Porous nanostructured poly-l-lactide scaffolds prepared by phase inversion using supercritical CO2 as a nonsolvent in the presence of ammonium bicarbonate particles

Supercritical fluid technology has been utilized in the development of tissue engineering scaffolds. However, it results in some problems, such as the poorly interconnected pores and the inability to load growth factor due to the salt leaching process for removal of the solid porogen. In this study, ammonium bicarbonate (AB) particles were used as a porogen and mixed uniformly with poly-l-lactide (PLLA) solution. Supercritical CO2 was used to immerse and flush through the resulting compound to allow the occurrence of phase inversion, subsequently generating a nanofibrous network. As the decomposition temperature of AB crystals is 36 °C, the temperature of the CO2 was increased to 40 °C to decompose the porogen, and the decomposition products were removed by washing with CO2. The resulting PLLA scaffolds possessed both large pores and micro pores with a controllable pore size, a high porosity (>95%), an interconnected structure, a nanofibrous network, good mechanical properties (compressive strength up to 100 kPa), and a very low organic solvent residue (12 ppm). The results of Fourier transform infrared spectroscopy (FTIR) and X-ray diffraction (XRD) measurements indicated that the molecular structure and physical state of PLLA were not changed after supercritical processing. The results reveal that the application of AB particles as a porogen in the supercritical phase inversion process is feasible to produce tissue engineering scaffolds with a high-performance.

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► Porous nanostructured scaffolds prepared by supercritical CO2 phase inversion combined with ammonium bicarbonate particles as porogen.
► The scaffold structure was strongly dependent on the solvent used in the process. When PLLA was precipitated from the dichloromethane solution, a micro cell structure was obtained However, the scaffolds obtained from the 1,4-dioxane solution presented a nanofibrous net structure.
► Increasing the ratios of ammonium bicarbonate to PLLA will increase the scaffold porosity. Increasing the ratios of ammonium bicarbonate to PLLA will decrease the scaffold mechanical strength.