Enhanced hydroxyapatite growth on polyfunctionalized polypropylene films for bone tissue engineering

Functionalized PP films with PNIPAAm and PGMA-Amin are used to improve the hydroxyapatite (HAp) growth by the biomimetic method using simulated body fluid (SBF). Initially, PP films are functionalized with maleimide groups (PP-MAL), and then, NIPAAm or GMA is photopolymerized onto the PP-MAL. The films containing PGMA are also submitted to chemical functionalization with ethylenediamine to produce hydroxyl and amine groups on the surface. Functionalized films are used to grow HAp via biomimetic mineralization in SBF for 7, 14, and 21 days. SEM images display that the different groups and time of mineralization influence the growth of HAp over the films and both PP-PGMA-Amin and PNIPAAm films promote hydroxyapatite growth. After 14 days, HAp layers of 18.1 ± 2.9 µm and 2.7 ± 0.3 µm are produced on PP-PGMA-Amin and PNIPAAm, respectively. At 21 days, these layers reached 54.1 ± 4.9 µm and 54.6 ± 5.6 µm. Films immersed for 21 days display better homogeneity than that immersed for 7 and 14 days. The biocompatibility of the films is evaluated using pre-osteoblast (MC3T3-E1). The contact angle of 63° ± 1° indicates that the HAP-coated surfaces exhibited greater hydrophilic behavior compared to the pristine PP films, consequently enhancing cell adhesion. SEM images after 48 h of incubation of pre-osteoblast exhibited strong adhesion of the cells on the films, suggesting the HAP-coated PP-PNIPAAm and PP-PGMA-Amin have promising potential as templates to support in vitro cell growth for tissue engineering applications.