Abstract
A DNA microarray system is usually comprised of DNA probes formatted on a microscale on a glass surface (chip), plus the instruments needed to handle samples (automated robotics), to read the reporter molecules (scanners) and analyse the data (bioinformatic tools). Biochips are formed by in situ (on chip) synthesis of oligonucleotides or peptide nucleic acids (PNAs) or spotting of DNA fragments. Hybridisation of RNA- or DNA-derived samples on chips allows the monitoring of expression of mRNAs or the occurrence of polymorphisms in genomic DNA. Basic types of DNA chips are the sequencing chip, the expression chip and chips for comparative genomic hybridisation. Advanced technologies used in automated microarray production are photolithography, mechanical microspotting and ink jets. Bioelectronic microchips contain numerous electronically active microelectrodes with specific DNA capture probes linked to the electrodes through molecular wires. Several biosensors have been used in combination with biochips. PN...