Fig. 4. Time-dependent rheology and compressive mechanics of silk and platelet gels.

(A) Dynamic time-dependent rheological behavior of sonicated 10% (solid line), 4% (dashed line), and 2% w/v (dotted line) silk solutions compared to platelet gel (X marker) behavior over 6 hours of oscillatory shear. Not shown are the monotonically-increasing modulus values for the silk groups for up to 16 hrs, whereas the platelet gel group begins decreasing at ~10 minutes of oscillatory shear. (B) Rheological behavior of sonicated 4% w/v silk solutions diluted 1:1 with platelet gel (+PG, solid line), Platelet Poor Plasma (+PPP, thick dotted line), or water as a control (fine dotted line). Platelet gels alone are also shown (X marker). (C) Re-plotted log-log data from (B) of the initial 100 minutes following gel initiation, showing the incidence of gel stiffening as indicated by the arrows. (D) Silk solutions were either autoclaved or sterile-filtered prior to mixing with either PG or PPP at a 1:1 dilution to generate the final silk concentration shown (therefore starting silk concentrations are 2X as listed, 10% was the maximum concentration that could be used from silk boiled for 30 minutes). Bar indicates significance between groups identified in post-hoc analysis of ANOVA (p< 0.05).