DESCRIPTION OF IN VIVO

In vivo ( Latin for "within the living") is experimentation using a whole, living organism as opposed to a partial or dead organism, or an in vitro controlled environment. Animal testing and clinical trials are two forms of in vivo research. In vivo testing is often employed over in vitro because it is better suited for observing the overall effects of an experiment on a living subject. This is often described by the maxim in vivo veritas.

In molecular biology in vivo is often used to refer to experimentation done in live isolated cells rather than in a whole organism, for example, cultured cells derived from biopsies. In this situation, the more specific term is ex vivo . Once cells are disrupted and individual parts are tested or analyzed, this is known as in vitro . in vivo experiment is in living; in vitro study is in test tube.

According to Christopher Lipinski and Andrew Hopkins, "Whether the aim is to discover drugs or to gain knowledge of biological systems, the nature and properties of a chemical tool cannot be considered independently of the system it is to be tested in. Compounds that bind to isolated recombinant proteins are one thing; chemical tools that can perturb cell function another; and pharmacological agents that can be tolerated by a live organism and perturb its systems are yet another. If it were simple to ascertain the properties required to develop a lead discovered in vitro to one that is active in vivo , drug discovery would be as reliable as drug manufacturing."

In the past, the guinea pig was such a commonly used in vivo experimental subject that they became part of idiomatic English: to be a guinea pig. However, they have largely been replaced by their smaller, cheaper, and faster-breeding cousins, rats and mice .

In vivo imaging provides a noninvasive method for imaging biological processes in live animals in order to understand metabolic processes, effects of drugs and disease progression. Near-infrared (NIR) fluorescent detection has proven useful for in vivo imaging in small animals. Low tissue autofluorescence at 800 nm makes it possible to use probes with NIR labels to image tumors and organs. In vivo imaging is an important tool for any research that uses animal models to study diseases, such as Alzheimer's disease.