In vivo, this pericellular matrix substance lies between the plasma membrane and the ECM to absorb secreted collagen molecules and to provide a scaffold for the final assembly of the ECM fibrils such as collagen [16]. _Electric fields, currents, and charges in tissues_: In their natural niche, many tissues in different areas, such as the brain, skin, muscles, heart, and bones not only generate but also are exposed to different levels of currents and electrical fields [17; 18]. Endogenous electric fields and currents occur e.g., during embryogenesis, as wound potential, as dynamic transmembrane potentials, or by piezoelectric effects in bone [19]. Piezoelectricity is the electric charge that originates from spatial shifts of ions in biological matter but also in solid materials such as crystals in response to applied mechanical stress [20]. Recent studies have shown that bone piezoelectricity may be associated with the piezoelectric properties of bone hydroxyapatite [21]. Although the currents generated in a single microcrystal of bone hydroxyapatite are negligible, the combination of currents generated by moist collagen fibers may probably add up [22], resulting in stronger currents and higher voltages at the ends of the collagen fibers, in whole trabeculae, and even on the surface of bone [21]. These generated \"bone\" currents can also affect bone collagen itself, especially the binding between collagen and hydroxyapatite. Currents generated during dynamic stress (during walking) could promote stability of these bonds [21]. However, also, the collagen molecules and fibrils itself generate piezoelectric effects. [PERSON] isolated individual Col-I fibrils (approximately 100 nm in diameter) from bovine Achilles tendons and revealed that the Col-I fibrils exhibit a piezoelectric coefficient of d\({}_{14}\approx\) 1 pC/N by nanoscale characterization via piezo-response force microscopy [23; 24]. During body movements, bones are under dynamic strain. Such deformations induce a fluid flow in the channels of bone with negative surface charges leading to streaming potentials of the order of a few 10 mV, under typical physiologic loads [25]. The electrical conductivity of bone was characterized via impedance measurements using a voltage of 10 mV [26]. Thisvoltage is below the typical cell membrane potential of 60 to 80 mV [27] and should not disrupt cellular membrane or kill cells in the tissue [26]. In physiological solution, there are no free electrons to carry the current. Thus, electric currents are carried by charged ions [18]. As mentioned above, in the extracellular matrix of tissues and around cells, the glycosaminoglycan hyaluron molecules possess carboxyl groups (C(= O)OH) that are negatively charged. Thus, the development of new surface modification strategies for implant materials can benefit from these physiological phenomena of endogenous fields and charges of the biosystem. _Bioactivation of biomaterial surfaces:_ Due to the aforementioned electrostatic forces between cells and materials at the interface, it was imaginable that positive surface charges could trigger the cell adhesion. Indeed, a chemical surface modification with a nanometer thin plasma polymer layer [28] is sufficient to push the cells' initial adhesion (already after 2 min), as this nanolayer provides positively charged amino groups. This effect is to a greater extent than binding of the ECM protein collagen to the material surface [29]. The early stages of cell-substrate interaction involve cellular attachment, adhesion, and spreading [30], whereby the cell shape changes from spherical to elongated, resulting in a decreased cell height and an increased cell contact area with strengthened adhesion force [31]. This process is critical for normal cell function and successful osseointegration [32], as further cell activities are triggered thereafter.