Cell viability refers to the state of a cell being alive, healthy, and functional. It represents the proportion of living cells within a given population. Understanding cell viability is fundamental in many scientific and medical fields.
Understanding Cell Viability
A cell is considered viable if it possesses several key characteristics that allow it to perform its biological roles. These include an intact cell membrane, active metabolic processes, and the capacity to carry out essential functions like growth and multiplication. Viable cells maintain their internal environment through a selective barrier, regulating what enters and exits.
In contrast, non-viable cells are damaged, dying, or already dead. These cells typically have a compromised or permeable cell membrane. They also lose metabolic activity and the ability to grow or reproduce.
Dead cells can release various substances into their surroundings. These released components can negatively affect the health and growth of the remaining viable cells. Distinguishing between viable and non-viable cells is therefore important for accurate biological assessment.
Why Cell Viability Matters
In drug discovery and development, researchers use cell viability tests to determine how new compounds affect cells. This helps to identify potential drug candidates by evaluating their effectiveness and toxicity, aiming to minimize harm to healthy cells while targeting diseased ones.
Cell viability also plays a role in disease research, where it helps scientists understand cell health under different conditions. For instance, in cancer research, it helps evaluate how tumor cells respond to treatments. In studies of neurodegenerative disorders, it helps investigate progressive cell loss.
In toxicology studies, measuring cell viability helps assess the harmful effects of various chemicals and environmental contaminants. This information is used to determine safe exposure levels and support risk evaluations. Such studies contribute to protecting public health by identifying hazardous substances.
Furthermore, in tissue engineering and regenerative medicine, cell viability ensures the quality and functionality of cells used for therapeutic purposes. It is a part of quality control to confirm that cells are healthy and potent before their use in treatments. This helps ensure the reliability and safety of cell-based therapies.
Common Ways to Assess Cell Viability
Scientists use several methods to assess cell viability, each focusing on different indicators of cell health. One common method involves evaluating membrane integrity. Tests like the Trypan Blue exclusion assay use dyes that cannot pass through the intact membrane of healthy cells but readily enter cells with damaged membranes.
Another approach measures cellular metabolic activity, reflecting the energy-producing processes within a cell. Viable cells actively produce adenosine triphosphate (ATP) and possess functional enzymes, such as mitochondrial oxidoreductases. These enzymes can convert specific substrates into detectable products, indicating metabolic health.
For example, the MTT assay relies on mitochondrial enzymes in viable cells to reduce a yellow dye into a purple product. The intensity of this color change is directly proportional to the number of metabolically active, viable cells. ATP-based assays measure the light produced from a reaction involving ATP, with more light indicating more viable cells.
Cellular proliferation, or the ability of cells to grow and divide, is also used as an indicator of viability. Methods assessing proliferation often involve measuring DNA synthesis or simply counting cell numbers over time. These diverse assessment methods provide varied insights into the complex state of cell health.