Identification of blood plasma proteins using heparin-coated magnetic chitosan particles.

Heparin was immobilized on magnetic chitosan particles to be used as a tool for human plasma protein identification. Chitosan was magnetized by co-precipitation with Fe2+/Fe3+ (MAG-CH). Heparin was functionalized with carbodiimide and N-hydroxysuccinimide and covalently linked to MAG-CH (MAG-CH-hep). X-ray diffraction confirmed the presence of chitosan and Fe3O4 in MAG-CH. This particle exhibited superparamagnetism and size between 100-300 µm. Human plasma diluted with 10 mM phosphate buffer (pH 5.5) or 50 mM Tris-HCl buffer (pH 8.5) was incubated with MAG-CH-hep, and the proteins fixed were eluted with the same buffers containing increasing concentrations of NaCl. The proteins obtained were investigated by SDS-PAGE, LC/MS, and biological activity tests (PT, aPTT, and enzymatic chromogenic assay). Inhibitors of the serpin family, prothrombin, and human albumin were identified in this study. Therefore, MAG-CH-hep can be used to purify these proteins and presents the following advantages: low-cost synthesis, magnetic separation, ion-exchange purification, and reusability.

Synthesis and characterisation of magnetised Dacron-heparin composite employed for antithrombin affinity purification.

Human antithrombin is a blood derivative widely used in the treatment of coagulation dysfunction. Affinity chromatography using heparin (HEP) derivatives is usually used for antithrombin purification. In this study, an affinity procedure based on a magnetic Dacron-HEP composite is proposed. Dacron was firstly converted to Dacron-hydrazide and magnetised by co-precipitation with of Fe2+/Fe3+ (mDAC). HEP was activated by carbodiimide and N-hydroxysuccinimide and covalently linked to mDAC (mDAC-HEP). EDX and infrared spectra analyses confirmed each synthesis step of mDAC-HEP. This composite exhibited superparamagnetism behaviour. Human plasma was incubated with mDAC-HEP (fresh and stored over a long period) and washed with phosphate buffer containing increasing concentrations of NaCl. Human plasma antithrombin activity was reduced by approximately 20% in the presence of the 1.0M NaCl fraction, and this eluate was able to prolong coagulation time (aPTT) using both preparations. Electrophoresis of the eluates revealed bands corresponding to the expected size of antithrombin (58kDa). The mDAC-HEP particles are reusable. This method presents the following advantages: easy, low-cost synthesis of the composite, magnet-based affinity purification steps, and reusability.