Ordering recombinant silk-elastin-like nanofibers on the microscale

Abstract

Self-assembled peptide/polypeptide nanofibers are appealing building blocks for creating complex three-dimensional structures. However, ordering assembled peptide/polypeptide nanofibers into three-dimensional structures on the microscale remains challenging and often requires the employment of top-down approaches. We report that silk-elastin-like protein polymers selfassemble into nanofibers in physiologically relevant conditions, the assembled nanofibers further form fiber clusters on the microscale, and the nanofiber clusters eventually coalesce into threedimensional structures with distinct nanoscale and microscale features. It is believed that the interplay between fiber growth and molecular diffusion leads to the ordering of the assembled silk-elastin-like nanofibers at the microscale. V C 2014 AIP Publishing LLC.[http://dx.doi.org/10.1063/1.4863077] Self-assembled peptide/protein nanostructures may find important applications in various areas, including tissue engineering, biosensors, and drug delivery. As an example, self-assembled peptide nanofibers enable the cells to interact with the matrix in three-dimensional microenvironments, enhancing neurite outgrowth. 1 However, it remains a daunting challenge to order self-assembled peptide nanofibers into three-dimensional structures on the microscale. It has been suggested to integrate top-down approaches and selfassembly in the fabrication of microscale-ordered nanostructures. 2 Nevertheless, this strategy not only requires additional capital investment in fabrication facilities but also comprises the elegance of molecular self-assembly, including ease of processing and energy efficiency. Here, we report that, driven by the interplay of fiber nucleation/growth with molecular diffusion, silk-elastin-like protein (SELP) polymers self-assemble into three-dimensional structures with distinct nanoscale and microscale features.Owing to relative ease of design, synthesis, and purification, most self-assembling peptides that have been extensively explored are small peptides, containing several to a few tens of amino acids. 3 In contrast, living systems often utilize high molecular-weight proteins, such as actin and collagen, as building blocks to create nanofiber-based intracellular and extracellular matrices. 4 Likely, large amino acid chains provide a rich source of structural/functional variability and complexity. Herein, two SELP polymers, SELP-47 K (MW: 69,814 theoretical calculation 5 and 69 699 mass spectroscopy 6 ) and SELP-815 K (MW: 65 374 theoretical calculation 7 ), are used as a model system to study self-assembly of high molecular-weight proteins. The complete amino acid sequences of SELP-47K and SELP-815 K are MDPVVLQRRDWENPGVTQLNRLAAHPPFASDPMGAG SGAGAGS[(GVGVP) 4 GKGVP(GVGVP) 3 (GAGAGS) 4 ] 12 (GVGVP) 4 GKGVP(GVGVP) 3 (GAGAGS) 2 GAGAMDPGR YQDLRSHHHHHH (one letter amino-acid abbreviation is used) 5 and MDPVVLQRRDWENPGVTQLNRLAAHPPF ASDPM[GAGS(GAGAGS) 2 (GVGVP) 4 GKGVP(GVGV P) 11 (GAGAGS) 4 GAGA] 6 MDPGRYQDLRSHHHHHH, respectively. 6 In the design of SE...

Engineering the Architecture of Elastin‐Like Polypeptides: From Unimers to Hierarchical Self‐Assembly

“…Zeng et al. showed that microscale porous hydrogels are derived from interconnected clusters of polymer nanofibers ( Figure ) . The stimuli‐responsive behavior of SELPs and the diversity of structures they form, combined with post‐processing techniques such as electrospinning or thin film deposition, have made them useful for various applications in drug delivery (chemoembolics, in situ enemas, and adenovirus delivery) as well as in tissue engineering, and wound healing …”

“…Temperature‐triggered phase separation of these POPs yields porous, physically crosslinked, viscoelastic networks. (a) Reproduced with permission . Copyright 2014, AIP Publishing.…”

“…(a) Reproduced with permission. [156] Copyright 2014, AIP Publishing. (b) Reproduced with permission.…”

Application of Thermoresponsive Intrinsically Disordered Protein Polymers in Nanostructured and Microstructured Materials

“…combined β ‐sheet forming GAGAGS motifs with ELPs to form silk‐elastin‐like protein (SELP) polymers which self‐assemble into nanofibers at 37 °C which further coalesce into microscale clusters leading to the formation of macroscopically continuous structures with distinct nanoscale and microscale architectures. [ 203 ] Mozhdehi et al. generated genetically encoded lipid‐polypeptide hybrid biopolymers called fatty acid modified ELPs (FAMEs).…”

Fibrous Scaffolds From Elastin-Based Materials

“…Concentration is an extra parameter that governs the growth of SELR nanofibers. Thus, the micelle-like nanoparticles that arise during the early stages of self-assembly act by increasing the polypeptide density, thus prompting close approach of the silk-like domains, which subsequently self-assemble into nanofibers (Zeng et al, 2014b). Upon reaching this state, the soluble SELR begin to add, via diffusion pathways, to the formed structures, which evolve into different arrangements depending on the concentration.…”