Analytical Sciences

Fabrication of an Implantable Fine Needle-Type Glucose Sensor Using γ -Polyglutamic Acid

Hiroki TAKAOKA*,** and Mikito YASUZAWA*

*Department of Chemical Science and Technology, Institute of Science and Technology, The University of Tokushima, 2-1 Minamijosanjima, Tokushima 770-8506, Japan
**Toyo Precision Parts MFG. Co., Ltd., Kashihara, Nara 634-0836 Japan

Implantable fine needle-type glucose sensors with an outer diameter of less that 0.2 mm were fabricated using a low-cost and non-animal origin polyamide, γ-polyglutamic acid (PGA) as a glucose oxidase (GOx) immobilizing material. Two types of PGA, γ-polyglutamic acid (PGAH) and γ-polyglutamic acid sodium salt (PGANa), were employed to prepare GOx immobilized film by the covalent attachment of GOx using water-soluble carbodiimide (EDC). Nafion/cellulose acetate composite film and polyurethane/polydimethylsiloxane composite film were employed as a permselective inner film and a biocompatible outer film, respectively. The procedure of enzyme-immobilized film fabrication affected the stability of the sensor; that is, GOx immobilized film prepared by pouring a mixture solution of GOx and EDC on a PGA precoated surface showed higher sensor stability than that prepared by pouring a mixture solution of GOx, PGA and EDC. Although, obvious differences in the sensor properties were not observed between the use of PGANa and PGAH, the electrode prepared with PGAH had a lower swelling degree. The glucose sensors prepared with both PGANa and PGAH were practically not affected by the existence of electroactive compounds, such as uric acid, and provided long-term stability for approximately 5 weeks. These sensors also showed good performance in horse serum.

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