Drug delivery to the skin and nail
The skin is an attractive target for drug delivery for both the treatment of skin conditions and to provide systemic effects. Skin conditions such as acne and eczema are common, have a significant impact on patients’ quality of life and treating them topically is desirable as it reduces side effects in comparison to systemic treatments. In contrast transdermal products which are designed to deliver drugs to the systemic circulation have a number of advantages over alternative dosage forms for example providing controlled release of drugs and avoiding first pass metabolism.
Nail disorders affect up to 10% of the population and range from innocuous discolouration of the nail plate, commonly seen in smokers, to chronic infections, which can be very painful and disfiguring for the sufferer. Nail infections are especially serious for immunocompromised patients and diabetics, where if untreated they can cause major complications and require limb amputation.
A major challenge with delivering drugs across the skin or nail is the barrier function of these tissues. These barriers reduce or prevent drug absorption and the inability to deliver sufficient quantities of drug into the tissue prevents many potential therapeutic treatments from being effective. The work of the Skin and Nail group within the Research Centre for Topical Drug Delivery and Toxicology (TDDT) focuses primarily on developing novel formulation strategies to overcome these barriers in order to improve therapeutic treatment and patients’ quality of life.
What we do
As part of the TDDT research centre we have successfully developed a centre of excellence for the development of topical dosage forms for application to skin which draws on the expertise of several members of the pharmaceutics team and colleagues from other disciplines. The work of the group ranges from in silico prediction of drug permeation across skin, formulation development and performance testing, through to toxicity testing of formulated products.
The centralisation of this knowledge and experience, as well as the availability of excellent research facilities and equipment has led to many successful research grants and publications. The in vitro testing laboratory that has been established has a strong track record of producing high quality data to the principles of GLP for a range of commercial clients.
Examples of our current activities include:
- Formulation optimisation
- Release testing
- Franz cell experiments
- Radiolabelled permeation studies
- Ungual permeation studies
- Clinical research trials (topical formulations)
Complementary characterisation analyses of formulations is also routinely performed with techniques including rheological testing, differential scanning calorimetry (DSC), Raman microscopy and ATR-FTIR spectroscopy in common use.
Key projects
Skin permeation of nanoparticles using a flexing skin model
This Health Protection Agency funded PhD studentship is investigating the potential for nanoparticles, such as titanium dioxide and zinc oxide from sunscreens to be absorbed in to the skin. 'Sebum as a biomonitoring matrix'.
The objectives of this internally-funded project are to establish the normal mixture of chemicals present on the skin surface and to subsequently identify the presence of individual chemicals which may be indicative of disease states or exposure to environmental pollutants.
Prediction of skin irritation and sensitisation using an ex vivo skin culture model
In collaboration with MedPharm Ltd this project is developing a model using excised human skin to predict the irritancy index and degree of sensitisation of topical excipients, APIs and formulations. The model is intended to reduce the need for animal testing thus presenting a cheaper, quicker and more ethically acceptable technique to existing models such as the Draize test. It advances current in vitro alternatives through its use of actual human skin and the combination of permeation and mechanistic parameters.
Tamperproof transdermal formulation development
This industrially-funded PhD studentship seeks to design transdermal formulations which can resist the extraction and abuse of an active drug contained in the formulation.
Abuse of prescription medications is a serious issue and this project intends to develop a platform that can be used to limit this for transdermal formulations improving the product safety.
Development of a novel heat producing system for dermal drug delivery
Often the barrier properties of human skin make it difficult to develop medicines that are capable of delivering sufficient quantities of drug across the skin. One strategy to improve this is the application physiologically tolerable heat to improve drug permeation across the skin.
This Medpharm Ltd funded PhD studentship seeks to explore the effects of heat on the delivery of different model drugs across skin and to develop a suitable platform which can use heat to improve therapeutic treatment.
Co-application of topical corticosteroids and emollients: impact on treatment and patient safety
Topical corticosteroids and emollients are developed separately by the pharmaceutical industry but are frequently applied at similar times in clinical practice. This has the potential to affect drug absorption and clinical guidelines on how to mitigate this are contradictory and lack an evidence base. Obtaining clearer guidance on this issue has been highlighted as a research priority by both patients and healthcare professionals.
This project will provide insight into the effects application of these products at similar times has on drug absorption and will hopefully be able to contribute to the development of evidence based guidance on the use of these products which will be of benefit in the treatment of eczema.
Get in touch
For more information about our work, please contact Dr William McAuley.