A Permanent Change in Protein Mechanical Responses Can be Produced by Thermally-Induced Microdomain Mixing

Abstract

Electrospinning was employed to fabricate three dimensional fiber networks from a recombinant amphiphilic elastin-mimetic triblock protein polymer and the effects of moderate thermal conditioning (60°C, 4h) on network mechanical responses investigated. Significantly, while cryo-high resolution scanning electron microscopy (cryo-HRSEM) revealed that macroscopic and microscopic morphology of the network structure was unchanged, solid-state 1H NMR spectroscopy demonstrated enhanced interphase mixing of hydrophobic and hydrophilic blocks. Significantly, thermal annealing triggered permanent changes in network swelling behavior (28.75 ± 2.80 non-annealed vs. 13.55 ± 1.39 annealed; p < 0.05) and uniaxial mechanical responses, including Young’s modulus (0.170 ± 0.010 MPa non-annealed vs. 0.366 ± 0.05 MPa annealed; p < 0.05) and ultimate tensile strength (0.079 ± 0.008 MPa vs 0.119 ± 0.015 MPa; p < 0.05). To our knowledge, these investigations are the first to note that mechanical responses of protein polymers can be permanently altered through a temperature-induced change in microphase mixing.

The use of microfiber composites of elastin-like protein matrix reinforced with synthetic collagen in the design of vascular grafts

“…5. Thermal annealing enhanced burst pressure and suture retention while reducing compliance, consistent with prior observations that thermal annealing can increase the strength and Young’s modulus of this protein polymer [67]. The magnitude of the thermal annealing effect demonstrates that the mechanical behavior of the elastin component strongly influenced the composite mechanics and burst pressure.…”

Recombinant elastin-mimetic biomaterials: Emerging applications in medicine

“…Elastin-based biomaterials have been processed as films [10,37-40], fibers [7,59], and hydrogels [34-36,56] for a variety of implant applications.…”

“…Tubular constructs have been produced by fiber deposition on a collecting mandrel with controlled rotational and translational speeds. Of interest, thermal annealing at 60 °C has been observed to changes the mechanical response of electrospun elastin protein polymer networks with a two fold increase in Young's modulus (0.366±0.05 MPa) and 30 % in tensile strength comparable to that within an arterial wall (Y ∼0.3 MPa) [59,71]. …”

“…(D) A tubular conduit was fabricated from electrospun protein fibers using a rotating mandrel as the collecting apparatus. (Reprinted from [59] with permission of Koninklijke Brill)…”

Designing protein-based biomaterials for medical applications

“…The final structure was very stable, with the size of the micelle controlled by both the total ELP length and the hydrophilic-to-hydrophobic ratio. Sallach et al [69] investigated protein tri-block structures, with a central hydrophilic block and two hydrophobic end blocks. These were found to form monodisperse micelles in a narrow range of R H ~ 100 nm; however, when the temperature was raised above T t , a swift protein folding transition between α-helix and β-sheet structures caused an abrupt increase in micelle internal density, with a concomitant reduction in micelle size.…”