The superparamagnetic multilayer hybrid hollow microspheres have been fabricated using the layer-by-layer assembly technique by the electrostatic interaction between the polyelectrolyte cation chitosan (CS) and the hybrid anion citrate modified ferroferric oxide nanoparticles (Fe 3 O 4 -CA) onto the sacrificial polystyrene sulfonate microspheres templates after etching the templates by dialysis. The saturation magnetization and magnetite contents of the superparamagnetic multilayer hybrid hollow microspheres were 32.46 emu/g and 51.3%, respectively. The hybrid hollow microspheres showed pH-sensitive characteristics. The adsorption and release of the basic dye (methylene blue) were applied to investigate the interaction between the amino groups of CS and the carboxyl groups of the Fe 3 O 4 -CA nanoparticles in different pH media. The superparamagnetic pH-sensitive multilayer hybrid hollow microspheres are expected to be used for the targeted controlled release of drugs or in diagnostics. V C 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 3135-3144, 2010 KEYWORDS: hybrid hollow microspheres; layer-by-layer assembly; pH sensitive; superparamagnetic; targeted controlled releaseRecently, surface-charged nanoparticles have been used for the fabrication of the multilayer hybrid hollow microspheres.
pH/ionic strength/temperature multiresponsive hollow microspheres were successfully prepared by the Ce(IV) initiated grafting polymerization of N-isopropylacrylamide (NIPAm) onto the multilayered polyelectrolyte shells encapsulating the polystyrene sulfonate (PSS) microsphere templates fabricated by the layer-by-layer assembly of chitosan (CS) and alginate (SAL), after etching the templates by dialysis. The hollow structure of the obtained multiresponsive hollow microspheres was characterized by transmission electron microscopy (TEM), which indicated that the inner diameter of the hollow microspheres was about 200 nm. The environmental responsive properties of the multiresponsive hollow microspheres were characterized with dynamic light scattering (DLS) in an aqueous system. The introduction of poly(N-isopropylacrylamide) (PNIPAm) brushes onto the pH/ionic strength dual-responsive hollow microspheres achieved temperature-responsive characteristics. It also could prevent flocculation among the obtained multiresponsive hollow microspheres in a solution with higher salt concentration. Their controlled release of drug molecules (a model hydrophobic drug, dipyridamole (DIP)) was also investigated.
As a mono-sodium salt form of alendronic acid, alendronate sodium presents multi-level ionization for the dissociation of its four hydroxyl groups. The dissociation constants of alendronate sodium were determined in this work by studying the piecewise linear relationship between volume of titrant and pH value based on acid-base potentiometric titration reaction. The distribution curves of alendronate sodium were drawn according to the determined pKa values. There were 4 dissociation constants (pKa1=2.43, pKa2=7.55, pKa3=10.80, pKa4=11.99, respectively) of alendronate sodium, and 12 existing forms, of which 4 could be ignored, existing in different pH environments.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.