Evaluation of eye and skin irritation of arginine-derivative surfactants using different in vitro endpoints as alternatives to the in vivo assays

Development of a hydrogel containing bisabolol-loaded nanocapsules for the treatment of atopic dermatitis in a Balb/c mice model

α-Bisabolol (αBIS), a plant-derived compound with anti-inflammatory properties, is potentially a therapeutic agent for Atopic dermatitis. However, its poor water solubility and photoinstability limit its topical application. Therefore, the present study, aimed to develop cationic polymeric nanocapsules of αBIS to improve its skin delivery, photostability, and therapeutic efficacy. The αBIS-loaded nanocapsules were prepared using the solvent displacement technique. A Box-Behnken (BB) design was employed to statistically optimize formulation variables and αBIS-loaded nanocapsules characterized by particle size, surface charge and encapsulation efficiency. The optimal formulation was selected, and the spherical shape of the nanocapsules was confirmed by scanning electron microscopy (SEM). Furthermore, hydrogel containing αBIS-loaded nanocapsules was prepared by thickening of nanocapsule suspension with Carbopol 934 and evaluated for rheology, in vitro drug release and skin permeation. Furthermore, a mice model of atopic dermatitis was used to evaluate the anti-inflammatory potential of the hydrogels. The optimal formulation displayed a spherical morphology under scanning electron microscopy (SEM) with an optimum particle size of 133.00 nm, polydispersity index (PDI) of 0.12, high EE% of 93 %, and improved optical stability of αBIS in the prepared nanocapsules compared to the free drug. The nano-based hydrogels demonstrated non-Newtonian pseudoplastic behavior and an increased αBIS in vitro release profile without causing skin irritation in rabbits. Drug retention within the dermis and epidermis layers significantly surpassed that of drug-free hydrogel. Moreover, in vivo histopathological studies and myeloperoxidase (MPO) enzyme activity, revealed that hydrogel containing bisabolol nanocapsules exhibited The best anti-inflammatory effect. The results showed that hydrogels containing bisabolol nanocapsules markedly alleviated dermatitis-related inflammation and reduced skin thickness in Balb/c mice. Our findings support nanocapsules as an effective drug delivery system to enhance αBIS stability, bioavailability, and therapeutic efficacy in AD treatment.

In vitro screening of topical formulation excipients for epithelial toxicity in cancerous and non-cancerous cell lines

Chemical excipients used in topical formulations may be toxic to living skin cells. Here, we compared the in vitro toxicity of some common solubilizing excipients against human melanoma cells, human keratinocytes (HaCaT) and primary skin fibroblasts (FB) as examples of cancerous, immortalized and primary human skin cells, often used as experimental models representative of in vivo conditions. Two distinct endpoint assays (3-(4,5-Dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) and crystal violet (CV)) were used. The mechanism of cell death after excipient exposure was assessed through Reactive Oxygen Species (ROS) production, cell membrane integrity and cell cycle progression. Results showed that the surfactants, Labrasol®, Labrafil® and Transcutol®, were less toxic than Triton X-100 (a model irritant) in all cell types whereas the oil, Labrafac®, was non-toxic. The human melanoma WM164 cell line showed the greatest sensitivity toward cytotoxicity after chemical exposure, while the other cell lines were more resistant. The relative excipient cytotoxicity responses observed in the MTT and CV assays were comparable and similar trends were seen in their estimated 50 % inhibitory concentration (IC50) values. DNA fragmentation by flow cytometry after exposing the cells to IC50 concentrations of the excipients showed negligible apoptotic populations. ROS production was increased in all cell types after toxic exposure; however, ROS elevation did not lead to apoptosis. The toxicity profiles of each excipient are not only relevant to their use in formulating safe topical products but also in the potential synergistic efficacy in the topical treatment of melanoma.

In vitro assessment of skin irritation and corrosion properties of graphene-related materials on a 3D epidermis

The increasing use of graphene-related materials (GRMs) in many technological applications, ranging from electronics to biomedicine, needs a careful evaluation of their impact on human health. Skin contact can be considered one of the most relevant exposure routes to GRMs. Hence, this study is focused on two main adverse outcomes at the skin level, irritation and corrosion, assessed following two specific Test Guidelines (TGs) defined by the Organization for Economic Co-operation and Development (OECD) (439 and 431, respectively) that use an in vitro 3D reconstructed human epidermis (RhE) model. After the evaluation of their suitability to test a large panel of powdered GRMs, it was found that the latter were not irritants or corrosive. Only GRMs prepared with irritant surfactants, not sufficiently removed, reduced RhE viability at levels lower than those predicting skin irritation (≤50%, after 42 min exposure followed by 42 h recovery), but not at levels lower than those predicting corrosion (<50%, after 3 min exposure or <15% after 1 h exposure). As an additional readout, a hierarchical clustering analysis on a panel of inflammatory mediators (interleukins: IL-1α, IL-1β, IL-6, and IL-18; tumor necrosis factor-α and prostaglandin E2) released by RhE exposed to these materials supported the lack of irritant and pro-inflammatory properties. Overall, these results demonstrate that both TGs are useful in assessing GRMs for their irritant or corrosion potential, and that the tested materials did not cause these adverse effects at the skin level. Only GRMs prepared using toxic surfactants, not adequately removed, turned out to be skin irritants.

Biodegradable Cationic and Ionizable Cationic Lipids: A Roadmap for Safer Pharmaceutical Excipients

Cationic and ionizable cationic lipids are broadly applied as auxiliary agents, but their use is associated with adverse effects. If these excipients are rapidly degraded to endogenously occurring metabolites such as amino acids and fatty acids, their toxic potential can be minimized. So far, synthesized and evaluated biodegradable cationic and ionizable cationic lipids already showed promising results in terms of functionality and safety. Within this review, an overview about the different types of such biodegradable lipids, the available building blocks, their synthesis and cleavage by endogenous enzymes is provided. Moreover, the relationship between the structure of the lipids and their toxicity is described. Their application in drug delivery systems is critically discussed and placed in context with the lead compounds used in mRNA vaccines. Moreover, their use as preservatives is reviewed, guidance for their design is provided, and an outlook on future developments is given.

Progress on Reconstructed Human Skin Models for Allergy Research and Identifying Contact Sensitizers

Contact with the skin is inevitable or desirable for daily life products such as cosmetics, hair dyes, perfumes, drugs, household products, and industrial and agricultural products. Whereas the majority of these products are harmless, a number can become metabolized and/or activate the immunological defense via innate and adaptive mechanisms resulting in sensitization and allergic contact dermatitis upon following exposures to the same substance. Therefore, strict safety (hazard) assessment of actives and ingredients in products and drugs applied to the skin is essential to determine I) whether the chemical is a potential sensitizer and if so II) what is the safe concentration for human exposure to prevent sensitization from occurring. Ex vivo skin is a valuable model for skin penetration studies but due to logistical and viability limitations the development of in vitro alternatives is required. The aim of this review is to give a clear overview of the organotypic in vitro skin models (reconstructed human epidermis, reconstructed human skin, immune competent skin models incorporating Langerhans Cells and T-cells, skin-on-chip) that are currently commercially available or which are being used in a laboratory research setting for hazard assessment of potential sensitizers and for investigating the mechanisms (sensitization key events 1-4) related to allergic contact dermatitis. The limitations of the models, their current applications, and their future potential in replacing animals in allergy-related science are discussed.

Development of an Oil-in-Water Self-Emulsifying Microemulsion for Cutaneous Delivery of Rose Bengal: Investigation of Anti-Melanoma Properties

The topical delivery route is proposed as an alternative or adjunctive approach to melanoma treatment, since the target site for melanoma treatment-the epidermal basal layer-is potentially accessible by this route. Microemulsion systems are effective delivery vehicles for enhanced, targeted skin delivery. This work investigated the effect of Rose Bengal (RB) and RB-loaded self-emulsifying microemulsions (SEMEs) on growth inhibition of human melanoma and normal skin cell monolayers, the safety of the excipients incorporated in SEMEs on human cell lines, and the in-vitro human skin penetration of RB delivered in SEMEs and control solution. Cellular toxicity was assessed by the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay, and the growth inhibitory mechanism of RB was investigated by flow cytometry using PI staining. Unloaded SEMEs caused reduced cellular toxicity compared to the surfactant excipient, Labrasol^®. RB-loaded SEMEs increased cell growth inhibition compared to the RB aqueous solution. Flow cytometry revealed apoptotic cells after treatment with RB-loaded SEMEs, indicating that apoptosis may be one of the mechanisms of cell death. Preliminary results of multiphoton microscopy with fluorescence lifetime imaging (MPM-FLIM) analysis showed deeper penetration with greater skin concentrations of RB delivered from SEMEs compared to the RB aqueous solution. This study highlights the enhanced skin penetration and antimelanoma effects of RB loaded in a SEME system.

In vivo biocompatibility and efficacy of dexamethasone-loaded PLGA-PEG-PLGA thermogel in an alkali-burn induced corneal neovascularization disease model

Challenges of ophthalmic drug delivery arise not only from the limited solubility of hydrophobic therapeutics, but also the restricted permeability and fast clearance of drugs due to the complex anatomy and physiology of eyes. Excellent biocompatibility of a thermosensitive polymer, PLGA-PEG-PLGA (1800-1500-1800, LA:GA ratio = 3:1), as an ophthalmic delivery system was demonstrated in our previous work. In this study, delivery of dexamethasone using this thermogel via a single subconjunctival injection for prolonged treatment was evaluated with corneal neovascularization using an alkali-burn diseased model in rat. Solubility of dexamethasone in the polymeric solution was increased by 5.2-fold and the resulting drug-loaded solution formed in situ rigid gel at body temperature. Prolonged in vitro release of dexamethasone from the gel structure was noted. Dexamethasone gel formulation was demonstrated to be more effective in reducing the burn stimulus and neovascularization in the rat diseased model. The findings suggest the PLGA-PEG-PLGA in situ gelling system can be applied for ophthalmic drug delivery to achieve sustained drug release and improved efficacy.

Poly traditional Chinese medicine formulation prepared with skin moisturizing properties

Many traditional Chinese medicine compositions can moisturize the skin and utilize in cosmetics. Using a combination of Chinese Medicine Materials and guided by Traditional Chinese Medicine principles, this study selected Echinacea purpurea to protect the skin barrier, Dendrobium nobile to clear heat and promote fluid production, Sophora flavescens to clear heat for diminished inflammation, and Aloe vera combined Lycium barbarum to nourish yin, to together form a "poly TCM moisturizing formulation." These poly plant extracts were investigated and optimized for the stability, safety, and moisturizing ability. The combination moisturizing effect was determined by measuring the expression of FLG mRNA, CLDN-1 mRNA, and AQP3 protein. Toxicological analysis included a red blood cell hemolysis test and a 3T3 phototoxicity test. It has been observed that by using polysaccharide yield as the evaluation criterion showed optimal extraction at a material-to-liquid ratio of 1:100, an extraction temperature of 100°C, and an extraction time of 3 hours. Moisturizing effect experiments showed that the expression of FLG mRNA, CLDN-1 mRNA, and AQP3 protein was significantly increased. Toxicological tests showed that the composition was safe and caused no irritating effects. Based on these results, this poly traditional Chinese medicine moisturizing formulation is safe within moisturizing effects and can be used as a moisturizing raw material in cosmetics.

Microbial Biosurfactants as Key Multifunctional Ingredients for Sustainable Cosmetics

A polar head and an apolar tail chemically characterize surfactants, they show different properties and are categorized by different factors such as head charge and molecular weight. They work by reducing the surface tension between oil and water phases to facilitate the formation of one homogeneous mixture. In this respect, they represent unavoidable ingredients, their main application is in the production of detergents, one of if not the most important categories of cosmetics. Their role is very important, it should be remembered that it was precisely soaps and hygiene that defeated the main infectious diseases at the beginning of the last century. Due to their positive environmental impact, the potential uses of microbial sourced surfactants are actively investigated. These compounds are produced with different mechanisms by microorganisms in the aims to defend themselves from external threats, to improve the mobility in the environment, etc. In the cosmetic field, biosurfactants, restricted in the present work to those described above, can carry high advantages, in comparison to traditional surfactants, especially in the field of sustainable and safer approaches. Besiede this, costs still remain an obsatcle to their diffusion; in this regard, exploration of possible multifunctional actions could help to contain application costs. To highlight their features and possible multifunctional role, on the light of specific biological profiles yet underestimated, we have approached the present review work.

Alternatives to In Vivo Draize Rabbit Eye and Skin Irritation Tests with a Focus on 3D Reconstructed Human Cornea-Like Epithelium and Epidermis Models

Human eyes and skin are frequently exposed to chemicals accidentally or on purpose due to their external location. Therefore, chemicals are required to undergo the evaluation of the ocular and dermal irritancy for their safe handling and use before release into the market. Draize rabbit eye and skin irritation test developed in 1944, has been a gold standard test which was enlisted as OECD TG 404 and OECD TG 405 but it has been criticized with respect to animal welfare due to invasive and cruel procedure. To replace it, diverse alternatives have been developed: (i) For Draize eye irritation test, organotypic assay, in vitro cytotoxicity-based method, in chemico tests, in silico prediction model, and 3D reconstructed human cornea-like epithelium (RhCE); (ii) For Draize skin irritation test, in vitro cytotoxicity-based cell model, and 3D reconstructed human epidermis models (RhE). Of these, RhCE and RhE models are getting spotlight as a promising alternative with a wide applicability domain covering cosmetics and personal care products. In this review, we overviewed the current alternatives to Draize test with a focus on 3D human epithelium models to provide an insight into advancing and widening their utility.

Biosurfactants in cosmetic formulations: trends and challenges

Cosmetic products play an essential role in everyone's life. People everyday use a large variety of cosmetic products such as soap, shampoo, toothpaste, deodorant, skin care, perfume, make-up, among others. The cosmetic industry encompasses several environmental, social and economic impacts that are being addressed through the search for more efficient manufacturing techniques, the reduction of waste and emissions and the promotion of personal hygiene, contributing to an improvement of public health and at the same time providing employment opportunities. The current trend among consumers is the pursuit for natural ingredients in cosmetic products, as many of these products exhibit equal, better or additional benefits in comparison with the chemical-based products. In this sense, biosurfactants are natural compounds with great potential in the formulation of cosmetic products given by their biodegradability and impact in health. Indeed, many of these biosurfactants could exhibit a "prebiotic" character. This review covers the current state-of-the-art of biosurfactant research for cosmetic purposes and further discusses the future challenges for cosmetic applications.

Effects of Ambient Fine Particles PM2.5 on Human HaCaT Cells

The current study was conducted to observe the effects of fine particulate matter (PM_2.5) on human keratinocyte cell line (HaCaT) cells. The potential mechanism linking PM_2.5 and skin was explored. HaCaT cells were cultured and then accessed in plate with PM_2.5. Cell viability was tested by Cell Counting Kit-8. The mRNA and protein expression of Filaggrin, Loricrin, Involucrin, and Repetin were analyzed. The levels of Granulocyte-macrophage Colony Stimulating Factor, Thymic Stromal Lymphopoietin, Tumor Necrosis Factor-α, Interleukin-1α, and Interleukin-8 were detected in the supernatant of the HaCaT cell with enzyme-linked immunosorbent assay kits. Cell viability decreased with the increase in PM_2.5. Compared with the control group, the protein expression of Filaggrin, Repetin, Involucrin, and Loricrin showed different expression patterns in PM_2.5 treatment groups. The level of Tumor Necrosis Factor-α, Thymic Stromal Lymphopoietin, Interleukin-1α, and Interleukin-8 significantly increased in the cells treated with PM_2.5. Ambient PM_2.5 may increase the risk of eczema and other skin diseases. The relative mechanism may be associated with the impairment of the skin barrier and the elevation of inflammatory responses.

Evaluation of fibrin-based dermal-epidermal organotypic cultures for in vitro skin corrosion and irritation testing of chemicals according to OECD TG 431 and 439

Reconstructed human epidermis (RhE) models have been used for in vitro testing of the potential harmful effects of exposure to chemical compounds on health. In the past, skin irritation and corrosion were evaluated in animal models; however, in recent years, due to the bioethics implications of the method and, to minimize the use of experimental animals, alternative procedures have been proposed. The Organisation for Economic Co-operation and Development (OECD) in its test guidelines (TG) 431 and 439 indicates the requirements for validating new methods for the evaluation of skin corrosion and irritation, respectively. Here, we present an in-house human dermal-epidermal model, useful for the performance of these tests. Using the methods described in this work, it was possible to obtain human fibrin-based dermal-epidermal organotypic skin cultures (ORGs) displaying similar histological characteristics to native skin and expressing specific differentiation epithelial proteins. The end points to classify a substance as irritant or corrosive were cell viability evaluated by MTT assay, and cytokine release measured by BD CBA for human inflammatory cytokines. According to the MTT test, the ORGs correctly classified irritating and corrosive substances. Moreover, the cytokine release assay was difficult to interpret in the context of testing chemical hazard classification. Further experiments are needed to validate this new model for the evaluation of surfactants because the fibrin matrix was affected in the presence of these substances.

The influence of microemulsion structure on their skin irritation and phototoxicity potential

The purpose of this study was to examine skin irritation and phototoxicity potentials of several microemulsions (ME), all comprising approximately the same percentage of surfactant mixture, but varying oil/water content and consequently inner structure being either droplet-like (o/w ME, o/w ME carbomer, w/o ME and w/o ME white wax) or lamellar (gel-like ME). Two different in vitro methods were used: MTT assay (performed either on reconstructed human epidermis (RHE) or NCTC 2544 cells) and pig ear test. Neither assay revealed the difference among ME with droplet-like structure. Then again, pig ear test and MTT assay performed on RHE indicated that gel-like ME is more irritant compared to other tested ME, whereas no difference among formulations were observed by MTT assay on NCTC 2544 cells. The reasonable explanation is destruction and consequently uniform structure of ME upon dilution that is inevitable for testing on cell cultures. The results of phototoxicity test again indicated the increased potential of gel-like ME to cause adverse effects on skin. It can be concluded that for ME consisting of the same amount of identical surfactants but having different structure the latter represent a crucial factor that determines their dermal toxicity.

Synthesis, Surface Active Properties and Cytotoxicity of Sodium N-Acyl Prolines

Sodium N-acyl prolines (NaNAPro) were synthesized using mixture of fatty acids obtained from coconut, palm, karanja, Sterculia foetida and high oleic sunflower oils via Schotten-Baumann reaction in 58-75% yields to study the synergetic effect of mixture of hydrophobic fatty acyl functionalities like saturation, unsaturation and cyclopropene fatty acids with different chain lengths and aliphatic hetero cyclic proline head group on their surface and cytotoxicity activities. The products were characterized by chromatographic and spectral techniques. The synthesized products were evaluated for their surface active properties such as surface tension, wetting power, foaming characteristics, emulsion stability, calcium tolerance, critical micelle concentration (CMC) and thermodynamic properties. The results revealed that all the products exhibited superior surface active properties like CMC, calcium tolerance and emulsion stability as compared to the standard surfactant, sodium lauryl sulphate (SLS). In addition, palm, Sterculia foetida and high oleic sunflower fatty N-acyl prolines exhibited promising cytotoxicity against different tumor cell lines.

Toxicity study in blood and tumor cells of laser produced medicines for application in fabrics

Phenothiazine derivatives are non-antibiotics with antimicrobial, fungistatic and fungicidal effects. We exposed to a high energy UV laser beam phenothiazines solutions in water at 20mg/mL concentration to increase antibacterial activity of resulting mixtures. Compared to previous results obtained on bacteria, more research is needed about UV laser irradiated phenothiazines applications on cancer cell cultures to evidence possible anticancerous properties. Evaluation of the safety of the newly obtained photoproducts in view of use on humans is also needed. Due to expensive animal testing in toxicology and pressure from general public and governments to develop alternatives to in vivo testing, in vitro cell-based models are attractive for preliminary testing of new materials. Cytotoxicity screening reported here shows that laser irradiated (4h exposure time length) chlorpromazine and promazine are more efficient against some cell cultures. Interaction of laser irradiated phenothiazines with fabrics show that promethazine and chlorpromazine have improved wetting properties. Correlation of these two groups of properties shows that chlorpromazine appears to be more recommended for applications on tissues using fabrics as transport vectors. The reported results concern stability study of phenothiazines water solutions to know the time limits within which they are stable and may be used.

Biocatalytic synthesis, antimicrobial properties and toxicity studies of arginine derivative surfactants

Two novel arginine-based cationic surfactants were synthesized using as biocatalyst papain, an endopeptidase from Carica papaya latex, adsorbed onto polyamide. The classical substrate N (α)-benzoyl-arginine ethyl ester hydrochloride for the determination of cysteine and serine proteases activity was used as the arginine donor, whereas decyl- and dodecylamine were used as nucleophiles for the condensation reaction. Yields higher than 90 and 80 % were achieved for the synthesis of N (α)-benzoyl-arginine decyl amide (Bz-Arg-NHC10) and N (α)-benzoyl-arginine dodecyl amide (Bz-Arg-NHC12), respectively. The purification process was developed in order to make it more sustainable, by using water and ethanol as the main separation solvents in a single cationic exchange chromatographic separation step. Bz-Arg-NHC10 and Bz-Arg-NHC12 proved antimicrobial activity against both Gram-positive and Gram-negative bacteria, revealing their potential use as effective disinfectants as they reduced 99 % the initial bacterial population after only 1 h of contact. The cytotoxic effect towards different cell types of both arginine derivatives was also measured. Bz-Arg-NHCn demonstrated lower haemolytic activity and were less eye-irritating than the commercial cationic surfactant cetrimide. A similar trend could also be observed when cytotoxicity was tested on hepatocytes and fibroblast cell lines: both arginine derivatives were less toxic than cetrimide. All these properties would make the two novel arginine compounds a promising alternative to commercial cationic surfactants, especially for their use as additives in topical formulations.

Gemini surfactants from natural amino acids

In this review, we report the most important contributions in the structure, synthesis, physicochemical (surface adsorption, aggregation and phase behaviour) and biological properties (toxicity, antimicrobial activity and biodegradation) of Gemini natural amino acid-based surfactants, and some potential applications, with an emphasis on the use of these surfactants as non-viral delivery system agents. Gemini surfactants derived from basic (Arg, Lys), neutral (Ser, Ala, Sar), acid (Asp) and sulphur containing amino acids (Cys) as polar head groups, and Geminis with amino acids/peptides in the spacer chain are reviewed.

DNA gel particles: an overview

A general understanding of interactions between DNA and oppositely charged compounds forms the basis for developing novel DNA-based materials, including gel particles. The association strength, which is altered by varying the chemical structure of the cationic cosolute, determines the spatial homogeneity of the gelation process, creating DNA reservoir devices and DNA matrix devices that can be designed to release either single- (ssDNA) or double-stranded (dsDNA) DNA. This review covers recent developments on the topic of DNA gel particles formed in water-water emulsion-type interfaces. The degree of DNA entrapment, particle morphology, swelling/dissolution behavior and DNA release responses are discussed as functions of the nature of the cationic agent used. On the basis of designing DNA gel particles for therapeutic purposes, recent studies on the determination of the surface hydrophobicity and the hemolytic and the cytotoxic assessments of the obtained DNA gel particles have been also reported.

Design and physicochemical characterisation of novel dissolving polymeric microneedle arrays for transdermal delivery of high dose, low molecular weight drugs

We describe formulation and evaluation of novel dissolving polymeric microneedle (MN) arrays for the facilitated delivery of low molecular weight, high dose drugs. Ibuprofen sodium was used as the model here and was successfully formulated at approximately 50% w/w in the dry state using the copolymer poly(methylvinylether/maleic acid). These MNs were robust and effectively penetrated skin in vitro, dissolving rapidly to deliver the incorporated drug. The delivery of 1.5mg ibuprofen sodium, the theoretical mass of ibuprofen sodium contained within the dry MN alone, was vastly exceeded, indicating extensive delivery of the drug loaded into the baseplates. Indeed in in vitro transdermal delivery studies, approximately 33mg (90%) of the drug initially loaded into the arrays was delivered over 24h. Iontophoresis produced no meaningful increase in delivery. Biocompatibility studies and in vivo rat skin tolerance experiments raised no concerns. The blood plasma ibuprofen sodium concentrations achieved in rats (263μgml(-1) at the 24h time point) were approximately 20 times greater than the human therapeutic plasma level. By simplistic extrapolation of average weights from rats to humans, a MN patch design of no greater than 10cm(2) could cautiously be estimated to deliver therapeutically-relevant concentrations of ibuprofen sodium in humans. This work, therefore, represents a significant progression in exploitation of MN for successful transdermal delivery of a much wider range of drugs.

In vitro study of the cytotoxicity and antiproliferative effects of surfactants produced by Sphingobacterium detergens

The application of biosurfactants in the biomedical field is growing due to their antimicrobial activity, low cytotoxicity and ability to induce apoptosis in cancer cells. In the light of this therapeutic potential, as well as possible applications in cosmetics or as drug vehicles in pharmaceutical products, a new biosurfactant produced by Sphingobacterium detergens was investigated for its haemolytic activity and cytotoxic and antiproliferative effects in different cell lines. Fraction A showed 100% haemolysis in rabbit erythrocytes, but in Fraction B the rate was only 83%. When comparing cytotoxicity values (IC50) of the two fractions in model fibroblast and keratinocyte cell cultures, Fraction B was less cytotoxic, showing lower values than the reference compound SDS, indicating low skin irritability. Finally, in non-differentiated intestinal Caco-2 cultures, Fractions A and B reduced cell proliferation and induced apoptosis by 44% and 75%, respectively. According to these results, biosurfactants produced by S. detergens have potential application in cosmetic and pharmaceutical formulations.

1,4-dihydroxy-2-naphthoic Acid Induces Apoptosis in Human Keratinocyte: Potential Application for Psoriasis Treatment

Psoriasis, which affects approximately 1–3% of the population worldwide, is a chronic inflammatory skin disorder characterized by epidermal keratinocytes hyperproliferation, abnormal differentiation, and inflammatory infiltration. Decrease in keratinocyte apoptosis is a specific pathogenic phenomenon in psoriasis. Chinese herbs have been used for the treatment of psoriasis in China showing promising effect in clinical trials. A traditional Chinese medicine has relatively fewer side effects with longer remission time and lower recurrence rate. The extract of Rubia cordifolia L. (EA) was previously found by us to induce HaCaT keratinocytes apoptosis. In this study we identified one of the components in Rubia cordifolia L., the anthraquinone precursor 1,4-dihydroxy-2-naphthoic acid (DHNA), induces HaCaT keratinocytes apoptosis through G0/G1 cell cycle arrest. We have also demonstrated that DHNA acts through both caspase-dependent and caspase-independent pathways. Besides, cytotoxicity and IL-1α release assays indicate that DHNA causes less irritation problems than dithranol, which is commonly employed to treat psoriasis in many countries. Since DHNA possesses similar apoptotic effects on keratinocytes as dithranol but causes less irritation, DHNA therefore constitutes a promising alternative agent for treating psoriasis. Our studies also provide an insight on the potential of using EA and DHNA, alternatively, as a safe and effective treatment modality for psoriasis.

Dicationic alkylammonium bromide gemini surfactants. Membrane perturbation and skin irritation

Dicationic alkylammonium bromide gemini surfactants represent a class of amphiphiles potentially effective as skin permeation enhancers. However, only a limited number of studies has been dedicated to the evaluation of the respective cytotoxicity, and none directed to skin irritation endpoints. Supported on a cell viability study, the cytotoxicity of gemini surfactants of variable tail and spacer length was assessed. For this purpose, keratinocyte cells from human skin (NCTC 2544 cell line), frequently used as a model for skin irritation, were employed. The impact of the different gemini surfactants on the permeability and morphology of model vesicles was additionally investigated by measuring the leakage of calcein fluorescent dye and analyzing the NMR spectra of ³¹P, respectively. Detail on the interaction of gemini molecules with model membranes was also provided by a systematic differential scanning calorimetry (DSC) and molecular dynamics (MD) simulation. An irreversible impact on the viability of the NCTC 2544 cell line was observed for gemini concentrations higher than 25 mM, while no cytotoxicity was found for any of the surfactants in a concentration range up to 10 mM. A higher cytotoxicity was also found for gemini surfactants presenting longer spacer and shorter tails. The same trend was obtained in the calorimetric and permeability studies, with the gemini of longest spacer promoting the highest degree of membrane destabilization. Additional structural and dynamical characterization of the various systems, obtained by ³¹P NMR and MD, provide some insight on the relationship between the architecture of gemini surfactants and the respective perturbation mechanism.

Comparative sensitivity of tumor and non-tumor cell lines as a reliable approach for in vitro cytotoxicity screening of lysine-based surfactants with potential pharmaceutical applications

Surfactants are used as additives in topical pharmaceuticals and drug delivery systems. The biocompatibility of amino acid-based surfactants makes them highly suitable for use in these fields, but tests are needed to evaluate their potential toxicity. Here we addressed the sensitivity of tumor (HeLa, MCF-7) and non-tumor (3T3, 3T6, HaCaT, NCTC 2544) cell lines to the toxic effects of lysine-based surfactants by means of two in vitro endpoints (MTT and NRU). This comparative assay may serve as a reliable approach for predictive toxicity screening of chemicals prior to pharmaceutical applications. After 24-h of cell exposure to surfactants, differing toxic responses were observed. NCTC 2544 and 3T6 cell lines were the most sensitive, while both tumor cells and 3T3 fibroblasts were more resistant to the cytotoxic effects of surfactants. IC(50)-values revealed that cytotoxicity was detected earlier by MTT assay than by NRU assay, regardless of the compound or cell line. The overall results showed that surfactants with organic counterions were less cytotoxic than those with inorganic counterions. Our findings highlight the relevance of the correct choice and combination of cell lines and bioassays in toxicity studies for a safe and reliable screen of chemicals with potential interest in pharmaceutical industry.

Filaggrin knockdown and Toll-like receptor 3 (TLR3) stimulation enhanced the production of thymic stromal lymphopoietin (TSLP) from epidermal layers

Keratinocytes constitute the first-line barrier against exogenous antigens and contain Toll-like receptors (TLRs), which function as pattern-recognition molecules to activate antimicrobial innate immune responses. In an effort to ascertain whether or not filaggrin (filament-aggregating protein) expression affected the TLR-mediated responses of keratinocytes, we transfected filaggrin siRNA into HaCaT human keratinocyte cells and determined that thymic stromal lymphopoietin (TSLP) and IL-6 secretion were increased by poly(I:C) stimulus. Additionally, TSLP expression is increased in filaggrin knockdown as well as TLR3 stimulation in reconstituted human epidermal layers. Therefore, the findings of this study show that reduced filaggrin levels may influence innate immune responses via TLR stimuli and may contribute to the pathogenesis of inflammatory skin disease via TSLP expression.

In vitro investigation and biomechanical modeling of the effects of PLF-68 on osteoarthritis in a three-dimensional model

In this study, it was hypothesized that Pluronic F-68 (PLF-68) increases matrix synthesis of osteoarthritis (OA) chondrocytes in addition to its well-documented cell survival effect. To test this hypothesis, rat articular chondrocytes were embedded in agarose discs and were exposed to 5-azacytidine (Aza-C) to induce OA-like alterations. Chondrocytes were then treated with PLF-68 (8 and 12 mg/ml) for 10 days. Aza-C-exposed and PLF-68-untreated chondrocytes and Aza-C-unexposed and PLF-68-untreated chondrocytes were used as negative and positive control groups, respectively. Dynamic hydrostatic pressure (max 0.2 MPa, 0.1 Hz) was applied to discs for 30 min/day (5 days/week). Cell viability, collagen and proteoglycan deposition in discs were determined. Unconfined compression stress relaxation tests were performed to determine peak stress and material parameters of discs--namely spring constants (k (1) and k (2)), damping coefficient (η), instantaneous modulus (E (0)) and relaxed modulus (E (∞)) using Kelvin model to evaluate the functional coherence of the matrix. PLF-68 treatment significantly increased the collagen deposition in discs and viability of OA-like chondrocytes. A dose-dependent increase was also observed for elastic stiffness parameters (k (1), k (2), E (0) and E (∞)). Same positive effect of PLF-68 was not observed for proteoglycan deposition. However, dose-dependent increase in η suggests that PLF-68 treatment resulted with the deposition of functional matrix. This is the first study which reports that PLF-68 has also positive effect on collagen synthesis of OA cells. As a conclusion, our results suggest that PLF-68 has a potential for recovery from OA-like alterations, which should be further analyzed.

Combined In Vitro Tests as an Alternative to In Vivo Eye Irritation Tests

Accurate methods that test the eye irritation potential of chemicals, which do not involve the use of animals, are needed to meet new regulatory standards. We evaluated the applicability and predictive capacity of five in vitro tests for eye irritation: the Hen's Egg Test-Chorioallantoic Membrane (HET-CAM) assay; the Chorioallantoic Membrane-Trypan Blue Staining (CAM-TBS) assay; the Fluorescein Leakage Test (FLT); the 3T3-Neutral Red Uptake (3T3-NRU) cytotoxicity assay; and the red blood cell (RBC) haemolysis assay. A panel of 16 chemicals (some at multiple concentrations) was assessed by using the five tests, and the results were compared with historical in vivo Draize test data. The results showed rank correlation and class concordance between the five alternative methods and the Draize test for the 16 chemicals. These in vitro assays had good predictive capacity, reproducibility and reliability when compared to the Draize test. The best relationship was between the HET-CAM, CAM-TBS and FLT results, and the modified maximum average score(s) (MMAS). A prediction model (PM) was developed, based on the maximum possible correlation between the MMAS and the HET-CAM, CAM-TBS and FLT results. The PM had a good predictive capacity when compared to the results of animal tests, indicating its potential value for the in vitro screening of chemicals for eye irritation effects.

A comparative study of leukaemia inhibitory factor and interleukin-1alpha intracellular content in a human keratinocyte cell line after exposure to cosmetic fragrances and sodium dodecyl sulphate

According to European laws animal testing in cosmetic industry will be prohibited in a few years and it will be replaced by alternative methods based on cell and tissue culture. Many ingredients of cosmetic formulations are potentially causes of skin inflammation and sensibilization. Since cytotoxicity is known, among other factors, to trigger irritation, in an alternative model for evaluation of skin irritation, it can be considered also the precocious release of inflammatory mediators, i.e. cytokines, originating mainly from keratinocytes. In this in vitro study we have analysed some parameters directly or indirectly related to irritation/inflammation, in NCTC 2544 human keratinocytes during short-time exposure to some potential irritants cosmetic fragrances, included in the European Laws 2003/15/EEC. IIC50 was extrapolated by MTT and NRU viability indexes after exposure of cell ultures to Geraniol Limonene and Benzylic Alcohol for 1, 3 and 6h. NCTC cells were then exposed to sub-toxic doses of selected compounds and interleukin-1alpha (IL-1alpha) and leukaemia inhibitory factor (LIF) expressions were analysed as early proinflammatory cytokines. To our knowledge our findings demonstrated for the first time that NCTC cells synthesize and modulate LIF after exposure to selected irritating stimuli. Moreover, our results give evidence on LIF role as in vitro precocious endpoint for the assessment of the risk in cosmetic field, because its response under irritation stimuli is very quick and comparable to IL-1alpha.

Alternative Methods for Eye and Skin Irritation Tests: An Overview

The evaluation of eye and skin irritation potential is essential to ensuring the safety of individuals in contact with a wide variety of substances designed for industrial, pharmaceutical or cosmetic use. The Draize rabbit eye and skin irritancy tests have been used for 60 years to attempt to predict the human ocular and dermal irritation of such products. The Draize test has been the standard for ocular and dermal safety assessments for decades. However, several aspects of the test have been criticised. These include: the subjectivity of the method; the overestimation of human responses; and the method's cruelty. The inadequacies of the Draize test have led to several laboratories over the last 20 years making efforts to develop in vitro assays to replace it. Protocols that use different types of cell cultures and other methods have been devised to study eye and skin irritation. Different commercial kits have also been developed to study eye and skin irritation, based on the action of chemicals on these tissues. This article presents a review of the main alternatives developed to replace the use of animals in the study of chemical irritation. Particular attention is paid to the reproducibility of each method.

Hemolysis and antihemolysis induced by amino acid-based surfactants

Surfactants have the special ability to interact with the lipid bilayer of cell membranes. The red blood cell is one of the most used cellular membrane models to study the mechanisms underlying surfactant-induced osmotic cell resistance. To increase our knowledge regarding the mechanisms of surfactant membrane interaction, we studied the action of five lysine-derivative anionic and three arginine-derivative cationic amino acid-based surfactants on hypotonic hemolysis. Results showed two different antihemolytic behaviors among amino acid-based surfactants, both related to the maximal protective concentration. How the physico-chemical properties and structure of these compounds determine the protection against hypotonic hemolysis is discussed in detail. We found a good correlation between the CMC and the concentrations resulting in maximum protection against hypotonic hemolysis for the cationic surfactants, but no correlation for the anionic surfactants. In the case of lysine derivative surfactants, which only differ in their counterions, the counterion is implicated in the differences in the antihemolytic potency and the hemolytic activities of this.

Disturbance of erythrocyte lipid bilayer by amino acid-based surfactants

In an attempt to increase our knowledge regarding the mechanisms of surfactant membrane interaction, we studied the action of several anionic and cationic amino acid-based surfactants on membrane fluidity using fluorescence anisotropy. Anisotropy measurements demonstrated that almost all of the surfactants studied disturbed the external region of the erythrocyte membrane without affecting the core of the bilayer. How the physico-chemical properties and structure of these compounds affect dynamics of the lipid bilayer is discussed in detail.

Ocular toxicology: the Draize eye test

PURPOSE OF REVIEW

Superficial ocular tissues are frequently exposed to damage produced by chemical compounds applied on or around the ocular surface for cosmetic, therapeutic or accidental reasons. An experimental test measuring objectively and in a reproducible way any potential damaging effect would certainly help in prospectively minimizing unwanted effects. The Draize eye test, although commonly employed to date, does not seem to be quite satisfactory in this respect.

RECENT FINDINGS

The limits of the Draize eye test and the results of some modified versions of the test are analysed. In particular, the good predictivity of the so-called low-volume Draize eye test and the recent findings of studies on the in-vitro and ex-vivo alternatives to the Draize eye test are presented.

SUMMARY

The Draize eye test, despite criticisms, has been used in the clinical setting for a long time and still remains the reference protocol. To date, only a combination of alternative methods, none of which is devoid of serious criticisms, seems to be able to exhaustively recognize potential irritants and avoiding for that purpose, in some cases, the use of living animals.