Opinion of the Scientific Committee on health, environmental and emerging risks on the safety of titanium dioxide in toys.

The Opinion of the Scientific Committee on Health, Environmental and Emerging Risks advises the European Commission on whether the uses of titanium dioxide in toys and toy materials can be considered to be safe in light of the identified exposure, and the classification of titanium dioxide as carcinogenic category 2 after inhalation. Four toy products including casting kits, chalk, powder paints and white colour pencils containing various amounts of TiO2 as colouring agent were evaluated for inhalation risks. For the oral route, childrens' lip gloss/lipstick, finger paint and white colour pencils were evaluated. When it can be demonstrated with high certainty that no ultrafine fraction is present in pigmentary TiO2 preparations used in toys and toy materials, safe use with no or negligible risk for all products considered is indicated based on the exposure estimations of this Opinion. However, if an ultrafine fraction is assumed to be present, safe use is not indicated, except for white colour pencils.

Physiologically-Based Kinetic Modeling of Intravenously Administered Gold (Au) Nanoparticles.

Physiologically-based kinetic (PBK) modeling is a valuable tool to understand the kinetics of nanoparticles (NPs) in vivo. However, estimating PBK parameters remains challenging and commonly requires animal studies. To develop predictive models to estimate PBK parameter values based on NP characteristics, a database containing PBK parameter values and corresponding NP characteristics is needed. As a first step toward this objective, this study estimates PBK parameters for gold NPs (AuNPs) and provides a comparison of two different NPs. Two animal experiments are conducted in which varying doses of AuNPs attached with polyethylene glycol (PEG) are administered intravenously to rats. The resulting Au concentrations are used to estimate PBK model parameters. The parameters are compared with PBK parameters previously estimated for poly(alkyl cyanoacrylate) NPs loaded with cabazitaxel and for LipImage 815. This study shows that a small initial database of PBK parameters collected for three NPs is already sufficient to formulate new hypotheses on NP characteristics that may be predictive of PBK parameter values. Further research should focus on developing a larger database and on developing quantitative models to predict PBK parameter values.

Transcriptomic Analysis in Human 3D Skin Model Injected with Resorbable Hyaluronic Acid Fillers Reveals Foreign Body Response.

Usage of injectable dermal fillers applied for aesthetic purposes has extensively increased over the years. As such, the number of related adverse reactions has increased, including patients showing severe complications such as product migration, topical swelling and inflammatory reactions of the skin. In order to understand the underlying molecular events of these adverse reactions we performed a genome-wide gene expression study on the multi-cell type human Phenion® Full-Thickness Skin Model exposed to five experimental hyaluronic acid (HA) preparations with increasing cross-linking degree, four commercial fillers from Perfectha®, and non-resorbable filler Bio-Alcamid®. In addition, we evaluated whether cross-linking degree or particle size of the HA-based fillers could be associated with the occurrence of adverse effects. In all cases, exposure to different HA fillers resulted in a clearly elevated gene expression of cytokines and chemokines related to acute inflammation as part of the foreign body response. Furthermore, for one experimental filler genes of OXPHOS complexes I-V were significantly down-regulated (adjusted p-value < 0.05), resulting in mitochondrial dysfunction which can be linked to over-expression of pro-inflammatory cytokines TNFα and IL-1ß and chemokine CCL2. Our hypothesis that cross-linking degree or particle size of the HA-based fillers is related to the biological responses induced by these fillers could only partially be confirmed for particle size. In conclusion, our innovative approach resulted in gene expression changes from a human 3D skin model exposed to dermal fillers that mechanistically substantiate aforementioned adverse reactions, and thereby adds to the weight of evidence that these fillers may induce inflammatory and fibrotic responses.

Regulatory safety evaluation of nanomedical products: key issues to refine.

Nanotechnologies enable great opportunities for the development and use of innovative (nano)medicines. As is common for scientific and technical developments, recognized safety evaluation methods for regulatory purposes are lagging behind. The specific properties responsible for the desired functioning also hamper the safety evaluation of such products. Pharmacokinetics determination of the active pharmaceutical ingredient as well as the nanomaterial component is crucial. Due to their particulate nature, nanomedicines, similar to all nanomaterials, are primarily removed from the circulation by phagocytizing cells that are part of the immune system. Therefore, the immune system can be potentially a specific target for adverse effects of nanomedicines, and thus needs special attention during the safety evaluation. This DDTR special issue on the results of the REFINE project on a regulatory science framework for nanomedical products presents a highly valuable body of knowledge needed to address regulatory challenges and gaps in currently available testing methods for the safety evaluation of nanomedicines.

Evaluation of Adverse Effects of Resorbable Hyaluronic Acid Fillers: Determination of Macrophage Responses.

Resorbable tissue fillers for aesthetic purposes can induce severe complications including product migration, late swelling, and inflammatory reactions. The relation between product characteristics and adverse effects is not well understood. We hypothesized that the degree of cross-linking hyaluronic acid (HA) fillers was associated with the occurrence of adverse effects. Five experimental HA preparations similar to HA fillers were synthesized with an increasing degree of cross-linking. Furthermore, a series of commercial fillers (Perfectha®) was obtained that differ in degradation time based on the size of their particulate HA components. Cytotoxic responses and cytokine production by human THP-1-derived macrophages exposed to extracts of the evaluated resorbable HA fillers were absent to minimal. Gene expression analysis of the HA-exposed macrophages revealed the responses related to cell cycle control and immune reactivity. Our results could not confirm the hypothesis that the level of cross-linking in our experimental HA fillers or the particulate size of commercial HA fillers is related to the induced biological responses. However, the evaluation of cytokine induction and gene expression in macrophages after biomaterial exposure presents promising opportunities for the development of methods to identify cellular processes that may be predictive for biomaterial-induced responses in patients.

A comparative biodistribution study of polymeric and lipid-based nanoparticles.

Biodistribution of nanoencapsulated bioactive compounds is primarily determined by the size, shape, chemical composition and surface properties of the encapsulating nanoparticle, and, thus, less dependent on the physicochemical properties of the active pharmaceutical ingredient encapsulated. In the current work, we aimed to investigate the impact of formulation type on biodistribution profile for two clinically relevant nanoformulations. We performed a comparative study of biodistribution in healthy rats at several dose levels and durations up to 14-day post-injection. The studied nanoformulations were nanostructured lipid carriers incorporating the fluorescent dye IR780-oleyl, and polymeric nanoparticles containing the anticancer agent cabazitaxel. The biodistribution was approximated by quantification of the cargo in blood and relevant organs. Several clear and systematic differences in biodistribution were observed, with the most pronounced being a much higher (more than 50-fold) measured concentration ratio between cabazitaxel in all organs vs. blood, as compared to IR780-oleyl. Normalized dose linearity largely showed opposite trends between the two compounds after injection. Cabazitaxel showed a higher brain accumulation than IR780-oleyl with increasing dose injected. Interestingly, cabazitaxel showed a notable and prolonged accumulation in lung tissue compared to other organs. The latter observations could warrant further studies towards a possible therapeutic indication within lung and conceivably brain cancer for nanoformulations of this highly antineoplastic compound, for which off-target toxicity is currently dose-limiting in the clinic.

The SCCS scientific advice on the safety of nanomaterials in cosmetics.

The Cosmetic Regulation (EC) No 1223/2009 specifically covers the risk of nanomaterials used in cosmetic products. If there are concerns regarding the safety of a nanomaterial, the European Commission refers it to the SCCS for a scientific opinion. The Commission mandated the SCCS to identify the scientific basis for safety concerns that could be used as a basis for identifying and prioritising nanomaterials for safety assessment, and to revisit previous inconclusive SCCS opinions on nanomaterials to identify any concerns for potential risks to the consumer health. The SCCS Scientific Advice identified the key general aspects of nanomaterials that should raise a safety concern for a safety assessor/manager, so that the nanomaterial(s) in question could be subjected to safety assessment to establish safety to the consumer. The Advice also developed a list of the nanomaterials notified to the Commission for use in cosmetics in an order of priority for safety assessment, and revisited three previous inconclusive opinions on nanomaterials to highlight concerns over consumer safety that merited further safety assessment.

Final opinion on the safety of breast implants in relation to anaplastic large cell lymphoma: Report of the scientific committee on health, emerging and environmental risks (SCHEER).

The Scientific Committee on Health, Environmental and Emerging Risks (SCHEER) was requested by the European Commission (EC) to provide a scientific opinion on the safety of breast implants in relation to anaplastic large cell lymphoma (ALCL). There are several types of textured breast implants; surface textures of breast implants are not all manufactured in the same way, and breast implants with diverse surface textures may also present different benefits. The magnitude of the risk per type of textured implant is difficult to establish due to the low incidence of the breast implants associated anaplastic large cell lymphoma (BIA-ALCL). Therefore, risk assessments per implant type are needed. Overall SCHEER considers that there is a moderate weight of evidence for a causal relationship between textured breast implants and BIA-ALCL, particularly in relation to implants with an intermediate to high surface roughness.The pathogenic mechanisms are not fully elucidated; current hypotheses include genetic drivers, chronic inflammation resulting either from bacterial contamination, shell shedding of particulates, or shell surface characteristics leading to friction, or by implant associated reactive compounds. Reporting of new BIA-ALCL cases by the national clinical registries is critically important to obtain a better estimate of the risk of BIA-ALCL for patients with a breast implant.

Pulmonary toxicity and gene expression changes after short-term inhalation exposure to surface-modified copper oxide nanoparticles.

Copper oxide nanoparticles (CuO NPs) have previously been shown to cause dose-dependent pulmonary toxicity following inhalation. Here, CuO NPs (10 nm), coated with polyethylenimine (PEI) or ascorbate (ASC) resulting in positively or negatively charged NPs, respectively, were evaluated. Rats were exposed nose-only to similar exposure dose levels of ASC or PEI coated CuO NPs for 5 consecutive days. On day 6 and day 27 post-exposure, pulmonary toxicity markers in bronchoalveolar lavage fluid (BALF), lung histopathology and genome-wide transcriptomic changes in lungs, were assessed. BALF analyses showed a dose-dependent pulmonary inflammation and cell damage, which was supported by the lung histopathological findings of hypertrophy/hyperplasia of bronchiolar and alveolar epithelium, interstitial and alveolar inflammation, and paracortical histiocytosis in mediastinal lymph nodes for both types of CuO NPs. Transcriptomics analysis showed that pathways related to inflammation and cell proliferation were significantly activated. Additionally, we found evidence for the dysregulation of drug metabolism-related genes, especially in rats exposed to ASC-coated CuO NPs. Overall, no differences in the type of toxic effects and potency between the two surface coatings could be established, except with respect to the (regional) dose that initiates bronchiolar and alveolar hypertrophy. This disproves our hypothesis that differences in surface coatings affect the pulmonary toxicity of CuO NPs.

The suitability of reconstructed human epidermis models for medical device irritation assessment: A comparison of In Vitro and In Vivo testing results.

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.

Nonclinical regulatory immunotoxicity testing of nanomedicinal products: Proposed strategy and possible pitfalls.

Various nanomedicinal products (NMPs) have been reported to induce an adverse immune response, which may be related to their tendency to accumulate in or target cells of the immune system. Therefore, before their market authorization, NMPs should be thoroughly evaluated for their immunotoxic potential. Nonclinical regulatory immunotoxicity testing of nonbiological medicinal products, including NMPs, is currently performed by following the guideline S8 "Immunotoxicity Studies for Human Pharmaceuticals" of the International Council for Harmonization of Technical Requirements for Pharmaceuticals for Human Use (ICH). However, this guideline does not cover all the immunotoxicity endpoints reported for NMPs in the literature, such as complement activation related pseudo allergy, hypersensitivity and immunosuppression. In addition, ICH-S8 does not provide any nanospecific testing considerations, which is important given their tendency to interfere with many commonly used toxicity assays. We therefore propose a nonclinical regulatory immunotoxicity assessment strategy, which considers the immunotoxicity endpoints currently missing in the ICH-S8. We also list the known pitfalls related to the testing of NMPs and how to tackle them. Next to defining the relevant physicochemical and pharmacokinetic properties of the NMP and its intended use, the proposed strategy includes an in vitro assay battery addressing various relevant immunotoxicity endpoints. A weight of evidence evaluation of this information can be used to shape the type and design of further in vivo investigations. The final outcome of the immunotoxicity assessment can be included in the overall risk assessment of the NMP and provide alerts for relevant endpoints to address during clinical investigation. This article is categorized under: Toxicology and Regulatory Issues in Nanomedicine > Regulatory and Policy Issues in Nanomedicine Toxicology and Regulatory Issues in Nanomedicine > Toxicology of Nanomaterials.

Role of chemical composition and redox modification of poorly soluble nanomaterials on their ability to enhance allergic airway sensitisation in mice.

BACKGROUND: Engineered nanoparticles (NPs) have been shown to enhance allergic airways disease in mice. However, the influence of the different physicochemical properties of these particles on their adjuvant properties is largely unknown. Here we investigate the effects of chemical composition and redox activity of poorly soluble NPs on their adjuvant potency in a mouse model of airway hypersensitivity. RESULTS: NPs of roughly similar sizes with different chemical composition and redox activity, including CeO2, Zr-doped CeO2, Co3O4, Fe-doped Co3O4(using Fe2O3 or Fe3O4) and TiO2 NPs, all showed adjuvant activity. OVA induced immune responses following intranasal exposure of BALB/c mice to 0.02% OVA in combination with 200 µg NPs during sensitization (on day 1, 3, 6 and 8) and 0.5% OVA only during challenge (day 22, 23 and 24) were more pronounced compared to the same OVA treatment regime without NPs. Changes in OVA-specific IgE and IgG1 plasma levels, differential cell count and cytokines in bronchoalveolar lavage fluid (BALF), and histopathological detection of mucosa cell metaplasia and eosinophil density in the conducting airways were observed. Adjuvant activity of the CeO2 NPs was primarily mediated via the Th2 response, while that of the Co3O4 NPs was characterised by no or less marked increases in IgE plasma levels, BALF IL-4 and IL-5 concentrations and percentages of eosinophils in BALF and more pronounced increases in BALF IL-6 concentrations and percentages of lymphocytes in BALF. Co-exposure to Co3O4 NPs with OVA and subsequent OVA challenge also induced perivascular and peribronchiolar lymphoid cell accumulation and formation of ectopic lymphoid tissue in lungs. Responses to OVA combined with various NPs were not affected by the amount of doping or redox activity of the NPs. CONCLUSIONS: The findings indicate that chemical composition of NPs influences both the relative potency of NPs to exacerbate allergic airway sensitization and the type of immune response. However, no relation between the acellular redox activity and the observed adjuvant activity of the different NPs was found. Further research is needed to pinpoint the precise physiological properties of NPs and biological mechanisms determining adjuvant activity in order to facilitate a safe-by-design approach to NP development.

Sensitive method for endotoxin determination in nanomedicinal product samples.

Aim: Nanomaterials and nanomedicinal products tend to interfere with various commonly used assays, including regulatory required endotoxin detection methods for medicines. We developed a method to quantify endotoxin levels that is compatible with nanomaterials and nanomedicinal products. Materials & methods: The method is based on measuring endotoxin indirectly via 3-hydroxylated fatty acids of lipid-A, using Ultra High Performance Liquid Chromatography coupled with mass spectrometry. The outcome was related to results of the commonly used Limulus Amebocyte Lysate method. Results: The ultra high performance liquid chromatography coupled with mass spectrometry method has clear advantages compared with other endotoxin determination assays; particularly the absence of nanospecific interference. Conclusion: The method is sensitive, straightforward and accurate in determining and quantifying endotoxin in nanomedicinal product samples.

Toxicity of copper oxide and basic copper carbonate nanoparticles after short-term oral exposure in rats.

Copper oxide (CuO) nanoparticles (NPs) and copper carbonate nanoparticles (Cu2CO3(OH)2 NPs have applications as antimicrobial agents and wood preservatives: an application that may lead to oral ingestion via hand to mouth transfer. Rats were exposed by oral gavage to CuO NPs and Cu2CO3(OH)2 NPs for five consecutive days with doses from 1 to 512 mg/kg and 4 to 128 mg/kg per day, respectively, and toxicity was evaluated at days 6 and 26. Both CuO NPs and Cu2CO3(OH)2 NPs induced changes in hematology parameters, as well as clinical chemistry markers (e.g. increased alanine aminotransferase, ALT) indicative of liver damage For CuO NPs histopathological alterations were observed in bone marrow, stomach and liver mainly consisting of an inflammatory response, ulceration, and degeneration. Cu2CO3(OH)2 NPs induced morphological alterations in the stomach, liver, intestines, spleen, thymus, kidneys, and bone marrow. In spleen and thymus lymphoid, depletion was noted that warrants further immunotoxicological evaluation. The NPs showed partial dissolution in artificial simulated stomach fluids, while in intestinal conditions, the primary particles simultaneously shrank and agglomerated into large structures. This means that both copper ions and the particulate nanoforms should be considered as potential causal agents for the observed toxicity. For risk assessment, the lowest bench mark dose (BMD) was similar for both NPs for the serum liver enzyme AST (an indication of liver toxicity), being 26.2 mg/kg for CuO NPs and 30.8 mg/kg for Cu2CO3(OH)2 NPs. This was surprising since the histopathology evidence demonstrates more severe organ damage for Cu2CO3(OH)2 NPs than for CuO NPs.

Differences in the toxicity of cerium dioxide nanomaterials after inhalation can be explained by lung deposition, animal species and nanoforms.

Considerable differences in pulmonary responses have been observed in animals exposed to cerium dioxide nanoparticles via inhalation. These differences in pulmonary toxicity might be explained by differences in lung deposition, species susceptibility or physicochemical characteristics of the tested cerium dioxide nanoforms (i.e. same chemical substance, different size, shape, surface area or surface chemistry). In order to distinguish the relative importance of these different influencing factors, we performed a detailed analysis of the data from several inhalation studies with different exposure durations, species and nanoforms, namely published data on NM211 and NM212 (JRC repository), NanoAmor (commercially available) and our published and unpublished data on PROM (industry provided). Data were analyzed by comparing the observed pulmonary responses at similar external and internal dose levels. Our analyses confirm that rats are more sensitive to developing pulmonary inflammation compared to mice. The observed differences in responses do not result purely from differences in the delivered and retained doses (expressed in particle mass as well as surface area). In addition, the different nanoforms assessed showed differences in toxic potency likely due to differences in their physicochemical parameters. Primary particle and aggregate/agglomerate size distributions have a substantial impact on the deposited dose and consequently on the pulmonary response. However, in our evaluation size could not fully explain the difference observed in the analyzed studies indicating that the pulmonary response also depends on other physicochemical characteristics of the particles. It remains to be determined to what extent these findings can be generalized to other poorly soluble nanomaterials.

A high crosslinking grade of hyaluronic acid found in a dermal filler causing adverse effects.

Facial treatments with dermal fillers for medical or esthetic purposes occasionally give rise to adverse effects, ranging from temporary effects such as reddening of the skin, to long term effects such as hardening of tissue. There appears to be a relationship between the lifetime of the filler product and the risk for adverse effects. The lifetime of hyaluronic acid-based fillers is dependent on the presence and amount of crosslinking agents such as 1,4-butanediol diglycidyl ether (BDDE). It would therefore make sense to establish methodology to analyze the crosslinking grade of HA-based filler products on a routine basis. To this end, an analytical method was developed and validated to identify HA-BDDE-based fillers and to quantify their modification and crosslinking grade. The method was subsequently applied to products from the legal supply chain and the illegal market. It was found that the product Hyacorp H 1000, previously taken from the market, indeed contains a high modification grade and crosslinking grade, as was the assumed reason for the increased risk for adverse effects of this product. However, it was also shown that the Hyacorp products are highly unreliable in relation to their product composition in general. In this study, authentic products could not be distinguished from the illegal market products based on their modification and crosslinking grade.

Pre-validation of an in vitro skin irritation test for medical devices using the reconstructed human tissue model EpiDerm™.

Assessment of dermal irritation is an essential component of the safety evaluation of medical devices. Reconstructed human epidermis (RhE) models have replaced rabbit skin irritation testing for neat chemicals and their mixtures (OECD Test Guideline 439). However, this guideline cannot be directly applied to the area of medical devices (MD) since their non-toxicity assessment is largely based on the testing of MD extracts that may have very low irritation potential. Therefore, the RhE-methods previously validated with neat chemicals needed to be modified to reflect the needs for detection of low levels of potential irritants. A protocol employing RhE EpiDerm was optimized in 2013 using known irritants and spiked polymers (Casas et al., 2013, TIV). In 2014 and 2015 MatTek In Vitro Life Science Laboratories (IVLSL) and RIVM assessed the transferability of the assay. After the successful transfer and standardization of the protocol, 17 laboratories were trained in the use of the protocol in the preparation for the validation. Laboratories produced data with 98% agreement of predictions for the selected references and controls. We conclude that a modified RhE skin irritation test has the potential to address the skin irritation potential of the medical devices. Standardization and focus on the technical issues is essential for accurate prediction.

The crystal structure of titanium dioxide nanoparticles influences immune activity in vitro and in vivo.

BACKGROUND: The use of engineered nanoparticles (NP) is widespread and still increasing. There is a great need to assess their safety. Newly engineered NP enter the market in a large variety; therefore safety evaluation should preferably be in a high-throughput fashion. In vitro screening is suitable for this purpose. TiO 2 NP exist in a large variety (crystal structure, coating and size), but information on their relative toxicities is scarce. TiO 2 NP may be inhaled by workers in e.g. paint production and application. In mice, inhalation of TiO 2 NP increases allergic reactions. Dendritic cells (DC) form an important part of the lung immune system, and are essential in adjuvant activity. The present study aimed to establish the effect of a variety of TiO 2 NP on DC maturation in vitro. Two NP of different crystal structure but similar in size, uncoated and from the same supplier, were evaluated for their adjuvant activity in vivo. METHODS: Immature DC were differentiated in vitro from human peripheral blood monocytes. Exposure effects of a series of fourteen TiO 2 NP on cell viability, CD83 and CD86 expression, and IL-12p40 and TNF-α production were measured. BALB/c mice were intranasally sensitized with ovalbumin (OVA) alone, OVA plus anatase TiO 2 NP, OVA plus rutile TiO 2 NP, and OVA plus Carbon Black (CB; positive control). The mice were intranasally challenged with OVA. OVA-specific IgE and IgG1 in serum, cellular inflammation in bronchoalveolar lavage fluid (BALF) and IL-4 and IL-5 production in draining bronchial lymph nodes were evaluated. RESULTS: All NP dispersions contained NP aggregates. The anatase NP and anatase/rutile mixture NP induced a higher CD83 and CD86 expression and a higher IL-12p40 production in vitro than the rutile NP (including coated rutile NP and a rutile NP of a 10-fold larger primary diameter). OVA-specific serum IgE and IgG1 were increased by anatase NP, rutile NP, and CB, in the order rutile

Preparation of irritant polymer samples for an in vitro round robin study.

A round robin study using reconstructed human epidermis (RhE) tissues was conducted to test medical device polymer extracts for skin irritation potential. Test samples were four irritant and three non-irritant medical device polymers. Five of these polymer samples were developed and two were obtained commercially. The three non-irritant samples were comprised of 100% 80A polyurethane, one-part silicone, and polyvinyl chloride (PVC). The polyurethane samples were made using a hot-melt process, while the silicone samples were created by mixing and casting. The PVC samples were commercially produced sheets. The four irritant samples were comprised of one-part silicone and 25% heptanoic acid (HA), two-part silicone and 15% sodium dodecyl sulfate (SDS), PVC and 4% Genapol® X-100, and PVC and 5.8% Genapol® X-080. The HA, SDS, and Genapol® X-100 samples were produced using the mixing and casting method, while the Genapol® X-080 sheet samples were obtained commercially. During development, irritant polymer samples were extracted using polar and non-polar solvents that were subsequently analyzed chemically. Samples with sufficient levels of extracted irritants were tested on RhE tissues to confirm their irritation potential. Polymers that passed this screening test were used in the round robin study described elsewhere in this special edition.

Evaluation of the medical devices benchmark materials in the controlled human patch testing and in the RhE in vitro skin irritation protocol.

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.