Plasma Polymerized Allylamine—The Unique Cell-Attractive Nanolayer for Dental Implant Materials

Abstract

Biomaterials should be bioactive in stimulating the surrounding tissue to accelerate the ingrowth of permanent implants. Chemical and topographical features of the biomaterial surface affect cell physiology at the interface. A frequently asked question is whether the chemistry or the topography dominates the cell-material interaction. Recently, we demonstrated that a plasma-chemical modification using allylamine as a precursor was able to boost not only cell attachment and cell migration, but also intracellular signaling in vital cells. This microwave plasma process generated a homogenous nanolayer with randomly distributed, positively charged amino groups. In contrast, the surface of the human osteoblast is negatively charged at −15 mV due to its hyaluronan coat. As a consequence, we assumed that positive charges at the material surface—provoking electrostatic interaction forces—are attractive for the first cell encounter. This plasma-chemical nanocoating can be used for several biomaterials in orthopedic and dental implantology like titanium, titanium alloys, calcium phosphate scaffolds, and polylactide fiber meshes produced by electrospinning. In this regard, we wanted to ascertain whether plasma polymerized allylamine (PPAAm) is also suitable for increasing the attractiveness of a ceramic surface for dental implants using Yttria-stabilized tetragonal zirconia.

Enhancement of Intracellular Calcium Ion Mobilization by Moderately but Not Highly Positive Material Surface Charges

“…In the present study, the behavior of osteoblastic MG-63s via intracellular Ca 2+ mobilization was systematically investigated on different Ti modifications and correlated with the materials' ζ-potential as a parameter for the electric surface property. We used unmodified Ti (−87.5 mV) and PPAAm coated Ti (+7.1 mV) as controls with negative and positive ζ-potential, respectively, as published before (Mörke et al, 2017;Nebe et al, 2019), knowing that the PPAAm surface modification enhances cell physiology concerning adhesion, spreading, motility (Rebl et al, 2010), actin filament network (Rebl et al, 2016), viability and Ca 2+ mobilization (Moerke et al, 2018;Staehlke et al, 2018), as well as the implant osseointegration (Hoene et al, 2010). Cells bind to this positively charged plasma polymer layer via electrostatic forces, as it is known that osteoblasts (Finke et al, 2007), epithelial cells and chondrocytes (Cohen et al, 2004) express i.a.…”

“…As it is known that the positively charged plasma polymerized allylamine (PPAAm) layer can improve several cell functions ( Rebl et al, 2012 ; Mörke et al, 2017 ; Staehlke et al, 2018 ; Nebe et al, 2019 ), this plasma functionalization of Ti was used as a positive control in all experiments. The specimens were coated with the PPAAm nanolayer by using a low-pressure plasma reactor (V55G, Plasma Finish, Germany) ( Rebl et al, 2012 ) with the following parameters: continuous wave oxygen/argon plasma (500 W, 50 Pa, 1000-sccm O 2 , 5 sccm Ar, 60 s), 480 s PPAAm deposition time.…”

“…In order to gain deeper insights into the impact of surface charges on the cell-material interaction, systematic experiments are required. Our previous work has shown that a plasma polymerized nanolayer of allylamine (PPAAm) provides positive charges on an otherwise negatively charged Ti surface that can boost cell behavior (reviewed in Nebe et al, 2019). The question arose whether a positive ζ-potential is generally considered to be a decisive factor for the cellular outcome.…”

The Hyaluronan Pericellular Coat and Cold Atmospheric Plasma Treatment of Cells

“…Fast cell attachment on the biomaterial surface regulates the cell-material contact and affects the "race for the surface" [10]. Positively charged biomaterial surfaces are shown to enhance the initial osteoblast cell adhesion by electrostatically attracting the cells through their pericellular HA coat [11][12][13][14]. After attachment of the cells to the biomaterial, the HA coat is degraded, and the cells build tighter connections by cell-ECM and cell-cell receptor interactions [15].…”

Efficacy of Plasma-Polymerized Allylamine Coating of Zirconia after Five Years

“…Due to the presence of positively charged carriers such as NH 2 groups on the surface coating [ 23 , 24 ], the net negative charged eukaryotic cells are attracted. For instance, plasma-polymerized allylamine (PPAAm) coatings have been applied on titanium [ 25 , 26 , 27 , 28 , 29 , 30 ], titanium alloy (Ti6Al4V) [ 22 ], porous calcium phosphate [ 31 ] and yttria-stabilized zirconia (Y-TZP) [ 32 ] to improve their hydrophilic properties by generating positively charged amine groups. The resulting zeta potential changed from negative into positive values, e.g., untreated titanium: −82.3 mV and PPAAm-coated Ti: +8.6 mV (pH 7.4) [ 33 ].…”