Fabrication of a disposable biochip for measuring percent hemoglobin A1c (%HbA1c)

A disposable biochip for measuring percent hemoglobin A1c, a glycosylated hemoglobin (HbA1c), in blood is presented, in which a pair of interdigitated array electrodes, a micropump, and a microchannel were on-chip integrated by bonding a glass wafer and a polydimethylsiloxane (PDMS) layer. The ratio of HbA1c to hemoglobin, %HbA1c, represents the average glucose level during the life span of red blood cells, and thus, it can be a more reliable and accurate index of diabetes. For %HbA1c measurement, the blood sample was split into two streams, one with HbA1c and the other without HbA1c by binding of HbA1c with m-amino-phenylboronic acid agarose beads. Each stream passed by the interdigitated electrodes resulting in an electric signal via an electrochemical reaction. The %HbA1c was calculated with both signals. A first device of 40 mm × 20 mm × 3 mm was fabricated by bonding two glass wafers and two PDMS layers with a vertical sample reservoir. A second device of 75 mm × 25 mm × 1.5 mm was produced by bonding one glass wafer and one PDMS layer yielding a simplified configuration compared to the first device. For verifying the devices, blood suspensions were transported and cell lysis was tested. A 50-μL blood suspension extracted from a mouse was mixed with ethylenediaminetetraacetic acid, diluted with phosphate buffered saline to lower its viscosity, and the suspension was then transported at approximately 30 μm/s in the microchannel by the micropump, which produced oxygen gas. The condition for blood lysis was determined empirically with 2% Triton X-100, a neutral detergent.