Evaluation of porous biodegradable composite scaffolds produced by gas foaming

Objectives: Investigation of different types of synthetic scaffolds in terms of processing conditions and material composition to propose a method to control mechanical and morphological behaviours is the aim of this study.

Methods: Porous Poly(D,L)lactic acid (PDLLA) scaffolds were prepared using Supercritical Carbon Dioxide (SC CO2) foaming. Hydroxyapatite (HA) with different weight fractions was added to PDLLA to control the degradation rate and acidity of the foams. Surface and internal morphology of PDLLA/HA scaffolds were examined using optical microscope and micro-CT. Compression and permeability tests were performed on the scaffolds. Effect of addition of different amounts of HA on morphological and mechanical properties of the composite foams was investigated. Degradation rate of neat PDLLA and composite scaffolds was measured and compared. Porosity and pore size can be tailored by varying the processing conditions. Effect of processing parameters such as CO2 saturation pressure, temperature and time and depressurisation rate on pore size and structure was investigated in this study using pure PDLLA scaffolds.

Results: Biodegradable scaffolds with porosity up to 90% ± 2% and average pore size ranging from 200 to 500 µm obtained using SC CO2 foaming. Incorporation of small amount of HA can lead to scaffolds with higher compressive strength but lower porosity. The degradation rate and permeability are reduced as a result of addition of HA to the foams.

Conclusion: Composite foams with high porosity and suitable pore size distribution for cell seeding were created using SC CO2 foaming technology. Composite scaffolds show enhanced compressive strength and controlled degradation rate compared with pure polymer. Morphological properties can be controlled by varying saturation pressure, time and temperature and venting rate of the foaming process.