Abstract
Surface charges at the cell–biomaterial interface are known to determine cellular functions. Previous findings on cell signaling indicate that osteoblastic cells favor certain moderately positive surface charges, whereas highly positive charges are not tolerated. In this study, we aimed to gain deeper insights into the influence exerted by surface charges on the actin cytoskeleton and the cell shape. We analyzed surfaces with a negative, moderately positive, and highly positive zeta (ζ) potential: titanium (Ti), Ti with plasma polymerized allylamine (PPAAm), and Ti with a polydiallyldimethylammonium chloride (PDADMA) multilayer, respectively. We used the software FilaQuant for automatic actin filament quantification of osteoblastic MG-63s, analyzed the cell edge height with scanning ion conductance microscopy (SICM), and described the cellular shape via a mathematical vertex model. A significant enhancement of actin filament formation was achieved on moderately positive (+7 mV) compared with negative ζ-potentials (−87 mV). A hampered cell spreading was reflected in a diminished actin filament number and length on highly positively charged surfaces (+50 mV). Mathematical simulations suggested that in these cells, cortical tension forces dominate the cell–substrate adhesion forces. Our findings present new insights into the impact of surface charges on the overall cell shape and even intracellular structures.
Highlights
In bone tissue engineering, chemical [1,2,3] and topographical [4,5,6] surface modifications have been proven to be a powerful tool in optimizing implant designs for clinical applications in dental and orthopedic surgery in terms of interaction with osteoblastic cells
Α2β1 integrin is the target for collagen I, α5β1 is the target for fibronectin, and αvβ3 is the target for bone sialo protein, molecules i.a. localized in the organic bone matrix
We focused on the quantification of the cellular actin organization on mithe three croscopy was applied to visualize the actin cytoskeleton after and h and the quantidifferently charged surfaces: Ti (−), plasma polymerized allylamine (PPAAm) (+), and polydiallyldimethylammonium chloride (PDADMA) (++)
Summary
Chemical [1,2,3] and topographical [4,5,6] surface modifications have been proven to be a powerful tool in optimizing implant designs for clinical applications in dental and orthopedic surgery in terms of interaction with osteoblastic cells. During the implantation of a biomaterial in the body, the cells and tissues immediately face the material surfaces, which are artificial for the biosystem These artificial surfaces, e.g., metals, are without any ligands for cellular adhesion, and the cells have to find a way to adhere and grow in the initial contact phase. One way is to provide vital biological cues for the specific adhesion by coating metal surfaces with molecules of the ECM including collagen I, fibronectin, peptides, and glucosamines [11,12,13]
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