Cellulose cryogels prepared by regeneration from phosphoric acid solutions

Abstract

The supermacroporous structure and ease of preparation of polysaccharide-based cryogels have led to their wide use in many areas and make them promising biomaterials for tissue engineering. One polysaccharide of particular interest for the production of tissue engineering scaffolds is cellulose, a natural biocompatible and nontoxic polymer. However, the complex supramolecular structure of cellulose creates difficulties in its dissolution and further processing into biomedical products. Conventional cellulose solvents have significant disadvantages, including poor removal from the resulting products. Therefore, this work proposes the preparation of cellulose-based cryogels using orthophosphoric acid, which can be easily removed and recovered. The effect of cellulose dissolution conditions on the structure and properties of cryogels were studied. Highly porous (88.3–93.4%) and light (ρ 0.091–0.161 g/cm3) cryogels with complex hierarchical morphologies were produced using a dissolution temperature of (20 ± 2) °C, a cellulose concentration in the solution > 3%, a dissolution time of 24–48 h (depending on the cellulose concentration), and precipitation with water or acetone. 13C CP-MAS NMR spectroscopy results confirmed that the regenerated cellulose is predominantly amorphous, with a crystallinity of 6.8–30.6% in the structure of cellulose II. The compressive modulus E for cryogels was from 330 to 3675 kPa. FTIR spectroscopy results showed that the regenerated cellulose had an increased number of aldehyde groups and a decreased number of hydrogen bonds decreases, indicating a decrease in crystallinity. No phosphoric acid esters of cellulose were detected in the cryogels by FTIR spectroscopy. These results pave the way for the easy preparation of biomaterials for tissue engineering.