Natural polyelectrolyte complex-based pH-dependent delivery carriers using alginate and chitosan

The pH-dependent complexation behaviors of natural and counterionic polyelectrolyte complexes (PECs) without crosslinkers have been rarely studied. In this work, alginate (0.5-2.5 wt %) and chitosan (0.5-2 wt %) were combined to formulate turbid gel-like assemblies. The PEC was consisted of ~100-mu m-sized porous structure observed by scanning electron microscope images and electrostatic interactions inside the complex were newly formed characterized by Fourier transform infrared spectra. Based on visual monitoring and ultraviolet-visible absorption measurement, the complex maintained the gel-like structure under acidic, while the complex was more dissolved under becoming basic. As a demonstration of potential pH-dependent delivery, distinct release profiles of the complexes encapsulating rhodamine 6G (R6G) or doxorubicin, were observed when they were immersed in acidic, neutral, and basic medium. Within 2 h, 7.4, 35.4, and 73.7% of R6G were released under acidic, neutral, and basic condition, respectively, with reasons of degree of protonation or deprotonation of each natural polyelectrolyte at certain pH. (c) 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019, 136, 48143.