A PDMS sample pretreatment microdevice to enable downstreamelectrokinetic manipulations in bovine serum

摘要

The notion of sample preconditioning, or pretreatment, as a micro-unit operation in a Lab on a Chip (LOC) system has yet to be realized in commercial practice. As is well known, Biomarker detection in complex, biological samples, such as blood, requires a series of pretreatment steps to enable detection of specific markers. On chip, such a process usually relies on "off-chip" sample pretreatment prior to "on-chip" analyte manipulations and detection. Presented in this paper is a PDMS, pretreatment chip based on the design of Oddy et al.' with a view to enable a self-contained LOC platform. The chip was designed to directly manipulate the suspended species while adjusting fluid properties using buffer volumes less than 1 ml. Using previous literature related to capillary electrophoresis, a bench-scale pretreatment protocol was developed to tune specific fluidic parameters to an optimal range, namely pH, conductivity, and viscosity. A PDMS device was fabricated and used to combine a raw, bovine serum sample with specific buffer solutions. Off-chip electrodes were used to induce DC-electrokinetic micro-mixing of the target analyte in the mixing chamber, where a homogeneous analyte distribution was achieved in less than one second using an 800V DC pulse wave. Additionally, the desired solution viscosity and pH were achieved using less than 1 ml of buffer solution. Adjustment of sample conductivity, which is driven by sample fluid volume, remains an open area of research.