Fabrication of a pure porous chitosan bead matrix: Influences of phase separation on the microstructure

The material properties and the microstructure of the scaffold are important parameters that determine the suitability of a material for tissue growth and controlled drug release. Because of its non-toxic, biocompatible, biodegradable, and antithrombogenic nature, chitosan has generated enormous interest for such applications. Chitosan bead-type scaffolds having various microstructures without any other material introduction were fabricated. For fabricating pure chitosan beads, a modified wet process and an extended thermally induced phase separation (TIPS) process were adapted. In the modified wet process, an acidic chitosan solution was phase-separated by changing its pH using an NaOH solution. The microstructure of the chitosan beads became looser with a decrease in the initial chitosan concentration, an increase in the acetic acid concentration, as well as with the addition of PEG to the dope solution. In contrast, the microstructure densified with an increase in the NaOH concentration in the coagulation bath. Through the modified wet process, porous chitosan beads with a relatively small pore size (0.01-13 μm) and moderate porosity (33-71%) could be prepared. In the extended TIPS process, chitosan solutions cast at different temperatures below 0°C resulted in different microstructures wherein the microstructure densified with an increase in the quenching rate. The chitosan beads fabricated via extended TIPS had large pore sizes (26-120 μm) and high porosity (85-92%). All of these matrices showed good interconnected pores.