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With the growing importance of alternative test methods that implement the 3Rs principles (Reduction, Refinement and Replacement) and the global importance of biological safety assessment data for medical devices is increasing. We have developed and optimized the 'KeraSkin™ Skin Irritation Test (KeraSkin™ SIT) for medical device' for regulatory application in biological evaluation according to ISO 10993-23. We conducted a round robin study to optimize and evaluate the performance of KeraSkin™ SIT for medical devices using KeraSkin™ Reconstructed Human Epidermis (RhE), which is developed and manufactured in Korea. This round robin study was performed to assess the transferability, reproducibility (within and between laboratories) and predictive capacity in 1 lead laboratory and 3 participating laboratories based on OECD Guidance Document 34. The predictive capacity, the results showed 83.3 % of sensitivity, 100 % of specificity and 91.6 % of accuracy. In conclusion, the results demonstrate that 'KeraSkin™ SIT for medical device' provides a robust test method for detecting irritant activity of medical device extracts and can be utilized for identifying low levels of potent irritants in medical device extracts. Therefore, it fulfills the requirements to be included as a 'me-too' test method to EpiDerm™ and SkinEthic™ skin irritation test in ISO 10993-23., Competing Interests: Declaration of competing interest The authors declare the following financial interests/personal relationships which may be considered as potential competing interests:Joohwan Kim reports financial support was provided by Ministry of Food and Drug Safety. Nam-Hee Kang reports financial support was provided by Ministry of Food and Drug Safety. If there are other authors, they declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Elsevier Ltd. All rights reserved.)

Toxicological assessment of chemicals is crucial for safeguarding human health and the environment. However, traditional animal experiments are associated with ethical, technical, and predictive limitations in assessing the toxicity of chemicals to the skin. With the recent development of bioengineering and tissue engineering, three-dimensional (3D) skin models have been commonly used as an alternative for toxicological studies. The skin consists of the subcutaneous, dermis, and epidermis. All these layers have crucial functions such as physical and biological protection and thermoregulation. The epidermis is the shallowest layer protecting against external substances and media. Because the skin is the first contact point for many substances, this organ is very significant for assessing local toxicity following skin exposure. According to the classification of the United Nations Global Harmonized System, skin irritation is a major potentially hazardous characteristic of chemicals, and this characteristic must be accurately assessed and classified for enhancing chemical safety management and preventing and reducing chemical accidents. This review discusses the research progress of 3D skin models and introduces their application in assessing chemical skin irritation., (© 2024 John Wiley & Sons Ltd.)

The purpose of this study is to evaluate a novel macromolecular test method for the identification of dermal corrosives. The simple in chemico test procedure involves allowing the material to be tested to interact with a skin biomarker for corrosivity and then adding a detection reagent. The corrosivity of the test substance is predicted based on the measured macromolecular damage, which results in reduced optical density of the detection reagent as compared with controls. This study aims to determine if such an extremely simple, cell-free test method can accurately identify dermal corrosives. To determine predictivity and repeatability, we tested 60 chemicals (30 in vivo dermal corrosives and 30 in vivo dermal noncorrosives; all tested in triplicate) representative of a broad range of chemical classes, functional groups, mixtures, and levels of toxicity. Validation results indicate the GHS multicategory and packing group assignment accuracy is on par with that of the Reconstructed Human Epidermis test method and the Membrane Barrier test method and for the global identification of corrosives, the method has a considerably higher accuracy (98 % vs. ∼80 %)., Competing Interests: Declaration of competing interest The authors declare the following financial interests/personal relationships which may be considered as potential competing interests: Supported by a NIEHS Small Business Innovative Research Grant. Research reported in this publication was supported by the National Institute of Environmental Health Sciences of the National Institutes of Health under Award Number R44ES036065. The content is solely the responsibility of the authors and does not necessarily represent the official views of the National Institutes of Health. Stewart Lebrun reports a relationship with Lebrun Labs that includes: board membership, equity or stocks, and funding grants. Stewart Lebrun and Linda Nguyen are inventors for patent #PCT/US24/15781 IN CHEMICO TEST FOR TOXICITY; pending and assigned to Lebrun Labs LLC. The DermaSafe Skin Corrosion test is sold by InChemico LLC, a wholly owned subsidiary of Lebrun Labs LLC. Stewart Lebrun owns Lebrun Labs LLC. Linda Nguyen and Kelly Ve Ho are Lebrun Labs LLC employees., (Copyright © 2024 Elsevier Ltd. All rights reserved.)

Introduction: In vitro methods have been widely used to assess adverse effects. Reconstructed Human Epidermis (RHE) poses as a fascinating test system employed to assess the dermal irritation hazard potential of chemicals. Although several RHE models are reported in the OECD Test Guideline No. 439, the OECD Document No. 220 encourages the scientific community to develop and validate new RHE test systems due to its relevance for socio-economic advancement., Methods: Following the criteria documented in the OECD No. 220, a blind study for skin irritation (OECD 439) was conducted employing the Minimum List of Reference Chemicals for Determination of Reproducibility and Predictive Capacity using ES®-RHE. Structural and functional characteristics were assessed alongside the prediction model., Results: The model has shown reproducibility of optical density and barrier function, similarly to internationally validated methods. Furthermore, it shows the cell layers' development and differentiation ability due to Cytokeratin14, Cytokeratin10, and filaggrin expression. The prediction model resulted in sensitivity, specificity and accuracy rates of 100, 70, and 77 %, respectively., Conclusions: The ES®-RHE demonstrated reliability and relevance, with similar structural and functional characteristics comparable to internationally validated models, in addition to the accepted predictive capacity according to OECD required minimum criteria, thus confirming the suitability of the national ES®-RHE in the hazard prediction of dermal irritation based on OECD Test Guideline No. 439., Competing Interests: Conflict of Interest The authors are collaborators of Eleve Science Pesquisa e Desenvolvimento Ltda, a start-up, located in SUPERA Parque Tecnológico de Ribeirão Preto - University of São Paulo/Brazil that has received financial support from FINEP and FAPESP in Brazil. However, the authors declare that there are no conflicts of interest related to the content of this manuscript., (Copyright © 2024 Elsevier Ltd. All rights reserved.)

Skin corrosion testing is integral to evaluating the potential harm posed by chemicals, impacting regulatory decisions on safety, transportation, and labeling. Traditional animal testing methods are giving way to in vitro alternatives, such as reconstructed human epidermis (RhE) models, aligning with evolving ethical standards. This study evaluates the QileX-RhE test system's performance for chemical subcategorization within the OECD TG 431 framework. Results demonstrate its ability to differentiate subcategories, accurately predicting 83% of UN GHS Category 1A and 73% of UN GHS Category 1B/1C chemicals with 100% sensitivity in corrosive prediction. Additionally, this study provides a comprehensive assessment of the test method's performance by employing nuanced parameters such as positive predictive value (PPV), negative predictive value (NPV), post-test odds and likelihood rations, offering valuable insights into the applicability and effectiveness of the QileX-RhE test method., Competing Interests: Declaration of competing interest The authors declare the following financial interests/personal relationships which may be considered as potential competing interests: M.Chacon reports financial support was provided by State Agency of Research. M.Chacon reports financial support was provided by Carlos III Health Institute. If there are other authors, they declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Elsevier Ltd. All rights reserved.)

After EU ban on animal testing for cosmetics in 2013, there has been an increasing global interest in alternatives test methods. To development for alternatives test method, we need to get the toxic data about in vitro and in vivo of chemicals. However, database sometimes provide limited in vivo and in vitro data on chemicals. Further, the data generated using the OECD TG439 (in vitro skin irritation) are scattered in difference databases, and it is not easy to navigate through them. Therefore, we complied 'Reference Chemical Database System for Skin Irritation Alternative Test (RCDS-Skin Irritation)' to allow easy, one-stop access to test chemical information. We established the systematic RCDS-Skin Irritation by collecting physiochemical properties, CAS number, human data, and in vivo (OECD TG404) data from overseas chemicals database including European Chemicals Agency (ECHA) etc., and in vitro data using Reconstructed human Epidermis (RhE) (OECD TG439). As a result, we developed the RCDS-Skin Irritation that contains information on 149 chemicals including the data we generated by performing tests using EpiDerm™ SIT, SkinEthic™ RHE and KeraSkin™ SIT. Therefore, the RCDS-Skin Irritation established based on our study will provide insight for safety assessment of chemicals and for development of alternative test methods., Competing Interests: Declaration of competing interest The authors declare the following financial interests/personal relationships which may be considered as potential competing interests: Nam-Hee Kang reports financial support was provided by Ministry of Food and Drug Safety. Min Kyung Hyun reports financial support was provided by Ministry of Food and Drug Safety. Seo Young Bang reports financial support was provided by Ministry of Food and Drug Safety. Both Nam-Hee Kang and Min-Kyung Hyun are the first co-author of this paper. If there are other authors, they declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024. Published by Elsevier Ltd.)

Despite the wide application of graphene-based materials, the information of the toxicity associated to some specific derivatives such as aminated graphene oxide is scarce. Likewise, most of these studies analyse the pristine materials, while the available data regarding the harmful effects of degraded forms is very limited. In this work, the toxicity of graphene oxide (GO), aminated graphene oxide (GO-NH 2 ), and their respective degraded forms (dGO and dGO-NH 2 ) obtained after being submitted to high-intensity sonication was evaluated applying in vitro assays in different models of human exposure. Viability and ROS assays were performed on A549 and HT29 cells, while their skin irritation potential was tested on a reconstructed human epidermis model. The obtained results showed that GO-NH 2 and dGO-NH 2 substantially decrease cell viability in the lung and gastrointestinal models, being this reduction slightly higher in the cells exposed to the degraded forms. In contrast, this parameter was not affected by GO and dGO which, conversely, showed the ability to induce higher levels of ROS than the pristine and degraded aminated forms. Furthermore, none of the materials is skin irritant. Altogether, these results provide new insights about the potential harmful effects of the selected graphene-based nanomaterials in comparison with their degraded counterparts., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 The Authors. Published by Elsevier B.V. All rights reserved.)

The skin is a potential route of exposure to antimicrobial cleaning products (ACP). Skin irritation, reversible damage to the skin, is an endpoint for protecting consumers and operators accidently exposed to these complex mixtures. To assess skin irritation of 24 ACP formulations, a new protocol was developed and adapted from OECD Test Guideline No. 439 with EpiDerm™ (epidermis model) replaced by Phenion® FT (full thickness tissue, including epidermis and dermis) as the test system. A full thickness tissue was utilized to provide a more human in vivo-like model. Formulations were applied to Phenion® FT and cell viability measured by MTT reduction after a 15-min exposure and 42 h post exposure period. A prediction model was applied, and results compared with in vivo rabbit skin irritation data. Concordance between in vivo and in vitro was demonstrated to be suitable (i.e., sensitivity 78%, specificity 83%, and accuracy 79%) using this modified OECD Test Guideline No. 439 method with a 70% cell viability selected as the most reasonable cut off for discriminating non-irritants (EPA Class IV). These results were considered suitable to develop a draft IATA i.e., with any ACP formulation identified as EPA Category IV in this test. The method will be further refined to distinguish irritant categories., Competing Interests: Declaration of Competing Interest The authors declare the following financial interests/personal relationships which may be considered as potential competing interests: KEP and TM are employees of The Clorox Company. CSR is a consultant working with The Clorox Company. KEP is a Special Government Employee for the National Institutes of Health (NIH) and the current chair of the Scientific Advisory Committee on Alternative Toxicological Methods (SACATM). WW is an employee of Charles River Laboratories, subcontracted to perform the in-life testing. KS was an employee of PCRM during the development, conduct and reporting of the project and is now an employee of IIVS., (Copyright © 2023. Published by Elsevier Ltd.)

For years, the strive for in vitro methods for toxicological assessment suitable to replace animal studies gained progressive importance. OECD Test Guideline (TG) 431 was implemented in 2004, allowing to circumvent animal testing according to OECD TG 404 while reliably predicting skin corrosion potential of many substances and products. However, non-animal assays often show protocol-dependent limitations, that complicate or even prevent the testing of several groups of substances. In this study, the suitability of the OECD TG 431 for assessment of the skin corrosion potential of known acidic, thus often skin corrosive or irritating acrylic and methacrylic acid-based adhesives and monomers, was investigated. The commercially available Phenion® Open Source Reconstructed Epidermis (OS-REp) model, developed at Henkel & Co. KGaA, was used. The EpiDerm™ prediction model was considered most applicable to the Phenion® OS-REp model. All Proficiency Substances listed in OECD TG 431, amongst them six acids, were correctly classified and subcategorized as Skin Corr. 1 A or 1B/C corrosives. The OS-REp model was shown to be suitable for the assessment of skin corrosion potential in accordance with OECD TG 431. However, our results also indicate that acrylic and methacrylic monomer-based adhesives might fall outside the applicability domain of this guideline., Competing Interests: Declaration of Competing Interest The authors declare that there are no competing interests associated with the manuscript., (Copyright © 2023. Published by Elsevier Ltd.)

The aim of this study is to validate an in vitro skin irritation test (SIT) using three-dimensional reconstructed human epidermal (RhE) skin equivalents prepared by layer-by-layer (LbL) method (LbL-3D Skin) in a series of interlaboratory studies. The goal of these validation studies is to evaluate the ability of this in vitro test to reliably discriminate skin irritant from nonirritant chemicals, as defined by OECD and UN GHS. This me-too validation study is to assess the within- and between-laboratory reproducibility, as well as the predictive capacity, of the LbL-3D Skin SIT in accordance with performance standards for OECD TG 439. The developed skin model, LbL-3D Skin had a highly differentiated epidermis and dermis, similar to the validated reference methods (VRM) and native human skin. The quality parameters (cell survival in controls, tissue integrity, and barrier function) were similar to VRM and in accordance with OECD TG 439. The LbL-3D Skin SIT validation study was performed by three participating laboratories and consisted of three independent tests using 20 reference chemicals. The results obtained with the LbL-3D Skin demonstrated high within-laboratory and between-laboratory reproducibility, as well as high accuracy for use as a stand-alone assay to distinguish skin irritants from nonirritants. The predictive potency of LbL-3D Skin SIT using total 54 test chemicals were comparable to those in other RhE models in OECD TG 439. The validation study demonstrated that LbL-3D Skin has proven to be a robust and reliable method for predicting skin irritation., (© 2023 John Wiley & Sons Ltd.)

The rabbit skin irritation test has been the standard for evaluating the irritation potential of chemicals; however, alternative methods that do not use animal testing are actively encouraged. Reconstructed human epidermis (RhE) models mimic the biochemical and physiological properties of the human epidermis and can be used as an alternative method. On RhE methods, the metabolic activity of RhE models is used to predict skin irritation, with a reduction in metabolic activity indicating a reduced number of viable cells and linking cell death to skin irritation processes. However, new challenges have emerged as the use of RhE models increases, including the need for non-invasive and marker-free methodologies to assess cellular states. Electrochemical impedance spectroscopy (EIS) is one such methodology that can meet these requirements. In this study, our results showed that EIS can differentiate between irritant and non-irritant chemicals, with a significant increase in the capacitance values observed in the irritant samples. A ROC curve analysis showed that the prediction method based on EIS met OECD TG 439 requirements at all time points and had 95% within-laboratory reproducibility. Comparison with the MTT viability assay showed that prediction using EIS achieved higher sensitivity, specificity, and accuracy. These results suggest that EIS could potentially replace animal testing in the evaluation of irritation potential and could be a valuable addition to in vitro testing strategies.

In the present study, a comparative human toxicity assessment between newly developed Mn 3 O 4 nanoparticles with enhanced electrochemical properties (GNA35) and their precursor material (Mn 3 O 4 ) was performed, employing different in vitro cellular models representing main exposure routes (inhalation, intestinal and dermal contact), namely the human alveolar carcinoma epithelial cell line (A549), the human colorectal adenocarcinoma cell line (HT29), and the reconstructed 3D human epidermal model EpiDerm. The obtained results showed that Mn 3 O 4 and GNA35 harbour similar morphological characteristics, whereas differences were observed in relation to their surface area and electrochemical properties. In regard to their toxicological properties, both nanomaterials induced ROS in the A549 and HT29 cell lines, while cell viability reduction was only observed in the A549 cells. Concerning their skin irritation potential, the studied nanomaterials did not cause a reduction of the skin tissue viability in the test conditions nor interleukin 1 alpha (IL- 1 α) release. Therefore, they can be considered as not irritant nanomaterials according to EU and Globally Harmonized System of Classification and Labelling Chemicals. Our findings provide new insights about the potential harmful effects of Mn 3 O 4 nanomaterials with different properties, demonstrating that the hazard assessment using different human in vitro models is a critical aspect to increase the knowledge on their potential impact upon different exposure routes., (© 2022. The Author(s).)

Irritation testing is an integral part of the biocompatibility assessment of medical devices and has historically been conducted on animals, either by direct contact or with polar and non-polar solvent extracts. In 2018 an ISO-sponsored interlaboratory validation study demonstrated that two reconstituted human epidermis (RhE) based assays, which were adapted from validated methods used for industrial chemicals, produced results essentially equivalent to those obtained with in vivo tests. This led to the publication of the ISO 10993-23:2021 standard on irritation testing, which states that RhE-based assays are now the preferred method. The 2018 validation study evaluated strong irritants, so we tested nine mild irritants (GHS Category 3), neat and spiked at different concentrations into medical device extracts, per ISO 10993-23:2021. The results substantiated the applicability of RhE-based assays for evaluating mild irritants in medical device extracts. Moreover, the 2018 validation study tested solid extractable medical device materials but did not consider non-extractable medical device materials (e.g., creams, gels, or sprays). By testing nine marketed non-extractable materials, either neat or spiked with irritants, we also confirmed that RhE-based assays are readily applicable to such medical device materials., (Copyright © 2022 Elsevier Ltd. All rights reserved.)

There is a global trend towards the development of physiologically relevant in vitro skin models to reduce or replace animal testing in the evaluation of therapeutic drug candidates. However, only commercial reconstructed human epidermis models (RHEm) have undergone formal validation. Although these commercial models are suitable for a wide range of applications, they are costly, lack flexibility, and the protocols used to generate them are not transparent. In this study, we present an open-source full-thickness skin model (FTSm) and assess its potential for drug testing. The FTSm was developed using endogenous extracellular matrix to recreate the dermal compartment, avoiding animal-derived hydrogels. An RHEm based on an open-source protocol was evaluated in parallel. The integrity of the skin barrier was analyzed by challenging the surface with detergents and measuring cell viability as well as by trans-epithelial electrical resistance (TEER) measurements. Skin irritation studies were performed based on OECD guidelines and complemented with an evaluation of the impact on the skin barrier by TEER measurement. The permeation of a dye through the developed models and a commercial membrane (Strat-M®) was compared using Franz diffusion cells and an infinite dose approach. The FTSm demonstrated structural and barrier properties comparable to native human skin. Although the RHEm showed a better performance in drug testing, the FTSm presented better barrier properties than commercial models as reported in the literature. These skin models can be a valuable contribution to accelerating the development and dissemination of alternatives to animal testing, avoiding the limitations of commercial models.

In this study, permeation behaviors and chemical stability of miroestrol and deoxymiroestrol from Pueraria candollei var. mirifica (PM), Thai traditional medicine, crude extract containing transdermal gels were firstly evaluated. Three different PM extract containing gels were formulated, including hydroalcoholic and microemulsion gels using carbomer, and silicone gel using silicone elastomer. In vitro permeation through porcine ear skin demonstrated that the flux and 24 h cumulative permeation of miroestrol and deoxymiroestrol were in the order of hydroalcoholic > silicone > microemulsion gels. Hydroalcoholic gel provided the highest partition coefficient from gel onto skin, and thus the skin permeability coefficient. After 24 h permeation, no miroestrol and deoxymiroestrol remained deposited in the skin. Accelerated study using heating-cooling revealed insignificant difference between the remaining percentages of miroestrol and deoxymiroestrol in aqueous and non-aqueous based gels. Long-term stability study showed that miroestrol contents remained constant for 90 d and 30 d under 5 ± 3 °C and 30 ± 2 °C, 75 ± 5%RH, respectively; whereas the percentage of deoxymiroestrol decreased significantly after 30 d storage, irrespective of storage conditions. Acute dermal irritation test on New Zealand White rabbits showed that PM hydroalcoholic gels were non-irritant, with no signs of erythema or oedema.[Figure: see text].

Aldehydes comprise a major portion of skin sensitizers because they can react with both cysteine and lysine. Moreover, cinnamaldehyde (CA) is a typical moderate sensitizer and is often used in an alternative test method for skin sensitization. The amino acid derivative reactivity assay (ADRA) is an in chemico test method that evaluates the reactivity of cysteine derivatives ( N -(2-(1-naphthyl)acetyl)-l-cysteine, NAC) and lysine derivatives with the test chemicals and uses CA as a proficiency substance. We found that NAC depletion for CA was only 10-20% when CA was used directly from the reagent bottle, although it increased to almost 100% when stored after being aliquoted from the reagent bottle. It was also found that this was due to the air oxidation of NAC itself rather than the reaction of NAC with CA, indicating that this result simply shows an increase in apparent reactivity. Aldehydes are known to produce active species, such as radicals, during air oxidation. Therefore, we investigated whether radicals were generated under storage conditions using the radical scavenger OH-TEMPO. LC/MS/MS analysis revealed that CA and OH-TEMPO complexes were produced during the air oxidation of CA. In the results of five aldehydes, similar to CA, active species were not generated as significantly as CA. Collectively, during the evaluation of the aldehydes, it can be seen that careful measures need to be taken to prevent the aldehydes from oxidizing during storage, indicating that assessment without preventing air oxidation carries an increased risk of overestimation compared with the intrinsic skin sensitization potency.

Skin irritation is a key human health endpoint assessed by in vitro and in vivo methods. The OECD TG 404 guideline (in vivo) is based on erythema and oedema translated semi-quantitatively into Draize scores, providing hazard statements for substance classification following EUCLP/UNGHS criteria. Draize scores require quantitation from subjective in vivo observations, to obtain a scoring index, the Primary Irritation Index (PII). However, it is not recognised under REACH due to translating difficulties, notably the cut-off limit for classification and non-inclusion of corrosive effects. The aim of this study was to determine if classification can be driven by just one of the observed effects, erythema only, to create a Simplified Irritation Index (SII SKIN ). This simplifies the scoring calculation and reduces subjectivity. A quantitative approach with cut-off limits is thus proposed for classification. Substances can be classified as non-irritant, potentially irritant, irritant, or corrosive. The Simplifed Irritation Index (SII SKIN) is based on validated studies, representing multiple chemical groups. A significant correlation between SII SKIN and the harmonised classification was observed, and a proportionate relationship between the SII SKIN and the corresponding PII. The index proved to be useful in the development of an in silico model., (Copyright © 2021 Elsevier Inc. All rights reserved.)

Biocides are widely used in household products. Humans are exposed to biocides through dermal, inhalational, and oral routes. However, information on the dermal and inhalational toxicity of biocides is limited. We evaluated the effects of biocides on the skin and airways using the reconstructed human epidermis model KeraSkin™ and the airway model SoluAirway™. We determined the irritancy of 11 commonly used biocides (1,2-benzisothiazol-3(2H)-one [BIT], 2-phenoxyethanol [PE], zinc pyrithione, 2-bromo-2-nitropropane-1,3-diol, 3-iodoprop-2-ynyl N-butylcarbamate [IPBC], 2-octyl-1,2-thiazol-3-one, 2,2-dibromo-2-cyanoacetamide, 4-chloro-3-methylphenol [CC], 2-phenylphenol, deltamethrin, and 4,5-dichloro-2-octyl-1,2-thiazol-3-one) in the KeraSkin™ and SoluAirway™ by viability and histological examinations. BIT and CC were found to cause skin irritation at the approved concentrations or at the concentration close to approved limit while the others were non-irritants within the approved concentration. These results were confirmed via histology, wherein skin irritants induced erosion, vacuolation, and necrosis of the tissue. In the SoluAirway™, most of the biocides decreased cell viability even within the approved limits, except for PE, IPBC, and deltamethrin, suggesting that the airway may be more vulnerable to biocides than the skin. Taken together, our result indicates that some biocides can induce toxicity in skin and airway. Further studies on the dermal and inhalational toxicity of biocides are warranted., (Copyright © 2021 Elsevier Ltd. All rights reserved.)

Three-dimensional skin models, also named 3D skin models, human skin equivalents (HSEs), or Human Epidermal Equivalents (HEEs), have been increasingly used for chemical assessments in terms of efficacy and safety. Considering this, we developed an HEE model using immortalized HaCaT cells, aiming to overcome the limitation of primary tissue source. Our 3D model (HaCaT-HEE) exhibited important markers of cell differentiation (CK10, CK14, involucrin, and filaggrin), although the stratum corneum was shown to be modest. Besides, the model showed a good prediction potential considering membrane permeability, sensitivity, specificity, and accuracy in distinguishing irritant and corrosive effects after exposure to selected chemicals recommended by the OECD protocols. We also validated the formazan determination for the MTT method using High-Performance Liquid Chromatography (HPLC). For that, we considered carry over, linearity, reproducibility/robustness, accuracy, precision, selectivity, and matrix effect, according to the Food and Drug Administration (FDA) guideline. Based on our results, we can conclude that our model has an acceptable predictive value for the safety evaluation of compounds after skin exposure, with the great advantage of being constructed using immortalized cells., (Copyright © 2020 Elsevier Ltd. All rights reserved.)

When developing new cosmetics, it is extremely important to consider the safety of consumers. Absence of potential irritancy is generally assessed using an OECD TG439 compliant Reconstructed Human Epidermis (RHE) systems and MTT assays, resulting in an irritant/not irritant classification. To gain insight into the irritancy of molecules/finished cosmetic products and to predict the outcome of irritation tests performed on subjects whatever their nature, we developed a test that uses skin explants and histological analysis. Results showed that this irritation test is sensitive enough to accurately and repeatably detect known irritants. If the diverse origin of the skin explants used led to variability in the histological alterations scored, the overall grading of irritancy is highly reproducible. Finally, when testing 120 non-alcoholic cosmetics of various galenic forms, comparison of data between the ex vivo irritation tests and of a 24-/48-h human patch test revealed a single false negative, very close to the limit, and a 10% false positive rate. It was not possible to calculate the sensitivity of the ex vivo irritation test; however, its specificity was 89.9% and its accuracy was 89.1%. Similar results, with a slightly higher false positive rate, were found when testing 49 alcoholic cosmetics. These values exceed the minimum requirements of OECD TG439., (Copyright © 2020. Published by Elsevier Ltd.)

This chapter presents the protocols for developing of skin equivalents (SE) and reconstructed human epidermis (RHE) models for dermal toxicity evaluation as an alternative method to animal use in research. It provides a detailed protocol for the in vitro reconstruction of human skin from primary keratinocytes, melanocytes, and fibroblasts obtained from foreskin biopsies, including the procedures for reconstruction of a stratified epidermis on a polyester membrane. SE and RHE developed through these methods have been proven suitable not only for dermal toxicity studies, but also for investigating of pathological conditions in the skin, such as diabetes and invasion of melanoma.

Contact allergy is of considerable importance to the toxicologist, and regulatory authorities worldwide require testing for skin sensitization potential and appropriate hazard labeling to enable management of the risk to human health. Although traditionally the identification of skin-sensitizing chemicals has been carried out using animal models, in Europe legislative changes have promoted, and now require, the use of non-animal methods (i.e., Cosmetic Directive, REACH). Several in vitro alternatives for hazard identification have now been validated, but do not provide information on the potency of a skin sensitizer. Here, we describe an animal model, the local lymph node assay (LLNA), and an in vitro model, the RhE IL-18 potency assay, in the context of the identification and potency classification of skin sensitizers. These two assays have been chosen among the different available tests as representative of an alternative in vivo model (the LLNA) and a promising in vitro method with the potential of both hazard identification and potency classification.

Skin irritation tests using reconstructed human epidermis (RhE) employ viability as an endpoint, but color interference or borderline results are often problematic. We examined whether the cytology of cells from treated RhE could determine skin irritancy. Six chemicals (three irritants; DnP, 1-B, PH, three non-irritants; DP, APA, HS) were evaluated in a RhE, Keraskin™. DP, HS, and PH were clearly classified with viability, but DnP, 1-B, and APA were often falsely determined, due to borderline values falling near the cutoff, 50%. In histology, the tissues treated with DnP, 1-B, and PH showed erosion of the stratum corneum, vacuolization, and necrosis in the basal layer. DP- and HS-treated tissues showed relatively normal morphology but APA induced necrosis similar to irritants. Cytology revealed that DnP, 1-B or PH depleted cells and induced irregular and abnormal cell shapes. In contrast, relatively regular and normal shapes and clear distinction between the nucleus and cytoplasm was observed for DP, APA and HS. To further confirm it, additional 10 substances, including false positives from OECD TG 439, were tested. Overall (16 substances in total), cytology: total area predicted the skin irritancy of test chemicals with the highest accuracy (87.5%) followed by cytology: cell count (81.3%), histology (75%) and viability (68.8%), confirming the utility of cytology as an alternative endpoint in the skin irritation test using RhE., Competing Interests: Declaration of Competing Interest The authors declare that there are no conflicts of interest., (Copyright © 2020 Elsevier Ltd. All rights reserved.)

The ISO 10993 standards on biocompatibility assessment of medical devices discourage the use of animal tests when reliable and validated in vitro methods are available. A round robin validation study of in vitro reconstructed human epidermis (RhE) assays was performed as potential replacements for rabbit skin irritation testing. The RhE assays were able to accurately identify strong irritants in dilute medical device extracts. However, there was some uncertainty about whether RhE tissues accurately predicted the results of the rabbit skin patch or intracutaneous irritation test. To address that question, this paper presents in vivo data from the round robin and subsequent follow-up studies. The follow-up studies included simultaneous in vitro RhE model and in vivo testing of round robin polymer samples and the results of dual in vitro/in vivo testing of currently marketed medical device components/materials. Our results show for the first time that for both pure chemicals and medical device extracts the intracutaneous rabbit test is more sensitive to detect irritant activity than the rabbit skin patch test. The studies showed that the RhE models produced results that were essentially equivalent to those from the intracutaneous rabbit skin irritation test. Therefore, it is concluded that RhE in vitro models are acceptable replacements for the in vivo rabbit intracutaneous irritation test for evaluating the irritant potential of medical devices., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2020 The Authors. Published by Elsevier Ltd.. All rights reserved.)

Capsaicin is an active compound in chili peppers ( Capsicum chinense ) that has been approved for chronic pain treatment. The topical application of high-strength capsaicin has been proven to reduce pain; however, skin irritation is a major drawback. The aim of this study was to investigate an appropriate and scalable technique for preparing nanostructured lipid carriers (NLCs) containing 0.25% capsaicin from capsicum oleoresin (NLC_C) and to evaluate the irritation of human skin by chili-extract-loaded NLCs incorporated in a gel formulation (Gel NLC_C). High-shear homogenization with high intensity (10,000 rpm) was selected to create uniform nanoparticles with a size range from 106 to 156 nm. Both the NLC_C and Gel NLC_C formulations expressed greater physical and chemical stabilities than the free chili formulation. Release and porcine biopsy studies revealed the sustained drug release and significant permeation of the NLCs through the outer skin layer, distributing in the dermis better than the free compounds. Finally, the alleviation of irritation and the decrease in uncomfortable feelings following the application of the Gel NLC_C formulation were compared to the effects from a chili gel and a commercial product in thirty healthy volunteers. The chili-extract-loaded NLCs were shown to be applicable for the transdermal delivery of capsaicin whilst minimizing skin irritation, the major noncompliance cause of patients.

We conducted a me-too validation study to confirm the reproducibility, reliability, and predictive capacity of KeraSkin™ skin irritation test (SIT) as a me-too method of OECD TG 439. With 20 reference chemicals, within-laboratory reproducibility (WLR) of KeraSkin™ SIT in the decision of irritant or non-irritant was 100%, 100%, and 95% while between-laboratory reproducibility (BLR) was 100%, which met the criteria of performance standard (PS, WLR≥90%, BLR≥80%). WLR and BLR were further confirmed with intra-class correlation (ICC, coefficients >0.950). WLR and BLR in raw data (viability) were also shown with a scatter plot and Bland-Altman plot. Comparison with existing VRMs with Bland-Altman plot, ICC and kappa statistics confirmed the compatibility of KeraSkin™ SIT with OECD TG 439. The predictive capacity of KeraSkin™ SIT was estimated with 20 reference chemicals (the sensitivity of 98.9%, the specificity of 70%, and the accuracy of 84.4%) and additional 46 chemicals (for 66 chemicals [20 + 46 chemicals, the sensitivity, specificity and accuracy: 95.2%, 82.2% and 86.4%]). The receiver operating characteristic (ROC) analysis suggested a potential improvement of the predictive capacity, especially sensitivity, when changing cut-off (50% → 60-75%). Collectively, the me-too validation study demonstrated that KeraSkin™ SIT can be a new me-too method for OECD TG 439., (Copyright © 2020 Elsevier Inc. All rights reserved.)

Background: Alcohol-based hand rub (ABHR) is recommended for hand hygiene, and application on dry skin is generally well tolerated. However, hydration of the skin may lead to increased susceptibility to ABHR., Objectives: To evaluate if increased skin hydration changes skin barrier response to ABHR, as compared to application on dry skin., Methods: Twenty healthy volunteers participated in a 3-day experimental setup. Intervention areas on the forearms were exposed to either water immersion or occlusion followed by repeated exposures to ABHR. Skin barrier function was assessed by measurement of transepidermal water loss (TEWL), electrical conductance, pH, and erythema at baseline and day 3., Results: The area exposed to water immersion preceding ABHR showed a significant increase in TEWL from baseline to day 3 (P = .04), and for the occluded area the same trend was found (P = .11), with an additional decrease in electrical conductance (P = .03). No significant differences were found for the control area. The assessments did not differ significantly between intervention and control sites., Conclusion: Our results indicate that extensive skin hydration may lead to increased susceptibility to ABHR. Further evaluation of this observation is important, since ABHRs are widely used, particularly among health care workers in whom hand eczema is a huge problem., (© 2020 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd.)

Background/aims: During dermatological forms development, one of the simplest non-invasive techniques used to evaluate cutaneous tolerance of formulations is to monitor the color changes using a tristimulus chromameter. Most published tolerance studies involving chromametric measurements are performed on Caucasian subjects. However, in the context of drug formulation for African-type populations, it is not always relevant to transpose tolerance results obtained on Caucasians populations to African-type ones due to histological ethnic differences of the skin. The goal of this work was to assess whether tristimulus chromameter can be used to highlight color variations following the application of dermatological topics on black skin in order to validate skin tolerance studies made on African-type subjects., Materials and Methods: After application of two commercial creams with opposite side effects (skin irritation and skin blanching) in both Africans and Caucasians populations, color variations were evaluated using a tristimulus chromameter in L * a * b * color system and compared between both populations. L * indicating color brightness, a * represents green and red directions and b * represents blue and yellow directions., Results: While skin irritation resulted in a significant increase of a * parameter in both studied populations, the skin blanching resulted in a decrease of a * associated with an increase of L * ., Conclusion: We established that tristimulus chromameter can be used to achieve in vivo skin tolerance study of dermatologic formulations in Africans despite their dark skin even though it appeared less sensitive. This study can speed up the development of dermatological forms dedicated to Africans and/or Caucasians subjects., (© 2019 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd.)

Purpose: The topical application of exosomes secreted by mesenchymal stem cells (MSC-Exos) on the skin is a very new and interesting topic in the medical field. In this study, we aimed to investigate whether marine sponge Haliclona sp. spicules (SHSs) could effectively enhance the skin delivery of human umbilical cord-derived MSC-Exos (hucMSC-Exos), and further evaluate the topical application of hucMSC-Exos combined with SHSs in rejuvenating photoaged mouse skin., Materials and Methods: SHSs were isolated from the explants of sponge Haliclona sp. with our proprietary method, and hucMSC-Exos were prepared from the conditioned medium of hucMSCs using ultracentrifugation. The effects of SHSs on the skin penetration of fluorescently labeled hucMSC-Exos were determined using confocal microscopy in vitro (porcine skin) and in vivo (mouse skin). The therapeutic effects of hucMSC-Exos coupled with SHSs against UV-induced photoaging in mice were assessed by using microwrinkles analysis, pathohistological examination and real-time RT-PCR. We also tested the skin irritation caused by the combination of hucMSC-Exos and SHSs in guinea pigs., Results: In vitro results showed that hucMSC-Exos could not readily penetrate through porcine skin by themselves. However, SHSs increased the skin absorption of exosomes by a factor of 5.87 through creating microchannels. Similar penetration enhancement of hucMSC-Exos was observed after SHSs treatment in mice. The combined use of hucMSC-Exos and SHSs showed significant anti-photoaging effects in mice, including reducing microwrinkles, alleviating histopathological changes, and promoting the expression of extracellular matrix constituents, whereas hucMSC-Exos alone produced considerably weaker effects. Skin irritation test showed that the combination of hucMSC-Exos and SHSs caused slight irritation, and the skin recovered shortly., Conclusion: SHSs provide a safe and effective way to enhance the skin delivery of MSC-Exos. Moreover, the combination of MSC-Exos and SHSs may be of much use in the treatment of photoaging., Competing Interests: Prof. Dr. Ming Chen reports a patent PCT/CN2020/073345 pending, a patent US 16/028,036 issued, a patent CN201910958941.9 pending. The authors declare no other conflict of interest., (© 2020 Zhang et al.)

An understanding of the bioavailability of topically applied cosmetics ingredients is key to predicting their local skin and systemic toxicity and making a safety assessment. We investigated whether short-term incubations with S9 from the reconstructed epidermal skin model, EpiSkin™, would give an indication of the rate of chemical metabolism and produce similar metabolites to those formed in incubations with human skin explants. Both have advantages: EpiSkin™ S9 is a higher-throughput assay, while the human skin explant model represents a longer incubation duration (24 hours) model integrating cutaneous distribution with metabolite formation. Here, we compared the metabolism of 10 chemicals (caffeine, vanillin, cinnamyl alcohol, propylparaben, 4-amino-3-nitrophenol, resorcinol, 4-chloroaniline, 2-amino-3-methyl-3H-imidazo[4,5-F]quinoline and 2-acetyl aminofluorene) in both models. Both models were shown to have functional Phase 1 and 2 enzymes, including cytochrome P450 activities. There was a good concordance between the models with respect to the level of metabolism (stable vs. slowly vs. extensively metabolized chemicals) and major early metabolites produced for eight chemicals. Discordant results for two chemicals were attributed to a lack of the appropriate cofactor (NADP + ) in S9 incubations (cinnamyl alcohol) and protein binding influencing chemical uptake in skin explants (4-chloroaniline). These data support the use of EpiSkin™ S9 as a screening assay to provide an initial indication of the metabolic stability of a chemical applied topically. If required, chemicals that are not metabolized by EpiSkin™ S9 can be tested in longer-term incubations with in vitro human explant skin to determine whether it is slowly metabolized or not metabolized at all., (© 2019 John Wiley & Sons, Ltd.)

The purpose of this study was to evaluate the sensitization potential of 82 compounds classified as volatile and/or semi-volatile organic compounds using the direct peptide reactivity assay (DPRA), given that these chemical compounds have been detected frequently and at high concentrations in a national survey of Japanese indoor air pollution and other studies. The skin sensitization potential of 81 of these compounds was evaluable in our study; one compound co-eluted with cysteine peptide and was therefore not evaluable. Twenty-five of the evaluated compounds were classified as positive. Although all glycols and plasticizers detected frequently and at high concentrations in a national survey of Japanese indoor air pollution were negative, hexanal and nonanal, which are found in fragrances and building materials, tested positive. Monoethanolamine and 1,3-butanediol, which cause clinical contact dermatitis, and several compounds reported to have weak sensitization potential in animal studies, were classified as negative. Thus, it was considered that compounds with weak sensitization potential were evaluated as negative in the DPRA. Although the sensitization potential of the formaldehyde-releasing preservative bronopol has been attributed to the release of formaldehyde (a well-known contact allergen) by its degradation, its degradation products-bromonitromethane and 2-bromoethanol-were classified as positive, indicating that these degradation products also exhibit sensitization potential. The compounds that tested positive in this study should be comprehensively assessed through multiple toxicity and epidemiological studies.

Laundry detergents that are free of fragrances and dyes should be recommended to patients with sensitive skin. To ensure mildness of these products, manufacturers typically conduct patch testing. A new method, which is more discerning than patch testing, called Detergent Mildness Index (DMI), has been described previously. Using the DMI method, 12 sensitive skin/baby laundry detergents, representing the top 85% of the marketplace, were evaluated. The product "all Free Clear®" was found to be the mildest liquid laundry detergent.

Some cosmetic ingredients can act as a chemical hapten to induce an immune response; therefore, evaluating the sensitizing potential of cosmetic ingredients is essential. We previously developed a novel in chemico direct peptide reactivity assay involving a spectrophotometric evaluation (Spectro-DPRA) for animal skin sensitization tests (local lymph node assay; LLNA). Based on previous research, we expanded the test materials to confirm the effectiveness of the Spectro-DPRA method for predicting the animal skin sensitization potential, and further determined the feasibility of the method for estimating the human skin sensitization potential. Spectro-DPRA showed 83.1% or 89.1% accuracy compared to a conventional LLNA or prediction based on human data, respectively, with a combination model using both a cysteine peptide and lysine peptide cut-off. To identify the effect of the lipophilicity of a chemical on predicting the skin sensitization potential, we applied our prediction model to chemicals with a Log P ow range of -1 to 4. Overall predictability was increased, and the accuracy compared to the LLNA and human data was 91.5% and 94.9%, respectively, in the combination cut-off prediction model. In conclusion, Spectro-DPRA serves as an easy, rapid, and high-throughput in chemico screening method with high accuracy to predict the human skin sensitization potential of chemicals., (Copyright © 2019 Elsevier B.V. All rights reserved.)

In Ukraine Globally Harmonized System of classification of chemicals has not been implemented yet. In this article we analyze differences between GHS/CLP classification systems and Hygienic Classification of Pesticides by the Degree of Hazard currently in force in Ukraine in respect of approach and criteria for classification of effects on skin. As a case study, we conducted in silico modelling of herbicide imazamox using skin irritation/corrosion modules of ToxTree. The prediction of ToxTree was "Not Corrosive to skin". Then skin irritation and skin corrosion in vitro tests (OECD TGs 439, 431) were conducted. Classification of this substance based on in vitro and in vivo results according to GHS/CLP was the same, while it was not possible based on in vitro results to assign certain hazard class of Ukrainian classification due to difference in its and GHS/CLP criteria. However, ongoing process of harmonization of Ukrainian legislation with EU will give opportunity not only use alternative methods, but also adopt most recent advances and incorporate data from non-animal methods directly into classification criteria., (Copyright © 2019 Elsevier Ltd. All rights reserved.)

In commercial products such as household deodorants or biocides, didecyldimethylammonium chloride (DDAC) often serves as an antimicrobial agent, citral serves as a fragrance agent, and the excipient ethylene glycol (EG) is used to dissolve the active ingredients. The skin sensitization (SS) potentials of each of these substances are still being debated. Moreover, mixtures of DDAC or citral with EG have not been evaluated for SS potency. The in vitro alternative assay called human Cell Line Activation Test (h-CLAT) and Direct Peptide Reactivity Assay (DPRA) served to address these issues. On three independent runs of h-CLAT, DDAC and citral were predicted to be sensitizers while EG was predicted to be a non-sensitizer and also by the DPRA. Mixtures of DDAC or citral with EG at ratios of 7:3 and 1:4 w/v were all positive by the h-CLAT in terms of SS potential but SS potency was mitigated as the proportion of EG increased. Citral and its EG mixtures were all positive but DDAC and its EG mixtures were all negative by the DPRA, indicating that the DPRA method is not suitable for chemicals with pro-hapten characteristics. Since humans can be occupationally or environmentally exposed to mixtures of excipients with active ingredients, the present study may give insights into further investigations of the SS potentials of various chemical mixtures.

There are currently three in vitro methods adopted by the Organization for the Economic Co-operation and Development for testing chemicals based on the third key event of the skin sensitization adverse outcome pathway, the activation of dendritic cells. All of them use culture medium supplemented with fetal bovine serum (FBS), which brings technical disadvantages and animal welfare concerns. The objective of this study was to analyze the possibility of eliminating the use of FBS in the human Cell Line Activation Test (h-CLAT). After successful implementation of the h-CLAT using THP-1 cells cultured in FBS-containing medium, several attempts to adapt THP-1 cells to four different serum-free media were made. The best results were obtained with gradual adaptation to RPMI-1640 medium with HL-1™ Supplement and to X-VIVO™ 10. Adapted cells were cryopreserved and submitted to the reactivity check. After being approved, they were used in dose finding and proficiency assays. Despite minor adjustments in the original protocol, it was possible to correctly predict the sensitizing potential of the ten proficiency substances using THP-1 cells adapted to X-VIVO™ 10, which indicates that it is possible to eliminate the use of FBS in the h-CLAT, using a chemically defined medium., (Copyright © 2018 Elsevier Ltd. All rights reserved.)

The occurrence of drug hypersensitivity reactions (DHRs) following administration of low molecular weight (LMW) drugs is an important health concern. However, in vivo animal models which could be used as tools for the prediction of DHRs are lacking. As a result, research has focused on development of in vitro tools for predicting DHRs. In this study a novel human in vitro pre-clinical skin explant test was used to predict T cell-mediated hypersensitivity responses induced by LMW drugs. Responses in the skin explant test for 12 LMW drugs associated with T cell-mediated hypersensitivity in the clinic (abacavir, amoxicillin, carbamazepine, diclofenac, lamotrigine, lapatinib, lumiracoxib, nevirapine, ofloxacin, phenytoin, propranolol, sulfamethoxazole) were compared with responses for 5 drugs with few/no reports of T cell-mediated hypersensitivity reactions (acetaminophen, cimetidine, flecainide, metformin, verapamil). Changes in skin histology following in vitro exposure to the drugs as well as T cell proliferation and interferon gamma (IFNγ) production were studied. The results of the skin explant assays showed a good positive correlation (r = 0.77, p < .001) between the test outcome (prediction of positive or negative) and the clinical classification of the tested drugs. The T cell proliferation assay showed a correlation of r = 0.60 (p < .01) and the IFNγ assay r = 0.51 (p < .04). The data suggest that the skin explant model could be a useful tool to predict the potential of LMW drugs to induce DHRs., (Copyright © 2019 Elsevier Inc. All rights reserved.)

Purpose: The purpose of this article is to offer practical guidance for pharmacists to successfully implement penicillin allergy skin testing (PAST)., Summary: Less than 10% of patients labeled as having a penicillin allergy are confirmed as present upon skin testing. This labeling results in use of alternative antibiotics and thus unwanted adverse consequences including potentiated antimicrobial resistance, increased costs, and worse clinical outcomes. Stewardship guidelines recommend PAST to enhance use of first-line agents; however, this was a weak recommendation with low-quality evidence. Recent efforts and subsequent research since publication of guidelines have demonstrated beneficial effects from increasing use of PAST among stewardship programs to improve outcomes. A number of different models exist demonstrating successful implementation of PAST at various healthcare facilities. There are important logistical factors to consider during implementation of PAST such as target population, optimal preparation, leadership structure, resource availability, and state regulations. Pharmacists as leaders of antimicrobial stewardship teams and experts in drug allergies are a natural fit to help implement PAST in healthcare settings to improve overall outcomes. This article offers guidance to institutions considering implementation of PAST., Conclusion: PAST is rapidly becoming an effective, long-term antimicrobial stewardship tool to optimize antimicrobial prescribing in both the inpatient and outpatient settings. Pharmacists have demonstrated significant benefit as providers of PAST services in a variety of healthcare settings with a number of different healthcare professionals.

In this study, the use of cubosomes for topical delivery of the antimicrobial peptide (AMP) LL-37 was investigated. Topical delivery of AMPs is of great interest for treatment of skin infections caused by bacteria, such as Staphylococcus aureus. AMP containing cubosomes were produced by three different preparation protocols and compared: (i) pre-loading, where LL-37 was incorporated into a liquid crystalline gel, which thereafter was dispersed into nanoparticles, (ii) post-loading, where LL-37 was let to adsorb onto pre-formed cubosomes, and (iii) hydrotrope-loading, where LL-37 was incorporated during the spontaneously formed cubosomes in an ethanol/glycerol monooleate mixture. Particle size and size distribution were analyzed using dynamic light scattering (DLS), liquid crystalline structure by small angle x-ray scattering (SAXS) and release of LL-37 by a fluorescamine assay. Proteolytic protection of LL-37 as well as bactericidal effect after enzyme exposure was investigated. The skin irritation potential of cubosomes was examined by an in vitro epidermis model. Finally, the bacterial killing property of the cubosomes was examined by an ex vivo pig skin wound infection model with Staphylococcus aureus. Data showed that a high loading of LL-37 induced formation of vesicles in case of cubosomes prepared by sonication (pre-loading). No release of LL-37 was observed from the cubosomes, indicating strong association of the peptide to the particles. Proteolysis studies showed that LL-37 was fully protected against enzymatic attacks while associated with the cubosomes, also denoting strong association of the peptide to the particles. As a consequence, bactericidal effect after enzyme exposure remained, compared to pure LL-37 which was subjected to proteolysis. No skin irritation potential of the cubosomes was found, thus enabling for topical administration. The ex vivo wound infection model showed that LL-37 in pre-loaded cubosomes killed bacteria most efficient., (Copyright © 2018 Elsevier B.V. All rights reserved.)

In vivo and in vitro irritation testing is important for evaluating the biological safety of medical devices. Here, the performance of positive reference materials for skin irritation testing was evaluated. Four reference standards, referred to as Y-series materials, were analyzed: a polyvinyl chloride (PVC) sheet spiked with 0 (Y-1), 1.0 (Y-2), 1.5 (Y-3), or 10 (Y-4) parts of Genapol X-080 per 100 parts of PVC by weight. Y-1, Y-2, and Y-3 did not induce skin irritation responses in an in vitro reconstructed human epidermis (RhE) tissue model, as measured by tissue viability or interleukin-1α release, or in an in vivo intracutaneous response test using rabbits. In contrast, Y-4 extracts prepared with saline or sesame oil at 37°C and 50°C clearly elicited positive irritation responses, including reduced viability (< 50%) and significantly higher interleukin-1α release compared with the solvent alone group, in the RhE tissue model and an intracutaneous response test, where substantial necrosis was observed by histopathology. The positive skin irritation responses induced in vitro under various extraction conditions, as well as those elicited in vivo, indicate that Y-4 is an effective extractable positive control material for in vivo and in vitro skin irritation tests of medical devices. © 2017 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 106B: 2807-2814, 2018., (© 2017 Wiley Periodicals, Inc.)

The basic purpose of this research work was to investigate the skin depigmenting and antierythmetic effects of emulgel containing Annona muricata L. fruit extract by comparing it with its control and the variation in these effects with the addition of penetration enhancer. The control (without extract and penetration enhancer i.e. clove oil 8%) and the two test formulations with 4% fruit extract FA and FB (without clove oil and with clove oil) were formulated and evaluated for in vitro characteristics (pH, conductivity and in vitro release). The emulgels were then applied on the cheeks of 26 healthy female human volunteers (n=26) for a study period of 12 weeks. Skin melanin and erythema contents were measured by Mexameter at base line and then after every 2 weeks. Both the test formulations showed significant decrease in melanin and erythema contents when compared to control but FB showed marked decrease in skin melanin when compared to the FA. While in case of skin erythema, the effects of FA were greater as compared to other formulation. When paired sample t test (5% level of significance) was applied, the test formulations showed significant results. This study reveals that the Annona muricata L. fruit extract naturally contains some important phenolic compounds and can be effectively used in topical preparations for the treatment of skin hyperpigmentation and dermatitis. Skin whitening effects can be increased by the addition of penetration enhancer.

Reporter cell lines are a particularly useful tool to screen for the skin sensitization potential of chemicals. Current cell models based on Keap1-Nrf2 mimic induction by conducting antioxidant response element-luciferase plasmids. However, plasmid-based reporters may ignore comprehensive aspects of induction, thus affecting the accuracy of hazard identification. Herein, we developed a novel HaCaT-based reporter system, EndoSens, whereby luciferase was specifically inserted into the cassette for heme oxygenase (decycling) 1 (HMOX1, the most consistent marker induced by skin sensitizers) by CRISPR/Cas9. Testing data from 20 coded substances showed an accuracy of 90%, sensitivity of 91.7%, and specificity of 87.5%, which exceeded the OECD requirement. Among the 35 chemicals examined, predictivity was better than reported for the validated KeratinoSens™. These results indicate that the EndoSens assay could advance the predictivity of skin sensitization, thus making it a promising tool for in vitro skin sensitization testing.

The epidermal sensitization assay (EpiSensA) is an in vitro skin sensitization test method based on gene expression of four markers related to the induction of skin sensitization; the assay uses commercially available reconstructed human epidermis. EpiSensA has exhibited an accuracy of 90% for 72 chemicals, including lipophilic chemicals and pre-/pro-haptens, when compared with the results of the murine local lymph node assay. In this work, a ring study was performed by one lead and two naive laboratories to evaluate the transferability, as well as within- and between-laboratory reproducibilities, of EpiSensA. Three non-coded chemicals (two lipophilic sensitizers and one non-sensitizer) were tested for the assessment of transferability and 10 coded chemicals (seven sensitizers and three non-sensitizers, including four lipophilic chemicals) were tested for the assessment of reproducibility. In the transferability phase, the non-coded chemicals (two sensitizers and one non-sensitizer) were correctly classified at the two naive laboratories, indicating that the EpiSensA protocol was transferred successfully. For the within-laboratory reproducibility, the data generated with three coded chemicals tested in three independent experiments in each laboratory gave consistent predictions within laboratories. For the between-laboratory reproducibility, 9 of the 10 coded chemicals tested once in each laboratory provided consistent predictions among the three laboratories. These results suggested that EpiSensA has good transferability, as well as within- and between-laboratory reproducibility., (Copyright © 2018 John Wiley & Sons, Ltd.)

Several irritants were used in the in vitro irritation medical device round robin. The objective of this study was to verify their irritation potential using the human patch test (HPT), an in vitro assay, and in vivo data. The irritants were lactic acid (LA), heptanoic acid (HA), sodium dodecyl sulfate (SDS), Genapol® X-80 (GP), and Y-4 polymer. Dilute saline and sesame seed oil (SSO) solutions of each were evaluated using a 4 and 18 h HPT and the EpiDerm™ SIT-MD RhE assay; results were then compared to existing rabbit skin irritation test data. Results from the 4 h HPT were negative in most cases except for GP and SDS, while the 18 h HPT also identified some LA, HA, and GP samples as irritants. EpiDerm™ SIT-MD correctly identified all irritants except GP in SSO due to limited solubility. Data from cutaneous rabbit irritation tests were negative, while all intracutaneous results were strongly or weakly positive except for the most dilute GP solutions. These findings indicate that EpiDerm™ SIT-MD results correlate with those from the rabbit intracutaneous test and confirm that RhE assays are suitable replacements for animals in evaluating the tissue irritation potential of medical devices., (Copyright © 2018 The Authors. Published by Elsevier Ltd.. All rights reserved.)

According to ISO 10993 standards for biocompatibility of medical devices, skin irritation is one of the three toxicological endpoints to be always addressed in a biological risk assessment. This work presents a new protocol to assess this endpoint in vitro rather than in vivo. The protocol was adapted to medical devices extracts from the OECD TG 439 with the SkinEthic™ RHE model as test system. It was challenged with irritant chemicals, Sodium Dodecyl Sulfate, Lactic Acid and Heptanoic Acid spiked in polar solvents, sodium chloride solution or phosphate buffer saline and non-polar solvent, Sesame Oil. Cell viability measured by MTT reduction after 24 h exposure was used as readout. Quantification of IL-1α release as secondary readout did not increased performance. Samples of heat-pressed polyvinyl chloride (PVC) and silicone sheets infused with or without known irritant (4% Genapol-X80, 6% Genapol-X100 and 15% SDS) were tested after extraction in polar and non-polar solvents. Medical device extracts are classified irritant when the cell viability is inferior or equal to 50%, compared to the negative controls tissues, in at least one extraction solvent. The correct classification of all the samples confirmed the good performance of this new protocol for in vitro skin irritation of medical devices extracts with the SkinEthic™ RHE model. Seven naïve laboratories were trained in prevision of the Round Robin Study to evaluate Reconstructed Human Epidermis (RhE) models as in vitro skin irritation test for detection of irritant potential in medical device extracts., (Copyright © 2018 The Authors. Published by Elsevier Ltd.. All rights reserved.)

Skin irritation is an important component of the biological safety evaluation of medical devices. This testing has typically been performed using in vivo models. However, in an effort to reduce the need for in vivo testing, alternative methods for assessing skin irritation potential in vitro have been developed using a Reconstructed Human Epidermis (RhE) model. During the development of the protocol for the round robin validation of in vitro irritation testing for medical device extracts, it became clear that there were three points in the procedure where different options may be validated within each laboratory for routine testing: sample exposure time (18 vs 24h), SDS positive control concentration, and cytokine (IL-1α) release testing. The goal of our study was to evaluate the effect of these variables. EpiDerm™ tissues were exposed to extracts of three plain polymer samples, and four polymers embedded with known irritant chemicals. Exposures were performed for 18 and 24h. Resulting tissue viability was assessed by MTT reduction and IL-1α release was assessed by ELISA. Testing was also performed using various concentrations of SDS ranging from 0.5 to 1% (w/v). Overall, results were similar for samples tested and 18 and 24h, but the 18h exposure time has the potential to have an impact on the results of some sample types. IL-1α testing was shown to be useful to clarify conflicting tissue viability results. Use of a lower concentration of SDS as a positive control can help prevent issues that arise from excessive tissue damage often caused by 1% SDS., (Copyright © 2018 The Authors. Published by Elsevier Ltd.. All rights reserved.)

Skin sensitization risk assessment of botanical ingredients is necessary for consumers' protection and occupational hazard identification. There are currently very few available alternative methods that can assist in the evaluation of complex mixtures. Chemical methods can provide essential information in a timely manner and thus help to reduce the need for in vivo testing, and they can complement and facilitate targeted in vitro assays. In the present work, the applicability of the high-throughput screening with dansyl cysteamine (DCYA) method for the systematic evaluation of skin sensitization of complex botanicals was explored. Botanical ingredients of four unrelated plant species were obtained and tested with the high-throughput fluorescence method at three concentrations. To illustrate the minimal matrix effects of the tested extracts on the developed method, the least DCYA-reactive extract (Rosa canina) was spiked with known sensitizers at different concentrations. The data obtained from the four plant extracts and the spiking experiments with known sensitizers, suggest that the high-throughput screening-DCYA method can be successfully applied for estimating the skin sensitization potential of complex botanical matrices. This is the first report of an attempt to develop a versatile in chemico method for the rapid detection of reactive skin sensitizers in complex botanical extracts, which could complement the battery of existing validated, non-animal methods., (Copyright © 2018 John Wiley & Sons, Ltd.)