Detailed evaluation of protein adsorption on alumina surface through surface plasmon resonance phenomenon

To investigate the adsorption of human serum albumin (HSA) on alumina, alumina films were studied in terms of their initial protein adsorption through the surface plasmon resonance (SPR) phenomenon using a multilayer device consisting of an alumina layer on Au. HSA in a phosphor buffer (PB) was used as a protein. Na2HPO4·12H2O, NaH2PO4·2H2O, and deionized water were mixed to coordinate the PB. From the attenuation of reflected light, the SPR angle was determined as the angle with minimum reflection intensity. The observed behavior of the SPR angle indicated that HSA cannot remain adsorbed on alumina for a long time. To understand this phenomenon, the etching rates of PB solutions were estimated, and were −3.44, −2.64, and −0.41 nm/h for 0.5, 0.3, 0.1 M solutions, respectively. Upon evaluating the adsorption of HSA, the observed SPR angle behavior indicated that HSA was immediately adsorbed on alumina films. After that, the adsorbed HSA was desorbed by the etching of the alumina layer. Hence, these results also indicated that HSA cannot remain adsorbed on an alumina layer for a long time.