Dermal Toxicity Influence of Gold Nanomaterials after Embedment in Cosmetics

Abstract

Gold nanomaterials (Au NMs) have been widely used in cosmetic products for improving the brightening, and reducing the wrinkling of, skin, etc.; however, the dermal safety of Au NMs is rarely concerned. A previous study found that cosmetics could enhance the toxicity of Au nanosheets, but different physicochemical properties of Au NMs will induce different interaction modes with ingredients of cosmetics, potentially leading to different toxicity profiles. In the present study, spherical and rodlike Au NMs were first found in commercial cosmetics, and then Au nanospheres (NSs) with different sizes and Au nanorods (NRs) with different aspect ratios were prepared to simulate these Au NMs in cosmetics and further investigate their toxicity before and after embedment in cosmetics. It was found that the primary sizes, morphologies, and optical absorptions of these Au NSs and NRs before and after embedment were similar; however, their hydrodynamic sizes and zeta potentials were noticeably different. Then, these Au NSs and NRs presented weak or no cytotoxicity against HaCaT keratinocytes, while cosmetic cream could alleviate their cytotoxicity. Moreover, the cream could enhance the accumulation of Au NSs and NRs in the skin of hairless mice, but it also alleviated the toxicological responses of Au NSs and NRs in terms of superoxide dismutase (SOD) elevation and malondialdehyde (MDA) reduction. Therefore, the embedment of Au NSs and NRs into cosmetics can alleviate the in vitro and in vivo dermal toxicities of Au NSs and NRs.

Physicochemical Properties of Gold Nanoparticles for Skin Care Creams

“…This study also compared the penetration of raw AuNPs and AuNPs embedded in skin creams. The results showed some accumulation of AuNPs in the skin, but no accumulation was detected in the major organs, meaning that AuNPs cannot enter the bloodstream and be transported to the major organs [2]. Regarding surface charge as a factor for permeability, neutrally charged AuNPs had the highest penetration in the skin's bilayer interior, while both positively and negatively charged AuNPs did not get into the bilayer [8].…”

“…No other impurities were detected. Extracting nanoparticles from skin creams was shown to completely alter their surface properties, which affects their hydrodynamic sizes [2] and may thus also affect their morphological properties due to agglomeration or other interactions with the cosmetic ingredients during the extraction procedure. Depending on the type of nanomaterial or cosmetic ingredients, the nanoparticles may have varied behaviors.…”

“…Gold nanoparticles (AuNPs) have now been used in luxury cosmetic products such as skin creams, lotions, hair products, facial masks, lipsticks, deodorants, etc. for several years, with declared beneficial anti-aging, hydrating, restorative, and regenerative properties [1][2][3][4][5]. AuNPs are considered as a valuable material in cosmeceutical products (cosmetic products with pharmaceutical, medically beneficial active ingredients) due to their strong antifungal and antibacterial properties.…”

“…There are several studies on the safety and functionality of using nanomaterials and AuNPs as cosmetic ingredients [3,4,8,9]. A thorough knowledge of the harmful effects of these nanoparticles has not been established for the use of nanomaterials in cosmetics, while it is accepted that the sizes, shapes, concentrations, and frequency of use have a great impact on the effects of nanomaterials applied on the skin [2,10]. Before releasing a cosmetic product in the European Union (EU) market, manufacturers are required to report their ingredients according to the regulation on cosmetic products No.…”

“…In practice, a cosmetic product is used in its entirety, not as single ingredients, and some arguments are made as to the applicability of safety studies of individual ingredients. As they are a single substance in a skin care product, other substances affect their physical and chemical characteristics, altering their behavior and making their toxicological aspects not easily translated to various cosmetic formulations [2].…”