Biomedical Engineering Reference
In-Depth Information
delivery. The aim of nanoparticle treatments will be to enhance the perme-
ation of drugs through the skin, shield drugs from metabolism occurring
during transport, and prolong drug-residence time in systemic circulation.
Many nano-sized formulations are currently being investigated for trans-
dermal delivery, in a diverse range of treatments.
Liposomes [109] have been
used to deliver a variety of therapeutics [126-128]. Dubey et al. [126] devel-
oped melatonin-loaded elastic liposomes approximately 126 nm in diameter
for the transcutaneous treatment of jet lag. Liposomal formulations loaded
with 1% melatonin were incubated with human cadaver skin at 32°C for time
periods up to 24 hours in a custom-built Franz diffusion cell. Melatonin lev-
els in a compartment across the cadaver skin were measured using high-
performance liquid chromatography (HPLC). This study showed improved
melatonin flux across skin with elastic liposomes as transdermal vector in
comparison to free drug. Moreover, topical liposomal formulations loaded
with ibuprofen have shown equivalent effectiveness compared to orally
administered ibuprofen in clinical trials [129]. In addition to the apparent
benefits of transdermal delivery in the medical field, nanoparticle technolo-
gies have also found a niche in other markets. The cosmetics industry looks
to nanoparticles for improved skin hydration, delivery of acne medication,
lubricant properties to increase comfort, and improved aesthetic value of
their products [130]. Isotretinoin, a retinoic acid derivative used to treat acne,
has been loaded into solid lipid nanoparticles 30-60 nm in diameter. This
formulation was able to reduce systemic distribution of isotretinoin and
elevate concentrations in the skin [131]. Lipid nanoparticles have been inves-
tigated for their ability to form a monolayer on the skin and retain the skin's
moisture. Polymeric and lipid nanoparticles may also act as solid lubricants,
thus improving patient comfort. Nanoparticle formulations can be synthe-
sized in ways that reduce irritation responses and may also be used to serve
as controlled release of active ingredients.
Mechanical stimuli have been used in conjunction or in series with lipo-
somal vectors to further enhance skin permeability and drug uptake. The
physical methods to improve skin permeability are generally done prior to
application of topical liposomal solutions. Thus, the skin permeability is
temporarily improved via micro pores formed by this treatment, and the
liposomal vectors can diffuse across the skin with less difficulty. Badkar
et al. [134] delivered 274 nm liposomes encapsulating colchicine by first
increasing skin permeability with electroporation and then mediating
liposomal transdermal delivery via iontophoresis. Microneedles represent
another physical method employed to improve transdermal drug delivery
and have been used in conjunction with liposomes to transdermally deliver
docetaxel [135]. McAllister et al. [118] have delivered 25-nm and 50-nm latex
nanoparticles across human cadaver and mouse epidermis by increas-
ing skin permeability with polymeric, metallic, and silicon microneedles.
Furthermore, iontophoresis has been combined with 110-nm enkaphalin-
loaded, charged liposomes to successfully transport drugs across the skin
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