Designing Nanostructured Ti₆Al₄V Bioactive Interfaces with Directed Irradiation Synthesis toward Cell Stimulation to Promote Host–Tissue-Implant Integration

Abstract

A new generation of biomaterials are evolving from being biologically inert toward bioactive surfaces, which can further interact with biological components at the nanoscale. Here, we present directed irradiation synthesis (DIS) as a novel technology to selectively apply plasma ions to bombard any type of biomaterial and tailor the nanofeatures needed for in vitro growth stimulation. In this work, we demonstrate for the first time, the influence of physiochemical cues (e.g., self-organized topography at nanoscale) of medical grade Ti6Al4V results in control of cell shape, adhesion, and proliferation of human aortic smooth muscle stem cells. The control of surface nanostructures was found to be correlated to ion-beam incidence angle linked to a surface diffusive regime during irradiation synthesis with argon ions at energies below 1 keV and a fluence of 2.5 × 1017 cm–2. Cell viability and cytoskeleton morphology were evaluated at 24 h, observing an advance cell attachment state on post-DIS surfaces. These modified surfaces showed 84% of cell biocompatibility and an increase in cytoplasmatic protusions ensuring a higher cell adhesion state. Filopodia density was promoted by a 3-fold change for oblique incidence angle DIS treatment compared to controls (e.g., no patterning) and lamellipodia structures were increased more than a factor of 2, which are indicators of cell attachment stimulation due to DIS modification. In addition, the morphology of the nanofeatures were tailored, with high fidelity control of the main DIS parameters that control diffusive and erosive regimes of self-organization. We have correlated the morphology and the influence in cell behavior, where nanoripple formation is the most active morphology for cell stimulation.

Ion Beam Nanopatterning of Biomaterial Surfaces

“…Furthermore, the orientation and symmetry of these patterns often shows a pronounced dependence on temperature [92]. For polycrystalline surfaces, these effects may result in different orientations of the nanopatterns obtained on different grains [93]. Similar crystallinityrelated effects may also be observed for certain amorphizable materials such as Si or Ge at high temperatures, where the ion-induced damage to the crystal lattice is dynamically annealed during sputtering [56].…”

“…Nanopatterned Ti6Al4V surfaces were also produced by Civantos et al using 1 keV Ar + irradiation at various incident angles [93]. At normal and oblique, non-grazing incidence, surface topographies similar to those described by Riedel et al [126] were obtained, i.e., sub-100 nm ripple patterns with different orientations on different grains.…”

“…Nevertheless, small patterns with periodicities below 100 nm and peak-to-peak amplitudes down to the sub-nanometer level have also been shown to induce significant changes in cell morphology. This in particular concerns the density, length, and alignment of cell extensions such as filopodia [89,93]. This in combination with the fact that ion beam surface modification is a well-established and scalable technology suitable for the processing of large surface areas makes ion beam nanopatterning a promising method for tissue engineering applications.…”

Directed Irradiation Synthesis as an Advanced Plasma Technology for Surface Modification to Activate Porous and “as-received” Titanium Surfaces

“…DIS experiments were performed at the Radiation Surface Science and Engineering Laboratory (RSSEL) in the School of Nuclear Engineering, Purdue University, in the Particle and Radiation Interaction with Soft and Hard Matter (PRIHSM) facility, originally developed and operated by Prof. Jean Paul Allain at Purdue University [27]. DIS conditions are summarized in Table 1; Energy, fluence, and incidence angle were chosen after an exhaustive revision of our previous DIS nano-structuring results on metallic materials [33,34], as well as from some other revised works on Ti, TiO 2 , Cu, Au, and Ag [35][36][37][38][39][40][41][42][43][44][45]. Argon (Ar + ) source at 1 and 0.5 keV was used to irradiate PPS samples and NPS; the selection of DIS parameters were designed to evaluate their effect on nanopatterning.…”

“…Afterwards, the fluorescence signal was read in a microplate reader (Biotek, Synergy) and the results were expressed as relative fluorescence units using c.p. Ti as a control surface for the PPS1 # and PPS1 samples following the method described in a previous work [33]. At 24 h, cytotoxic experiments were performed using The Comet Assay ® (cat.…”