The use of Brillouin spectroscopy to study the effects of matrix metalloproteinases on the extracellular matrix during cancer metastasis

A cancer cell secretes certain matrix metalloproteinases (enzymes) to degrade the surrounding extracellular matrix (ECM), and disrupt the basement membrane. However, the exact mechanism by which the cell affects the surrounding tissue and the cancer begins to metastasize is not well documented. To better understand how the cells affect the ECM, we use Brillouin spectroscopy to study how these enzymes change the bulk modulus of the ECM. Brillouin spectroscopy is a technique used to measure the energy difference between light that is elastically and inelastically scattered by the sample. The energy difference is caused by the annihilation or creation of a phonon in the sample, and can be used to determine the speed of sound in a material. From these values the bulk moduli can be calculated. Our samples are Matrigel, a basement membrane matrix, that has been exposed to type I collagenase such that the proteins in Matrigel are cleaved by the enzyme. The degree of matrix degradation is quantified by the exposure time, and therefore, the percent of the proteins that have been cleaved by the enzyme. The corresponding Brillouin spectra are used to show that there is a nonlinear relationship between the elastic constant of Matrigel and the percent scission of the proteins.