Alumina−Pepsin Hybrid Nanoparticles with Orientation-Specific Enzyme Coupling

Hybrid alumina nanoparticles with pepsin were prepared in a controlled and efficient manner. Phosphorylated pepsin can be coupled to alumina through the interaction between phosphoserine on pepsin and the alumina surface in an orientation-specific manner. A comparison of data obtained with nanoparticles and microsized alumina particles reveals that the conjugated pepsin retained much higher enzymatic activity when it was immobilized on nanoparticles mainly because of the lack of diffusion limitations of the substrate. Additionally, upon attachment to the alumina nanoparticles, the thermal stability of pepsin is enhanced. The coupled enzyme can be quantitatively released by simply incubating the hybrid nanoparticles with phosphate buffer.