Holger Klapproth

Polysaccharide microarrays with a CMOS based signal detection unit

Microarray based test assays have become increasingly important tools in diagnostics for fast multi-parameter detection especially where sample volumes are limited. We present here a simple procedure to create polysaccharide microarrays, which can be used to analyze antibodies using an integrated, complementary metal-oxide-semiconductor (CMOS) based electric signal readout process. To accomplish this chips are used which consist of an array of silicon photodiodes and where different types of polysaccharides from the bacteria Streptococcus pneumoniae are printed on the (silicon dioxide) chip surface. Typical amounts of polysaccharide deposited in the printing process are around 12 attomol/spot. In a subsequent reaction step the polysaccharide microarrays were used for the measurement of IgG antibody concentrations in human blood sera using either chemiluminescence or fluorescence based detection. To understand the device performance the influence of surface density of the immobilized polysaccharide molecules and other parameters on the assay performance are investigated. The dynamic measurement range of the sensor is shown to reach over more than 3 decades of concentration and covers the whole physiologically relevant range for the analysis of antibodies against a large panel of pneumococcal polysaccharides.