The role of material’s zeta potential on intracellular calcium ion signalingTuesday (18.06.2019) 20:02 - 20:03
Biomaterial surfaces for bone implants are modified to achieve a faster attachment of osteoblasts and thus a better osseointegration and regeneration of the surrounding tissue. In this, the material´s physico-chemical properties play an essential role as they are known to affect the cell physiology at the interface . It has been found out that a positively charged, amino-group containing titanium (Ti) surface can amplify osteoblastic cell functions [2-4] such as the calcium ion (Ca2+) mobilization . We hypothesize that surface charges play a crucial role in the material-cell interaction.To confirm this, we currently investigate the intracellular Ca2+ dynamic on Ti modifications with different surface charges.
We chemically modify plane silicon-Ti arrays (10x10 mm, ZfM, TU Chemnitz) by (i) amino functionalization via coating with the monomer allylamine by a pulsed plasma polymerization process (PPAAm) , (ii) polyelectrolyte multilayers (terminated with polydimethyldiallylammonium chloride using layer-by-layer assembly  and (iii) coatings with collagen-type I, Matrigel (basement membrane-like matrix) and the integrin adhesion peptide sequence Arg-Gly-Asp (RGD). We determine the surface charge by zeta potential measurements and the wettability by water contact angle measurements . To evaluate the surface property-dependent mobilization of intracellular Ca2+, human MG-63 osteoblasts (ATCC) are stained with the calcium dye Fluo 3-acetoxymethyl ester and stimulated with adenosine 50-triphosphate to induce an immediate Ca2+ signal .
Our data have shown, especially for the positively charged PPAAm surface (zetapotential:+ 8.6 mV), a high increase of intracellular Ca2+ ions following an ATP stimulation (mean fluorescence intensity (MFI) level at 188–480 s: 89.1±1.9, mean±sem) compared to cells on uncoated Ti (MFI level at 188–480 s: 51.9±0.6, mean±sem) (n=3) .
Hence, we assume that the influence of a positive zeta potential on the cellular behavior dominates other surface properties like wettability. However, it is important to extend these studies to investigate which properties are favored by osteoblastic cells.
 Moerke et al, J Cell Sci 131: jcs207001, 2018
 Finke et al, Biomaterials 28: 4521-4534, 2007
 Rebl et al, Acta Biomater 8: 3840-3851, 2012
 Kunz et al, Eur Cell Mater 29: 177-189, 2015
 Staehlke et al, Cell Biosci 8(22), 2018
 Decher et al, CurrOpin Colloid Interface Sc 3(1): 32-39, 1998