Detection of single nucleotide polymorphisms by minisequencing on a polypyrrole DNA chip designed for medical diagnosis

With the increasing availability of genetic information and its relationship to human diseases, there is a growing need in the medical diagnostic field for technologies that can proceed to the parallel genotyping of multiple markers. In this paper, we report the development of a new flexible microarray-based method that aims to be inexpensive, accurate, and adapted to routine analysis. The construction of the MICAM® (MICrosystem for Analysis in Medicine) DNA chip is based on the controlled electrosynthesis of a conducting polymer film bearing oligonucleotide probes on gold electrodes. First, accessible 3'OH-ends of grafted probes are directly used to conduct single template-dependent nucleotide extension reactions with fluorescence-labeled chain terminators. Then, the fluorescence of incorporated dideoxynucleotides on controls and probes of interest are recorded to assess base calling. Here, we present the development of the methodology to assign the genotype of TP53 (tumor protein p53) codon 72 polymorphism and its application to analysis of genomic DNA from cell lines and from human colorectal samples. The genotyping results obtained by minisequencing on the polypyrrole DNA chip were 100% concordant with data obtained by polymerase chain reaction-restriction fragment length polymorphism and direct sequencing. Moreover, the developed probe array assay has been successfully applied to the detection of TP53 loss of heterozygosity.