Preparation and stability of dexamethasone-loaded polymeric scaffolds for bone regeneration processed by compressed CO₂ foaming
Compressed CO₂ foaming allows for obtaining porous solid drug-loaded scaffolds for regenerative medicine under mild conditions and in the absence of organic solvents. However, a precise process design and optimization as well as certain modifications of the technology are still needed to tackle certain limitations like the control of the porosity of scaffolds from certain low molecular weight biopolymers. Besides, stability under storage is a critical quality attribute to define the usefulness of scaffolds. In the particular case of bone scaffolds, the information on this regard is still very limited and strongly dependent on each particular composition and architecture. In order to gain an insight into this issue, scaffolds composed of poly(lactic-co-glycolic acid) (PLGA) and poly(ε-caprolactone) (PCL) as polymeric matrix, with and without pre-gelified starch (St) as release-controlling agent and dexamethasone (DXMT) as bioactive compound were designed and prepared by a modified compressed CO₂ foaming technique (26 °C, 60 bar) and assessed regarding stability under storage. The scaffolds were stored at 25 °C and 65% relative humidity (zone II ICH-climatic conditions for Europe, USA and Japan) for up to three months to determine the effect of storage on the structural, physicochemical and mechanical properties, and DXMT release. Changes in the scaffolds point out the importance of stability assays and storage conditions. Namely, a decrease in the viscoelastic moduli of the scaffolds and a faster degradation rate were observed after prolonged storage periods. DXMT release from the scaffolds was erosion-controlled and thus modified for scaffolds stored for longer time periods.