Circular dichroism (CD) spectroscopy was used to examine if the observed differences in released sGAGs stemmed from a direct interaction between the NPs and degraded products, or a direct influence by the NPs on the enzymatic activity (Figure ), as CD spectra report on alterations in protein secondary structure as well as the chirality of optically active molecules. We first measured the CD spectra of the pure biopolymer substrates (HA, ACAN, COL2)