SAM-Modified Microdisc Electrode Arrays (MDEAs) with Functionalized Carbon Nanotubes for Amperometric Biosensors

A novel biosensor for glucose, one that makes use of covalent conjugation of glucose oxidase (GOx) to acid-chopped, chemically modified single-walled carbon nanotubes (SWNT) that were themselves covalently immobilized via alkane thiol SAMs onto gold microdisc electrode arrays (MDEAs) has been constructed and evaluated. Amperometric biotransducers fabricated by chemisorbing self-assembled monolayers (SAM) of cysteamine (CA) and 11-amino-1-undecanethiol (11-AUT) onto 100 mm diameter gold microdisc arrays, resulting in MDEA-Au|CA|SWNT-COOH and MDEA-Au|11-AUT|SWNT-COOH electrodes, were characterized electrochemically using cyclic voltammetry and amperometry in the presence of ferrocene. Subsequent covalent conjugation of GOx to free -COOH groups using EDC NHS hetero bifunctional coupling, produced MDEA-Au|CA|SWNT-CONH-GOx and MDEA-Au|11-AUT|SWNT-CONH-GOx electrodes that were similarly characterized in changing concentrations of glucose. The combination of SWNT at the CA-modified MDEA surface compared to the other electrode surfaces gave a well-resolved voltammogram with highest peak currents (I_pa = 5.54 x 10^-4 A, I_pc = 2.34 x 10^-4 A at 100 mV/s). The resulting amperometric glucose biosensor displayed linear responses between 0.5 and 3.0 mM glucose with a response time of 40s and was superior to constructs using 11-AUT.