FAQ: Radius™ Cell Migration Assays

Q: How does the Radius™ assay work?

A: Our Radius assay uses a plate that contains a biocompatible hydrogel at the center of the well; seeded cells will attach everywhere but on the hydrogel. After cells attach, the gel is removed by addition of a removal solution and the assay begins. 


Q: What cell lines are compatible with the Radius assay?

A: Any adherent cell line is compatible with the Radius assay. 


Q: Can the Radius™ plate be used over multiple experiments?

A: Each well of the Radius Cell Migration plate may be used only once, but the plate may be stored and unused wells may be used up to two additional times.  We do not recommend using the Radius plate more than three times because this will result in the plate undergoing extended incubation periods that can affect the integrity of the gel spot, causing it to become weaker and possibly lifting off the plate.  


Q:  Can I coat the wells of the Radius™ plate myself?

A: Unfortunately it is not possible to coat the wells of the Radius assay, which have a gel spot already on the plate, since any coating that is applied to the well will not get under the gel spot.  We offer 24-well Radius Assays that are pre-coated with either Collagen, Fibronectin, Laminin, or an ECM array of all 3 proteins.


Q: Are the gel spots the same size on both the 24 and 96-well plates?

A: Yes, both plates have the same size gel spot.


Q: Is the gel spot visible on the plate? 

A: The gel spot is only 0.68mm and is difficult to see under a phase contrast microscope.  The spot will become visible once a cell monolayer forms.


Q: Can the Radius™ Assay be used in place of a Boyden Chamber Assay?

A: The Radius Assays can be used for most applications including the following:

  • Measuring the effect of a drug treatment on cell migration rates
  • Measuring the effect of gene up- or down-regulation on cell migration rates
  • Measuring the relative migration rates of normal vs. diseased cells

The only application that would not be suitable with the Radius™ Assays is studying the effect of a chemoattractant on cell migration, where a concentration gradient is required between the cells and the location where they are moving.


Q: Can this be used for chemotaxis?

A: This assay measures migration of cells towards the center of the well, but it is not designed to be used with a chemoattractant because it is not possible to establish a chemoattractant gradient.


Q: Is the gel removal step toxic to cells?

A: The Radius™ Gel Removal Solution uses an enzyme to remove the hydrogel spot in less than 30 minutes and is not toxic to cells, regardless of cell type.


Q: Can I seed a higher number of cells than recommended?

A: Cells can be seeded at a higher concentration as long as the cells are 80-90% confluent when starting the assay. If over confluent, the cells can put pressure on the hydrogel spot and start growing underneath.


Q: What is the maximum time for incubating cells prior to gel spot removal?

A: The gel spot is only stable for up to 24 hours when in media. Incubation periods longer than this can affect the integrity of the gel spot, causing it to become weaker and possibly lifting off the plate. 


Q: Is there a recommended positive control cell line?

A: Our recommended cell lines to use a positive control are HT-1080, HeLa, MDA-MB-231, MCF7, or A549


Q: When should the cells be stained with Calcein AM when performing a time course experiment?

A: To perform a time course with this assay, we recommend staining cells with Calcein AM before the gel removal step.  This will allow you to monitor time 0 immediately after the gel removal with the cells already stained.


Q: How can I inhibit cell proliferation and measure only migration?

A: In order for cells to migrate, they must reorganize their cytoskeleton and microtubules, which are processes that are also involved in cell proliferation.  Because of the complexity and similarity of these two processes, we don’t believe that there is a cell proliferation specific inhibitor that will not also affect migration.  The incubation period for this assay is 4-24 hours, so growth should not be a concern if at the low end of this range.   Cell density can be optimized so that a shorter incubation time can be used.


Q: There are cells growing over the gel spot. Should I be worried?

A: The cells that are growing over the gel spot will not affect the results.  There will always be some cells that settle onto the top of the gel but they will be removed after the gel removal step to form a perfect, clear circle.  Cell density can be optimized using a regular 24 well plate prior to running the assay so that cells reach 80-90% confluency.


Q: After removing the gel spot there is a confluent monolayer of cells where the gel spot was. What happened?

A: It is possible that the cell seeding density was too high and the cells are over confluent, which will put pressure on the gel spot during the attachment period.  When this happens, the cells can slip underneath the gel and start growing in the middle before the gel removal step.  To avoid this, you can seed with fewer cells and reduce the time for cell attachment.