Tissue Engineering Measurands

Summary

Cell viability is often measured as a quality metric of tissue engineered medical products.  However, there are a number of inherent assumptions about cell viability measurements that make them difficult to discuss.  A “measurand chart” maps each of the measurands present in a measurement process to graphically represent their relationships and uncover the hidden assumptions. 

Description

Making a Measurand Chart: 

• A measurand chart can be created for any measurement by writing down all the measurands that occur during the measurement.
• The panels should not be procedural steps, such as “wash the sample with buffer” or “centrifuge the microfuge tubes”.
• Consider if the measurement has a light source, a sensor, or a detector, since these will generate measurands.
• If there is a numerical readout or generation of a data file, consider how these may be analyzed.
• Think about equations that are used.
• Identify the "primary measurand," which should plainly state what is being measured in only a few words.
• Think about key assumptions.
• Consider how the data will be used in terms of decision-making.
• The panels should start with words such as “amount of”, “concentration of”, or “number of”.
• Finally, the panels should be linkable by placing the words Measure the in front of the first measurand and by measuring between the rest.
• These are not firm rules but guidelines. If the chart helps improve understanding of a measurement, then the goal is met.

 

Definition of “Measurand”:

noun, the quantity or property intended to be measured

• Use of the word “intended” in this definition is intentional
  • It may not be possible to measure what you intend to measure
  • Or you may not be measuring what you intend to measure (due to experimental artifacts) 
• A measurement can have multiple measurands
• Source: International Vocabulary of Metrology - Basic and General Concepts and Associated Terms (VIM), 3rd Edition. Joint Committee for Guides in Metrology (JCGM) 200:2012.

Definition of a “Viable Cell”:

noun, a cell that has 1) an intact membrane and the 2) capacity for metabolism, 3) motility, 4) proliferation, and 5) reaction to stimuli

Slides: TE_measurands.pdf

References: 

Arora D, Babakhanova G, Simon Jr CG (2020) Tissue engineering measurands. ACS Biomaterials Science & Engineering 6, 5368-5376. https://doi.org/10.1021/acsbiomaterials.0c00475

Simon CG, Borgos SE, Calzolai L, Nelson BC, Parot J, Petersen EJ, Roesslein M, Xu X, Caputo F (2023) Orthogonal and complementary measurements of properties of drug products containing nanomaterials. Journal of Controlled Release 354, 120-127. https://doi.org/10.1016/j.jconrel.2022.12.049

Simon Jr CG, Bozenhardt EH, Celluzzi CM, Dobnik D, Grant ML, Lakshmipathy U, Nebel T, Peltier L, Ratcliffe A, Sherley JL, Stacey GN, Taghizadeh RR, Tan EHP, Vessillier S (2024) Mechanism of Action, Potency and Efficacy: Considerations for Cell Therapies. Journal of Translational Medicine 22:416. https://doi.org/10.1186/s12967-024-05179-7