Processes performed outside a living organism in controlled laboratory settings
Explanation
In vitro, meaning “in glass,” refers to experiments and procedures conducted outside of living organisms. Biological materials such as cells, tissues, enzymes or nucleic acids are isolated from their normal context and studied in test tubes, petri dishes or multi-well plates. In vitro systems allow investigators to control temperature, pH, nutrient composition and other variables to study specific biochemical pathways or cellular responses without the complexity of a whole organism. Cell culture, for example, permits growth of mammalian or microbial cells under defined conditions for studying gene expression, drug responses or microbial pathogenicity. In vitro assays are essential for high-throughput screening of potential therapeutics, assessing toxicology, analysing enzyme kinetics and detecting pathogens. They can employ purified proteins, organoids or synthetic matrices to model aspects of physiology. However, in vitro results may not fully predict in vivo behaviour because they lack systemic influences such as metabolism, immune responses, hormonal signals and three-dimensional tissue architecture. Researchers often use in vitro studies as initial steps before moving to animal models or clinical trials.
Illustrative examples and uses
Examples of in vitro techniques include polymerase chain reaction for amplifying DNA, enzyme-linked immunosorbent assays to measure antibodies, and antibiotic susceptibility testing using bacterial cultures. In vitro fertilization involves combining gametes in a culture dish before implantation. Cytotoxicity assays expose cultured cells to chemicals or nanoparticles to evaluate safety. Viral neutralization tests mix virus particles with serum or antibodies to assess immune protection. Biochemical assays performed on purified enzymes or receptor proteins determine binding affinities and reaction rates. In the pharmaceutical industry, high-throughput screening of compound libraries relies on automated in vitro assays to identify candidates with desired biological activity.
In vitro methods provide reproducible and ethical approaches to dissect biological mechanisms and screen interventions before more complex studies. They complement in vivo research by offering precise control and scalability.
Related Terms: In vivo, Cell culture, Ex vivo, Organ culture, Assay