Quaternized Fe₃O₄@chitosan nanoparticles for efficient and selective isolation of heparin

Heparin, a highly sulfated polysaccharide, is industrially produced for clinical applications. To realize highly efficient and selective adsorption of heparin from complex biological components (e.g., proteins, nucleic acids) remains a challenge in the isolation process. This study reported a simple and green approach to fabricate heparin adsorbent of quaternized Fe₃O₄@chitosan nanoparticles (QFCNs) by using the natural polysaccharides of chitosan coated and cross-linked with glutaraldehyde on the Fe₃O₄ and further quaternized using glycidyltrimethylammonium chloride. The effects of adsorbent type, pH, initial heparin concentration, and temperature on the adsorption performance were investigated. The QFCNs demonstrated a high adsorption efficiency of 90.02 % and a remarkable adsorption capacity of 33.04 mg g^-1, surpassing the performance of previously reported adsorbents, and the adsorption process was found to be more closely aligned with the pseudo-first-order model, Langmuir and Sips isotherm model. Furthermore, the QCNFs exhibited a distinct selectivity for heparin in the presence of BSA at pH 7.0 in 0.3 mol L^-1 of NaCl. The adsorption capacity of QFCNs was 1.63 times that of the commercial Amberlite FPA98Cl resin in the adsorption process of crude heparin, and the purity of the crude heparin was enhanced from 37.10 % to 78.10 %. Besides, the adsorption capacity remained at an acceptable level after five cycles. The X-ray photoelectron spectroscopy results elucidated the heparin adsorption follows the mechanism of the electrostatic attraction with the quaternary ammonium groups of QCNFs. QFCNs could become an ideal adsorbent for the selective capture of heparin and other negatively charged natural polysaccharides, offering high efficiency, environmental friendliness, and facile recyclability.