Detection of human apolipoprotein E genotypes by DNA biosensors coupled with PCR

Apolipoprotein E (apoE) is an important constituent of several plasma lipop roteins and has been associated with the risk of developing cardiovascular diseases and in familiar type In hyperlipoproteinemia. We developed new pro cedures for the detection of apolipoprotein E polymorphism in human blood b ased on coupling DNA electrochemical or piezoelectric sensors with polymera se chain reaction (PCR), The electrochemical sensor was obtained by immobil izing single-stranded oligonucleotides onto graphite screen-printed electro des by adsorption at controlled potential. The hybridization reaction that occurred on the electrode surface was evidenced by chronopotentiometric str ipping analysis-using daunomycin as indicator. In the piezoelectric sensor, biotinylated 23-mer probes were immobilized on the streptavidin-coated gol d surface of a quartz crystal; streptavidin was covalently bound to the thi ol/dextran modified gold surface. The hybridization of the immobilized prob es with complementary and mismatched DNA was investigated. With the use of two different probes, it was possible to investigate both positions in whic h apoE polymorphism takes place and consequently, to distinguish the differ ent genotypes, The procedure was validated with both kinds of biosensor wit h a reference method based on polyacrilamide gel electrophoresis. (C) 2001 Published by Elsevier Science B.V.