Ex Vivo Irritation Evaluation of a Novel Brimonidine Nanoemulsion Using the Hen's Egg Test on Chorioallantoic Membrane (HET-CAM).

INTRODUCTION: The hen's egg test on chorioallantoic membrane (HET-CAM) assay is a cost-effective and well-validated, non-animal-based ex vivo method for evaluating the irritant potential and eye toxicity of substances. A colloidal dispersion of a surfactant and a cosurfactant with a nanosize range is called a nanoemulsion (NE), which is formed by mixing immiscible liquids and stabilized by surfactants. Patients with glaucoma are commonly prescribed Brimonidine (BR), an alpha-2 adrenergic agonist, to lower their intraocular pressure. MATERIALS AND METHODS: In this study, surfactant-cosurfactant blends were prepared by mixing Tween 80 (surfactant) and propylene glycol (cosurfactant) in a 4:1(v/v) ratio. Triacetin served as the oil phase, while deionized water was used as the aqueous phase. Using the drop method, a range of NE formulations (F1, F2, F3, FB1, FB2, and FB3) were developed and subsequently evaluated for their potential to irritate, and then the results were compared to those of a commercially available BR eye drop formulation. RESULTS: According to the average cumulative HET-CAM test scores (IS), from excipients, propylene glycol caused moderate irritation by causing slight damage to blood vessels. The formulations FB1 and F1 were found to have the highest level of irritation among other formulations in the investigation, recording 1.05 ±0.07 and 1.2 ±0.10, respectively. All other NE formulations exhibited non-irritating potential, as confirmed by the HET-CAM test, and were comparable to the marketed BR eye drop formulation. CONCLUSION: The NE formulations created for BR were determined to be safe and non-irritating. The findings indicate that the prepared NE could be a beneficial solution for addressing problems with conventional eye drops and delivering BR effectively to the eyes.

New approach methodologies (NAMs) for the in vitro assessment of cleaning products for respiratory irritation: workshop report.

The use of in vitro new approach methodologies (NAMs) to assess respiratory irritation depends on several factors, including the specifics of exposure methods and cell/tissue-based test systems. This topic was examined in the context of human health risk assessment for cleaning products at a 1-day public workshop held on 2 March 2023, organized by the American Cleaning Institute® (ACI). The goals of this workshop were to (1) review in vitro NAMs for evaluation of respiratory irritation, (2) examine different perspectives on current challenges and suggested solutions, and (3) publish a manuscript of the proceedings. Targeted sessions focused on exposure methods, in vitro cell/tissue test systems, and application to human health risk assessment. The importance of characterization of assays and development of reporting standards was noted throughout the workshop. The exposure methods session emphasized that the appropriate exposure system design depends on the purpose of the assessment. This is particularly important given the many dosimetry and technical considerations affecting relevance and translation of results to human exposure scenarios. Discussion in the in vitro cell/tissue test systems session focused on the wide variety of cell systems with varying suitability for evaluating key mechanistic steps, such as molecular initiating events (MIEs) and key events (KEs) likely present in any putative respiratory irritation adverse outcome pathway (AOP). This suggests the opportunity to further develop guidance around in vitro cell/tissue test system endpoint selection, assay design, characterization and validation, and analytics that provide information about a given assay's utility. The session on applications for human health protection emphasized using mechanistic understanding to inform the choice of test systems and integration of NAMs-derived data with other data sources (e.g., physicochemical properties, exposure information, and existing in vivo data) as the basis for in vitro to in vivo extrapolation. In addition, this group noted a need to develop procedures to align NAMs-based points of departure (PODs) and uncertainty factor selection with current human health risk assessment methods, together with consideration of elements unique to in vitro data. Current approaches are described and priorities for future characterization of in vitro NAMs to assess respiratory irritation are noted.

Dermal toxicity studies of 1,2-benzisothiazolin-3-one (CAS number: 2634-33-5) in Sprague-Dawley rats.

Biocides are used as preservatives in various household products, and 1,2-benzisothiazolin-3-one (BIT) is one of the popular chemicals. Therefore, BIT is highly likely to be exposed to human skin, necessitating dermal toxicity evaluation. In this study, we aimed to investigate dermal toxicity, eyes and skin irritation, and skin sensitization of BIT. All studies were conducted according to the Organisation for Economic Co-operation and Development testing guidelines. In acute dermal toxicity using rats, no treatment-related responses were observed at the highest dose (2000 mg/kg). A 28-day repeated dermal toxicity study at 1, 4, and 12 mg/kg/day showed transient local skin irritation lesions, including erythema, exfoliation, and crust formation. Based on no systemic effects, the no observed adverse effect level (NOAEL) of BIT of the 28-day repeated dermal toxicity study was determined to be 12 mg/kg/day. Eye and skin irritation tests showed that BIT is a strong irritant and corrosive to the eyes and a mild irritant to the skin. However, BIT showed no skin sensitization reactions in a local lymph node assay. These dermal toxicity studies can provide valuable information for the risk assessment of BIT.

The analysis of raw and processed Polygonatum kingianum saponins and stimulatory mechanism in Caenorhabditis elegans.

Polygonati Rhizoma, a Chinese medicine often used in the clinic, can irritate the tongue and throat, so it must be processed before use. Polygonati Rhizoma contains a variety of chemical components, with saponins being one of the main active ingredients. Saponins can be highly irritating to human mocous membranes and have toxicity. In this study, total saponins were extracted from raw and processed Polygonati Rhizoma and detected by UPLC-Q-TOF-MS to identify their constituents. A total of 46 saponins were detected in TSRPR(total saponins of raw Polygonati Rhizoma), TSSPR(total saponins of steamed Polygonati Rhizoma) and TSWPR(total saponins of Polygonati Rhizoma steamed in wine). Of these, 9 compounds that were present in TSRPR were not detected in TSSPR and TSWPR. C.elegans was used as a model animal to study the neurotoxic effect and its mechanisms. TSRPR was found to have neurotoxic effects on C.elegans, but TSSPR and TSWPR had no adverse effects on the nematodes. The disappearance of the irritant effect of raw Polygonati Rhizoma after processing might be related to the changes in the composition of saponins, and the main reason might be the structural transformation of saponins. In particular, the sugar chains of some highly irritating saponins may have been removed or highly irritating saponins isomerized into weakly irritating saponins. The mechanisms of neurotoxic effects on C.elegans may include upregulation of ced-3 and egl-1 expression to promote apoptosis, damage to GABAergic and cholinergic neurons, downregulation of the GABA transmitter receptor genes ggr-1 and gab-1, and a decrease in glutamate levels that impairs nerve signal transmission.

The assessment of the phototoxic potential of drugs forming complexes with melanin - Screening in vitro studies using normal skin cells with varying pigmentation irradiated by a sunlight simulator.

Phototoxic reactions are among the most common skin-related adverse effects induced by drugs. It is believed that the binding of chemicals to melanin biopolymers is a significant factor influencing skin toxicity. The formation of drug-melanin complexes can lead to the accumulation of drugs or their photodegradation products in pigmented cells, potentially affecting phototoxic reactions. Current procedures for assessing the phototoxic potential of drugs are based on tests using immortalized mouse fibroblasts. This study aimed to assess the phototoxic potential of selected drugs that form complexes with melanin (chloroquine, chlorpromazine, doxycycline) using human melanocytes with varying degrees of pigmentation. Parallel research was conducted on human dermal fibroblasts. To induce phototoxicity, cell cultures were irradiated using a sunlight simulator (5 J/cm2 for UVA spectrum). To account for the process of drug accumulation, two experimental models with different incubation times of cells with drugs before irradiation were used. The photo-irritation factor (PIF) was calculated based on NRU and WST-1 screening tests. Additionally, cell viability was examined cytometrically, and analyses of the cell cycle and reduced glutathione levels were conducted. The results indicated that drugs binding with melanin exhibited different levels of cytotoxicity and phototoxicity towards fibroblasts and melanocytes. These observed differences impact the values of PIF, potentially complicating the interpretation of the studies. Additional analyses, such as examining cell subpopulations in the sub-G1 phase and determining the level of reduced glutathione, can enhance the assessment of the phototoxicity of drugs on pigmented cells.

Unlocking relief: formulation, characterization, and in vivo assessment of salicylic acid-loaded microemulgel for psoriasis management.

Psoriasis, a chronic skin condition, affects around 2-5% of the population. Topical corticosteroids treat the vast majority of cases (> 80%). Because of the physicochemical characteristics of the damaged stratum corneum, all treatments are ineffective. Nevertheless, systemic immunosuppression, the oral strategy, has substantial adverse effects that may be avoided using the topical procedure. The research sought to determine if a salicylic acid-loaded microemulsion-based gel (emulgel) could successfully infiltrate and maintain salicylic acid in skin tissue for psoriasis treatment. The pseudo-ternary phase was generated in different Smix ratios (1:1, 2:1, and 3:1; Labrasol:Transcutol® P). At a 3:1 ratio, the Smix had a substantial microemulsion area. Microemulsion was characterized for particle size, pH, etc. For topical application, the selected microemulsion was combined with Carbopol 940 gel, and ex vivo permeation and drug retention study were conducted. The effectiveness of the developed gel was checked using the IMQ-induced psoriatic plaque model. Salicylic acid microemulsion has an average globule size of 79.72 nm, pH 5.93, and 100% transmittance. In an ex vivo diffusion study, emulgel revealed greater penetration and more drug retention than ordinary salicylic acid gel. The emulgel was non-irritating on the skin of rats. In vivo studies revealed significant antipsoriatic activity of microemulsion-loaded gel compared to the marketed product. Developed emulgel was considered a potential product for an effective and safe way to administer salicylic acid for the treatment of skin diseases such as psoriasis.

Reliability and relevance of the ES®-RHE model for in vitro skin irritation test application.

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.

Substrate Modification for Atrial Fibrillation Induced by Mechanical Irritation That May Be Associated With Non-Pulmonary Vein Foci.

The importance of treating non-pulmonary vein (PV) foci is increasing with improvements in the durability of PV isolation. We describe two cases wherein non-PV foci were induced by mechanical irritation and conventional induction in the same area, which was impossible to induce after ablation, suggesting a relationship between mechanical irritation and induction of non-PV foci. In a recurrent case of non-PV foci, atrial fibrillation (AF) was induced only by mechanical irritation. No recurrence has been observed since the ablation of the area. Thus, treatment of the AF induction site with mechanical irritation could be considered an effective therapy for non-PV foci.

Follicular mediated etodolac phosalosomal gel for contact dermatitis alleviation, insights from optimization to in-vivo appraisal.

Despite its long history as a preferential cyclooxygenase-2 inhibitor, the topical application of etodolac in inflammatory disorders does not achieve the desired clinical efficiency because of its poor water solubility and poor skin permeation. In the ongoing study, phosalosomes were designed to mitigate the etodolac drawbacks and to enhance its skin localization. Hyaluronic acid was utilized to prepare a dermal gel for the alleviation of skin inflammation. Etodolac loaded hyaluronic acid phosalosomal gel had a sustainable release profile and 10.59-fold enhanced skin retention compared to free etodolac, with boosted skin tolerability on histopathological examination after acute and chronic applications. Confocal laser microscopy imaging indicated that the etodolac amounts accumulated in the liver and kidney following dermal application were 29 and 5.7-fold lower than those following the systemic dose, respectively. For in vivo studies, etodolac loaded hyaluronic acid phosalosomal gel presented superior anti-oedemic and significant anti-nociception potential. The promising homogenous localization highlighted its potential for the delivery of lipophilic drugs for the targeted treatment of other localized skin disorders.

Development of levamlodipine long-acting patches based on an ion-pair strategy: Investigation of the mechanism for reducing skin irritation.

The aim of this study was to develop a long-acting transdermal patch of levamlodipine (LAM) using an ion-pair strategy to reduce the skin irritation induced by topical application of LAM and explore the mechanism underlying the improvement of skin irritation. The formulation was optimized through porcine in vitro transdermal experiments and rabbit in vivo skin irritation tests. The obtained formulation consisted of poly (2-Ethylhexyl acrylate-co-N-Vinyl-2-pyrrolidone-co-N-(2-Hydroxyethyl) acrylamide) (PENH) as the adhesive matrix, 13.00 % levamlodipine-sorbic acid ion-pair complex (LAM-SA) (w/w), and 10 % isopropyl myristate (IPM) (w/w), with a patch thickness of 70 µm, achieving an erythema index of 188 for rabbit skin and 117-187 for human skin (264 for rabbit skin and 110-260 for human skin in the absence of sorbic acid (SA)). In vivo rabbit and human skin erythema analysis and H&E staining verified that the optimized ion-pair patch effectively reduced skin irritation. Drug distribution experiments in the skin, ATR-FTIR, and molecular simulation were used to characterize the mechanism by which the ion-pair reduced skin irritation. Excessive accumulation of LAM in the epidermis induced secondary structural changes in keratin, resulting in skin barrier damage and inflammatory response. The formation of the LAM-SA ion pair altered physicochemical properties of LAM, reducing drug retention in the epidermis and, thereby, reducing skin irritation. This study demonstrated the potential of the ion-pair strategy to improve the safety of transdermal drug delivery system (TDDS) and provided a means for reducing skin irritation caused by the active pharmaceutical ingredient (API) itself.

Blinded by smoke: Wildfire smoke exposure and eye irritation in australian wildland firefighters.

PURPOSE: Wildfire occurrence is increasing worldwide, putting firefighters and general public at increased risk of eye injuries from smoke exposure. This study explored ocular symptoms and use of protective eyewear amongst wildland firefighters in Australia. METHODS: Australian wildland firefighters were invited to complete an online survey about the occurrence of eye irritation, use of protective eyewear and behaviours associated with occupational smoke exposure. Responses were analysed using logistic regression and qualitative inductive content analysis. RESULTS: 338 wildland firefighters completed the survey. Eye irritation was reported by 90 % of firefighters at least sometimes during work and by 70 % after work. Frequency of eye irritation was greater amongst females than males (OR 2.01, CI 1.22-3.31, p < 0.001). Protective eyewear was used often or always by 67 % of firefighters on the fireground, however 55 % had to remove their protective eyewear due to sweat, fogging or another reason. Goggles were more likely to be removed compared to sunglasses and safety glasses (OR 4.28, CI 2.75-6.68, p < 0.001). Firefighters reported that, at times smoke exposure necessitated eye closure and impaired vision on the fireground. Firefighters also reported that protective eyewear helped to reduce eye symptoms, but its consistent use on the fireground was difficult. The severity and recovery from eye symptoms varied between participants. CONCLUSION: Australian wildland firefighters frequently experience eye irritation from smoke exposure, and this can affect operational capabilities. These findings can support the development of evidence-based strategies to help protect and aid recovery of the eye surface following smoke exposure.

Effect of Various Vital Bleaching Systems on Clinical Outcomes and Patient Satisfaction.

Objective To evaluate the clinical behavior of different bleaching products - the hydrogen peroxide (H2O2), carbamide peroxide (CP), and titanium dioxide bleaching systems. Methods Three bleaching systems with different concentrations (H2O2 15%, 38%, CP 15%, 35%, and titanium dioxide 20% H2O2) were used. Sixty participants with discolored teeth were enrolled and equally divided into six groups. Each group was rendered the assigned bleaching protocol against the control group, which received plain dentifrice polishing. Each case was evaluated immediately, two weeks, three months, six months, and one year after the bleaching treatment. The clinical evaluation was made for color change by (shade guide and digital images with L*a*b* parameters), tooth sensitivity, gingival irritation, and participants' satisfaction. Results All bleaching systems showed color improvement after bleaching regimens with significant effect showed by in-office titanium dioxide 20% H2O2 followed by 38% H2O2 with Δ=10.26 and Δ=6.52, respectively, when compared to other bleaching techniques. Higher sensitivity was recorded in group III with 50% of the participants reporting postoperative sensitivity. Higher gingival irritation was recorded in group IV (15% CP) where 60% of the patients reported gingival irritation. Thirty-five of the 60 participants (58.5%) recorded that the treatment whitened their teeth "moderately" and "a lot" while seven participants recorded "a slight" difference. There was a highly significant difference in participants' satisfaction between all bleaching groups (p < 0.05). Conclusion It is evident that there is a development of dental sensitivity and gingival irritation irrespective of the bleaching system used. The color assessment showed that the desired result can be achieved with variable levels of patient satisfaction with excellent overall results with the titanium dioxide system.

Development of Sensitive In Vitro Protocols for the Biocompatibility Testing of Medical Devices and Pharmaceuticals Intended for Contact with the Eyes: Acute Irritation and Phototoxicity Assessment.

This study introduces a novel in vitro methodology that employs the 3-D reconstructed tissue model, EpiOcular, to assess the irritation and phototoxicity potential of medical devices and drugs in contact with the eye. Our study evaluated diverse test materials, including medical devices, ophthalmological solutions and an experimental drug (cemtirestat), for their potential to cause eye irritation and phototoxicity. The protocols used in this study with the EpiOcular tissue model were akin to those used in the ultra-mildness testing of cosmetic formulations, which is challenging to predict with standard in vivo rabbit tests. To design these protocols, we leveraged experience gained from the validation project on the EpiDerm skin irritation test for medical devices (ISO 10993-23:2021) and the OECD TG 498 method for photo-irritation testing. The predictions were based on the tissue viability and inflammatory response, as determined by IL-1α release. By developing and evaluating these protocols for medical devices, we aimed to expand the applicability domain of the tests referred to in ISO 10993-23. This will contribute to the standardisation and cost-effective safety evaluation of ophthalmic products, while reducing reliance on animal testing in this field. The findings obtained from the EpiOcular model in the photo-irritation test could support its implementation in the testing strategies outlined in OECD TG 498.

Overcommitment, Work-Related Behavior, and Cognitive and Emotional Irritation in Veterinarians: A Comparison of Different Veterinary Working Fields.

Mental health is a serious problem among veterinarians. The aim of this study was to analyze work-related behaviors and experience (AVEM), overcommitment (OC), and cognitive and emotional irritation (IS) in different veterinary working fields. The survey included 724 German veterinarians (average age 41.0 ± 9.72 years). Validated questionnaires were used to assess overcommitment, work-related behavior and experience patterns (health-promoting pattern G or S; health-hazardous risk pattern A or B), and irritation in several working fields. A correlation analysis and a multivariate test were performed. Increased OC was observed in 35.8% of veterinarians (mixed animals vs. inspectors, p = 0.042; small vs. mixed animals, p = 0.001). A total of 66% of veterinarians exhibited AVEM risk pattern A or B. There was no significant association of AVEM risk patterns and veterinary specialty. Only the AVEM dimension "tendency toward resignation in the face of failure" differed among working fields (p = 0.04). Regardless of direct animal contact, German veterinarians showed increased psychological stress. Inadequate compensation and prolonged stress are significant factors that can lead to burnout or depression. These risks should be considered in the context of occupational healthcare.

Opisthotonic posturing in Guillian-Barre syndrome.

INTRODUCTION: Here we report a child of Gullian Barre syndrome (GBS) with opisthotonic posturing and we subsequently detected Scrub typhus in him. CASE REPORT: An 11-year-old boy presented with progressive motor quadriparesis with transient bladder retention, bilateral facial weakness, diminished gag reflex, absent reflexes and his nerve conduction studies suggested Acute Motor Axonal Neuropathy (AMAN) GBS. His power gradually started recovering after one week. However, he had opisthotonus and signs of meningeal irritation. The child's CSF examination was consistent with GBS. His bacterial, fungal, tubercular microscopy and cultures and viral markers were negative. IgM for Borrelia and Leptospira and HIV ELISA were negative. IgM for scrub typhus, however, came out to be positive. Hence, we gave him azithromycin and he recovered almost completely in 3 months. CONCLUSIONS: To our knowledge there is no previous report of opisthotonic posturing in GBS patients. This could be due to radicular involvement in immune mediated etiology of GBS.

Time dependency and individual variation in human sensory irritation from acrolein - a controlled exposure study.

Acrolein is considered a risk factor for indoor air health problems due to its reactivity. An objective of the study was to investigate prevalence of sensory irritation in terms of time-dependent detection and perceived intensity of symptoms in human volunteers. Another objective was to investigate individual variation in sensory irritation. Participants (n=40) were exposed twice in an exposure chamber (15 min), once to heptane and once to acrolein and heptane. Symptoms and sensory irritation thresholds were rated continuously and 70% of the participants detected eye irritation from the acrolein exposure. A significant interaction between time and exposure (ƞp2=0.19) was identified, indicating time-dependent activation. This group also reported a higher level of stress and lower self-reported health (p<0.05). The results suggest that the eye is the primary system affected by exposure to acrolein, and that duration of exposure and perceived stress play important roles in symptom reactions due to acrolein exposure.

Formation mechanism, prevention of malignant ascites effusion and reduction of intestinal mucosal irritation of natural microemulsion from Euphorbia lathyris Pulveratum.

Malignant ascites effusion (MAE) is a common complication of advanced malignant tumors with limited treatments. Euphorbia lathyris (EL) has a long history of application in patients with edema and ascites. Herein, we reported for the first time a mode in which EL and EL Pulveratum (PEL) spontaneously formed natural microemulsions (ELM and PELM) without the addition of any carriers and excipients, and found that the protein and phospholipid contained in them encapsulated fatty oil and diterpenoid esters through non-covalent interactions. The denaturation and degradation of protein in PELM resulted in stronger binding of diterpenoid esters to the hydrophobic region of protein, which facilitated the sustained and slow release of diterpenoid esters and improved their bioavailability in vivo, thereby retaining the efficacy of preventing MAE while alleviating the irritation of intestinal mucosa. The mechanism by which PELM retained efficacy might be related to increased feces moisture and urine volume, and decreased expression of AVPR2, cAMP, PKA and AQP3 in MAE mice. And its mechanism of reducing intestinal mucosal irritation was related to decreased cell apoptosis, amelioration of oxidative stress, elevation of mitochondrial membrane potential, and up-regulation of Occludin and Claudin-1 expression in IEC-6 cells. This nano-adjuvant-free natural microemulsions may be a promising therapeutic strategy in the field of phytochemistry for promoting the application of natural and efficient nano-aggregates spontaneously formed by medicinal plants in MAE, and provide a new perspective for advancing the development of the fusion of Chinese herbal medicine and nanomedicine and its clinical translation.

Acid-form Sophorolipids Exhibit Minimal Cytotoxicity, Similar to Solvents and Oils Used in Personal Care Products, despite Being Surfactants.

Surfactants are amphiphilic substances that induce surface tension reduction, washing, and emulsification and are used for various purposes. Recently, biosurfactants manufactured from renewable resources and with high biocompatibility have gained increasing attention. Sophorolipid (SL), a type of biosurfactant derived from Starmerella bombicola, possesses detergency and emulsification properties, making it suitable for household and personal care applications. However, there are limited toxicological data on SLs. In this study, we conducted cytotoxicity and skin-irritation tests using SLs, revealing that cytotoxicity and skin irritation induced by SLs were extremely low (logIC 50 = 4.76 mg/L) and equivalent to those of solvents and oils used in personal care products.

Round Robin Study for Evaluation an in vitro skin irritation test for medical device extracts using KeraSkinTM in Korea.

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.

Human relevance of in vivo and in vitro skin irritation tests for hazard classification of pesticides.

Background: Test methods to inform hazard characterization and labeling of pesticides to protect human health are typically conducted using laboratory animals, and for skin irritation/corrosion the rabbit Draize test is currently required by many regulatory agencies. Although the Draize test is generally regarded to provide protective classifications for human health, new approach methodologies (NAMs) have been developed that offer more human relevant models that circumvent the uncertainty associated with species differences that exist between rabbits and humans. Despite wide applicability and use of these test methods across a broad range of chemicals, they have not been widely adopted for testing pesticides and pesticidal formulations. One of the barriers to adoption of these methods in this sector is low concordance with results from the Draize rabbit test, particularly for chemicals within the mild to moderate irritation spectrum.Methods: This review compares and contrasts the extent to which available models used in skin irritation testing mimic the anatomy and physiology of human skin, and how each aligns with the known key events leading to chemically-induced adverse skin irritation and corrosion. Doing so fully characterizes the human relevance of each method.Results: As alternatives to the rabbit Draize test, several protocols using ex vivo, in chemico, and in vitro skin models are available as internationally harmonized test guidelines. These methods rely on a variety of models of human skin, including excised rodent skin, synthetic biochemical models of barrier function, cell culture systems, and reconstructed human tissue models. We find these models exhibit biological and mechanistic relevance aligned with human skin irritation responses. Further, recent retrospective analyses have shown that the reproducibility of the Draize test is less than 50% for mild and moderate responses, with many of the replicate predictions spanning more than one category (e.g., a moderate response reported in one study followed by a non-irritant response reported in another study).Conclusions: Based on this comparative evaluation, we recommend top-down and bottom-up testing strategies that use the most human relevant in vitro test methods for skin irritation and corrosion classification of pesticides and pesticide formulations. To further discriminate among mild and non-irritant formulations, optimization of a cytokine release protocol and subsequent analyses of reference formulation test results is recommended.