Adsorption Of Human Hemoglobin Onto Chitin and Cellulose Surfaces

When a chitosan (chitin derivative) acetate buffer system is combined with a hemoglobin (Hb) acetate buffer system, three distributions of hydrodynamic radii are observed: Chitosan/H2O, Hb/H2O, and a third unexpected distribution – Chitosan/Hb/H2O complex. This suggests that chitosan and Hb interact aggregate. Neither human serum albumin nor fibrinogen interact or form complexes with either chitin or cellulose. Therefore, chitosan and possibly chitin may be selective to which proteins it binds to. The adsorption of hemoglobin onto chitin and cellulose has yet to be quantified, and this work aims to investigate and quantify a possible affinity of hemoglobin to chitin, cellulose or both. In the present work, hemoglobin solutions were prepared in 50 mM, pH = 7.4 phosphate buffer at concentrations of 0.0125 – 0.5 mg·ml-1 and adsorption onto gold, chitin, and cellulose surfaces was studied with surface plasmon resonance (SPR) spectroscopy. First, the hydroxyl groups of chitin and cellulose were masked with trimethylsilyl groups to improve solubility in common organic solvents. Solutions with concentrations of 0.05 mg·ml-1 were prepared, in chloroform for chitin and toluene for cellulose for the purpose of preparing spincoated films. Polymer films were spincoated onto gold SPR surfaces, and the hydroxyl groups were regenerated using 10% aq. hydrochloric acid vapor. Hemoglobin solutions were passed across gold, chitin, and cellulose surfaces and resonant angle changes from SPR were converted into surface concentrations. In all systems, hemoglobin failed to cover the entire surface, therefore equilibrium SPR were less than a monolayer. Hemoglobin adsorbed onto gold surfaces with and reached equilibrium within 70 min, independent of hemoglobin concentration. Hemoglobin adsorbed faster onto gold than chitin, however for adsorption onto chitin exceeded gold at high solution concentrations. For cellulose surfaces, hemoglobin adsorption led to smaller at all concentrations tested relative to chitin. Adsorption rates for hemoglobin onto cellulose were substantially smaller than those observed with gold and chitin. These studies suggest stronger interactions between hemoglobin and chitin than hemoglobin and cellulose which are consistent with strong interactions seen between hemoglobin and chitosan derivatives used in drug delivery formulations