Type I collagen-PEO fibers and non-woven fiber networks were produced by the electrospinning of a weak acid solution of purified collagen at ambient temperature and pressure. As determined by high-resolution SEM and TEM. fiber morphology was influenced by solution viscosity, conductivity, and flow rate. Uniform fibers with a diameter range of 100-150 nm were produced from a 2-wt% solution of collagen-PEO at a flow rate of 100 microl min(-1). Ultimate tensile strength and elastic modulus of the resulting non-woven fabrics was dependent upon the chosen weight ratio of the collagen-PEO blend. 1H NMR dipolar magnetization transfer analysis suggested that the superior mechanical properties, observed for collagen-PEO blends of weight ratio 1:1, were due to the maximization of intermolecular interactions between the PEO and collagen components. The process outlined herein provides a convenient, non-toxic, non-denaturing approach for the generation collagen-containing nanofibers and non-woven fabrics that have potential application in wound healing, tissue engineering, and as hemostatic agents.

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Elastin-mimetic peptide polymers have been synthesized, and the morphological properties of fabricated small diameter fibers and nonwoven fabrics have been characterized. An 81 kDa recombinant protein based upon the repeating elastomeric peptide sequence of elastin (Val-Pro-Gly-Val-Gly)4(Val-Pro-Gly-Lys-Gly) was obtained through bacterial expression of an oligomerized gene coding for tandem repeats of the monomer. The protein was processed into fibers by an electrospinning technique and morphology defined by SEM and TEM. The choice of processing parameters influenced both fiber diameter and morphology with diameters varying between 200 and 3000 nm and three morphological patterns noted:  beaded fibers, thin filaments, and broad ribbonlike structures. Detailed image analysis of nonwoven textile fabrics produced from elastin-mimetic fibers revealed that the distribution of single fiber orientation was isotropic with an associated unimodal distribution of protein fiber diameter. In a dry state, the ultimate tensile strength of nonwoven fabrics generated from elastin-mimetic peptides was 35 MPa with a material modulus of 1.8 GPa.

The objective of the present study is to investigate the possibility of preparing pure protein microspheres from regenerated silk fibroin (RSF). It is found that RSF microspheres, with predictable and controllable sizes ranging from 0.2 to 1.5 mm, can be prepared via mild selfassembling of silk fibroin molecular chains. The merits of this novel method include a rather simple production apparatus and no potentially toxic agents, such as surfactants, initiators, crosslinking agents, etc. The results show that the particle size and size distribution of RSF microspheres are greatly affected by the amount of ethanol additive, the freezing temperature and the concentration of silk fibroin. Finally, the mechanism of RSF microspheres formation is also discussed based on our experimental results.

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Synchrotron FTIR (S-FTIR) microspectroscopy was used to monitor both protein secondary structures (conformations) and their orientations in single cocoon silk fibers of the Chinese Tussah silk moth ( Antheraea pernyi ). In addition, to understand further the relationship between structure and properties of single silk fibers, we studied the changes of orientation and content of different secondary structures in single A. pernyi silk fibers when subjected to different strains. The results showed that the content and orientation of β-sheet was almost unchanged for strains from 0 to 0.3. However, the orientation of α-helix and random coil improved progressively with increasing strain, with a parallel decrease in α-helix content and an increase in random coil. This clearly indicates that most of the deformation upon stretching of the single fiber is due to the change of orientation in the amorphous regions coupled with a conversion of some of the α-helix to random coil. These observations provide an explanation for the supercontraction behavior of certain animal silks and are likely to facilitate understanding and optimization of postdrawing used in the conjunction with the wet-spinning of silk fibers from regenerated silk solutions. Thus, our work demonstrates the power of S-FTIR microspectroscopy for studying biopolymers.

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Solid-state cross-linking of elastin-mimetic fibers was investigated. Through available lysine residues, an elastin-mimetic protein polymer, poly((Val-Pro-Gly-Val-Gly)4(Val-Pro-Gly-Lys-Gly))39, was modified to incorporate an acrylate moiety. The degree of acrylate functionalization could be varied by changing the reactant ratio of anhydride to elastin. Acrylate modified elastomeric (AME) proteins were associated with lower inverse transition temperatures than the unmodified recombinant protein. The inverse transition temperature in turn dictated the temperature for fiber formation. Fibers and fabric samples of AME were prepared by electrospinning at appropriate temperatures and cross-linked by visiblelight-mediated photoirradiation. Fibers in the diameter range of 300 nm-1.5 µm were produced. Fabrics were found to have an average pore size of 78 µm. The occurrence of cross-linking was confirmed by 13 C solid-state NMR with a commensurate increase in modulus.