Electroresponsive Aqueous Silk Protein As “Smart” Mechanical Damping Fluid

Here we demonstrate the effectiveness of an electroresponsive aqueous silk protein polymer as a smart mechanical damping fluid. The aqueous polymer solution is liquid under ambient conditions, but is reversibly converted into a gel once subjected to an electric current, thereby increasing or decreasing in viscosity. This nontoxic, biodegradable, reversible, edible fluid also bonds to device surfaces and is demonstrated to reduce friction and provide striking wear protection. The friction and mechanical damping coefficients are shown to modulate with electric field exposure time and/or intensity. Damping coefficient can be modulated electrically, and then preserved without continued power for longer time scales than conventional “smart” fluid dampers

Biocompatibility as assessed with MSC culture.

<p>(A) Plating efficiency calculated as a ratio of MSCs adherent to scaffolds following a 48-hour incubation period. (B) Total cell count at 96 hours obtained via MTS assay, indicating no significant reduction in proliferation or metabolic activity on DTS. (C) Fluorescence micrographs portraying representative samples of untreated and decellularized tendon, with live cells stained green (calcein) and dead cells stained red (EthD-1).</p

Treatment alters tendon matrix composition.

<p>Biochemical analysis of tendon scaffolds, including DNA (A), total protein (B), soluble collagen (C), and GAG content (D). Statistical significance between untreated control and treatment is annotated by use of an asterisk. Statistical differences between treatments are indicated by different letters (repeated measures MANOVA).</p

DTS biomechanics.

<p>Tensile testing indicated no statistically significant alterations in scaffold mechanics following decellularization. Data represents mean ± standard error values.</p

Scaffold ultrastructure.

<p>(A) Scanning electron micrograph of untreated tendon strip, angled to show both longitudinal and transverse section architecture. (B) Histological sections stained with Masson’s trichrome indicate maintenance of collagen content with a slight increase in porosity. (C) Comparison of SEM images obtained from untreated and 2% SDS decellularized tendon samples, shown at 100x and 5000x magnifications longitudinally, and 5000x transversely. Collagen ultrastructure is not adversely altered by detergent treatment.</p

Loss of nuclear content following decellularization.

<p>Brightfield images of H&E-stained histological cross-sections (5 µm-thick) and fluorescence micrographs of scaffolds imaged with EthD-1 (400 µm-thick). Marked loss of DNA content is evident in SDS-decellularized experimental groups, with 2% SDS resulting in the most dramatic decellularization. All images are representative and were acquired from the same horse for ease of comparison.</p