Poster Presentation ASDR-AWTRS-MEPSA 2018 Joint Meeting

Using elongated microparticles to enhance tailorable nanoemulsion delivery in excised human skin and volunteers (#76)

Miko Yamada 1 2 , Hossam Tayeb 3 4 , Hequn Wang 5 , Nhung Dang 1 2 , Yousuf H Mohammed 6 , Sam Osseiran 5 7 , Paul J Belt 8 , Michael S Roberts 6 9 , Conor L Evans 5 , Frank Sainsbury 3 , Tarl W Prow 1 2
  1. Dermatology Research Centre, The University of Queensland, Queensland
  2. Future Industries Institute, University of South Australia, Mawson Lakes, SOUTH AUSTRALIA, Australia
  3. Australian Institute for Bioengineering and Nanotechnology, The University of Queensland, St Lucia, Queensland
  4. Faculty of Applied Medical Sciences, King Abdulaziz, Jeddah, Saudi Arabia
  5. Wellman Centre for Photomedicine, Massachusetts General Hospital, Harvard Medical School, Massachusetts
  6. Therapeutic Research Centre, School of Medicine, The University of Queensland, Princess Alexandra Hospital, Woolloongabba
  7. Harvard-MIT Division of Health Sciences and Technology, Massachusetts
  8. Department of Plastic and Reconstructive Surgery and Orthopaedic Surgery, Princess Alexandra Hospital, Brisbane
  9. School of Pharmacy and Medical Science, University of South Australia, Adelaide

This study demonstrates, for the first time, clinical testing of elongated silica microparticles (EMP) combined with tailorable nanoemulsions (TNE) to enhance topical delivery of hydrophobic drug surrogates. Likewise, this is the first report of 6-carboxyfluorescein (a model molecule for topically delivered hydrophobic drugs) AM1 & DAMP4 (novel short peptide surfactants) used in volunteers. The EMP penetrate through the epidermis and stop at the dermal-epidermal junction (DEJ). TNE are unusually stable and useful because the oil core allows high drug loading levels and the surface properties can be easily controlled. At first, we chose alginate as a crosslinking agent between EMP and TNE. We initially incorporated a fluorescent lipophilic dye, DiI, as a hydrophobic drug surrogate into TNE for visualization with microscopy. We compared four different coating approaches to combine EMP and TNE and tested these formulations in freshly excised human skin. The delivery profile characterization was imaged by dye- free coherent anti-Stoke Raman scattering (CARS) microscopy to detect the core droplet of TNE that was packed with pharmaceutical grade lipid (glycerol) instead of DiI. These data show the EMP penetrating to the DEJ followed by controlled release of the TNE. Freeze-dried formulations with crosslinking resulted in a sustained release profile, whereas a freeze-dried formulation without crosslinking showed an immediate burst-type release profile. Finally, we tested the crosslinked TNE coated EMP formulation in volunteers using multiphoton microscopy (MPM) and fluorescence-lifetime imaging microscopy (FLIM) to document the penetration depth characteristics. These forms of microscopy have limitations in terms of image acquisition speed and imaging area coverage but can detect fluorescent drug delivery through the superficial skin in volunteers. 6-Carboxyfluorescein was selected as the fluorescent drug surrogate for the volunteer study based on the similarity of size, charge and hydrophobicity characteristics to small therapeutic drugs that are difficult to deliver through skin. The imaging data showed a 6-carboxyfluorescein signal deep in volunteer skin supporting the hypothesis that EMP can indeed enhance the delivery of TNE in human skin. There were no adverse events recorded at the time of the study or after the study, supporting the use of 6-carboxyfluorescein as a safe and detectable drug surrogate for transdermal research. In conclusion, dry formulations, with controllable release profiles can be obtained with TNE coated EMP that can effectively enhance hydrophobic payload delivery deep into the human epidermis.