Abstract
The extracellular matrix (ECM) consists of polymerized protein monomers that form a unique fibrous network providing stability and structural support to surrounding cells. We harnessed the fibrillogenesis mechanisms of naturally occurring ECM proteins to produce artificial fibers with a heterogeneous protein makeup. Using ECM proteins as fibril building blocks, we created uniquely structured multi-component ECM fibers. Sequential incubation of fibronectin (FN) and laminin (LAM) resulted in self-assembly into locally stacked fibers. In contrast, simultaneous incubation of FN with LAM or collagen (COL) produced molecularly stacked multi-component fibers because both proteins share a similar assembly mechanism or possess binding domains specific to each other. Sequential incubation of COL on FN fibers resulted in fibers with sandwiched layers because COL molecules bind to the external surface of FN fibers. By choosing proteins for incubation according to the interplay of their fibrillogenesis mechanisms and their binding domains (exposed when they unfold), we were able to create ECM protein fibers that have never before been observed.
Highlights
The animal extracellular matrix (ECM) is a heterogeneous connective fiber network composed of various fibrous glycoproteins, proteoglycans (PGs), and small molecules[1,2,3,4,5]
We investigated the formation of multi-component ECM protein fibers, and whether fibrillogenensis mechanisms and protein binding sites could be chosen to form a specific type of multi-component fiber
We discovered that the negatively charged polystyrene sulfonated acid (PSS) surface induced protein unfolding of FN and LAM and subsequent self-assembly into fiber networks but did not have the same effect on COL fibers or adsorbed ELAS fibers, which instead were randomly distributed
Summary
The animal extracellular matrix (ECM) is a heterogeneous connective fiber network composed of various fibrous glycoproteins, proteoglycans (PGs), and small molecules[1,2,3,4,5]. Fibrillogenesis of FN or LAM is a two-step process: self-assembly (propagation step) followed by glycoprotein unfolding (initiation step). The process begins with conformational unfolding of the glycoproteins, followed by spontaneous fibrillogenesis to form FM or LAM fibers. This process depends on the presence of an anionic environment, which is provided by PGs in the ECM. We hypothesized that if fibrillogenesis of two ECM proteins could be initiated and propagated on a charged surface in a similar manner, the proteins would assemble into a single fiber. Fibers were formed by incubating these proteins singly, sequentially, or simultaneously on two types of surfaces, one spin-coated with polystyrene sulfonated acid (PSS) and the other printed www.nature.com/scientificreports/
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