Biocidal Properties of a Glycosylated Surface: Sophorolipids on Au(111)

Abstract

Classical antibacterial surfaces usually involve antiadhesive and/or biocidal strategies. Glycosylated surfaces are usually used to prevent biofilm formation via antiadhesive mechanisms. We report here the first example of a glycosylated surface with biocidal properties created by the covalent grafting of sophorolipids (a sophorose unit linked by a glycosidic bond to an oleic acid) through a self-assembled monolayer (SAM) of short aminothiols on gold (111) surfaces. The biocidal effect of such surfaces on Gram+ bacteria was assessed by a wide combination of techniques including microscopy observations, fluorescent staining and bacterial growth tests. About 50% of the bacteria are killed via alteration of the cell envelope. In addition, the role of the sophorose unit and aliphatic chain configuration are highlighted by the lack of activity of substrates modified respectively with sophorose-free oleic acid and sophorolipid-derivative having a saturated aliphatic chain. This system 2 demonstrates thus the direct implication of a carbohydrate in the destabilization and disruption of the bacterial cell envelope.3

Morphological and ultrastructural changes in bacterial cells as an indicator of antibacterial mechanism of action

“…A forerunner of the molecular biology approach was the examination of bacteria treated with test agent for changes to their morphology and ultrastructure [24]. This strategy remains extremely popular among researchers investigating antibacterial mechanism of action, both as an early exploratory step [26][27][28][29][30] and for confirmation of a suspected mechanism [31][32][33]. Requiring only access to an electron microscopy suite, it is an approach that is open to researchers in even relatively low resource settings.…”

Nanoscale antiadhesion properties of sophorolipid-coated surfaces against pathogenic bacteria

“…Analysis of WT bacterial adhesion forces on SL monolayers (water contact angle B501) 22 (Fig. 2a, right panel; Fig.…”

“…15,[17][18][19] Sophorolipids (SLs) are glycolipids featuring strong antimicrobial action, 20 yet the underlying molecular mechanism remain controversial. 15,16,[21][22][23] Using single-cell force nanoscopy, 24,25 we measure the nanoscale adhesive forces between single bacteria and monolayers of alkanethiols or deacetylated C18:1 acidic, where the carboxyl group has been modified to allow binding onto gold surfaces (Fig. 1a).…”

“…1a). 16,22 We focus on the Gram-positive bacterium Staphylococcus aureus, a nosocomial pathogen frequently implicated in the colonization of biomaterials such as central venous catheters and prosthetic joints, 26 as well as on the uropathogenic Gram-negative Escherichia coli, known to be commonly involved in catheter-associated urinary tract infections. 5 We compare the passivating activity of SL-surfaces with that of surfaces modified with sophorose-free oleic acid (OA) which mimics only the aliphatic chain of sophorolipids or with a C18:0 SL-derivative having a fully saturated aliphatic chain (SL 0 ) ( Fig.…”

Self‐Assembly of Bolaamphiphilic Molecules

“…Baccile et al used the self‐assembled structures of SLs as a template for the preparation of nanostructured silica . They have also studied the biocidal effect of SLs towards Listeria ivanovii . We have also shown the cellular uptake of sophorolipid‐conjugated gellan gum reduced gold nanoparticles and their cytotoxicity towards human glioma cell line LN‐229 and human glioma stem cell line HNGC‐2.…”