Publications by authors named "Sébastien Grégoire"

22 Publications

  • Page 1 of 1

Effective exposure of chemicals in in vitro cell systems: A review of chemical distribution models.

Toxicol In Vitro 2021 Mar 1;73:105133. Epub 2021 Mar 1.

Institute for Risk Assessment Sciences, Utrecht University, Utrecht, The Netherlands.

Nominal effect concentrations from in vitro toxicity assays may lead to inaccurate estimations of in vivo toxic doses because the nominal concentration poorly reflects the concentration at the molecular target in cells in vitro, which is responsible for initiating effects and can be referred to as the biologically effective dose. Chemicals can differentially distribute between in vitro assay compartments, including serum constituents in exposure medium, microtitre plate plastic, headspace and extracellular matrices. The partitioning of test chemicals to these extracellular compartments reduces the concentration at the molecular target. Free concentrations in medium and cell-associated concentrations are considered better proxies of the biologically effective dose. This paper reviews the mechanisms by which test chemicals distribute between in vitro assay compartments, and also lists the physicochemical properties driving the extent of this distribution. The mechanisms and physicochemical properties driving the distribution of test chemical in vitro help explain the makeup of mass balance models that estimate free concentrations and cell-associated concentrations in in vitro toxicity assays. A thorough understanding of the distribution processes and assumptions underlying these mass balance models helps define chemical and biological applicability domains of individual models, as well as provide a perspective on how to improve model predictivity and quantitative in vitro-in vivo extrapolations.
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http://dx.doi.org/10.1016/j.tiv.2021.105133DOI Listing
March 2021

Metabolism and plasma protein binding of 16 straight- and branched-chain parabens in in vitro liver and skin models.

Toxicol In Vitro 2021 Apr 11;72:105051. Epub 2020 Nov 11.

L'Oreal Research & Innovation, Aulnay-Sous-Bois, France.

Parabens are alkyl esters of 4-hydroxybenzoic acid (4-HBA), with short-chain parabens used as antimicrobials in cosmetics. We investigated the impact of chain structure on skin and liver metabolism. Incubations with primary human hepatocytes and human liver S9 indicated that methyl-, ethyl-, propyl- and butylparaben were rapidly metabolized to similar metabolites, including 4-HBA plus the corresponding alcohols. Liver and EpiSkin™ S9 were used to investigate the metabolism of 16 short and long straight- and branched-chain parabens. The rate of hydrolysis generally decreased with increasing chain length in liver S9, whereas the reverse was true for EpiSkin™ S9. Chain length also correlated with the number of metabolites, with more oxidized metabolites detected from longer chain parabens. The identity of the alcohol group impacted metabolism the most, in terms of the rate of metabolism and the contribution of cofactors. The majority of parabens (13/16) exhibited high plasma protein binding (PPB) (>90%); whereas, 4-HBA PPB was 38%. PPB was related to the LogP of the parabens. In conclusion, the major and common paraben metabolite in PHH, liver S9 and EpiSkin™ S9 was 4-HBA. The rate of metabolism, type of metabolite and contribution of hydrolysis was tissue-specific (liver, skin) and was influenced by the chain length (and hence LogP), structural isomeric form (straight vs branched), and/or the identity of the alkyl group. SHORT ABSTRACT: We investigated how the chain structure of parabens affects their metabolism by liver and EpiSkin™ S9. The major and common metabolite in primary human hepatocytes, liver S9 and EpiSkin™ S9 was 4-HBA plus the corresponding alcohols. The rate of metabolism, type of metabolite and contribution of hydrolysis was tissue-specific and influenced by the chain length, structural isomeric form (straight vs branched), and/or the identity of the alkyl group. Most parabens exhibited high PPB (>90%), whereas the PPB of 4-HBA was 38%.
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http://dx.doi.org/10.1016/j.tiv.2020.105051DOI Listing
April 2021

Partition coefficient and diffusion coefficient determinations of 50 compounds in human intact skin, isolated skin layers and isolated stratum corneum lipids.

Toxicol In Vitro 2020 Dec 1;69:104990. Epub 2020 Sep 1.

Beiersdorf AG, Hamburg, Germany.

A standard protocol was used to determine partition (K) and diffusion (D) coefficients in dermatomed human skin and isolated human skin layers for 50 compounds relevant to cosmetics ingredients. K values were measured in dermatomed skin, isolated dermis, whole epidermis, intact stratum corneum (SC), delipidized SC and SC lipids by direct measurements of the radioactivity in the tissue layers/lipid component vs. buffer samples. D determinations were made in dermatomed skin, isolated dermis, whole epidermis and intact SC using a non-linear regression of the cumulative receptor fluid content of radiolabeled compound, fit to the solution of Fick's 2nd Law. Correlation analysis was completed between K, D, and physicochemical properties. The amount of interindividual (donor) and intraindividual (replicate) variability in the K and D data was characterized for each skin layer and chemical. These data can be further used to help inform the factors that influence skin bioavailability and to help improve in silico models of dermal penetration.
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http://dx.doi.org/10.1016/j.tiv.2020.104990DOI Listing
December 2020

Imaging and quantifying drug delivery in skin - Part 2: Fluorescence andvibrational spectroscopic imaging methods.

Adv Drug Deliv Rev 2020 01 23;153:147-168. Epub 2020 Mar 23.

Wellman Center for Photomedicine, Massachusetts General Hospital, Harvard Medical School, CNY149-3, 13(th) St, Charlestown, MA 02129, United States of America. Electronic address:

Understanding the delivery and diffusion of topically-applied drugs on human skin is of paramount importance in both pharmaceutical and cosmetics research. This information is critical in early stages of drug development and allows the identification of the most promising ingredients delivered at optimal concentrations to their target skin compartments. Different skin imaging methods, invasive and non-invasive, are available to characterize and quantify the spatiotemporal distribution of a drug within ex vivo and in vivo human skin. The first part of this review detailed invasive imaging methods (autoradiography, MALDI and SIMS). This second part reviews non-invasive imaging methods that can be applied in vivo: i) fluorescence (conventional, confocal, and multiphoton) and second harmonic generation microscopies and ii) vibrational spectroscopic imaging methods (infrared, confocal Raman, and coherent Raman scattering microscopies). Finally, a flow chart for the selection of imaging methods is presented to guide human skin ex vivo and in vivo drug delivery studies.
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http://dx.doi.org/10.1016/j.addr.2020.03.003DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7483684PMC
January 2020

Use of human liver and EpiSkin™ S9 subcellular fractions as a screening assays to compare the in vitro hepatic and dermal metabolism of 47 cosmetics-relevant chemicals.

J Appl Toxicol 2020 03 8;40(3):416-433. Epub 2020 Jan 8.

Pierre Fabre Dermo-Cosmétique, Toulouse, France.

The abundance of xenobiotic metabolizing enzymes (XMEs) is different in the skin and liver; therefore, it is important to differentiate between liver and skin metabolism when applying the information to safety assessment of topically applied ingredients in cosmetics. Here, we have employed EpiSkin™ S9 and human liver S9 to investigate the organ-specific metabolic stability of 47 cosmetic-relevant chemicals. The rank order of the metabolic rate of six chemicals in primary human hepatocytes and liver S9 matched relatively well. XME pathways in liver S9 were also present in EpiSkin S9; however, the rate of metabolism tended to be lower in the latter. It was possible to rank chemicals into low-, medium- and high-clearance chemicals and compare rates of metabolism across chemicals with similar structures. The determination of the half-life for 21 chemicals was affected by one or more factors such as spontaneous reaction with cofactors or non-specific binding, but these technical issues could be accounted for in most cases. There were seven chemicals that were metabolized by liver S9 but not by EpiSkin S9: 4-amino-3-nitrophenol, resorcinol, cinnamyl alcohol and 2-acetylaminofluorene (slowly metabolized); and cyclophosphamide, benzophenone, and 6-methylcoumarin. These data support the use of human liver and EpiSkin S9 as screening assays to indicate the liver and skin metabolic stability of a chemical and to allow for comparisons across structurally similar chemicals. Moreover, these data can be used to estimate the systemic bioavailability and clearance of chemicals applied topically, which will ultimately help with the safety assessment of cosmetics ingredients.
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http://dx.doi.org/10.1002/jat.3914DOI Listing
March 2020

Measurement of the penetration of 56 cosmetic relevant chemicals into and through human skin using a standardized protocol.

J Appl Toxicol 2020 03 22;40(3):403-415. Epub 2019 Dec 22.

Beiersdorf AG, Hamburg, Germany.

OECD test guideline 428 compliant protocol using human skin was used to test the penetration of 56 cosmetic-relevant chemicals. The penetration of finite doses (10 μL/cm ) of chemicals was measured over 24 hours. The dermal delivery (DD) (amount in the epidermis, dermis and receptor fluid [RF]) ranged between 0.03 ± 0.02 and 72.61 ± 8.89 μg/cm . The DD of seven chemicals was comparable with in vivo values. The DD was mainly accounted for by the amount in the RF, although there were some exceptions, particularly of low DD chemicals. While there was some variability due to cell outliers and donor variation, the overall reproducibility was very good. As six chemicals had to be applied in 100% ethanol due to low aqueous solubility, we compared the penetration of four chemicals with similar physicochemical properties applied in ethanol and phosphate-buffered saline. Of these, the DD of hydrocortisone was the same in both solvents, while the DD of propylparaben, geraniol and benzophenone was lower in ethanol. Some chemicals displayed an infinite dose kinetic profile; whereas, the cumulative absorption of others into the RF reflected the finite dosing profile, possibly due to chemical volatility, total absorption, chemical precipitation through vehicle evaporation or protein binding (or a combination of these). These investigations provide a substantial and consistent set of skin penetration data that can help improve the understanding of skin penetration, as well as improve the prediction capacity of in silico skin penetration models.
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http://dx.doi.org/10.1002/jat.3913DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7027575PMC
March 2020

Imaging and quantifying drug delivery in skin - Part 1: Autoradiography and mass spectrometry imaging.

Adv Drug Deliv Rev 2020 01 26;153:137-146. Epub 2019 Nov 26.

Wellman Center for Photomedicine, Massachusetts General Hospital, Harvard Medical School, CNY149-3, 13th St, Charlestown, MA 02129, United States of America. Electronic address:

In this two-part review we present an up-to-date description of different imaging methods available to map the localization of drugs on skin as a complement of established ex-vivo absorption studies. This first part deals with invasive methods which are grouped in two classes according to their underlying principles: i) methods using radioactivity such as autoradiography and ii) mass spectrometry methods such as MALDI and SIMS. For each method, a description of the principle is given along with example applications of imaging and quantifying drug delivery in human skin. Thanks to these techniques a better assessment of the fate of drugs is obtained: its localization on a particular skin structure, its potential accumulation, etc. A critical comparison in terms of capabilities, sensitivity and practical applicability is included that will help the reader to select the most appropriate technique depending on the particular problem to be solved.
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http://dx.doi.org/10.1016/j.addr.2019.11.004DOI Listing
January 2020

Comparison of the metabolism of 10 cosmetics-relevant chemicals in EpiSkin™ S9 subcellular fractions and in vitro human skin explants.

J Appl Toxicol 2020 02 7;40(2):313-326. Epub 2019 Nov 7.

L'Oreal, Aulnay-Sous-Bois, France.

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.
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http://dx.doi.org/10.1002/jat.3905DOI Listing
February 2020

Dermal absorption study OECD TG 428 mass balance recommendations based on the EFSA database.

Regul Toxicol Pharmacol 2019 Nov 17;108:104475. Epub 2019 Sep 17.

BASF Oesterreich GmbH, Handelskai 94-96, 1200, Vienna, Austria. Electronic address:

The European Food Safety Authority (EFSA) guidance (EFSA, 2017) for dermal absorption (DA) studies recommends stringent mass balance (MB) limits of 95-105%. EFSA suggested that test material can be lost after penetration and requires that for chemicals with <5% absorption the non-recovered material must be added to the absorbed dose if MB is <95%. This has huge consequences for low absorption pesticides. Indeed, one third of the MBs in the EFSA DA database are outside the refined criteria. This is also true for DA data generated by Cosmetics Europe (Gregoire et al., 2019), indicating that this criterion is often not achieved even when using highly standardized protocols. While EFSA hypothesizes that modern analytical and pipetting techniques would enable to achieve this criterion, no scientific basis was provided. We describe how protocol procedures impact MB and evaluate the EFSA DA database to demonstrate that MB is subject to random variation. Generic application of "the addition rule" skews the measured data and increases the DA estimate, which results in unnecessary risk assessment failure. In conclusion, "missing material" is just a random negative deviation to the nominal dose. We propose a data-driven MB criterion of 90-110%, fully in line with OECD recommendations.
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http://dx.doi.org/10.1016/j.yrtph.2019.104475DOI Listing
November 2019

In vivo quantitative molecular absorption of glycerol in human skin using coherent anti-Stokes Raman scattering (CARS) and two-photon auto-fluorescence.

J Control Release 2019 08 15;308:190-196. Epub 2019 Jul 15.

Aix Marseille Univ, CNRS, Centrale Marseille, Institut Fresnel, Marseille, France. Electronic address:

The penetration of small molecules through the human skin is a major issue for both safety and efficacy issues in cosmetics and pharmaceutic domains. To date, the quantification of active molecular compounds in human skin following a topical application uses ex vivo skin samples mounted on Franz cell diffusion set-up together with appropriate analytical methods. Coherent anti-Stokes Raman scattering (CARS) has also been used to perform active molecule quantification on ex vivo skin samples, but no quantification has been described in human skin in vivo. Here we introduce and validate a framework for imaging and quantifying the active molecule penetration into human skin in vivo. Our approach combines nonlinear imaging microscopy modalities, such as two-photon excited auto-fluorescence (TPEF) and coherent anti-Stokes Raman scattering (CARS), together with the use of deuterated active molecules. The imaging framework was exemplified on topically applied glycerol diluted in various vehicles such as water and xanthan gel. In vivo glycerol quantitative percutaneous penetration over time was demonstrated, showing that, contrary to water, the xanthan gel vehicle acts as a film reservoir that releases glycerol continuously over time. More generally, the proposed imaging framework provides an enabling platform for establishing functional activity of topically applied products in vivo.
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http://dx.doi.org/10.1016/j.jconrel.2019.07.018DOI Listing
August 2019

Use of a Simple in vitro Test to Assess Loss of Chemical due to Volatility during an in vitro Human Skin Absorption Study.

Skin Pharmacol Physiol 2019 19;32(3):117-124. Epub 2019 Mar 19.

Beiersdorf AG, Hamburg, Germany.

Background: We tested the cutaneous distribution of 50 chemicals in frozen human skin. The mass balance (MB) values for 48% of the chemicals were < 90%, possibly due to evaporation.

Methods: We confirmed the reduction in MB was due to evaporation for two chemicals tested in skin penetration experiments using a carbon filter above the skin to trap airborne chemical. An in vitro assay was used to predict the reduction in MB due to evaporation by comparing the recovery of chemicals after 4 h of incubation at room temperature in open and closed vials.

Results: Evaporative losses in vitro correlated well with measured MBs (i.e., < 90%) in skin penetration experiments (R2 = 0.81). There was a correlation of the MB with the vapour pressure (VP) which could be used to group chemicals according to their likelihood to evaporate during the course of a skin penetration study. There was also a correlation of MB with Henry's law constants, melting and boiling points.

Conclusion: Our data support the use of a quick and simple test for volatility to account for the loss of MB in skin penetration experiment due to volatility. The best parameter to indicate the potential of a chemical to evaporate is the VP.
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http://dx.doi.org/10.1159/000497105DOI Listing
November 2019

Challenges in working towards an internal threshold of toxicological concern (iTTC) for use in the safety assessment of cosmetics: Discussions from the Cosmetics Europe iTTC Working Group workshop.

Regul Toxicol Pharmacol 2019 Apr 15;103:63-72. Epub 2019 Jan 15.

European Commission, Joint Research Centre, Ispra, Italy.

The Threshold of Toxicological Concern (TTC) is an important risk assessment tool which establishes acceptable low-level exposure values to be applied to chemicals with limited toxicological data. One of the logical next steps in the continued evolution of TTC is to develop this concept further so that it is representative of internal exposures (TTC based on plasma concentration). An internal TTC (iTTC) would provide threshold values that could be utilized in exposure-based safety assessments. As part of a Cosmetics Europe (CosEu) research program, CosEu has initiated a project that is working towards the development of iTTCs that can be used for the human safety assessment. Knowing that the development of an iTTC is an ambitious and broad-spanning topic, CosEu organized a Working Group comprised a balance of multiple stakeholders (cosmetics and chemical industries, the EPA and JRC and academia) with relevant experience and expertise and workshop to critically evaluate the requirements to establish an iTTC. Outcomes from the workshop included an evaluation on the current state of the science for iTTC, the overall iTTC strategy, selection of chemical databases, capture and curation of chemical information, ADME and repeat dose data, expected challenges, as well as next steps and ongoing work.
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http://dx.doi.org/10.1016/j.yrtph.2019.01.016DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6644721PMC
April 2019

Imaging the distribution of skin lipids and topically applied compounds in human skin using mass spectrometry.

Sci Rep 2018 11 12;8(1):16683. Epub 2018 Nov 12.

L'OREAL Research and Innovation, 93601, Aulnay-sous-Bois, France.

The barrier functions of skin against water loss, microbial invasion and penetration of xenobiotics rely, in part, on the spatial distribution of the biomolecular constituents in the skin structure, particularly its horny layer (stratum corneum). However, all skin layers are important to describe normal and dysfunctional skin conditions, and to develop adapted therapies or skin care products. In this work, time-of-flight secondary ion mass spectrometry (ToF-SIMS) combined with scanning electron microscopy (SEM) was used to image the spatial distribution of a variety of molecular species, from stratum corneum down to dermis, in cross-section samples of human abdominal skin. The results demonstrate the expected localization of ceramide and saturated long-chain fatty acids in stratum corneum (SC) and cholesterol sulfate in the upper part of the viable epidermis. The localization of exogenous compounds is demonstrated by the detection and imaging of carvacrol (a constituent of oregano or thyme essential oil) and ceramide, after topical application onto ex vivo human skin. Carvacrol showed pronounced accumulation to triglyceride-containing structures in the deeper parts of dermis. In contrast, the exogenous ceramide was found to be localized in SC. Furthermore, the complementary character of this approach with classical ex vivo skin absorption analysis methods is demonstrated.
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http://dx.doi.org/10.1038/s41598-018-34286-xDOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6232133PMC
November 2018

Inter-laboratory study of the skin distribution of 4-n-butyl resorcinol in ex vivo pig and human skin.

J Chromatogr B Analyt Technol Biomed Life Sci 2018 Sep 27;1093-1094:77-79. Epub 2018 Jun 27.

L'Oreal Research and Innovation, 550 Jinyu Road, Shanghai, China. Electronic address:

4-n-butyl resorcinol (4-nBR) is a highly effective tyrosinase inhibitor, and can be used in cosmetic product for depigmentation purpose. Its efficacy correlates with 4-nBR that absorbed by skin. In this study, skin distribution of 4-nBR within either human or pig skin ex vivo was studied and compared by three independent laboratories. Good agreement was observed in each compartment considering usual inter-lab variability. This study supports the use of pig skin as an alternative source of skin when the availability of human skin is a limiting factor.
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http://dx.doi.org/10.1016/j.jchromb.2018.06.048DOI Listing
September 2018

A strategy for systemic toxicity assessment based on non-animal approaches: The Cosmetics Europe Long Range Science Strategy programme.

Toxicol In Vitro 2018 Aug 2;50:137-146. Epub 2018 Mar 2.

Procter & Gamble Technical Centres Ltd, Rusham Park Whitehall Lane TW20 9NW, Egham, Surrey, UK. Electronic address:

When performing safety assessment of chemicals, the evaluation of their systemic toxicity based only on non-animal approaches is a challenging objective. The Safety Evaluation Ultimately Replacing Animal Test programme (SEURAT-1) addressed this question from 2011 to 2015 and showed that further research and development of adequate tools in toxicokinetic and toxicodynamic are required for performing non-animal safety assessments. It also showed how to implement tools like thresholds of toxicological concern (TTCs) and read-across in this context. This paper shows a tiered scientific workflow and how each tier addresses the four steps of the risk assessment paradigm. Cosmetics Europe established its Long Range Science Strategy (LRSS) programme, running from 2016 to 2020, based on the outcomes of SEURAT-1 to implement this workflow. Dedicated specific projects address each step of this workflow, which is introduced here. It tackles the question of evaluating the internal dose when systemic exposure happens. The applicability of the workflow will be shown through a series of case studies, which will be published separately. Even if the LRSS puts the emphasis on safety assessment of cosmetic relevant chemicals, it remains applicable to any type of chemical.
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http://dx.doi.org/10.1016/j.tiv.2018.02.017DOI Listing
August 2018

Comparison of the Skin Penetration of 3 Metabolically Stable Chemicals Using Fresh and Frozen Human Skin.

Skin Pharmacol Physiol 2017 27;30(5):234-245. Epub 2017 Jul 27.

Pierre Fabre Dermo-Cosmétique, Toulouse, France.

Background: The Cosmetics Europe ADME Task Force is developing in vitro and in silico tools for predicting skin and systemic concentrations after topical application of cosmetic ingredients. There are conflicting reports as to whether the freezing process affects the penetration of chemicals; therefore, we evaluated whether the storage of human skin used in our studies (8-12 weeks at -20°C) affected the penetration of model chemicals.

Methods: Finite doses of trans-cinnamic acid (TCA), benzoic acid (BA), and 6-methylcoumarin (6MC) (non-volatile, non-protein reactive and metabolically stable in skin) were applied to fresh and thawed frozen skin from the same donors. The amounts of chemicals in different skin compartments were analysed after 24 h.

Results: Although there were some statistical differences in some parameters for 1 or 2 donors, the penetration of TCA, BA, and 6MC was essentially the same in fresh and frozen skin, i.e., there were no biologically relevant differences in penetration values. Statistical differences that were evident indicated that penetration was marginally lower in frozen than in fresh skin, indicating that the barrier function of the skin was not lost.

Conclusion: The penetration of the 3 chemicals was essentially unaffected by freezing the skin at -20°C for up to 12 weeks.
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http://dx.doi.org/10.1159/000475472DOI Listing
June 2018

Inter-laboratory skin distribution study of 4-n-butyl resorcinol: The importance of liquid chromatography/mass spectrometry (HPLC-MS/MS) bioanalytical validation.

J Chromatogr B Analyt Technol Biomed Life Sci 2017 Aug 26;1060:416-423. Epub 2017 May 26.

L'Oreal Research and Innovation, 1 Avenue Eugene Schueller, Aulnay Sous Bois, France. Electronic address:

In the present study, three laboratories independently compared percutaneous absorption and distribution of 4-n-butylresorcinol, using human skin from five donors. Each laboratory used the same protocol for percutaneous absorption studies but different LC-MS/MS analytical methods to quantify the test compound. All laboratories respected the mass balance criteria (i.e. 100±15%; average 96.5-102% of applied dose). Regarding usual inter-lab variability, good agreement was observed for all compartments with the greatest difference in the epidermis: 3.3 fold increase. The data obtained demonstrate that robustness of skin absorption data rely on properly validated analytical methods including sample extraction and LC-MS/MS method. It also includes clearly defined cutaneous absorption protocol for dose skin preparation, application, washing and tape stripping.
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http://dx.doi.org/10.1016/j.jchromb.2017.05.026DOI Listing
August 2017

A Microfluidic Diffusion Cell for Fast and Easy Percutaneous Absorption Assays.

Pharm Res 2015 Aug 28;32(8):2704-12. Epub 2015 Feb 28.

LIMMS/CNRS-IIS (UMI 2820), Institute of Industrial Science, The University of Tokyo, 4-6-1 Komaba, Meguro-ku, 153-8505, Tokyo, Japan,

Purpose: Percutaneous absorption assays of molecules for pharmaceutical and cosmetology purposes are important to determine the bioavailability of new compounds, once topically applied. The current method of choice is to measure the rate of diffusion through excised human skin using a diffusion cell. This method however entails significant drawbacks such as scarce availability and poor reproducibility of the sample, low sampling rate, and tedious assay setup.

Methods: The objective of the present work is to propose an alternative method that overcomes these issues by integrating an experimental model of the skin (artificial stratum corneum) and online optical sensors into a microfluidic device.

Results: The measurement of the diffusion profile followed by the calculation of the permeability coefficients and time lag were performed on seven different molecules and obtained data positively fit with those available from literature on human skin penetration. The coating of the lipid mixture to generate the artificial stratum corneum also proved robust and reproducible. The results show that the proposed device is able to give fast, real-time, accurate, and reproducible data in a user-friendly manner, and can be produced at a large scale.

Conclusion: These assets should help both the cosmetics and pharmaceutics fields where the skin is the target or a pathway of a formulated compound, by allowing more candidate molecules or formulations to be assessed during the various stages of their development.
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http://dx.doi.org/10.1007/s11095-015-1654-xDOI Listing
August 2015

Quantitative 3D molecular cutaneous absorption in human skin using label free nonlinear microscopy.

J Control Release 2015 Feb 27;200:78-86. Epub 2014 Dec 27.

Aix-Marseille Université, CNRS, Centrale Marseille, Institut Fresnel, UMR 7249, Domaine Universitaire de Saint Jérôme, F-13397 Marseille Cedex 20, France. Electronic address:

Understanding the penetration mechanisms of drugs into human skin is a key issue in pharmaceutical and cosmetics research. To date, the techniques available for percutaneous penetration of compounds fail to provide a quantitative 3D map of molecular concentration distribution in complex tissues as the detected microscopy images are an intricate combination of concentration distribution and laser beam attenuation upon deep penetration. Here we introduce and validate a novel framework for imaging and reconstructing molecular concentration within the depth of artificial and human skin samples. Our approach combines the use of deuterated molecular compounds together with coherent anti-Stokes Raman scattering spectroscopy and microscopy that permits targeted molecules to be unambiguously discriminated within skin layers. We demonstrate both intercellular and transcellular pathways for different active compounds, together with in-depth concentration profiles reflecting the detailed skin barrier architecture. This method provides an enabling platform for establishing functional activity of topically applied products.
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http://dx.doi.org/10.1016/j.jconrel.2014.12.033DOI Listing
February 2015

Parameters and mechanistic studies on the oxidative ring cleavage of synthetic heterocyclic naphthoquinones by Streptomyces strains.

Appl Microbiol Biotechnol 2004 Sep 16;65(4):446-56. Epub 2004 Jun 16.

Groupe Biocatalyse et Chimie Pharmacologique, Laboratoire de Chimie et Biochimie Pharmacologiques et Toxicologiques, UMR 8601, Université René Descartes-Paris V, 45 rue des Saints-Pères, 75006, Paris, France.

Screening of fungal and bacterial strains allowed selection of two Streptomyces strains ( S. platensis and S. cinnamonensis) that oxidatively cleave, in moderate to high yields (up to 65% in 24 h), the quinonic ring of a thiazole fused 1,4-naphthoquinone compound, INO5042, used as a model compound for a series of homologous substituted heterocyclic naphthoquinones. The respective products of these whole-cell biotransformations were identified as isomeric phenol-carboxylic acids resulting from a C-C bond cleavage at a position vicinal to each one of the carbonyl groups. The culture and incubation conditions have been optimised and the mechanism of this biotransformation investigated using oxygen isotope incorporation. The results of 18O2 incorporation indicate a dioxygenase reaction, the mechanism of which is discussed in relation with that of hydroquinone-epoxidases, a family of oxygenating enzymes involved in the biosynthesis of polyketide antibiotics in Streptomyces.
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http://dx.doi.org/10.1007/s00253-004-1588-4DOI Listing
September 2004