Quantitative Determination of Skin Penetration of PEG-Coated CdSe Quantum Dots in Dermabraded but not Intact SKH-1 Hairless Mouse Skin

Abstract

Many cosmetics, sunscreens, and other consumer products are reported to contain nanoscale materials. The possible transdermal absorption of nanoscale materials and the long-term consequences of the absorption have not been determined. We used polyethylene glycol coated cadmium selenide (CdSe) core quantum dots (QD; 37 nm diameter) to evaluate the penetration of nanoscale material into intact, tape stripped, acetone treated, or dermabraded mouse skin. QD were suspended in an oil-in-water emulsion (approximately 9 microM) and the emulsion was applied at 2 mg/cm(2) to mouse dorsal skin pretreated as follows: intact; tape stripped to remove the stratum corneum; acetone pretreated; dermabraded to remove stratum corneum and epidermis. QD penetration into the skin was monitored in sentinel organs (liver and regional draining lymph nodes) using inductively coupled plasma mass spectrometry analysis of cadmium (from the CdSe QD). No consistent cadmium elevation was detected in the sentinel organs of mice with intact, acetone pretreated, or tape-stripped skin at 24- and 48-h post-QD application; however, in dermabraded mice, cadmium elevations were detected in the lymph nodes and liver. QD accumulation (as cadmium) in the liver was approximately 2.0% of the applied dose. The passing of QD through the dermabraded skin was confirmed using confocal fluorescence microscopy. These results suggest that transdermal absorption of nanoscale materials depends on skin barrier quality, and that the lack of an epidermis provided access to QD penetration. Future dermal risk assessments of nanoscale materials should consider key barrier aspects of skin and its overall physiologic integrity.

In vitro and in vivo percutaneous absorption of seleno-L-methionine, an antioxidant agent, and other selenium species

“…Whether the quantum dots can permeate the skin is controversial. Recent investigations reported that skin penetration by quantum dots did not occur in intact mouse skin [45] , was minimal in a murine model [46] , and was detected in the lower SC layer of a human skin equivalent [47] . In our case, neither CdSe nor CdSe/ZnS quantum dots were absorbed by porcine skin.…”

Perturbation of physiological systems by nanoparticles

“…323 After the exposure of skin-abraded mice to polyethylene glycol coated Cd/Se QD (37 nm) for 24 and 48 hours, the QD were detected in the lymph nodes and liver, suggesting that they were absorbed into the circulation. 324 As noted above, some nanoparticles can reach the dermal layer. QDs (4.6 nm) coated with polyethylene glycol penetrated the epidermis and reached the dermis of porcine skin over a time window similar to that of occupational exposure (8 and 24 hours).…”

Confocal laser scanning microscopy to estimate nanoparticles’ human skin penetration in vitro

“…30 However, NP penetration through tape stripped skin did not always lead to marked penetration enhancement. It varied qualitatively in magnitude from none [31][32][33][34] to some NPs detected. 15,35,36 Differences may be affected by skin species, number of strips and type of tape used and/or NP characteristics.…”