A concave microchannel surface was formed by nanosecond pulse laser ablation to allow antibody immobilization on a capillary flow immunoassay chip. Microscopic analysis showed that UV laser ablation of poly(methyl methacrylate) at 193 nm and 1.76 J · cm−2 allowed excellent immobilization of Cy5 conjugated antibody. The concave structure was 10 µm deep and 260 µm wide and supported uniform antibody printing on the microchannel surface. The characteristics of immobilized antibodies on this surface and on a commercially available polymer coating were comparable. Quantitative analysis of procollagen type I C-peptide (PICP) at different concentrations provided a linear relationship in the range 0–600 ng ml−1 PICP, which is sufficient for clinical estimation of PICP in the blood. The results may provide a new benchmark for a mechatronic antibody immobilization-based capillary flow immunoassay chip.
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, gamma-polyglutamic acid (PGA) as a glucose oxidase (GOx) immobilizing material. Two types of PGA, gamma-polyglutamic acid (PGAH) and gamma-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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