Abstract
Skin absorption and toxicity on keratinocytes of cobalt oxide nanoparticles (Co3O4NPs) have been investigated. Co3O4NPs are commonly used in industrial products and biomedicine. There is evidence that these nanoparticles can cause membrane damage and genotoxicity in vitro, but no data are available on their skin absorption and cytotoxicity on keratinocytes. Two independent 24 h in vitro experiments were performed using Franz diffusion cells, using intact (experiment 1) and needle-abraded human skin (experiment 2). Co3O4NPs at a concentration of 1000 mg/L in physiological solution were used as donor phase. Cobalt content was evaluated by Inductively Coupled–Mass Spectroscopy. Co permeation through the skin was demonstrated after 24 h only when damaged skin protocol was used (57 ± 38 ng·cm−2), while no significant differences were shown between blank cells (0.92 ± 0.03 ng cm−2) and those with intact skin (1.08 ± 0.20 ng·cm−2). To further investigate Co3O4NPs toxicity, human-derived HaCaT keratinocytes were exposed to Co3O4NPs and cytotoxicity evaluated by MTT, Alamarblue® and propidium iodide (PI) uptake assays. The results indicate that a long exposure time (i.e., seven days) was necessary to induce a concentration-dependent cell viability reduction (EC50 values: 1.3 × 10−4 M, 95% CL = 0.8–1.9 × 10−4 M, MTT essay; 3.7 × 10−5 M, 95% CI = 2.2–6.1 × 10−5 M, AlamarBlue® assay) that seems to be associated to necrotic events (EC50 value: 1.3 × 10−4 M, 95% CL = 0.9–1.9 × 10−4 M, PI assay). This study demonstrated that Co3O4NPs can penetrate only damaged skin and is cytotoxic for HaCat cells after long term exposure.
Highlights
The use of nanoparticles (NPs) has grown in the last decades in many fields of every day life, and imposes to the scientific community to take into account their toxicological potential
Observed in water was centered in 318 nm, while it changed considerably when assessed in synthetic sweat, reaching a value higher than 800 nm (Figure 2) and quite stable during all the time of the experiment (824 at t0 and 882 nm at t24)
Skin absorption of NPs is a matter of concern for workers and users that can be exposed to objects, powders and solution containing NPs
Summary
The use of nanoparticles (NPs) has grown in the last decades in many fields of every day life, and imposes to the scientific community to take into account their toxicological potential. NPs may have an unpredictable impact on human health, since traditional toxicological knowledge, based on data derived from materials in their bulk form, is not applicable in the nano size range. [5,6,7,8,9,10,11] These NPs are used as contrast agents in magnetic resonance [12], as drug delivery system [13] and as adjuvants for use in human vaccination too, especially when both lymphocytes Th1 and Th2 responses are needed to clear pathogens [14].
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