Cell viability and cell toxicity are related but distinct concepts in cellular biology, particularly when assessing cellular health and responses to various treatments. They focus on opposite ends of the spectrum, measuring different aspects of cellular state.
Cell Viability
Definition: Cell viability refers to the ability of cells to live, function, and proliferate. It is a measure of how many cells in a population are alive and healthy at a given time. Cell viability assays determine the number of living cells within a sample, either relative to a control or as an absolute number.
Key characteristics of cell viability:
- Focus: Measures the number or proportion of living cells.
- Indicators: Assesses markers of cell health and activity such as:
- Metabolic activity (e.g., reduction of tetrazolium salts)
- Membrane integrity
- Enzyme activity
- Cellular proliferation.
- Function: A function of cellular proliferation (growth and division) and death.
- Example: A cell viability assay could determine if a cell culture is successfully growing or if a treatment is hindering proliferation.
- Measured using: A cell viability assay.
Cell Toxicity (Cytotoxicity)
Definition: Cell toxicity or cytotoxicity measures the extent to which a substance or condition is harmful or lethal to cells. It quantifies the number or proportion of dead cells in a population, indicating the destructive effect of a specific agent.
Key characteristics of cell toxicity:
- Focus: Measures the number or proportion of dead cells.
- Indicators: Assesses markers of cell death, such as:
- Membrane damage (e.g., release of cellular contents)
- DNA fragmentation
- Apoptosis (programmed cell death)
- Necrosis (uncontrolled cell death)
- Function: Directly indicates cellular damage and cell death induced by external factors.
- Example: A cytotoxicity assay might determine if a drug is effectively killing cancer cells or if an environmental toxin is causing cellular damage.
- Measured using: A cytotoxicity assay.
Key Differences Summarized
| Feature | Cell Viability | Cell Toxicity (Cytotoxicity) |
|---|---|---|
| Focus | Living cells | Dead cells |
| Measurement | Number or proportion of living cells | Number or proportion of dead cells |
| Indicators | Markers of cellular health and activity | Markers of cell death and damage |
| Relationship | Affected by cell proliferation and cell death | Indicates cell damage and death |
| Assays | Cell Viability Assays | Cytotoxicity Assays |
Practical Implications
Understanding both cell viability and cytotoxicity is critical in various research fields:
- Drug discovery: Evaluating if a new drug candidate is effectively killing cancer cells while preserving healthy cells (high cytotoxicity, low impact on viability).
- Toxicology: Assessing the effects of chemicals, pollutants, or other substances on cells.
- Biomaterials research: Measuring the biocompatibility of materials by determining their impact on cellular health.
- Cell-based therapies: Ensuring that cells used for therapy are viable and functional.
In conclusion, cell viability and cytotoxicity are complementary measures. While cell viability assays assess the health and proliferation of living cells, cytotoxicity assays quantify cell death and damage, providing a comprehensive view of cellular responses to various factors.
