In recent years, intensive research has been devoted towards the development of DNA diagnostic and prognostic biochip devices. Such micro-devices can be extremely useful in screening and identifying genes associated with specific diseases and disorders. To aid in this endeavor, many amperometric DNA sensing systems have been developed that utilize ferrous-based electroactive ligands. However, this study will focus on employing potassium ferricyanide, as a surrogate for conjugatable ferrocene, to develop our amperometric method of detection.

Amperometric detection of potassium ferricyanide was performed initially off-chip within a 25 mL breaker using a 25 um diameter platinum electrode (working electrode), a thin stainless steel metal strip (counter electrode) and a miniaturized Ag/AgCl reference electrode. A 0.1 M KCl solution served as the background electrolyte and a potential of 0.3V was applied to reduce ferricyanide. As a result, a linear relationship between current and concentration was achieved over a dynamic range of two orders of magnitude. Actual ferricyanide concentrations ranged from 10-4 to 10-2 M, and the measured limit of detection was 8 x 10-4 M. In addition, a reproducibility < 3% was calculated for five sample injections of a 5 x 10-3 M ferricyanide solution.

Future work will include: (1) integrating 25 um diameter platinum electrode with a microfluidic chip and repeating the above experimental results while under computer control and (2) immobilizing single stranded DNA on both a single microelectrode and on an interdigitated microsensor electrode (IME) to detect hybridization with the DNA complement.