The use of single walled carbon nanotubes dispersed in a chitosan matrix for preparation of a galactose biosensor

Chitosan was chosen as a natural polymer for dispersion of single walled carbon nanotubes (SWNT) based on its ability to efficiently solubilize SWNTs to form a stable dispersion. Moreover, chitosan films deposited on a surface of a glassy carbon (GC) electrode are mechanically stable. Further stabilisation of the chitosan film containing SWNT (CHIT-SWNT) was done by chemical crosslinking with glutaraldehyde and free aldehyde groups produced a substrate used for covalent immobilisation of galactose oxidase (GalOD). Different galactose biosensor configurations were tested with optimisation of composition of inner and outer membrane; and enzyme immobilisation procedure, as well. Detection of oxygen uptake by GalOD on CHIT-SWNT layer at -400 mV is robust and, when flow injection analysis (FIA) was applied for assays, a low detection limit (25 microM) and very high assay throughput rate (150 h-1) was achieved. This new galactose biosensor offers highly reliable detection of galactose with R.S.D. well below 2% and it has been successfully applied to assaying galactose in a blood sample with recovery index between 101.2 and 102.7%.