A hybrid poly(dimethylsiloxane) microsystem for on-chip whole blood filtration optimized for steroid screening

Miniaturized biochemical devices in glass, silicon and polymer materials are starting to find their way from the academic laboratories to real-life applications. However, most attention has been given to miniaturize the downstream functions of various microfluidic systems, leaving the sample introduction and preparation steps to more conventional, bulkier solutions. For point-of-care diagnostics in particular, it becomes crucial to be able to handle complex human samples in a miniaturized format. In this work, we report on a microsystem for on-chip sample preparation that is able to remove blood cells from whole blood. The hybrid system consists of a commercially available membrane filter incorporated into a poly(dimethylsiloxane) (PDMS) casted device. Membrane materials were evaluated on the bases of low nonspecific adsorption of free and protein-bound testosterone as analyte substance. The hybrid system including a hydrophilic polypropylene filter successfully removed blood cells from diluted human whole blood. Surface oxidation was sufficient to make the plasma filtrate flow through the membrane filter and the channel system by capillary force alone and thus no external pumping source was needed.