The continuous increase in the popularity of tattoos and permanent make-up (PMU) has led to substantial changes in their societal perception. Besides a better understanding of pathological conditions associated with the injection of highly diverse substances into subepidermal layers of the skin, their regulation has occupied regulatory bodies around the globe. In that sense, current regulatory progress in the European Union is an exemplary initiative for improving the safety of tattooing. On one hand, the compilation of market surveillance data has provided knowledge on hazardous substances present in tattoo inks. On the other hand, clinical data gathered from patients enabled correlation of adverse reactions with certain substances. Nevertheless, the assessment of risks remains a challenge due to knowledge gaps on the biokinetics of highly complex inks and their degradation products. This review article examines the strategies for regulating substances in tattoo inks and PMU in light of their potential future restriction in the frame of the REACH regulation. Substance categories are discussed in terms of their risk assessment and proposed concentration limits.

Aluminium is one of the most abundant elements in earth's crust and its manifold uses result in an exposure of the population from many sources. Developmental toxicity, effects on the urinary tract and neurotoxicity are known effects of aluminium and its compounds. Here, we assessed the health risks resulting from total consumer exposure towards aluminium and various aluminium compounds, including contributions from foodstuffs, food additives, food contact materials (FCM), and cosmetic products. For the estimation of aluminium contents in foodstuff, data from the German "Pilot-Total-Diet-Study" were used, which was conducted as part of the European TDS-Exposure project. These were combined with consumption data from the German National Consumption Survey II to yield aluminium exposure via food for adults. It was found that the average weekly aluminium exposure resulting from food intake amounts to approx. 50% of the tolerable weekly intake (TWI) of 1 mg/kg body weight (bw)/week, derived by the European Food Safety Authority (EFSA). For children, data from the French "Infant Total Diet Study" and the "Second French Total Diet Study" were used to estimate aluminium exposure via food. As a result, the TWI can be exhausted or slightly exceeded-particularly for infants who are not exclusively breastfed and young children relying on specially adapted diets (e.g. soy-based, lactose free, hypoallergenic). When taking into account the overall aluminium exposure from foods, cosmetic products (cosmetics), pharmaceuticals and FCM from uncoated aluminium, a significant exceedance of the EFSA-derived TWI and even the PTWI of 2 mg/kg bw/week, derived by the Joint FAO/WHO Expert Committee on Food Additives, may occur. Specifically, high exposure levels were found for adolescents aged 11-14 years. Although exposure data were collected with special regard to the German population, it is also representative for European and comparable to international consumers. From a toxicological point of view, regular exceedance of the lifetime tolerable aluminium intake (TWI/PTWI) is undesirable, since this results in an increased risk for health impairments. Consequently, recommendations on how to reduce overall aluminium exposure are given. Article Highlights • Risk assessment of total aluminium exposure from different sources for different age groups. • Use of data from the European TDS-Exposure project for the estimation of aluminium exposure from foodstuff. • Comprehensive overview of the toxicological properties of aluminium.

Topical administration permits targeted, sustained delivery of therapeutics to human skin. Delivery to the skin, however, is typically limited to lipophilic molecules with molecular weight of < 500 Da, capable of crossing the stratum corneum. Nevertheless, there are indications protein delivery may be possible in barrier deficient skin, a condition found in several inflammatory skin diseases such as psoriasis, using novel nanocarrier systems.Methods: Water in water thermo-nanoprecipitation; dynamic light scattering; zeta potential measurement; nanoparticle tracking analysis; atomic force microscopy; cryogenic transmission electron microscopy; UV absorption; centrifugal separation membranes; bicinchoninic acid assay; circular dichroism; TNFα binding ELISA; inflammatory skin equivalent construction; human skin biopsies; immunohistochemistry; fluorescence microscopy; western blot; monocyte derived Langerhans cells; ELISAResults: Here, we report the novel synthesis of thermoresponsive nanogels (tNG) and the stable encapsulation of the anti-TNFα fusion protein etanercept (ETR) (~150 kDa) without alteration to its structure, as well as temperature triggered release from the tNGs. Novel tNG synthesis without the use of organic solvents was conducted, permitting in situ encapsulation of protein during assembly, something that holds great promise for easy manufacture and storage. Topical application of ETR loaded tNGs to inflammatory skin equivalents or tape striped human skin resulted in efficient ETR delivery throughout the SC and into the viable epidermis that correlated with clear anti-inflammatory effects. Notably, effective ETR delivery depended on temperature triggered release following topical application.Conclusion: Together these results indicate tNGs hold promise as a biocompatible and easy to manufacture vehicle for stable protein encapsulation and topical delivery into barrier-deficient skin.

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Thermo-nanoprecipitation is presented as a versatile, surfactant-free, and mild synthetic method for the preparation of thermoresponsive nanogels and in situ encapsulation of bioactives.

(2017) Biocompatibility and characterization of polyglycerol-based thermoresponsive nanogels designed as novel drug-delivery systems and their intracellular localization in keratinocytes, Nanotoxicology, 11:2, 267-277, DOI: 10.1080/17435390.2017 ABSTRACTNovel nanogels that possess the capacity to change their physico-chemical properties in response to external stimuli are promising drug-delivery candidates for the treatment of severe skin diseases. As thermoresponsive nanogels (tNGs) are capable of enhancing penetration through biological barriers such as the stratum corneum and are taken up by keratinocytes of human skin, potential adverse consequences of their exposure must be elucidated. In this study, tNGs were synthesized from dendritic polyglycerol (dPG) and two thermoresponsive polymers. tNG_dPG_tPG are the combination of dPG with poly(glycidyl methyl ether-co-ethyl glycidyl ether) (p(GME-co-EGE)) and tNG_dPG_pNIPAM the one with poly(N-isopropylacrylamide) (pNIPAM). Both thermoresponsive nanogels are able to incorporate high amounts of dexamethasone and tacrolimus, drugs used in the treatment of severe skin diseases. Cellular uptake, intracellular localization and the toxicological properties of the tNGs were comprehensively characterized in primary normal human keratinocytes (NHK) and in spontaneously transformed aneuploid immortal keratinocyte cell line from adult human skin (HaCaT). Laser scanning confocal microscopy revealed fluorescently labeled tNGs entered into the cells and localized predominantly within lysosomal compartments. MTT assay, comet assay and carboxy-H2DCFDA assay, demonstrated neither cytotoxic or genotoxic effects, nor any induction of reactive oxygen species of the tNGs in keratinocytes. In addition, both tNGs were devoid of eye irritation potential as shown by bovine corneal opacity and permeability (BCOP) test and red blood cell (RBC) hemolysis assay. Therefore, our study provides evidence that tNGs are locally well tolerated and underlines their potential for cutaneous drug delivery. ARTICLE HISTORY

Nanoparticles with a size of several hundred nanometers can effectively penetrate into the hair follicles and may serve as depots for controlled drug delivery. However, they can neither overcome the hair follicle barrier to reach the viable cells nor release the loaded drug adequately. On the other hand, small drug molecules cannot penetrate deep into the hair follicles. Thus, the most efficient way for drug delivery through the follicular route is to employ nanoparticles that can release the drug close to the target structure upon exposure to some external or internal stimuli. Accordingly, 100-700 nm sized thermoresponsive nanogels with a phase transition temperature of 32-37 °C were synthesized by the precipitation polymerization technique using N-isopropylacrylamide as a monomer, acrylated dendritic polyglycerol as a crosslinker, VA-044 as an initiator, and sodium dodecyl sulphate as a stabilizer. The follicular penetration of the indodicarbocyanine (IDCC) labeled nanogels into the hair follicles and the release of coumarin 6, which was loaded as a model drug, in the hair follicles were assessed ex vivo using porcine ear skin. Confocal laser scanning microscopy (CLSM) enabled independent tracking of the nanogels and the loaded dye, although it is not as precise and accurate as standard analytical methods. The results showed that, unlike smaller nanogels (<100 nm), medium and larger sized nanogels (300-500 nm) penetrated effectively into the hair follicles with penetration depths proportional to the nanogel size. The release of the loaded dye in the hair follicles increased significantly when the investigation on penetration was carried out above the cloud point temperature of the nanogels. The follicular penetration of the nanogels from the colloidal dispersion and a 2.5% hydroxyethyl cellulose gel was not significantly different.

Highly hydrophilic, responsive nanogels are attractive as potential systems for the topical delivery of bioactives encapsulated in their three-dimensional polymeric scaffold. Yet, these drug carrier systems suffer from drawbacks for efficient delivery of hydrophobic drugs. Addressing this, β-cyclodextrin (βCD) could be successfully introduced into the drug carrier systems by exploiting its unique affinity toward dexamethasone (DXM) as well as its role as topical penetration enhancer. The properties of βCD could be combined with those of thermoresponsive nanogels (tNGs) based on dendritic polyglycerol (dPG) as a crosslinker and linear thermoresponsive polyglycerol (tPG) inducing responsiveness to temperature changes. Electron paramagnetic resonance (EPR) studies localized the drug within the hydrophobic cavity of βCD by differences in its mobility and environmental polarity. In fact, the fabricated carriers combining a particulate delivery system with a conventional penetration enhancer, resulted in an efficient delivery of DXM to the epidermis and the dermis of human skin ex vivo (enhancement compared to commercial DXM cream: ∼2.5 fold in epidermis, ∼30 fold in dermis). Furthermore, DXM encapsulated in βCD tNGs applied to skin equivalents downregulated the expression of proinflammatory thymic stromal lymphopoietin (TSLP) and outperformed a commercially available DXM cream.