Fabrication of the polyphosphates patched cellulose sulfate-chitosan hydrochloride microcapsules and as vehicles for sustained drug release.

Polyphosphates are important polyanionic electrolytes that play a major role in stabilization and consolidation of colloids surface and interior microstructures. In this study, the polyelectrolyte complexes (PEC) microcapsules (sodium cellulose sulfate-chitosan hydrochloride, sample 1), and the patched ones via sodium tripolyphosphate (sample 2), sodium pyrophosphate (sample 3) and sodium hexametaphosphate (sample 4) were fabricated under mild conditions. The effects of polyphosphates on the formation of the PEC microcapsules were investigated systematically. Scanning electron microscope (SEM) and confocal laser scanning microscope (CLSM) observation showed that both of the sample 2 and sample 3 had more compact interior microstructures with higher fluorescence intensity, compared with the sample 4 with macroporous ones and sample 1 with irregular ones. Fourier transform-infrared spectroscopy (FT-IR) and thermogravimetric analysis (TGA) showed the electrostatic interactions occurred among the -NH3+ groups, -SO3- groups, HP3O104- groups, P2O74- groups and H2PO4- groups, and the sample 2 and sample 3 had a more thermal stability comparatively. The sample microcapsules showed good capacity of drug loading and encapsulation efficiency (max. 66.9 ± 4.6% and 74.2 ± 5.1%). In the in vitro release studies showed that the sample 2 and sample 3 had a larger accumulative drug release rate of 5-aminosalicylic acid (5-ASA) at the same time point and released completely at 12 h; the drug release mechanisms analysis indicated that the sample 1 and sample 3 were mainly diffusion controlled, while the sample 2 and sample 4 were followed the mechanism of non-Fickian transport. Under the polyphosphate's consolidation, the PEC microcapsules fabricated with sustained drug release profiles could be used as the promising drug vehicles.