Dense lamellar scaffold based on collagen, silk fibroin and polyethylene glycol 400 produced by a novel plastic compression technique

The aim of this study was to develop a dense lamellar scaffolding composed by collagen (COL), silk fibroin (SF) and polyethylene glycol 400 (PEG 400) and evaluate the influence of freezing parameters (-80,-50, and-18 degrees C) associated with its plastic compression. The physicochemical characterization of the developed scaffolds was done by mechanical and morphological properties. Fourier Transform Infrared Spectroscopy (FTIR) and Differential scanning calorimetry (DSC) showed crosslinking between PEG and polymers, the change in the COL structure confirming electrostatic interaction between functional groups, in addition to beta-sheet conformations of SF induced by lyophilization. Morphological analyzes showed changes in pore size between 69.8 and 97.3 mu m (-80), 73.7-121.8 mu m (-50) and 84.3-134.0 mu m (-18). Interconnectivity was found to be 60.83% (-80), 62.62% (-50) and 66.76% (-18), confirming the pore connectivity which is key for cell growth. The percentage of closed pores of 0.19% (-80), 0.13% (-50) and 0.11% (-18) were recorded, together with the pore volume of 12.97 mm-3 (-80), 2.31 mm-3 (-50) and 1.61 mm-3 (-18). The freezing significantly modulated the aniso-tropic degree, obtaining anisotropic (-18 degrees C), partially anisotropic (-50 degrees C), and isotropic (-80 degrees C) scaffolds. The scaffolds showed similar swelling values after 120 h, however, a lower rate of biodisintegration was confirmed by the scaffold COL-SF-PEG 400 (-80). Hydrolytic degradation did not influence the pH values, which remained between 7.39 and 7.45 over the same timeframe. The freezing rate changed the mechanical properties, showing greater resistance to the scaffold COL-SF-PEG 400 (-50), except for elasticity. Considering the results of this study, the different freezing rates were able to modulate scaffolds with unique characteristics and of interest for potential tissue engineering applications, with an emphasis in obtaining anisotropic or isotropic structures.