Production of ethyl cellulose scaffolds by supercritical co2 phase separation

Ethyl Cellulose scaffolds were prepared using a supercritical fluid phase inversion process in which carbon dioxide acts as the non-solvent. Ethyl Cellulose is a derivative of cellulose in which some of the hydroxyl groups on the repeating glucose units are converted into ethyl ether groups; it is a biocompatible but non-biodegradable polymer. It is an extensively studied encapsulating material for the controlled release of pharmaceuticals in tissue engineering applications. Series of experiments were performed at various polymer concentrations, temperatures, pressures, and kind of organic solvent. The structures of the resulting scaffolds were analysed using scanning electron microscopy. We operated with polymer concentrations ranging between 5 and 20 % w/w, using N-methyl pyrrolidone and chloroform as organic solvents and we obtained scaffolds characterized by homogeneous cellular structures with different pore mean size. The mean diameter of the pores ranged from 3 μm to 15 μm, decreasing the polymer concentration from 20 to 5 % w/w. Additional experiments were performed varying the operating pressure from 100 and 200 bar, and varying the operating temperature from 35 to 55 °C. Increasing pressure and/or decreasing temperature, the scaffolds pore size largely decreases; both the effects can be related to carbon dioxide density modification. Ethyl Cellulose scaffolds formation mechanisms were also discussed.