Biological response to pre-mineralized starch based scaffolds for bone tissue engineering

It is known that calcium-phosphate (Ca-P) coatings are able not only to improve the bone bonding behaviour of polymeric materials, but at the same time play a positive role on enhancing cell adhesion and inducing the differentiation of osteoprogenitor cells. Recently an innovative biomimetic methodology, in which a sodium silicate gel was used as a nucleative agent, was proposed as an alternative to the currently available biomimetic coating methodologies. This methodology is especially adequate for coating biodegradable porous scaffolds. In the present work we evaluated the influence of the referred to treatment on the mechanical properties of 50/50 (wt%) blend of corn starch/ethylene-vinyl alcohol (SEVA-C) based scaffolds. These Ca-P coated scaffolds presented a compressive modulus of 224.6 ± 20.6 and a compressive strength of 24.2 ± 2.20. Cytotoxicity evaluation was performed according ISO/EN 10993 part 5 guidelines and showed that the biomimetic treatment did not have any deleterious effect on L929 cells and did not inhibit cell growth. Direct contact assays were done by using a cell line of human osteoblast like cells (SaOS-2). 3 × 105 cells were seeded per scaffold and allowed to grow for two weeks at 37 ◦C in a humidified atmosphere containing 5% CO2. Total protein quantification and scanning electron microscopy (SEM) observation showed that cells were able to grow in the pre-mineralized scaffolds. Furthermore cell viability assays (MTS test) also show that cells remain viable after two weeks in culture. Finally, protein expression studies showed that after two weeks osteopontin and collagen type I were being expressed by SaOS-2 cells seeded on the pre-mineralized scaffolds. Moreover, alkaline phosphatase (ALP) activity was higher in the supernatants collected from the pre-mineralized samples, when compared to the control samples (non Ca-P coated). This may indicate that a faster mineralization of the ECM produced on the pre-mineralized samples was occurring. Consequently, biomimetic pre-mineralization of starch based scaffolds can be a useful route for applying these materials on bone tissue engineering