained with consent from willing donors. Ethical approval for the acquisition and use of the donated skin was granted under reference number NWU-00114-11-A5. The formulations each contained 1% of caffeine as API. The skin used for the diffusion studies was prepared with the use of a Zimmer Dermatome®. The receptor phase of each Franz cell was withdrawn at predetermined time intervals and subsequently analysed with high performance liquid chromatography (HPLC) in order to determine the concentration of caffeine that permeated through the skin. Stratum corneum-epidermis (SCE) and epidermis-dermis (ED) samples were prepared and left overnight at a temperature of 4 °C, and they were analysed the following day with the use of HPLC in order to determine the concentration of caffeine that had accumulated in the particular skin layers. The SDG value for each caffeine formulation was calculated and it was compared to the flux and tape stripping results obtained from the diffusion studies. To ultimately prove or disprove the SDG theory, the skin diffusion studies and tape stripping results were used to determine whether any difference occurred in the absorption or penetration of the API from the different formulations into the skin. The formulation with the intermediate polarity (Cream 1) produced the highest transdermal flux of caffeine due to the hydrophilic and lipophilic nature of caffeine and the formulation, respectively. Cream 1 is sufficiently lipophilic to transport caffeine into the SC and at the same time sufficiently hydrophilic (more polar than Cream 2) to cause a greater driving force of caffeine through to the more hydrophilic epidermis, dermis and systemic circulation. The results from the tape stripping yielded that Cream 2 (the more lipophilic formulation) produced the highest concentration of caffeine into the SCE due to the hydrophilic and lipophilic nature of caffeine and the formulation, respectively. The difference in polarity between the formulation and the API in Cream 2 was the greatest compared to the other formulations, which significantly increased the driving force of caffeine to partition into the SC (Wiechers et al., 2004:177). The hydrophilic gel showed the highest concentration of caffeine in the ED layer of the skin due to the hydrophilic compounds formulated in the Gel, which showed greater ability to partition into the aqueous dermis and viable epidermis (Imai et al., 2013:372). Cream 2 had the lowest calculated SDG value compared to that of the Gel and Cream 1. The smaller the delivery gap, the greater the delivery of the API should be into the skin (Wiechers, 2010). Considering this, it was expected that Cream 2 would deliver greater amounts of caffeine into the skin than the more hydrophilic formulations. Cream 2, which showed the lowest calculated SDG value delivered the highest amount of caffeine into the SCE during the diffusion studies. The calculated SDG values therefore are consistent with the concentration of caffeine in the SCE (the lowest SDG value produced the highest concentration of API in the SCE). However, no correlations were found between the calculated SDG values and ED delivery or the flux of caffeine. The final conclusion for this study is that the SDG theory proved to be effective and trustworthy regarding the delivery of caffeine into the SC. / MSc (Pharmaceutics), North-West University, Potchefstroom Campus, 2014

Caffeine is frequently used in cosmetics due to its well-characterised skin permeation properties and is widely incorporated in cosmetic-related products intended for skin (Samah & Heard, 2013:631). Despite its polar characteristics (Dias et al., 1999:41), caffeine is an important biologically and cosmetically active compound (Herman & Herman, 2012:13). This active pharmaceutical ingredient (API) has a broad range of advantages in the world of cosmetics, including the improvement of microcirculation in the capillaries (Lupi et al., 2007:107), showing anti-cellulite activity in the fatty tissue (Velasco et al., 2008:24), anti-oxidation activity in sunscreens & anti-ageing products (Koo et al., 2007:964) and the stimulation of hair growth (Fisher et al., 2007:27). Caffeine has also shown significant decreases in UV-induced skin tumour multiplicity (Lu et al., 2001:5003, 5008) and has been proven to prevent photo-damaged skin, which includes the formation of wrinkles and histological alterations (Mitani et al., 2007:86). It is therefore clear that the challenge for the dermal delivery of the hydrophilic caffeine is for it to be retained in the specific skin layers (dermal delivery) where it can exert its action, rather than to permeate through the skin and into the hydrophilic systemic circulation (transdermal delivery) (Wiechers et al., 2008:10). In this study the calculated skin delivery gap (SDG) values, and the transdermal and dermal delivery of caffeine from three different semi-solid topical formulations were compared. The SDG theory was developed to evaluate the effectiveness of dermal delivery of API from topical formulations and is known as the ratio between the concentration required to achieve minimum effect relative to the concentration obtained at the target site (JW Solutions, 2011). During this study the principle of the SDG was investigated by using the formulating strategy, Formulating for Efficacy (FFE™), which aims to optimise skin delivery of APIs from different formulations. The SDG was therefore implemented and in vitro transdermal studies were utilised to ultimately prove or disprove the hypothesis of SDG on the prediction of the topical delivery of caffeine. The human skin consists of two distinctive layers namely the epidermis (including the stratum corneum (SC) and viable dermis) and the dermis (Menon, 2002:S3). The main barrier to dermal and transdermal permeation is the outermost layer of the skin, the SC (Fang et al., 2007:343). The difference between the target site for dermal and transdermal delivery of APIs is crucial to be mentioned. Dermal delivery includes the delivery of an API to the skin surface, SC, viable epidermis or dermis, whereas transdermal delivery requires the API to permeate all the way through the various skin layers and into the systemic circulation (Wiechers, 2000:42). Since this study involves the optimisation of the topical delivery of caffeine, the physicochemical properties of this API as well as those of the skin should be considered. As mentioned before, caffeine is a rather polar molecule (Dias et al., 1999:41), whereas the SC (lipophilic) provides the rate-limiting barrier to the percutaneous absorption of polar (hydrophilic) molecules, such as caffeine (Barry, 1983:105). Caffeine was incorporated into three different formulations: a gel and two creams (differing only in the ratio of the primary and secondary emollient). The three topical formulations each had different polarities, where the Gel represented the hydrophilic formulation (more polar than the skin), whereas the first cream, Cream 1 (containing 5% DMI and 9% glycerine), served as the intermediate formulation (similar polarity as the SC), and the second cream, Cream 2 (10% DMI and 4% glycerine), was the formulation less polar (therefore more lipophilic) than the SC. Franz cell type transdermal diffusion studies were performed on the three semi-solid formulations (Gel, Cream 1 and Cream 2). The diffusion studies were conducted over a period of 12 h, followed by the tape stripping of the skin directly after each diffusion study. Caucasian female abdominal skin was obtained with consent from willing donors. Ethical approval for the acquisition and use of the donated skin was granted under reference number NWU-00114-11-A5. The formulations each contained 1% of caffeine as API. The skin used for the diffusion studies was prepared with the use of a Zimmer Dermatome®. The receptor phase of each Franz cell was withdrawn at predetermined time intervals and subsequently analysed with high performance liquid chromatography (HPLC) in order to determine the concentration of caffeine that permeated through the skin. Stratum corneum-epidermis (SCE) and epidermis-dermis (ED) samples were prepared and left overnight at a temperature of 4 °C, and they were analysed the following day with the use of HPLC in order to determine the concentration of caffeine that had accumulated in the particular skin layers. The SDG value for each caffeine formulation was calculated and it was compared to the flux and tape stripping results obtained from the diffusion studies. To ultimately prove or disprove the SDG theory, the skin diffusion studies and tape stripping results were used to determine whether any difference occurred in the absorption or penetration of the API from the different formulations into the skin. The formulation with the intermediate polarity (Cream 1) produced the highest transdermal flux of caffeine due to the hydrophilic and lipophilic nature of caffeine and the formulation, respectively. Cream 1 is sufficiently lipophilic to transport caffeine into the SC and at the same time sufficiently hydrophilic (more polar than Cream 2) to cause a greater driving force of caffeine through to the more hydrophilic epidermis, dermis and systemic circulation. The results from the tape stripping yielded that Cream 2 (the more lipophilic formulation) produced the highest concentration of caffeine into the SCE due to the hydrophilic and lipophilic nature of caffeine and the formulation, respectively. The difference in polarity between the formulation and the API in Cream 2 was the greatest compared to the other formulations, which significantly increased the driving force of caffeine to partition into the SC (Wiechers et al., 2004:177). The hydrophilic gel showed the highest concentration of caffeine in the ED layer of the skin due to the hydrophilic compounds formulated in the Gel, which showed greater ability to partition into the aqueous dermis and viable epidermis (Imai et al., 2013:372). Cream 2 had the lowest calculated SDG value compared to that of the Gel and Cream 1. The smaller the delivery gap, the greater the delivery of the API should be into the skin (Wiechers, 2010). Considering this, it was expected that Cream 2 would deliver greater amounts of caffeine into the skin than the more hydrophilic formulations. Cream 2, which showed the lowest calculated SDG value delivered the highest amount of caffeine into the SCE during the diffusion studies. The calculated SDG values therefore are consistent with the concentration of caffeine in the SCE (the lowest SDG value produced the highest concentration of API in the SCE). However, no correlations were found between the calculated SDG values and ED delivery or the flux of caffeine. The final conclusion for this study is that the SDG theory proved to be effective and trustworthy regarding the delivery of caffeine into the SC. / MSc (Pharmaceutics), North-West University, Potchefstroom Campus, 2014

In pharmaceutical sciences, topical delivery is a transport process of an active pharmaceutical ingredient (API) from a formulated dosage form to the target site of action. For most topical delivery systems, the skin surface, or the specific skin layers, such as the outermost layer of the stratum corneum, the lipids amid the corneocytes within the stratum corneum, the corneocytes themselves, the epidermis, dermis, Langerhans cells, Merckle cells or the appendageal structures can be the target delivery location. When an API is delivered to the skin, it has to firstly diffuse from the formulation in which it is applied, to the skin surface. From there the API may partition into the stratum corneum, permeate across the stratum corneum and partition into the viable epidermis, from where it may partition further into the dermis and permeate across the dermis into the bloodstream (Wiechers, 2008:1-3, 7). With respect to the barrier function of the skin, the intercellular spaces within the stratum corneum contain lipids and its main purpose is to operate as a barrier to water-loss and to provide an imperative diffusional barrier to the absorption of APIs. This resistance is comprised of a complex interaction of lipids that creates a hydrophilic and lipophilic penetration pathway. The fundamental aspect underlying the impermeability of the skin, therefore, is the lipophilic nature of the stratum corneum (Bouwstra et al., 2003:4; Franz & Lehman, 2000:25; Walker & Smith, 1996:296). A common approach for the promotion of poorly penetrating APIs in transdermal delivery is the incorporation of chemical penetration enhancers in delivery systems, in order to promote the partitioning of an API into the stratum corneum. These chemicals are also referred to as accelerants, promoters and absorption promoters. Penetration enhancers are added to topical formulations and usually also partition into the stratum corneum, where they temporarily and reversibly disrupt its fundamental diffusional barrier properties, hence facilitating the absorption of an API through the skin (Büyüktimkin et al., 1997:358-359; Sinha & Kaur, 2000:1131; Walker & Smith, 1996:296). The mechanisms for the enhancement of diffusion of the API should therefore increase the solubility and partitioning of the drug from the formulation into the skin. It should further increase the solubility of the API within the skin and promote its permeability and diffusion coefficient (Rajadhyaksha et al., 1997:489). Fatty acids are recognised to effectively enhance the penetration of transdermally delivered hydrophilic and lipophilic APIs. Many penetration enhancers contain saturated and unsaturated hydrocarbon chains, and a popular fatty acid that has been used in this regard is oleic acid (Williams & Barry, 2004:609-610). It is believed that fatty acids disrupt the lipid organisation of the intercellular lipids within the stratum corneum to cause fluidisation of these bilayers, making the stratum corneum more permeable to APIs. Excipients with polar (hydrophilic) head groups and long hydrophobic chains i.e. fatty acids, can penetrate into the intercellular lipids of the stratum corneum and disrupt these endogenous lipid components, thereby increasing diffusion of an API within the skin (Barry, 2006:9-10; Hadgraft & Finnin, 2006:367-368; Kanikkannan et al., 2006:18; Williams & Barry, 2004:610). Natural oils are widely used in topical formulations and were an obvious choice in this study. Oils are liquids at room temperature, whereas fats are in solid form. They are relatively easy to obtain from both plants and animals. The main constituents of fats and oils are triglycerides comprising of fatty acids and a glycerol. Oils control the evaporation of moisture from the skin, spread easily and evenly and are partly metabolised in the skin to release valuable fatty acids (Fang et al., 2004:170,173; Lautenschläger, 2004:46; Mitsui, 1997:121-122). The focus of this study was not formulation per se, but included the formulation of avocado-, grapeseed-, emu-, crocodile, olive and coconut oil into semisolid emulgel- and two foam formulations. This was done in order to investigate the penetration enhancing properties of their fatty acid content on flurbiprofen which was chosen as the marker API. The emulgels containing the natural oils were compared to the same emulgel formulation containing liquid paraffin, and a hydrogel without the inclusion of an oil. Six natural oils were analysed by gas chromatography (GC) in order to quantify their fatty acid compositions, whilst also providing qualitative information by indicating the retention times of the materials with an alkyl chain composition (Mitsui, 1997:260). Data obtained with the GC indicated that olive- (76%), avocado- (68%), emu- (46%) and crocodile oil (40%) presented with high levels of oleic acid, also known as a mono-unsaturated fatty acid (MUFA). Lower levels of oleic acid were observed within grapeseed- (27%) and coconut oil (8%). The only oil demonstrating high levels of the poly-unsaturated fatty acid (PUFA), linoleic acid, was grapeseed oil (61%), whereas the remainder of the oils showed levels below 24%. Contrary, coconut oil seemed to have been the only oil high in saturated fatty acids (SFAs) and consisted of a lauric acid content of 52% and medium levels of myristic acid (21%). Average levels of palmitic acid (SFA) were found in crocodile- (21%) and in emu oil (21%), both of animal origin, whereas avocado-, grapeseed-, olive- and coconut oils from plants presented with levels below 15%. Stearic acid was also present in levels below 10% in all of these oils, with the oils of animal origin portraying the highest values. A method was developed and validated to determine the concentration of the marker flurbiprofen after diffusion from the formulations into the skin, as well as concentrations of the marker that diffused through the skin, by means of high performance liquid chromatography (HPLC). Franz cell membrane diffusion studies were conducted prior to the skin diffusion studies in order to verify the actual release of the marker from the semisolid formulations. Skin diffusion experiments were performed using dermatomed excised, human skin to which the six emulgel formulations, containing the natural oils, were applied. A comparative study was performed utilising liquid paraffin and a hydrogel, in order to compare the diffusion of the marker, flurbiprofen, into and through the skin. The two oil emulgel formulations that had indicated the best flux values were subsequently formulated into foam preparations in order to compare the penetration enhancement properties on flurbiprofen of these two oils in a foam preparation, to those in the equivalent emulgels. The data generated for all ten the formulations were compared, and the formulations that yielded the best results with regards to median flux values and the flurbiprofen concentrations within the stratum corneum-epidermis and epidermis-dermis, were identified. Application of the liquid paraffin emulgel (21.29 μg/ml) depicted the highest average concentration of the diffused lipophilic flurbiprofen within the stratum corneum-epidermis, followed by the olive oil foam (21.47 μg/ml), olive oil emulgel (17.82 μg/ml) and grapeseed oil emulgel (17.78 μg/ml). Very similar concentrations for the marker were demonstrated by the hydrogel (16.73 μg/ml) and crocodile oil emulgel (14.89 μg/ml), whereas a lower concentration was shown for coconut oil emulgel (7.18 μg/ml). The remainder of the formulations yielded concentrations below 3%, i.e. the avocado oil emulgel (2.72 μg/ml), the coconut oil foam (1.57 μg/ml) and finally the emu oil emulgel (1.25 μg/ml). The penetration of the marker, flurbiprofen, being trapped within the skin seemed to have been enhanced more by the oleic acid (UFA) containing emulgels and foam, especially. This was followed by oils containing high linoleic acid values, which indicated that the more kinked shaped the fatty acids, the more difficult it became to insert themselves within the lipid structures of the stratum corneum, with a resulting accumulation of the marker (Fang et al., 2003:318-319). It therefore seemed that those oils that predominantly consisted of unsaturated fatty acids (UFAs) (grapeseed-, crocodile- and olive oils) seemed to have increased the concentration of the diffused marker more significantly than those oils containing an almost even combination of MUFAs and PUFAs (avocado oil), or those mainly consisting of SFAs (coconut oil). Average concentrations of the diffused flurbiprofen found in the epidermis-dermis region of the skin for all of the formulations demonstrated low concentrations, ranging between 0.97 - 5.39 μg/ml, with the exception of the emu oil emulgel that presented with a higher concentration of 16.15 μg/ml. The reason for the high accumulation of the marker might have been as a result of epidermal proliferation, with subsequent accumulation of the marker within the epidermis-dermis due to high oleic- and linoleic acid values, as well as small amounts of palmitoleic acid present within this oil (Katsuta et al., 2005:1011). The resistance of the epidermis-dermis region to the general permeation of flurbiprofen might have been caused by its lipophilic nature, resulting in a reduced solubility within the hydrophilic environment of this region (Hadgraft, 1999:5). Median results from the skin diffusion studies demonstrated that the hydrogel (23.79 μg/cm2.h) had the highest flux, followed by the olive oil- (17.99 μg/cm2.h), liquid paraffin- (15.70 μg/cm2.h), coconut oil- (13.16 μg/cm2.h), grapeseed oil- (11.85 μg/cm2.h), avocado oil- (8.31 μg/cm2.h), crocodile oil- (6.68 μg/cm2.h) and emu oil emulgels (4.41 μg/cm2.h). The fact that the hydrogel presented a higher flux value for the marker could have been as a result of its high water content that had caused hydration of the skin. Hydration opens up the dense lipid structures inside of the stratum corneum, due to swelling of the corneocytes, with a subsequent increase in the marker‘s flux (Benson, 2005:28; Ranade & Hollinger, 2004:213). The high flux value of flurbiprofen with the liquid paraffin emulgel might also have resulted from the fact that it occluded the skin, which increased the hydration of the stratum corneum, with a subsequent increase in the flux (Mitsui, 1997:124; Thomas & Finnin, 2004:699). Results from the skin diffusion studies could be explained by the fact that the fatty acids differ in their hydrocarbon chain by (1) the length of the chain, and (2) the position- and number of the double bonds (Babu et al., 2006:144). It is suggested that fatty acids with hydrocarbon (lipophilic) chains between C12 to C14 (also present within coconut oil) have an optimal balance of the partition coefficient and its affinity for the skin (Ogiso & Shintani, 1990:1067). It appears as though the branched UFAs, especially oleic acid, present in high quantities in olive oil, were more powerful enhancers of the diffusion of the marker, flurbiprofen (Chi et al., 1995:270). Foam formulations were manufactured with the olive- and coconut oil emulgels that had demonstrated the best median flux values of flurbiprofen from the natural oil emulgel formulations. These formulated foams, however, did not significantly increased flux values for flurbiprofen through the skin, but only achieved values of 5.56 μg/cm2.h for the olive oil foam and 4.36 μg/cm2.h for the coconut oil foam formulations. The low flux values could have been attributed to the nature of the formulation itself, which was filled with trapped air that could have resulted in the formulation not making optimal direct contact with the available skin surface. Throughout this study, it became evident that olive oil, predominantly consisting of oleic acid (UFA), was most effective in enhancing the flux of the lipophilic marker, flurbiprofen, through the skin, closely followed by coconut oil consisting of SFAs, with lauric- and myristic acid as its main constituents. Better enhancement effects were observed with those oils containing high amounts of oleic acid (MUFA), than oils consisting of almost equal amounts of both PUFAs and MUFAs (avocado-, emu- and crocodile oil), or oils mainly consisting of PUFAs (grapeseed oil) as its main components, but their effect was not more significant than the oil containing SFAs (coconut oil) as its key components. / Thesis (MSc (Pharmaceutics))--North-West University, Potchefstroom Campus, 2013.

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

In pharmaceutical sciences, topical delivery is a transport process of an active pharmaceutical ingredient (API) from a formulated dosage form to the target site of action. For most topical delivery systems, the skin surface, or the specific skin layers, such as the outermost layer of the stratum corneum, the lipids amid the corneocytes within the stratum corneum, the corneocytes themselves, the epidermis, dermis, Langerhans cells, Merckle cells or the appendageal structures can be the target delivery location. When an API is delivered to the skin, it has to firstly diffuse from the formulation in which it is applied, to the skin surface. From there the API may partition into the stratum corneum, permeate across the stratum corneum and partition into the viable epidermis, from where it may partition further into the dermis and permeate across the dermis into the bloodstream (Wiechers, 2008:1-3, 7). With respect to the barrier function of the skin, the intercellular spaces within the stratum corneum contain lipids and its main purpose is to operate as a barrier to water-loss and to provide an imperative diffusional barrier to the absorption of APIs. This resistance is comprised of a complex interaction of lipids that creates a hydrophilic and lipophilic penetration pathway. The fundamental aspect underlying the impermeability of the skin, therefore, is the lipophilic nature of the stratum corneum (Bouwstra et al., 2003:4; Franz & Lehman, 2000:25; Walker & Smith, 1996:296). A common approach for the promotion of poorly penetrating APIs in transdermal delivery is the incorporation of chemical penetration enhancers in delivery systems, in order to promote the partitioning of an API into the stratum corneum. These chemicals are also referred to as accelerants, promoters and absorption promoters. Penetration enhancers are added to topical formulations and usually also partition into the stratum corneum, where they temporarily and reversibly disrupt its fundamental diffusional barrier properties, hence facilitating the absorption of an API through the skin (Büyüktimkin et al., 1997:358-359; Sinha & Kaur, 2000:1131; Walker & Smith, 1996:296). The mechanisms for the enhancement of diffusion of the API should therefore increase the solubility and partitioning of the drug from the formulation into the skin. It should further increase the solubility of the API within the skin and promote its permeability and diffusion coefficient (Rajadhyaksha et al., 1997:489). Fatty acids are recognised to effectively enhance the penetration of transdermally delivered hydrophilic and lipophilic APIs. Many penetration enhancers contain saturated and unsaturated hydrocarbon chains, and a popular fatty acid that has been used in this regard is oleic acid (Williams & Barry, 2004:609-610). It is believed that fatty acids disrupt the lipid organisation of the intercellular lipids within the stratum corneum to cause fluidisation of these bilayers, making the stratum corneum more permeable to APIs. Excipients with polar (hydrophilic) head groups and long hydrophobic chains i.e. fatty acids, can penetrate into the intercellular lipids of the stratum corneum and disrupt these endogenous lipid components, thereby increasing diffusion of an API within the skin (Barry, 2006:9-10; Hadgraft & Finnin, 2006:367-368; Kanikkannan et al., 2006:18; Williams & Barry, 2004:610). Natural oils are widely used in topical formulations and were an obvious choice in this study. Oils are liquids at room temperature, whereas fats are in solid form. They are relatively easy to obtain from both plants and animals. The main constituents of fats and oils are triglycerides comprising of fatty acids and a glycerol. Oils control the evaporation of moisture from the skin, spread easily and evenly and are partly metabolised in the skin to release valuable fatty acids (Fang et al., 2004:170,173; Lautenschläger, 2004:46; Mitsui, 1997:121-122). The focus of this study was not formulation per se, but included the formulation of avocado-, grapeseed-, emu-, crocodile, olive and coconut oil into semisolid emulgel- and two foam formulations. This was done in order to investigate the penetration enhancing properties of their fatty acid content on flurbiprofen which was chosen as the marker API. The emulgels containing the natural oils were compared to the same emulgel formulation containing liquid paraffin, and a hydrogel without the inclusion of an oil. Six natural oils were analysed by gas chromatography (GC) in order to quantify their fatty acid compositions, whilst also providing qualitative information by indicating the retention times of the materials with an alkyl chain composition (Mitsui, 1997:260). Data obtained with the GC indicated that olive- (76%), avocado- (68%), emu- (46%) and crocodile oil (40%) presented with high levels of oleic acid, also known as a mono-unsaturated fatty acid (MUFA). Lower levels of oleic acid were observed within grapeseed- (27%) and coconut oil (8%). The only oil demonstrating high levels of the poly-unsaturated fatty acid (PUFA), linoleic acid, was grapeseed oil (61%), whereas the remainder of the oils showed levels below 24%. Contrary, coconut oil seemed to have been the only oil high in saturated fatty acids (SFAs) and consisted of a lauric acid content of 52% and medium levels of myristic acid (21%). Average levels of palmitic acid (SFA) were found in crocodile- (21%) and in emu oil (21%), both of animal origin, whereas avocado-, grapeseed-, olive- and coconut oils from plants presented with levels below 15%. Stearic acid was also present in levels below 10% in all of these oils, with the oils of animal origin portraying the highest values. A method was developed and validated to determine the concentration of the marker flurbiprofen after diffusion from the formulations into the skin, as well as concentrations of the marker that diffused through the skin, by means of high performance liquid chromatography (HPLC). Franz cell membrane diffusion studies were conducted prior to the skin diffusion studies in order to verify the actual release of the marker from the semisolid formulations. Skin diffusion experiments were performed using dermatomed excised, human skin to which the six emulgel formulations, containing the natural oils, were applied. A comparative study was performed utilising liquid paraffin and a hydrogel, in order to compare the diffusion of the marker, flurbiprofen, into and through the skin. The two oil emulgel formulations that had indicated the best flux values were subsequently formulated into foam preparations in order to compare the penetration enhancement properties on flurbiprofen of these two oils in a foam preparation, to those in the equivalent emulgels. The data generated for all ten the formulations were compared, and the formulations that yielded the best results with regards to median flux values and the flurbiprofen concentrations within the stratum corneum-epidermis and epidermis-dermis, were identified. Application of the liquid paraffin emulgel (21.29 μg/ml) depicted the highest average concentration of the diffused lipophilic flurbiprofen within the stratum corneum-epidermis, followed by the olive oil foam (21.47 μg/ml), olive oil emulgel (17.82 μg/ml) and grapeseed oil emulgel (17.78 μg/ml). Very similar concentrations for the marker were demonstrated by the hydrogel (16.73 μg/ml) and crocodile oil emulgel (14.89 μg/ml), whereas a lower concentration was shown for coconut oil emulgel (7.18 μg/ml). The remainder of the formulations yielded concentrations below 3%, i.e. the avocado oil emulgel (2.72 μg/ml), the coconut oil foam (1.57 μg/ml) and finally the emu oil emulgel (1.25 μg/ml). The penetration of the marker, flurbiprofen, being trapped within the skin seemed to have been enhanced more by the oleic acid (UFA) containing emulgels and foam, especially. This was followed by oils containing high linoleic acid values, which indicated that the more kinked shaped the fatty acids, the more difficult it became to insert themselves within the lipid structures of the stratum corneum, with a resulting accumulation of the marker (Fang et al., 2003:318-319). It therefore seemed that those oils that predominantly consisted of unsaturated fatty acids (UFAs) (grapeseed-, crocodile- and olive oils) seemed to have increased the concentration of the diffused marker more significantly than those oils containing an almost even combination of MUFAs and PUFAs (avocado oil), or those mainly consisting of SFAs (coconut oil). Average concentrations of the diffused flurbiprofen found in the epidermis-dermis region of the skin for all of the formulations demonstrated low concentrations, ranging between 0.97 - 5.39 μg/ml, with the exception of the emu oil emulgel that presented with a higher concentration of 16.15 μg/ml. The reason for the high accumulation of the marker might have been as a result of epidermal proliferation, with subsequent accumulation of the marker within the epidermis-dermis due to high oleic- and linoleic acid values, as well as small amounts of palmitoleic acid present within this oil (Katsuta et al., 2005:1011). The resistance of the epidermis-dermis region to the general permeation of flurbiprofen might have been caused by its lipophilic nature, resulting in a reduced solubility within the hydrophilic environment of this region (Hadgraft, 1999:5). Median results from the skin diffusion studies demonstrated that the hydrogel (23.79 μg/cm2.h) had the highest flux, followed by the olive oil- (17.99 μg/cm2.h), liquid paraffin- (15.70 μg/cm2.h), coconut oil- (13.16 μg/cm2.h), grapeseed oil- (11.85 μg/cm2.h), avocado oil- (8.31 μg/cm2.h), crocodile oil- (6.68 μg/cm2.h) and emu oil emulgels (4.41 μg/cm2.h). The fact that the hydrogel presented a higher flux value for the marker could have been as a result of its high water content that had caused hydration of the skin. Hydration opens up the dense lipid structures inside of the stratum corneum, due to swelling of the corneocytes, with a subsequent increase in the marker‘s flux (Benson, 2005:28; Ranade & Hollinger, 2004:213). The high flux value of flurbiprofen with the liquid paraffin emulgel might also have resulted from the fact that it occluded the skin, which increased the hydration of the stratum corneum, with a subsequent increase in the flux (Mitsui, 1997:124; Thomas & Finnin, 2004:699). Results from the skin diffusion studies could be explained by the fact that the fatty acids differ in their hydrocarbon chain by (1) the length of the chain, and (2) the position- and number of the double bonds (Babu et al., 2006:144). It is suggested that fatty acids with hydrocarbon (lipophilic) chains between C12 to C14 (also present within coconut oil) have an optimal balance of the partition coefficient and its affinity for the skin (Ogiso & Shintani, 1990:1067). It appears as though the branched UFAs, especially oleic acid, present in high quantities in olive oil, were more powerful enhancers of the diffusion of the marker, flurbiprofen (Chi et al., 1995:270). Foam formulations were manufactured with the olive- and coconut oil emulgels that had demonstrated the best median flux values of flurbiprofen from the natural oil emulgel formulations. These formulated foams, however, did not significantly increased flux values for flurbiprofen through the skin, but only achieved values of 5.56 μg/cm2.h for the olive oil foam and 4.36 μg/cm2.h for the coconut oil foam formulations. The low flux values could have been attributed to the nature of the formulation itself, which was filled with trapped air that could have resulted in the formulation not making optimal direct contact with the available skin surface. Throughout this study, it became evident that olive oil, predominantly consisting of oleic acid (UFA), was most effective in enhancing the flux of the lipophilic marker, flurbiprofen, through the skin, closely followed by coconut oil consisting of SFAs, with lauric- and myristic acid as its main constituents. Better enhancement effects were observed with those oils containing high amounts of oleic acid (MUFA), than oils consisting of almost equal amounts of both PUFAs and MUFAs (avocado-, emu- and crocodile oil), or oils mainly consisting of PUFAs (grapeseed oil) as its main components, but their effect was not more significant than the oil containing SFAs (coconut oil) as its key components. / Thesis (MSc (Pharmaceutics))--North-West University, Potchefstroom Campus, 2013.

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