Electrospinning of peptide and protein fibres: approaching the molecular scale

Abstract

For the example of peptides and proteins, we contrast "natural" self-assembly, i.e. aggregation in solutions, with "forced" assembly by electrospinning, i.e. by application of strong electrical fields to concentrated solutions. We were able to spin fibres that contain short stretches of diameters down to 5 nm; the ultimate aim is a fibre of the size of a single molecule. Besides their wide biochemical relevance, small peptides can assemble to defined supramolecular structures such as fibres and tubes. While the main driving mechanism in electrospinning is certainly based on electrostatics, aromatic groups in peptides might play a directing role. We used fluorenyl and phenyl, whose i-stacking is not manifested in vibrational spectra, but is clearly visible in their crystal structures. The main differences between solid phases and single molecules are found for O-H and N-H stretching and bending vibrations, due to extensive hydrogen bonding in solids. However, we found that only proteins, but not peptides, can be spun into ultrathin fibres. Therefore, nanoscale analysis by SEM and AFM, and by infrared near-field microscopy are especially useful. The comparison of the amide bands from the infrared and Raman spectra, combined with circular dichroism spectroscopy, allowed us to assign secondary structures. Our results are not only useful for interpreting and refining current theories of self-assembly and electrospinning, but also for creating new scaffolds for the growth of sensitive cells.

Fibrous scaffolds for building hearts and heart parts

“…Numerous methods now exist to electrospin nanofibers, including traditional needle arrays and needle-free techniques [25, 26] developed to improve fiber formation and production rates: these include bubble electrospinning [180] and microfluidic electrospinning [181]. Synthetic polymers and biological proteins are electrospun using these techniques independently [182, 183] or in combination [184, 185]. The diversity of electrospinning techniques and electrospun materials has translated to numerous fibrous tissue engineering applications including ligament, tendon, skeletal muscle, skin, blood vessel, and neural scaffolding [186].…”

Additive nanomanufacturing – A review

“…The growth is affected by cell adhesion to the substrate, chemical growth, small-molecule extracellular signalling and mechanical strain. 178 ANM technologies such as EHD Jet printing have the ability to print protein fibres with sub-cellular resolution 84 which could solve some of the biocompatibility problems and potentially accelerate growth in the field. The challenge will be to build biocompatible or living structures in three-dimensions rapidly for medical applications.…”

“…Nuansing et al 84 who were able to deposit peptide and protein nanowires with a diameter around 100 nm but on occasion down to 5 nm, corresponding to a single molecule ( see FIG. 10).…”

Electrospinning of tyrosine‐based oligopeptides: Self‐assembly or forced assembly?

“…Successful examples of electrospun biological molecules have utilized relatively large proteins such as silk, chitin, and collagen (Elsabee, Naguib, & Morsi, 2012;Min et al, 2004;Rho et al, 2006). However, studies involving electrospinning of oligomeric and dimeric peptides are sparse and have yet to be successful in the synthesis of uniform and continuous fibers (Nuansing et al, 2013;Singh, Bittner, Loscher, Malinowski, & Kern, 2008;Tayi, Pashuck, Newcomb, McClendon, & Stupp, 2014). The ability to synthesize nanofibers composed of oligopeptides allows understanding of forces involved in peptide assembly, as well as opens up a plethora of opportunities in regenerative medicine such as scaffolds for blood vessels, bone tissue engineering, and drug delivery (Khadka & Haynie, 2012).…”