A term first used with regard to an electronic device that utilizes biological molecules as the “framework” for other molecules acting as semiconductors and functioning as an integrated circuit.

1. During the 1990s, this term also became commonly used to refer to various “laboratories on a chip” to:

• Analyze very small samples of DNA
• Assess the impact of pharmaceuticals — or pharmaceutical drug candidate molecules — on specific cells (i.e., attached to the biochip’s surface) or on specific cellular receptors (ligand-receptor response of cell)
• Size and sort DNA fragments (genes) via the (proportional) fluorescence of dyes intercalated in the DNA molecules
• Detect presence of specific DNA fragments (genes) via hybridization to a probe (that was fabricated onto the chip)
• Size and sort protein molecules (via various cells fabricated onto the chip)
• Assess pharmaceuticals via adhesion molecules attached to the chip
• Detect specific pathogens or cancerous cells in a blood sample (e.g., by applying controlled electrical fields to cause those cells to collect at electrodes on the chip)
• Screen for compounds that act against a disease (e.g., by applying antibodies linked to fluorescent molecules, then measuring electronically the fluorescence triggered by antibody-binding)
• Conduct gene expression analysis by measuring the fluorescence of messenger RNA (specific to which particular gene is “turned on”) when that mRNA hybridizes with DNA (from genome) on hybridization surface on the chip

2. Shortly after the 1990s, several companies manufactured biochips capable of sequencing (determining the sequence of) DNA samples. Such biochips have, attached to their surfaces, all possible “DNA probes” (short sequences of DNA). The sample (i.e., the unknown DNA molecule) is passed over the probe-covered surface of the biochip, where each relevant segment (within the large unknown DNA molecule) hybridizes (“pairs”) with the short “DNA probe” attached to a known location on the surface of the biochip. Because the sequence of each DNA probe — at each specified location on the biochip — is known, that information (i.e., the probes’ sequences to which the unknown DNA molecule hybridized) is then used to “assemble the complete sequence” of the unknown DNA molecule.

3. Sometimes refers to an electronic device that uses biological molecules as the framework for other molecules that act as semiconductors and function as an integrated circuit. The future working parts of the science of bioelectronics, biochips may consist of two- or threedimensional arrays of organic molecules used as switching or memory elements. If biochip technology proves to be feasible, one application will be to shrink currently existing biosensors in size. This would enable the biosensors to be implanted in the body or in organs and tissues for the sake of monitoring and controlling certain bodily functions. A future possibility is to try to provide sight for the blind using lightsensitive (e.g., protein-covered electrode) biochips implanted in the eyes to replace a damaged retina. For example, during 2001, Alan Chow implanted such biochips into several men whose retinas had been damaged by the disease retinitis pigmentosa.