2.4. Immobilization of Hb
Functionalized SPIONs at the particle concentration range of
2.5–25 mg mL−1 were mixed with 1 mg mL−1 of hemoglobin (Hb) in
2 mL of 20 mM × Tris–HCl (pH 7.4, in 150 mM NaCl) for 2 h at 4 °C
[13]. Hb immobilized GPTS–SPIONs were separated magnetically from
the supernatant. Then, Hb immobilized particles were washed with
20 mM × Tris–HCl (pH 7.4) twice. The supernatant was kept at 4 °C
for the analysis of protein concentration. The amount of immobilized
Hb was measured by using fluorescence spectroscopy. For this aim,
the intrinsic fluorescence of the protein was recorded at 280 and
342 nm of excitation and emission wavelengths [16]. Protein concentration
after immobilization was determined from the regression equation
of the calibration curve.