Surfactants are multifunctional molecules widely used in personal care and healthcare formulations to cleanse, help disperse active ingredients (e.g., forming emulsions) and stabilise products. With increasing demands on improving biosafety, there is now mounting pressure to understand how different surfactants elicit toxicities at molecular and cellular levels. This work reports the membrane-lytic behaviour of a group of sulphonated methyl ester (SME) surfactants together with representative conventional surfactants. All surfactants displayed the clear rise of lysis of the model lipid bilayer membranes around their CMCs, but the two ionic surfactants SDS and C12TAB even caused measurable lysis below their CMCs, with membrane-lytic actions increasing with monomer concentration. Furthermore, whilst ionic and nonionic surfactants could achieve full membrane lysis once above their CMCs, this ability was weak from the SME surfactants and decreased with increasing the acyl chain length. In contrast to the conventional anionic surfactants such as SDS and SLES, the protein solubilizing capability of the SME surfactants was also low. On the other hand, MTT assays against 3T3 fibroblast cells and human chondrocyte cells revealed high toxicity from SDS and C12TAB against the other surfactants studied, but the difference between SME and the rest of conventional surfactants was small. Similar behaviour was also observed in their bactericidal effect against E. coli and S. aureus. The trend is broadly consistent with their membrane-lytic behaviour, indicating little selectivity in their cytotoxicity and bactericidal action. These results thus reveal different toxicities implicated from different surfactant head groups. Increase in acyl chain length as observed from SME surfactants could help improve surfactant biocompatibility. Copyright =C2=A9 2018. Published by Elsevier Inc.

Fabrication of antibacterial materials with sustained release of active components is of great importance for long-term antibacterial applications. Graphene oxide (GO) has been found to be an excellent carrier for accumulating the antibacterial peptide of G(IIKK)4I-NH2 and mediating its loading into the layer-by-layer (LBL) films for sustained release applications. G(IIKK)4I-NH2 takes random coiled conformation in monomeric state below 0.17 mM but self-assembles into supramolecular aggregates with alpha-helical secondary structure at higher concentrations. It can bind onto GO surface in both monomeric and aggregate states to form stable GO@G(IIKK)4I-NH2 composites. Upon binding, the local amphiphilic environment of GO surface induces a conformational transition of G(IIKK)4I-NH2 monomers from random coils to alpha-helix. The aggregate binding enhances the loading amount greatly. GO (1 mg) can load as high as 1.7 mg of peptide at saturation. This enables the GO@G(IIKK)4I-NH2 composites to serve as reservoirs for sustained release of active G(IIKK)4I-NH2 monomers. Moreover, G(IIKK)4I-NH2 itself shows low efficiency in LBL assembly, whereas the GO@G(IIKK)4I-NH2 composites are ideal LBL assembling units with highly enhanced loading efficiency of G(IIKK)4I-NH2. The LBL films involving degradable poly(beta-amino esters) can realize sustained release of G(IIKK)4I-NH2 for bacteria killing in a well-controlled manner. This study demonstrates an efficient strategy for fabrication of long-durable antibacterial materials and surface coatings by using GO as the carrier for drug accumulation and loading.=20