The first extracellular matrix (ECM) I used when I first started to do 3D assays was Matrigel – as pictured by SEM on the left. However, my concern with Matrigel (an extract from an EHS tumor) is that it is a poorly defined mixture. It is intended to mimic the basement membrane – but there are many assays where a less dense, or better characterized gel is needed.
To that end, I tried a Collagen Type I rat tail extract. It is a far better characterized system (composed of only one protein) and is a looser network, getting closer to the type of ECM cells would expect in an interstitial space.
Above is a movie of melanoma cancer cells moving on top of a Collagen Type I (rat tail) gel which has been stained with Alexa Fluor 647-SE. This stain allows visualization of the collagen fibers. Parts of the matrix can be seen to degrade over time; specifically, a cell in the bottom right quadrant eats through the matrix and then adheres to the underlying glass substrate.