In order to confirm the presence of biofunctional catechol units from L-DOPA on the surface of cured films, we stained samples with an amine-functionalized far-red dye (ATTO 643-amine, imaged in the Cy5 fluorescence channel). If reactive catechols were present on the surface of the cured films, then the primary amine of the dye would be able to attack them via Michael addition or by forming a Schiff base, resulting in an increase in fluorescence (Figure )(in Supplementary Information Figure ). Importantly, this is the same mechanism that is responsible for the pro-adhesive role of catechols , so our assay can confirm both the conjugated amine-functionalized ATTO 643 dye. We further quantified the differences between histograms by Wasserstein distance (also known as "earth mover's distance" or EMD), which can be considered the cost or energy needed to convert one histogram into another . It takes into account both the number of pixels and the intensity difference (distance they need to be moved). Using this approach, we were able to confirm an increase in fluorescence with the higher amounts of L-DOPA: Wasserstein distances for films containing 5% L-DOPA and 10% L-DOPA were 2 and 2.8 times higher versus controls (no L-DOPA), respectively, as compared to within group comparisons and the Wasserstein distance between the two L-DOPA concentrations was 86% of the distance between 5% L-DOPA and the control group, indicating close to a dose response (Figure ). Finally, the fluorescence of the control samples without L-DOPA units was similar to that of sham stained (no dye) samples, confirming specificity of the fluorescence signal to the bioavailability of L-DOPA catechol groups. Overall, we conclude that this fluorescence assay indicates the presence and biofunctionality of L-DOPA catechol units on the surface, with greater amount of L-DOPA content resulting in higher bioavailability of L-DOPA catechol units on the surface of cured films.