Tryptophan complexed hydroxyapatite nanoparticles for immunoglobulin adsorption.

The selective removal of immunoglobulin using different affinity-type particulate adsorbents has clinical significance in certain autoimmune diseases. This study reports the use of modified nanosized hydroxyapatite as a matrix for affinity based immunoglobulin adsorption. The adsorbent matrix consists of cyclodextrin complexed hydroxyapatite nanoparticles modified with tryptophan. It appears that presence of cyclodextrin has a synergic effect in the adsorption of immunoglobulin proteins having affinity with tryptophan complexed hydroxyapatite. The complexes were analyzed by X-ray diffraction (XRD), transmission electron microscopy (TEM), Fourier transform infrared (FT-IR) spectroscopy, thermal gravimetric analysis (TG) and differential scanning analysis (DSC) methods. The preferential affinity of the immunoglobulin towards tryptophan complexed particles was confirmed with polyacrylamide gel electrophoresis (PAGE) and Lowry adsorption techniques. Immunoglobulin adsorption was confirmed by quantitative turbidimetric assay using a standard immunoglobulin kit. The cytotoxicity index of the nanoparticle complexes were evaluated by MTT assay. Our proposed matrix for immunoglobulin adsorption is cost effective and adaptable for applications towards plasma perfusion.