The role of well-defined nanotopography of titanium implants on osseointegration: cellular and molecular events in vivo

Abstract

Purpose Mechanisms governing the cellular interactions with well-defined nanotopography are not well described in vivo. This is partly due to the difficulty in isolating a particular effect of nanotopography from other surface properties. This study employed colloidal lithography for nanofabrication on titanium implants in combination with an in vivo sampling procedure and different analytical techniques. The aim was to elucidate the effect of well-defined nanotopography on the molecular, cellular, and structural events of osseointegration. Materials and methods Titanium implants were nanopatterned (Nano) with semispherical protrusions using colloidal lithography. Implants, with and without nanotopography, were implanted in rat tibia and retrieved after 3, 6, and 28 days. Retrieved implants were evaluated using quantitative polymerase chain reaction, histology, immunohistochemistry, and energy dispersive X-ray spectroscopy (EDS). Results Surface characterization showed that the nanotopography was well defined in terms of shape (semispherical), size (79±6 nm), and distribution (31±2 particles/µm 2 ). EDS showed similar levels of titanium, oxygen, and carbon for test and control implants, confirming similar chemistry. The molecular analysis of the retrieved implants revealed that the expression levels of the inflammatory cytokine, TNF-α , and the osteoclastic marker, CatK , were reduced in cells adherent to the Nano implants. This was consistent with the observation of less CD163-positive macrophages in the tissue surrounding the Nano implant. Furthermore, periostin immunostaining was frequently detected around the Nano implant, indicating higher osteogenic activity. This was supported by the EDS analysis of the retrieved implants showing higher content of calcium and phosphate on the Nano implants. Conclusion The results show that Nano implants elicit less periimplant macrophage infiltration and downregulate the early expression of inflammatory ( TNF -α) and osteoclastic ( CatK ) genes. Immunostaining and elemental analyses show higher osteogenic activity at the Nano implant. It is concluded that an implant with the present range of well-defined nanocues attenuates the inflammatory response while enhancing mineralization during osseointegration.

Inflammatory cell response to ultra-thin amorphous and crystalline hydroxyapatite surfaces

“…This assumption is supported by an in vitro study showing that a murine-macrophage (RAW264.7) increased the expression of TNF-α in response to surfaces with a groove-shaped nano-topography [32]. Another plausible explanation is that the macrophage response is also dependent on other surface characteristics, including surface chemistry, regardless of whether it is HA, as in the present study, or titanium, as in the previous in vivo study [46]. The influence of chemistry in relation to nano-topography has been previously addressed in an in vivo study, where nano-topography did not modify the in vivo bone response to the same extent as the chemistry did [47].…”

“…This finding implies an association between nano-topography and increased pro-inflammatory activity. In contrast, a recent in vivo study has shown that titanium implants with controlled nano-topography (80 nm hemispherical protrusions) resulted in the lower recruitment of macrophages and lower TNF-α expression in the implant-adherent cells compared with implants without nano-topography [46]. One plausible explanation is that the effect of nano-topography on macrophages is dependent on the shape and size of the nano-features.…”

Pheochromocytoma (PC12) Cell Response on Mechanobactericidal Titanium Surfaces

“…Enhanced osseointegration has frequently been observed in cases where modified Ti substratum have been implanted into an animal model, and under conditions where the Ti implants are exposed to normal bodily fluids and proteins [ 34 , 35 , 36 ]. A study investigating the implantation and response of a modified Ti surface possessing titanium dioxide nanorods in rabbit femurs achieved better osseointegration and higher rates of bone tissue apposition of the nanostructured Ti, compared to classically treated (acid etched, grit blasted) micro-rough Ti surfaces [ 34 ].…”

The Role of the Chemokine System in Tissue Response to Prosthetic By-products Leading to Periprosthetic Osteolysis and Aseptic Loosening

“…Moreover, there is a growing body of evidence about the direct and rapid influence of implant surface treatments on the modulation of the expression of chemokine receptors that are important for cell recruitment and adhesion, both processes being crucial for the inflammatory and regenerative processes in vivo ( 110 , 111 ). An appropriate implant surface may attenuate the inflammatory response while enhancing mineralization during osseointegration, as shown for implants with nano-surfaces ( 112 ) or the synthetic lipid polymer 2-methacryloyloxyethyl phosphorylcholine ( 113 ).…”