Highly stable oil-in-water emulsions with a gemini amphiphilic pseudopeptide† Ahmed H. Lotfallah, a M. Isabel Burguete, a Ignacio Alfonso * b and Santiago V. Luis * a A gemini amphiphilic pseudopeptide promotes the spontaneous formation of an oil-in-water emulsion with a high thermal, mechanical and acid-medium stability. The micro-droplets thus formed are dis- assembled by strong bases or after the action of an enzyme, showing a potential for stimulus-responsive material formulations. The preparation of stable emulsions has recently attracted attention in chemical research, 1 especially aer understanding some of the basis for the design of new self-assembling enti- ties. 2 Surfactant-based emulsions display a wide range of tech- nological and industrial applications in pharmaceutics, 3 food 4 and cosmetic 5 formulations or catalysis. 6 However, some of the conventional surfactant agents have some limitations for long- term stability, 7 availability and chemical modularity for tailor- made structural modications. 8 In this regard, the use of amino acid-based amphiphilic molecules for phase separation and emulsion stabilization will offer a tremendous advantage in terms of synthetic and structural versatility. 9 Recently, we reported on the synthesis and study of a family of new Gemini Amphiphilic Pseudopeptides (GAP) 10 that were able to self- assemble into different nanostructures depending on the environment, and even to respond to simple stimuli, like polarity 11 or pH changes of the medium. 12 The delicate tuning of the chemical structures allowed us to modulate the amphiphilic nature for optimizing their self-assembling abilities at the organic–aqueous or air–water interphases. 13 Here we exploit that knowledge for the efficient preparation of emulsions with a high mechanical, thermal and chemical stability. Our pseudo- peptidic systems show advantages in terms of biocompatibility and synthetic modularity, making them highly appealing for future biotechnological applications. The designed GAP (1) is a exible C 2 symmetric pseudo- peptide with a central polar linker (Fig. 1, in blue) and two lipophilic tails. The Val derivative was selected because the corresponding pseudopeptides bearing this side chain have shown specic self-assembling advantages. 14 This molecule can be readily synthesized in relatively large scale from Fig. 1 (A) Chemical structure of the Gemini Amphiphilic Pseudopetide (GAP) 1, (B) SEM, (C) AFM and (D) TEM micrographs of dried samples of 1 grown from 1 : 1 water : MeOH solvent mixture at pH 2. a Departamento de Qu´ ımica Inorg´ anica y Org´ anica, Universidad Jaume I, Avenida Sos Baynat, s/n, Castell´ on, Spain. E-mail: luiss@uji.es; Fax: +34 964728214; Tel: +34 964728239 b Departamento de Qu´ ımica Biol´ ogica y Modelizaci´ on Molecular, IQAC-CSIC, Jordi Girona 18-26, Barcelona, Spain. E-mail: ignacio.alfonso@iqac.csic.es; Fax: +34 932045904; Tel: +34 934006100 † Electronic supplementary information (ESI) available: Synthetic procedures, experimental details, additional microscopy images. See DOI: 10.1039/c5ra05121e Cite this: RSC Adv. , 2015, 5, 36890 Received 23rd March 2015 Accepted 16th April 2015 DOI: 10.1039/c5ra05121e www.rsc.org/advances 36890 | RSC Adv., 2015, 5, 36890–36893 This journal is © The Royal Society of Chemistry 2015 RSC Advances COMMUNICATION Published on 16 April 2015. Downloaded by Universitat Jaume I on 16/02/2016 10:18:34. View Article Online View Journal | View Issue