Composite of Polymer and Alkaline Phosphatase: Potential for Bone Substitution

Polymer derived from Ricinus Communis (PRC) has been applied as bone substitute because it is biocompatible and biodegradable. Alterations in the PRC chemical composition may be undertaken to improve its biological properties. Alkaline phosphatase, an enzyme required in osteogenesis, retained its catalytic properties when immobilized inside polymers. Objectives: The goal of this study was to investigate the activity of ALP incorporated at PRC and the formation of hydroxyapatite nodules (calcospherites) on hybrid biomaterial (PRC+ALP). Methods: Discs of pure PRC (PRCp) and blended with ALP (6 mg/mL) (PRC+ALP) were incubated at 37ºC and 5% CO₂ in supplemented α-MEM and ALP activity was measured during 21 days. For evaluation of calcospherites formation, PRCp and PRC+ALP discs were incubated at 37ºC and 5% CO₂ in synthetic body fluid for 17 days and, after this, observed under scanning electron microscopy. Results: ALP activity of PRC+ALP discs was reduced in a time-dependent way until day 5 and maintained among days 5 and 21. It was not observed significant ALP activity on PRCp discs. Formation of calcospherites was observed on both surfaces, PRCp and PRC+ALP. However, number and size of calcospherites were greater on PRC+ALP discs when compared with PRCp discs. Conclusion: These results indicate that ALP incorporation can improve the biocompatibility of PRC, since ALP activity and calcospherites have important roles in the process of mineralization of bone extracellular matrix. Financial Support: FAPESP