Assessment of the Potential Skin Irritation of Lysine-Derivative Anionic Surfactants Using Mouse Fibroblasts and Human Keratinocytes as An Alternative to Animal Testing

Abstract

Purpose. The aim of this study was to identify new surfactants with low skin irritant properties for use in pharmaceutical and cosmetic formulations, employing cell culture as an alternative method to in vivo testing. In addition, we sought to establish whether potential cytotoxic properties were related to the size of the counterions bound to the surfactants.Methods. Cytotoxicity was assessed in the mouse fibroblast cell line 3T6, and the human keratinocyte cell line NCTC 2544, using the MTT assay and uptake of the vital dye neutral red 24 h after dosing (NRU).Results. Lysine-derivative surfactants showed higher IC 50 s than did commercial anionic irritant compounds such as sodium dodecyl sulphate, proving to be no more harmful than amphoteric betaines. The aggressiveness of the surfactants depended upon the size of their constituent counterions: surfactants associated with lighter counterions showed a proportionally higher aggressivity than those with heavier ones.Conclusions Synthetic lysine-derivative anionic surfactants are less irritant than commercial surfactants such as sodium dodecyl sulphate and Hexadecyltrimethylammonium bromide and are similar to Betaines. These surfactants may offer promising applications in pharmaceutical and cosmetic preparations, representing a potential alternative to commercial anionic surfactants as a result of their low irritancy potential.

The role of counterions in the membrane-disruptive properties of pH-sensitive lysine-based surfactants

“…These findings show that an increased in surfactant concentrations also caused membrane disruption within the pH range characteristic of early endosomes. However, these concentrations may present toxic effects, as determined by the cytotoxicity assays performed in the 3T3 fibroblast cell line (data shown in section 3.6), and also as reported in previous cytotoxicity studies in 3T6 fibroblasts and NCTC 2544 keratinocyte cell lines [25].…”

“…1). These surfactants were synthesized in our laboratory as previously described [25,29]. The commercial anionic surfactant sodium dodecyl sulfate (SDS) was used as reference compound.…”

“…Here we selected N α ,N ε -dioctanoyl lysine derivatives, a class of amino acid-based surfactants synthesized as lecithin analogs, since homologs with eight carbon atom chains are the least hemolytic and show the least irritant activity, thus proving the most suitable for practical applications [24]. Moreover, earlier studies by our group demonstrated the biocompatibility and low in vitro toxicity of this series of anionic lysine-based surfactants [25][26][27][28].…”

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

“…The knowledge about the cytotoxicity and potential mechanisms of surfactant interaction with healthy and tumor cells may help on the development of specific and effective devices for cancer therapy. In previous studies, we identified a number of toxic effects of this class of surfactants (Sanchez et al, 2004(Sanchez et al, , 2006a(Sanchez et al, , 2006b). Nevertheless, given that no single in vitro assay has the capacity to mimic all events that occur in vivo, and in order to complete these toxicological studies, here we performed a comparative evaluation using six cell types and two cytotoxicity assays, MTT and NRU.…”

Straightforward Method for the Preparation of Lysine-Based Double-Chained Anionic Surfactants

“…[26] The same research group has also explored some lysine-derived surfactants, including N a ,N e -dioctanoyl-lysine, which performed significantly better than classical anionic surfactants in terms of ocular and skin irritancy, haemolytic activity, antimicrobial properties, and aquatic toxicity. [31][32][33][34][35][36] The wide potentialities of lysine-based double-chain anionic amphiphiles as bio-and ecofriendly surfactants with prospective industrial interest prompted us to explore alternative methods for their preparation. Synthetic methodologies were developed to give high yields at a multigram scale and involve inexpensive, safe, simple, and high-yield experimental procedures, as these are key factors for a feasible industrial development of novel surfactants.…”