Sulfated alginate based complex for sustained calcitonin delivery and enhanced osteogenesis.

Direct medications of salmon calcitonin (sCT) through subcutaneous or intramuscular injection are limited for its low effeciency. Drug delivery systems with sustained delivery property and high bioactivity are imminently needed. In consideration of the clinic application, a cost-effective and effective carrier is demanded, which is still a challenge until now. In this study, a simple alginate/ alginate sulfate-sCT (Alg/AlgS-sCT) complex was succesfully constructed for sustained release of sCT. The negtively charged sulphate groups facilitate the bonding with sCT, which avoids the burst release of sCT and extends the release time up to 15 days (only 2 days for pure sCT). More importantly, the bioactivity of the released sCT is not affected during such long release time, suggesting a conformation similar to native sCT. In vitro analysis implies the biocompatibility of the complex. Moreover, the combination of AlgS and sCT synergistically impoved the osteogenic ability of MC3T3 cells, showing higher ALP level, intracellular and extracellular calcium ions concentrations. Note that the concentration of intracellular calcium ions displays 5.26 fold increments of control group after 10 days of incubation. We envision this simple yet effective system has potential applications in clinical trails and give inspiration for the design of other protein delivery system.