Fabrication and evaluation of calcium alginate/ calcium polyphosphate composite

Calcium polyphosphate (CPP) incorporated calcium alginate (CA) composite beads were prepared via adding sodium polyphosphate (STPP) contained sodium alginate (SA) solution dropwise to calcium chloride (CaCl2) solution. In the process Ca2+ ion may attach to the -COO− in SA because of electrostatic attraction. Additionally, there is an interaction of PP to Ca2+ to generate CPP, inducing intermolecular crosslinkages between CA and CPP. The rotational rheometer showed STPP addition had no significant impacts on the rheological properties of SA solution. While a combination of SEM, AFM, FTIR and swelling behavior study demonstrated CPP was successfully formed within the gel network of CA gel beads and played an active role in restricting the movability of the alginate polymer chains. The in vitro study implied CPP can promote the expression of ALP, Col-I, OCN and OPN of osteoblasts.