Biomedical Engineering Reference
In-Depth Information
FIGURE 9.1
A sufferer from argyria developed from improper dosage of nasal drops containing silver in
childhood. (Reproduced from Jacobs R. Argyria: My life story.
Clinics in Dermatology
. 2006;24(1):66-9;
discussion 9. Epub 2006/01/24.)
pigmentation, a characteristic of argyria (Figure 9.1) [9-11]. For example, a case of argyria has been
reported due to the chewing of photographic film [12].
Another source of exposure is intentional application, such as the application of sunblock to the
skin. More companies have been using nanoparticles in sunblock and topical creams [13]. Because
of repeated application, the penetration and toxicity of nanoparticles through the skin becomes a
concern. The goal of any topical treatment applications is to ensure the safe and effective delivery
of a therapeutic effect without compromising the integrity of the barrier and the health of deeper
layers of tissues and organs; this also applies to nanoparticles designed for skin application. There
are numerous reports that have been published that assess the impact of nanoparticle parameters
on the ability to penetrate the stratum corneum [14-17]. At first glance, published data may seem
contradicting, perhaps due to variations in the models used and the nature of nanoparticles. Also,
skin nanoparticle absorption capacity may correlate with its physiochemical properties. The abil-
ity of the skin to absorb liposomes has already been established [18-20]. The nanoparticles most
commonly utilized in the UV-exposure protective creams are titanium oxide (TiO
2
) and zinc oxide
(ZnO) nanoparticles, which render their application as photon blockers through the ability to reflect,
scatter, and absorb UV radiation. Studies on porcine skin demonstrated that metal nanoparticles on
average of 50 nm do not permeate intact stratum corneum; however, cracked and razor-treated skin
may be susceptible to nanomaterial penetration [13].
On the other hand, it is has been repeatedly shown that, depending on the properties of the nano-
materials, the nanoparticles may penetrate the skin via hair follicles, which may act as a shunt for
the transport and storage of pharmacological substances [21]. This ability renders an opportunity for
the design of topical medications with the capacity for sustained release of API with the advantages
of improved patient compliance, due to a decrease in the frequency of applications. In addition, topi-
cal administration reduces the risk of adverse effects and overdosing as compared with other routes
of exposure, such as intravenous injection and inhalation. The potential for using topical administra-
tion in drug delivery methods is greatly due to the utilization ability of hair shafts as a shunt for the
transport of nanomaterials, as well as the structural capacity of the hair shaft, specifically the fol-
licular infandibulum, to act as a reservoir for nanoparticles [21]. Furthermore, recent developments
in nanotechnology allow for the design of nanoparticles with parameters specifically tailored to be
taken up by skin cells. Owing to the high versatility of the materials utilized in nanoparticle syn-
thesis and their properties, nanotechnology allows for a multitude of therapeutic delivery designs,
enhancing the barrier integrity of the stratum corneum in dermatitis, improved moisturizers for
eczema, sustained release antiseptics in wound care, improved efficacy hair treatments for apole-
cia, and sebaceous gland targeting for rosacea, among many other applications. Numerous topi-
cal application products are already available on the market—such as ActisorbSilver 220
®
wound
dressing, Nanoclorex
®
, Dermaviduals
®
(USA) eczema cream, and Regenerationscheme Intensiv
®
regenerative cream—the list is ever expanding. More studies are required to understand the benefits
