Macrophage-like Cells Are Responsive to Titania Nanotube Intertube Spacing—An In Vitro Study

Abstract

With the introduction of a new interdisciplinary field, osteoimmunology, today, it is well acknowledged that biomaterial-induced inflammation is modulated by immune cells, primarily macrophages, and can be controlled by nanotopographical cues. Recent studies have investigated the effect of surface properties in modulating the immune reaction, and literature data indicate that various surface cues can dictate both the immune response and bone tissue repair. In this context, the purpose of the present study was to investigate the effects of titanium dioxide nanotube (TNT) interspacing on the response of the macrophage-like cell line RAW 264.7. The cells were maintained in contact with the surfaces of flat titanium (Ti) and anodic TNTs with an intertube spacing of 20 nm (TNT20) and 80 nm (TNT80), under standard or pro-inflammatory conditions. The results revealed that nanotube interspacing can influence macrophage response in terms of cell survival and proliferation, cellular morphology and polarization, cytokine/chemokine expression, and foreign body reaction. While the nanostructured topography did not tune the macrophages’ differentiation into osteoclasts, this behavior was significantly reduced as compared to flat Ti surface. Overall, this study provides a new insight into how nanotubes’ morphological features, particularly intertube spacing, could affect macrophage behavior.

Nanotopographical cues for regulation of macrophages and osteoclasts: emerging opportunities for osseointegration

“…In addition, the specific nanotube topography engineered in each research exists differences compared to others. For example, the gaps between adjacent nanotubes may be different even with same diameter [ 125 ].…”

Osteointegration of Ti Bone Implants: A Study on How Surface Parameters Control the Foreign Body Response

“…For example, Necula et al observed that RAW 264 macrophages on superhydrophilic Ti nanotubes with 80 nm diameter and 80 nm spacing decreased the expression of pro-inflammatory marker CCR7 after 1 and 3 days compared to 20 nm spaced nanotubes. 80 The effect of nanocavitation, or the formation of nanospaces, was observed by Ariganello et al on Ti nanonetworks with pits of 20−22 nm diameter, root−mean−square roughness of 17 nm, and depths of 10−20 nm. These surfaces promoted U937 macrophage secretion of anti-inflammatory markers by decreasing IP10/ CXCL10 and MIP3α/CCL20 ratios.…”

“…Macrophages also respond to the nanofeature spacing and nanofeature depth. For example, Necula et al observed that RAW 264 macrophages on superhydrophilic Ti nanotubes with 80 nm diameter and 80 nm spacing decreased the expression of pro-inflammatory marker CCR7 after 1 and 3 days compared to 20 nm spaced nanotubes . The effect of nanocavitation, or the formation of nanospaces, was observed by Ariganello et al on Ti nanonetworks with pits of 20–22 nm diameter, root–mean–square roughness of 17 nm, and depths of 10–20 nm.…”

“…Integrins are transmembrane receptors that connect the extracellular matrix to the cytoskeleton and adhesion-associated scaffolding and signaling proteins (e.g., paxillin, talin, focal adhesion kinase (FAK), Pyk2, and Src) which traduce mechanical stimuli into biological signals that regulate macrophage functions and expression (Figure 4b). 80,82,96 The activation of FAK and Src leads to activation of Rho/ ROCK pathways (Figure 3c) involved in actin polymerization. Polymerization of actin results in the nuclear translocation of transcription factors such as yes-associated protein (YAP), mechanosensitive transcriptional cofactors, and myocardin related transcription factor-A (MRTF-A), activating NFκB signaling pathway and upregulating pro-inflammatory genes (Figure 4d).…”

Surface characterization, electrochemical properties and in vitro biological properties of Zn-deposited TiO2 nanotube surfaces

“…Numerous well-ordered TiO 2 nanotube arrays can be fabricated on Ti surfaces by altering the AO parameters such as current, voltage, time, electrolyte composition etc. 19 , 20 .…”