Spontaneous Alignment of Self-Assembled Cationic and Amphiphilic β-Sheet Peptides

Many of the bio-functionalities in living systems rely upon the alignment of the tissue (e.g., bones, heart, and spinal cord); hence aligned materials are very attractive for biomedical applications such as scaffold creation for tissue engineering. Scaffolds composed of self-assembling peptides offer biocompatibility and the versatility necessary to create tailor-made materials. Yet, utilizing the material’s ability to self-assemble to create an aligned material without the application of external stimuli is still a challenge.<br/>Here we present a novel material based on amphiphilic and charged β-sheet peptide (Pro-Lys-(Phe-Lys)₅-Pro) that undergoes a spontaneous time-dependent isotropic–nematic phase transition in an aqueous solution without the need for any external force.<br/>This natural, timely orientation of the peptide fibrils in an aqueous solution, confirmed by small angle x-ray scattering and cryo-transmission electron microscopy, creates a highly dynamic system, for which the degree of alignment and the time required to achieve a complete isotropic–nematic phase transition is found to be concentration dependent and can be predicted by a model based on Onsager’s excluded volume theory. Remarkably, the nematic phases remain aligned over the course of several months without the application of any external stimuli and can be cross-linked to form aligned gels by mild shearing through a salty medium.<br/>This spontaneously aligned peptide-based material offers a novel platform for various biomedical applications such as bio-sensors, tissue engineering scaffolds, or drug delivery vehicles.