Principles and Strengths of In Vitro Testing

Principles of In Vitro Testing

In vitro is the Latin term for “in glass,” meaning that the testing is performed in a container that is outside of a living organism. This testing uses cell-based biological models instead of animals or humans. In vitro efforts help fulfil the FDA’s “3Rs approach” to replace, reduce, and/or refine animal testing.

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Cytotoxic response to positive control material

In Vitro model systems can be specified to the test sample’s intended use. 2D cell cultures are grown rapidly for high-throughput or multi-sample analysis with minimized variation between treatments. Cell cultures can also be made into 3D tissue models. These models contain differentiated cell layers to physiologically represent complex tissues and evaluate specific endpoints. Using specific geometries, in vitro cell culture models can be used to evaluate simple and complex biological responses.

To assess different biological endpoints, various forms of analytical methods may be implemented. Measurable responses of the in vitro models include cell death, growth inhibition, genetic alterations, changes in surface marker expression and altered metabolism.

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Healthy cell culture

Technical Specifications

  • Cytotoxicity
    • Qualitative evaluation of cell cultures under a microscope
    • Quantification of cell morphology and growth via automated cytotoxicity scoring
    • Quantification using a cell viability reagent, measured by a spectrophotometer
  • Irritation
    • Quantification using a cell viability reagent, measured by a spectrophotometer

Strengths of In Vitro Testing

  • Rapid results
  • Suitable for high throughput testing
  • Economically and ethically favorable compared to animal testing
  • Minimized presence of biological variables
  • 3D tissues results include the effects of cell-cell interaction
  • Several endpoints can be measured
  • Customization of study details during early-stage sample development

Limitations of In Vitro Testing

  • Not all models account for the impact of complex physiological systems such as hormones and immunity
  • Some in vitro models for biological endpoint assessment may not be accepted by all regulatory bodies
  • Cannot identify mechanisms that lead to adverse biological results without further testing or chemical characterization

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