Supramolecular polymers are promising architectures for different applications in the materials or biological fields between others. Their inherent dynamicity and versatility give to these materials interesting application-related properties but at the same time make their construction intricate. The control over these assembly processes of supramolecular polymers is still nowadays a big challenge to overcome. Therefore, there is a need of new methods that shed light in the understanding of the supramolecular driven assembly processes in different situations.
In a recent study reported in Nanoscale Horizons, Montenegro et al. conveniently employed water micro-droplets to investigate the assembly of tubular peptidic nanotubes in a confined space. They employed cyclic peptides decorated in one hand with histidine that confer the system a pH-responsive self-assembly and in the other hand with a pyrene moiety that serves as a fluorescent reported of the fibrillation process.
Figure 1. a) Structure and pH-dependent self-assembly of the cyclic peptide (CP1) b) Histidine hydrogen-bonded networks and pyrene p-stacking driven aggregation of single peptide nanotubes by hierarchical micro-fibrillation. c) Supramolecular polymerization of CP1 in confined spaces [(i) CP1 in water (1–2% w/w); (ii) CP1 (1–2% w/w) in HEPES 30 mM at pH 8; (iii) addition of propanamine] shown in epifluorescence images and confocal microscopy projections of individual droplets. Scale bars from left to right are 20, 5 μm, and 10 μm. Images reproduced with permission of the Royal Society of Chemistry.
The observed deformation of the droplet upon basic pH trigger was produced by the strong directional self-assembly reflecting the strong directionality of the process. These findings with the one-dimension hierarchical assemblies open the possibility to a better comprehension of the physics and mechanism involved in the assembly of tubular networks in confined environments. Moreover, the reported system can already serve as a platform to further study such assembly processes in a biological scenario and eventually be applied for several biomedical purposes like drug delivery.
Article written by Dr. Julián Bergueiro Álvarez (Freie Universität Berlin). His current research is focused on thermoresponsive helical poylmers, polymer-gold nanoparticle supramolecular assemblies, and thermoresponsive nanogels as novel drug delivery nanocarriers. Find out more about his work on his website (http://www.nanominions.com/) and on Twitter (@nanominions).