The separation and subsequent isolation of the metastatic human cervical carcinoma cell line (HeLa cells) from normal human peripheral blood cells has been achieved by exploiting their differential dielectric properties. The isolation process is carried out on a silicon chip containing a five-by-five array of microlocations. These microlocations contain underlying circular platinum electrodes with 80μm diameters and center-tocenter spacing of 200μm. The surface of the electrodes and the rest of the nonmetallized areas have been coated with a permeation layer to prevent the direct contact of cells with the electrode and also to minimize the non-specific adhesion of the cells to the chip surface. An inhomogenous AC field is applied to the electrodes to create the conditions for dielectrophoretic separation of cells. Cell separation using dielectrophoresis as well as electronic lysis on a silicon chip would provide essential sample processing steps which may be combined with a later multiplex electronichybridization step in an integrated assay system.

Random amplification of the human genome using the degenerate oligonucleotide primed-polymerase chain reaction (DOP-PCR) was performed in a siliconglass chip. An aliquot of the DOP-PCR amplified genomic DNA was then introduced into another siliconglass chip for a locus-specific, multiplex PCR of the dystrophin gene exons in order to detect deletions causing Duchenne/Becker muscular dystrophy. Amplicons were analyzed by both conventional capillary electrophoresis and microchip electrophoresis and results were compared to those obtained using standard non-chip-based PCR assays. Results from microchip electrophoresis were consistent with those from conventional capillary electrophoresis. Whole genome amplification products obtained by DOP-PCR proved to be a suitable template for multiplex PCR as long as amplicon size was <250 bp. Successful detection and resolution of all PCR products from the multiplex PCR clearly shows the feasibility of performing complex PCR assays using microfabricated devices.