Establishment and In Vitro Evaluation of Porous Ion-Responsive Targeted Drug Delivery System

Background: Protein drugs have disadvantages, such as short half-lives, unstable biological activities, and low utilization efficiency. Objective: In this paper, a porous ion-responsive targeted drug delivery system was designed, combining biodegradable carriers with ion exchange technology to overcome problems for protein drug delivery systems. Methods: Carboxymethyl Chitosan Porous Microspheres (CCPM) were prepared using an emulsification- chemical crosslinking method. Chitosan-bovine serum albumin-carboxymethyl chitosan porous microspheres (CBCCPM) were prepared using a dynamic ion exchange method and static self-assembly technology. Results: CCPM were round in appearance mostly with a particle size distribution of 5-15 μm, which facilitates passive targeting to the lungs. CCPM had a total ion exchange capacity of 9.97 ± 0.07 mmol/g and showed a strong ability to attract and contain positively charged drugs. A potentiometric titration curve was used to identify the dissociation behavior of exchangeable groups on the microspheres; the optimal pH for ion exchange of microspheres was ≥ 4.3. CCPM had ion responsiveness, in vitro degradation ability, thermal stability and biocompatibility. In vitro release results confirmed that BSA and CCPM were mainly bound together by ionic bonds and the drug release mechanism of the self-assembled microspheres changed from particle diffusion to membrane diffusion under pH 7.4 PBS solution containing 0.02% Tween 80. Circular dichroism and sodium dodecyl-sulfate polyacrylamide gel electrophoresis results showed no significant change in the secondary structure and purity of BSA after binding to CCPM. The cumulative in vitro release rate of microspheres after 24 h was 86.78%. Conclusion: In this paper, CBCCPM, a porous ion-responsive targeted drug delivery system, was designed.