This work describes a new oral pharmaceutical formulation of insulin that is complexed with cationic beta-cyclodextrin polymers (CP beta CDs), and then encapsulated into alginate/chitosan microspheres, which are prepared by ionotropic pregelation/polyelectrolyte method. CP beta CDs were synthesized through a one-step polymerization of P-cyclodextrin (beta CD), epichlorohydrin, and choline chloride. CP beta CDs have enhanced ability to complex with insulin due to the assistance of their polymeric chains, as well as the electrostatic interactions between insulin (negatively charged while pH>5.3) and quaternary ammonium groups of CP beta CDs. The noncovalent inclusion complex formed between CP beta CDs and insulin was analyzed by Fourier transform infrared and fluorescence emission spectra. With the increase of zeta potential of CP beta CDs from 1.8 to 14.2 mV, the insulin association efficiency (AE) of current system was increased from 55.2 to 71.8%, whereas the AE of insulin-loaded microspheres at the same condition was only 50.7%. The cumulative insulin release in simulated intestinal fluid was also higher than that of the insulin-loaded microspheres and beta CD-insulin encapsulated microspheres. (C) 2009 Wiley Periodicals, Inc. J Appl Polym Sci 115: 1371-1379, 2010