Study On Recombinant Human Bone Morphogeneticprotein-2/Dextran Sulfate/Chitosan Nanoparticles Controlled Release By Resonance Light Scattering Spectrum Method

In recent years, the rapid development of controlled-release microspheres technology and artificial biodegradable materials, impell the development of controlled-release technology of active cytokines and formation of artificial bone. BMPs controlled-release microspheres were prepared by many researchers in home and abroad. The results indicate that BMPs controlled-release microspheres have good osteogenic effect. Resonance light scattering is a new technology developed in the twentieth Century90’s. In particular, RLS techonology has a sensitive and rich singal in studying biomolecular recognition, assembly and aggregation, So it has become a very useful method on biological macromolecules.This dissertation mainly focused on interactions between rhBMP-2, dextran sulfate sodium and chitosan by resonance light scattering (RLS), combined with fluorescence spectra and UV absorption spectra. Therefore, this dissertation researched sustained release of rhBMP-2/dextran sulfate sodium/chitosan nanoparticles.The process of chitosan/dextran sulfate sodium complex polyelectrolyte was studied. RLS results indicate that DSS and CS have good compatibility and form stable colloid composite solution in low mass ratio With the change of external environment, RLS intensity of composite solution also changed dramatically. When pH increased, RLS intensity gradually decreased. In the presence of a certain amount of Zn2+, Zn2+not only increases the RLS intensity, but also induces the micellar-aggregation transition of CS/DSS complex in dilute solution. Its composite thermodynamic parameters in the process of micelle formation were also measured by the RLS technique under different temperature conditions. It concludes that micelles formation in the CS/DSS polyelectrolyte complex solution is driven by both enthalpy and entropy.The binding of chitosan and rhBMP-2was studied. RLS results indicate that the binding ability between CS and rhBMP-2is weak by RLS. With the concentration of CS increased, the fluorescence intensity of rhBMP-2decreased. Fluorescence quenching of rhBMP-2is static quenching, caused by the formation of compound The apparent binding constant and the binding sites indicate that the interaction between CS and rhBMP-2is relatively weak. Thermodynamic parameters indicate that the interaction between CS and rhBMP-2is mainly driven by van der Waals force and hydrogen bond.The binding of DSS and rhBMP-2was studied. RLS results indicate that the interaction between DSS and rhBMP-2is strong by RLS. especially in acidic conditions. As DSS in low concentration, fluorescence quenching of rhBMP-2is dynamic quenching. As DSS in high concentration, fluorescence intensity of rhBMP-2increased. The apparent binding constant and the binding interaction sites indicate that the interaction between DSS and rhBMP-2is strong. Gibbs free energy, enthalpy change and entropy change indicate that DSS and rhBMP-2in solution is mainly driven by hydrophobic interaction.