A novel hemoperfusion adsorbent for selective removal of circulating histones in septic blood

Abstract BACKGROUND AND AIMS Circulating histones play a crucial role in the development and progression of sepsis and is associated with high mortality. Hemadsorption with the CytoSorb® filter has been shown to non-specifically eliminate systemic circulating histones in plasma from injured patients ex vivo and in vitro. The aim of this study was to fabricate another novel hemoperfusion adsorbent for selective removal of histones in the blood of septic patients. METHOD Chitosan-cellulose composite hydrogels (CSCE) were first prepared using a liquid-liquid inversion method. Then, negatively charged heparin was grafted onto the surfaces of the CSCE hydrogels by EDC chemistry to obtain the histone sorbents (CSCEHEP hydrogels). The chemical structure of CSCEHEP hydrogels was characterized by Fourier transform infrared spectroscopy (FTIR) and its hemocompatibility was evaluated. The adsorption capacity and adsorption selectivity of CSCEHEP hydrogels for histone were then analysed by BCA protein quantitative method. Besides, the antagonistic effect of CSCEHEP hydrogels on histone-induced cytotoxicity was verified by in vitro cell experiments using HK-2 cell lines. RESULTS The obtained CSCEHEP hydrogels showed characteristic adsorption peaks of the sulfonic group at 1217 and 940 cm-1 in their FTIR spectrum, suggesting the successful immobilization of heparin onto the surface of the sorbent. The clotting time of plasma after a 30-min incubation with CSCEHEP hydrogels was significantly prolonged by 3 times while no obvious hemolysis, platelet activation, complement activation and other blood-material adverse reactions occurred during this incubation. With a heparin grafting, the adsorption capacity of CSCEHEP hydrogels towards histones (from calf thymus) increased significantly to 314.3 μg/g, with a clearance rate of 62.8%, compared to that of pristine CSCE, which is dependent on the initial histone concentrations in testing solutions. On the contrary, the adsorption capacity of bovine serum albumin by CSCEHEP hydrogels was significantly lower than that of histones, suggesting that the adsorption process of histone by CSCEHEP in plasma was selective. Meanwhile, CSCEHEP hydrogels significantly antagonized histone-induced cytotoxicity by binding histones, and the cell viability increased significantly from 47.1% (model group) to 72.0% (CSCEHEP-treat group). CONCLUSION CSCEHEP hydrogels are of good hemocompatibility and can effectively adsorb histones in PBS solution and antagonize histone-induced cytotoxicity. It is believed that the use of such a histone sorbent for extracorporeal blood purification may provide a novel insight into the modulation of aberrant immune responses in patients with sepsis.