Cytotoxicity evaluation of microbial sophorolipids and glucolipids using normal human dermal fibroblasts (NHDF) in vitro

Abstract

Fibroblasts are considered a key player in the wound healing process. Although this cellular family is constituted by several distinct subtypes, dermal fibroblasts are crucial thanks to their ability to secrete pro-regenerative growth factors, extracellular matrix (ECM) proteins and their immune and anti-inflammatory role. Sophorolipids (SL), sophorosides (SS) and glucolipids (G), mono-unsaturated (C18:1) or saturated (C18:0), glycolipids derived from microbial fermentation of wild type or engineered yeast Starmerella bombicola, constitute a novel sustainable class of bio-based chemicals with interesting physicochemical characteristics, which allow them to form soft diverse structures from hydrogels to vesicles, micelles or complex coacervates with potential interest in skin regeneration applications. In this study, we first tested the cytocompatibility of a broad set of molecules from this family on normal human dermal fibroblasts (NHDF). Our results show that, up to an upper threshold (0.1 % w/v), the microbial glycolipids (SL-C18:1, G-C18:1, SS_bola-C18:1, SL-C18:0 and G-C18:0) under study were able to sustain cell growth. Furthermore, we selected the least cytotoxic glycolipids (SL-C18:1, SS_bola-C18:1, SL-C18:0) to study their potential to promote wound healing by measuring the gene expression of several key skin regeneration markers (i.e. collagen, elastin, transforming growth factor β, fibroblast growth factor …) using qPCR. Unfortunately, none of these glycolipids modulated the gene expression of molecules involved in tissue repair. However, this study aims to encourage the community to test this novel class of molecules for novel high-end biomedical applications.

Importance

Biosurfactants prepared by microbial fermentation are natural amphiphiles of growing importance, with the goal of replacing synthetic surfactants in commercial formulations. However, their cytotoxicity profile is still poorly known, especially for new molecules like single-glucose lipids or bolaform sophorolipids. This wants to contribute to all those applications, which could be developed with biosurfactants in contact with the skin (cosmetics, wound healing). We test the cytotoxicity of five structurally-related molecules (C18:1 and C18:0 sophorolipids, C18:1 and C18:0 single-glucose lipids, C18:1 di-sophoroside) against normal human dermal fibroblasts (NHDF) and evaluate the metabolic activity of the least toxic among them. To the best of our knowledge, cytotoxicity of these molecules, and of microbial biosurfactants in general, was never tested against NHDF.