Adsorption of bovine serum albumin onto immobilized cobalt microporous and mesoporous silica adsorbents

Abstract

The adsorptions of Bovine Serum Albumin (BSA) onto mesoporous and microporous silica adsorbents were done. The cobalt (Co) metal cation had been immobilized into mesoporous silica adsorbents (MCM-41 and SBA-15) and microporous silica adsorbents (Beta and ZSM-5). These absorbents have been characterized with x-ray diffraction (XRD) and nitrogen gas by Burreut, Emmer and Teller (BET) method. Adsorption of BSA onto these adsorbents has been studied with 5 different pH buffer solutions which were 2, 4, 5, 9 and 11. The results varied with the different pH used. The highest BSA adsorption for these adsorbents was at pH 4 which was close to isoelectric point (pI) for BSA. This is due to the zero net charge of BSA and thus no electrostatic repulsion or attraction between the amino acid. Result also showed that, the best adsorbent was Co-SBA-15 with the concentration of BSA at 0.005 mmol and pH 4 which produced 5.59 × 10-4 mmol per gram of dry adsorbent. When a comparison was made between mesoporous (MCM-41 and SBA-15) and microporous (Beta and ZSM-5) silica adsorbents, mesoporous silica adsorbents produces good adsorption capacity compared to microporous silica adsorbent. The cobalt cation showed its suitability with the adsorbents and produced good adsorption processes. In addition, when the adsorption was assisted with an ultrasound, the adsorption process become much better as can be seen from the results for adsorption using Co-MCM-41 compared to the conventional stirring. From the Fourier transform infrared (FTIR) study, the binding of protein and adsorbent can be explained by the interaction between the molecule of the protein and surface of the adsorbent.