Phenyl alanine, tryptophan immobilized chitosan beads as adsorbents for selective removal of immunoproteins.

ABSTRACT

The use of adsorbents for the treatment of patients suffering from various immune diseases is still in its infancy. Therefore, the development of selective absorbents for the removal or decrease of immunoproteins from plasma is of great importance. In this study, chitosan, a natural polysaccharide having structural characteristics similar to glycosamino glycans, which is non-toxic and biocompatible, has been used for protein adsorption studies. Amino acids like phenyl alanine and tryptophan in different ratios are bonded to these polymers to observe immunoadsorption. Several layers of phenyl alanine or tryptophan have been coated covalently on chitosan beads using N2-plasma, carbodiimide or glutaraldehyde treatments. Scanning electron micrographs have revealed the surface morphological changes after such modifications. The surface modified chitosan beads have exhibited high binding affinity for gamma-globulin compared to bare beads. It is also observed that the amount of fibrinogen adsorption is reduced on modified substrate. A selective removal of IgG and IgM has also been observed with these modified matrix when tested with human plasma, using immuno diffusion methods. The modified chitosan membranes have demonstrated a reduction in platelet attachment, showing that these substrates have become more blood compatible. Hence, it appears that modified chitosan surfaces may be an excellent sorbent system for haemoperfusion due to their high binding affinity for immunoproteins and blood compatibility. Further studies are needed to determine the behaviour under clinical conditions.