Role of liquid crystal behavior of CNC/PEGDA/collagen suspensions on their orthotropic organization obtained by ultrafiltration and ultrasound

This study explored the effect of adding biologically relevant macromolecules on the preservation of cellulose nanocrystal (CNC) orthotropic organization already obtained in aqueous media, via the combined action of frontal ultrafiltration (FU) and ultrasound (US). In particular, the effect of a photocurable polymer poly(ethylene glycol) diacrylate (PEGDA) with aqueous CNC suspension, in 80/20 weight ratio [water/PEGDA] and collagen were explored. Rheometric and polarized light microscopy measurements were used to reveal the liquid crystal behavior of suspensions. In situ dichroism during the FU/US process allowed to examine the conservation of orthotropic organization. First, the results have proved that the liquid crystal-like behavior is essential for achieving the desired orthotropic orientation of CNC/PEGDA/Collagen suspensions under FU and US. Second, acoustic power and filtration time have been identified as key parameters in preserving the orthotropic arrangement. Third, specific formulation conditions have been found to successfully achieved the orthotropic structure: i) without collagen, 20 wt% PEGDA and 5 to 8 wt% CNC; and ii) with collagen at acidic pH, 20 wt% PEGDA, 6 to 8 wt% CNC, and 0.01 to 0.1 mg/mL collagen. These findings pave the way for future investigations to produce orthotropic hydrogels for tissue engineering, by combining FU/US process with photocrosslinking.