Functional histidine/nickel hexacyanoferrate nanotube assembly for biosensor applications.

By exploring the properties of histidine, functional histidine/nickel hexacyanoferrate nanotube assembly was prepared using nanopore alumina template via a sequential deposition strategy and demonstrated for improved biosensing. The vertically oriented nanotube assembly has a nanotube density approximately 8x10(8)cm(-2) and can be stably attached to the glassy carbon electrode surface. The nanotube assembly formed provides an ordered well-defined three-dimensional (3D) structure with good electron transfer efficiency and a large specific surface area with abundant electroactive sites. Gold nanoparticles were then absorbed onto nanotube surfaces through amino group provided by histidine, and were used for further absorption of glucose oxidase into the 3D matrix. The histidine and gold nanoparticles on the nanotube surface provide a favorable microenvironment to keep the bioactivity of the enzymes with a low apparent Michaelis-Menten constant (K(Mapp)) of 2.15 mM, and the ordered orientation of the nanotube assembly facilitated enzyme-substrate contact. The biosensor was sensitive and selective toward glucose with a linear range covered from 2 microM to 20 mM of glucose. The biosensor was used to determine glucose concentration in real blood samples with satisfactory results.