(A) Tubes formed from 5MB, 10MB, 20MB, 30MB, (14%,16%,26%,34% w/v concentrations, respectively) characterized by SEM showed different pore structures after lyophilization. Scale bars 100 μm for cross-sectional images. Inset shows the inner lumen of each tube (inset scale bar =500 μm). (B) Mercury Intrusion Porosimetry was used to evaluate the pore size distribution (between 10 nm and ~300 μm) for tubes shown in panel (A). The dark hashed section of the histogram indicates the overlap between each MB group.