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. Author manuscript; available in PMC: 2020 Oct 22.
Published in final edited form as: ACS Nano. 2019 Oct 1;13(10):11320–11333. doi: 10.1021/acsnano.9b04477

Figure 5.

Figure 5.

Decorin mediates the molecular adhesion of aggrecan. (a, b) Colloidal adhesion force spectroscopy for the measurement of molecular adhesions (a) between aggrecan−aggrecan molecules and (b) between aggrecan−collagen II fibrils in 1× PBS, in the presence and absence of 20 μg/mL free decorin protein. Left panels: Schematics of experimental setup. Middle panels: Representative force−distance curves with or without the addition of free decorin protein. Inset illustrates the calculation of maximum adhesion force, Fad, and total adhesion energy, Ead. Right panels: The addition of free decorin protein significantly increases Fad and Ead of both aggrecan−aggrecan adhesion and aggrecan−collagen II fibrils adhesion (n > 200 repeats for each condition, *: p < 0.001). (c) Ultrastructure of aggrecan−decorin protein complex and aggrecan-only monomers reconstituted on positively charged, APTES-treated mica surface. Left panel: Schematics of experimental setup. Right panel: Tapping mode AFM height images measured in ambient conditions (nominal R < 10 nm, k ≈ 2 N/m) show that aggrecan molecules form interconnected networks when reconstituted with the addition of free decorin protein, but remain as individual monomers when reconstituted without.