Fast and continuous preparation of high polymerization degree cellulose nanofibrils and their three-dimensional macroporous scaffold fabrication

Abstract

C6-carboxy-cellulose with a carboxylate content of 0.8 mmol g⁻¹ was obtained by oxidation of once-dried cellulose, using the 2,2,6,6-tetramethylpiperidinyl-1-oxyl (TEMPO)/NaClO/NaClO₂ system at pH 6.8 and 60 °C for 16 h. This method, with the addition of reagents in the order TEMPO, NaClO and NaClO₂, was 38 h faster than a previously published method. Individualized cellulose nanofibrils with a width of 3–5 nm and a length of several hundred nanometers were prepared by homogenizing the C6-carboxy-cellulose–water suspension. Macroporous cellulose nanofibril/poly(vinyl alcohol) scaffolds with interconnected large pores of 20–100 μm diameter and small pores of 2–10 μm diameter were fabricated. The cellulose nanofilaments formed nanofibrous structures on the surface of the PVA wall, which was similar to that of the collagen skeleton of the extracellular matrix. NIH/3T3 cells were cultured in the scaffolds for 4 weeks, SEM observation showed that the cells were anchored and clustered on the cellulose nanofilaments, forming spherical colonies. The extracellular matrix (ECM) was filled with mineralized particles.