Nanomechanics on FGF-2 and Heparin Reveal Slip Bond Characteristics with pH Dependency

Sevim, Semih, Ozer, Sevil, Jones, Gabriel, Wurzel, Joel, Feng, Luying, Fakhraee, Arielle, Shamsudhin, Naveen, Ergeneman, Olgaç, Pellicer, Eva, Sort, Jordi, Pané, Salvador, Nelson, Bradley, Torun, Hamdi and Lühmann, Tessa (2017) Nanomechanics on FGF-2 and Heparin Reveal Slip Bond Characteristics with pH Dependency. ACS Biomaterials Science & Engineering, 3 (6). pp. 1000-1007. ISSN 2373-9878

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Abstract

Fibroblast growth factor 2 (FGF-2), an important paracrine growth factor, binds electrostatically with low micromolar affinity to heparan sulfates present on extracellular matrix proteins. A single molecular analysis served as a basis to decipher the nanomechanical mechanism of the interaction between FGF-2 and the heparan sulfate surrogate, heparin, with a modular atomic force microscope (AFM) design combining magnetic actuators with force measurements at the low force regime (1 × 101 to 1 × 104 pN/s). Unbinding events between FGF-2–heparin complexes were specific and short-lived. Binding between FGF-2 and heparin had strong slip bond characteristics as demonstrated by a decrease of lifetime with tensile force on the complex. Unbinding forces between FGF-2 and heparin were further detailed at different pH as relevant for (patho-) physiological conditions. An acidic pH environment (5.5) modulated FGF-2–heparin binding as demonstrated by enhanced rupture forces needed to release FGF-2 from the heparin-FGF-2 complex as compared to physiological conditions. This study provides a mechanistic and hypothesis driven model on how molecular forces may impact FGF-2 release and storage during tissue remodeling and repair.

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