Multi-porous quaternized chitosan/polystyrene microbeads for scalable, efficient heparin recovery

Heparin is a commercially valuable polysaccharide used as an anticoagulant for surgical procedures. However, it is difficult to isolate at high concentrations from the complex tissues from which it is derived. To address this problem, we fabricated novel porous polystyrene (PS) supported chitosan (CS)-coated microbeads by electrostatic assembly for the efficient, scalable, and selective recovery of heparin. These CS/PS microbeads were further reacted and quaternized using glycidyltrimethylammonium chloride to improve their heparin adsorption efficiency at high pH values. Additionally, a tetrahydrofuran/n-heptane treatment was used to introduce multi-porosity throughout the quaternized-CS/PS microbead structure, increasing the functional surface area. Scanning electron microscopy was used to evaluate the effects of pre- and post-treatments on the bead surface morphology. The adsorption efficiency of the CS/PS microbeads vs. Amberlite FPA98 Cl resin, a commercially available adsorbent, was evaluated as a function of pH (4.1-9.2). Heparin adsorption was demonstrated to improve with both the introduction of a multi-porous bead structure and the quaternization of the CS/PS microbeads to provide a pH-independent cationic polyelectrolyte character. We also demonstrated that the CS/PS microbeads could be effectively regenerated using a saturated NaCl solution and used for repeated heparin recovery without significant adsorption capacity loss. Moreover, multi-porous quaternized-CS/PS microbeads selectively adsorbed heparin in the presence of bovine serum albumin at pH 9 by adding 0.5M NaCl to screen electrostatics between the CS and proteins. In addition, microbeads selectively adsorbed heparin in a real sample, composed of a mixture of biological solution containing heparin isolated from porcine intestinal mucosa.