A bioinspired microhairy sensor is developed to enable ultraconformability on nonflat surfaces and significant enhancement in the signal-to-noise ratio of the retrieved signals. The device shows ≈12 times increase in the signal-to-noise ratio in the generated capacitive signals, allowing the ultraconformal microhair pressure sensors to be capable of measuring weak pulsations of internal jugular venous pulses stemming from a human neck.

Tissue engineered vascular grafts require long fabrication times, in part, due to the requirement of cells from a variety of cell sources to produce a robust load bearing, extracellular matrix. Herein, we propose a design strategy for the fabrication of tubular conduits comprised of collagen fiber networks and elastin-like protein polymers to mimic native tissue structure and function. Dense fibrillar collagen networks exhibited an ultimate tensile strength (UTS) of 0.71 ± 0.06 MPa, strain to failure of 37.1 ± 2.2%, and Young’s modulus of 2.09 ± 0.42 MPa, comparing favorably to an UTS and a Young’s modulus for native blood vessels of 1.4 – 11.1 MPa and 1.5 ± 0.3 MPa, respectively. Resilience, a measure of recovered energy during unloading of matrices, demonstrated that 58.9 ± 4.4% of the energy was recovered during loading-unloading cycles. Rapid fabrication of multilayer tubular conduits with maintenance of native collagen ultrastructure was achieved with internal diameters ranging between 1 to 4 mm. Compliance and burst pressures exceeded 2.7 ± 0.3%/100 mmHg and 830 ± 131 mmHg, respectively, with a significant reduction in observed platelet adherence as compared to ePTFE (6.8 ± 0.05 × 105 vs. 62 ± 0.05 × 105 platelets/mm2, p < 0.01). Using a rat aortic interposition model, early in vivo responses were evaluated at 2 weeks via Doppler ultrasound and CT angiography with immunohistochemistry confirming a limited early inflammatory response (n=8). Engineered collagen-elastin composites represent a promising strategy for fabricating synthetic tissues with defined extracellular matrix content, composition, and architecture.

The universal structural role of collagen fiber networks has motivated the development of collagen gels, films, coatings, injectables, and other formulations. However, reported synthetic collagen fiber fabrication schemes have either culminated in short, discontinuous fiber segments at unsuitably low production rates, or have incompletely replicated the internal fibrillar structure that dictates fiber mechanical and biological properties. We report a continuous extrusion system with an off-line phosphate buffer incubation step for the manufacture of synthetic collagen fiber. Fiber with a cross-section of 53±14 by 21±3 µm and an ultimate tensile strength of 94±19 MPa was continuously produced at 60 m/hr from an ultrafiltered monomeric collagen solution. The effect of collagen solution concentration, flow rate, and spinneret size on fiber size was investigated. The fiber was further characterized by microdifferential scanning calorimetry, transmission electron microscopy (TEM), second harmonic generation (SHG) analysis, and in a subcutaneous murine implant model. Calorimetry demonstrated stabilization of the collagen triple helical structure, while TEM and SHG revealed a dense, axially aligned D-periodic fibril structure throughout the fiber cross-section. Implantation of glutaraldehyde crosslinked and non-crosslinked fiber in the subcutaneous tissue of mice demonstrated limited inflammatory response and biodegradation after a 6-week implant period.

Collagen and elastin networks contribute to highly specialized biomechanical responses in numerous tissues and species. Biomechanical properties such as modulus, elasticity, and strength ultimately affect tissue function and durability, as well as local cellular behavior. In the case of vascular bypass grafts, compliance at physiologic pressures is correlated with increased patency due to a reduction in anastomotic intimal hyerplasia. In this report, we combine extracellular matrix (ECM) protein analogues to yield multilamellar vascular grafts comprised of a recombinant elastin-like protein matrix reinforced with synthetic collagen microfibers. Structural analysis revealed that the fabrication scheme permits a range of fiber orientations and volume fractions, leading to tunable mechanical properties. Burst strengths of 239–2760 mm Hg, compliances of 2.8–8.4%/100 mm Hg, and suture retention strengths of 35–192 gf were observed. The design most closely approximating all target criteria displayed a burst strength of 1483 ± 43 mm Hg, a compliance of 5.1 ± 0.8%/100 mm Hg, and a suture retention strength of 173 ± 4 gf. These results indicate that through incorporation of reinforcing collagen microfibers, recombinant elastomeric protein-based biomaterials can play a significant role in load bearing tissue substitutes. We believe that similar composites can be incorporated into tissue engineering schemes that seek to integrate cells within the structure, prior to or after implantation in vivo.