Surface Engineering of Nanostructured Titanium Implants with Bioactive Ions

Abstract

Surface nanofeatures and bioactive ion chemical modification are centrally important in current titanium (Ti) oral implants for enhancing osseointegration. However, it is unclear whether the addition of bioactive ions definitively enhances the osteogenic capacity of a nanostructured Ti implant. We systematically investigated the osteogenesis process of human multipotent adipose stem cells triggered by bioactive ions in the nanostructured Ti implant surface. Here, we report that bioactive ion surface modification (calcium [Ca] or strontium [Sr]) and resultant ion release significantly increase osteogenic activity of the nanofeatured Ti surface. We for the first time demonstrate that ion modification actively induces focal adhesion development and expression of critical adhesion–related genes (vinculin, talin, and RHOA) of human multipotent adipose stem cells, resulting in enhanced osteogenic differentiation on the nanofeatured Ti surface. It is also suggested that fibronectin adsorption may have only a weak effect on early cellular events of mesenchymal stem cells (MSCs) at least in the case of the nanostructured Ti implant surface incorporating Sr. Moreover, results indicate that Sr overrides the effect of Ca and other important surface factors (i.e., surface area and wettability) in the osteogenesis function of various MSCs (derived from human adipose, bone marrow, and murine bone marrow). In addition, surface engineering of nanostructured Ti implants using Sr ions is expected to exert additional beneficial effects on implant bone healing through the proper balancing of the allocation of MSCs between adipogenesis and osteogenesis. This work provides insight into the future surface design of Ti dental implants using surface bioactive ion chemistry and nanotopography.

Multifunctional effects of a modification of SLA titanium implant surface with strontium‐containing nanostructures on immunoinflammatory and osteogenic cell function

“…Cells were cultured for 24 h for the evaluation of mRNA levels of certain integrin genes (α1, α2, α5, αν, β1, and β3) affecting subsequent osteogenic cell functions. Real‐time PCR was performed according to a previously described method, using the primers shown in Table . The gene expression results were expressed as the expression level relative to the SLA surface.…”

“…To produce a microstructured SLA‐type clinical oral implant surface, commercially pure Ti disks (ASTM grade 4, 15 mm diameter and 3 mm thick) were sandblasted using Al 2 O 3 blast media, then acid‐etched in a mixed solution of H 2 SO 4 and HCl (i.e., the SLA surface). Surface Sr modification was performed on SLA samples by wet chemical treatment according to a slight modification of the previously described method . Briefly, SLA samples were treated hydrothermally in a mixed solution of NaOH and SrO at 200°C for 2 h (the Sr‐SLA surface), then thoroughly cleaned and dried.…”

“…J774.A1 cells were cultured on Ti disks in 24‐well culture plates at an initial seeding density of 4 × 10 4 cells/well ( n = 7 per group). Early cellular attachment (at 4 h) and proliferation (at 24 and 48 h) were assessed by CCK‐8 (Dojindo Molecular Technologies, Tokyo, Japan) according to a previously described method …”

“…Mouse bone marrow‐derived ST2 cells were cultured on Ti disks at an initial seeding density of 1 × 10 4 cells/well. The focal adhesion formation and organization of actin filaments of the attached ST2 cells were evaluated after double staining of actin and vinculin using monoclonal anti‐vinculin (Sigma‐Aldrich, St. Louis, MO), goat anti‐mouse IgG (Invitrogen), and fluorescein isothiocyanate (FITC)‐labeled phalloidin (Sigma‐Aldrich) according to a method described previously …”

“…For the evaluation of early cell attachment (at 4 h) and proliferation (at 24 and 48 h of culture) of ST cells, cells were cultured on Ti disks in 24‐well culture plates at an initial seeding density of 2 × 10 4 cells/well. Cell attachment and proliferation were assessed using a CCK‐8 assay kit according to a previously described method ( n = 7 per group) . The absorbance value at the indicated incubation time‐point was measured at 450 nm.…”