Preparation, characterization, and in vitro drug release behavior of 6-mercaptopurine-carboxymethyl chitosan

A series of 6-mercaptopurine-carboxymethyl chitosans (6-MP-CMC) were prepared and structurally characterized. Their in vitro drug release behaviors in the buffer solutions containing glutathione (GSH) were investigated. 6-MP-CMC did not release any 6-MP in the media without GSH and containing 2   μM GSH. By comparison, the obvious 6-MP release could be observed within an hour in the media containing 2   mM and 10   mM GSH. And the maximum cumulative release rates were 65.1% and 74.4%, respectively. The buffer pH and the 6-MP content in 6-MP-CMC had obvious influences on the 6-MP release. At 10   mM GSH, the maximum cumulative release rate at pH 5 was higher than that at pH 7.4. 6-MP-CMC in pH 7.4 PBS could self-assemble into nanoparticles. Their mean hydrodynamic diameter determined by dynamic light scattering (DLS) was 155.8   ±   6.0   nm. The particles observed by transmission electron microscopy (TEM) were spherical in shape and had the size of about 100   nm.