Nanotextured porous titanium scaffolds by argon ion irradiation: Toward conformal nanopatterning and improved implant osseointegration

Abstract

Stress shielding and osseointegration are two main challenges in bone regeneration, which have been targeted successfully by chemical and physical surface modification methods. Direct irradiation synthesis (DIS) is an energetic ion irradiation method that generates self‐organized nanopatterns conformal to the surface of materials with complex geometries (e.g., pores on a material surface). This work exposes porous titanium samples to energetic argon ions generating nanopatterning between and inside pores. The unique porous architected titanium (Ti) structure is achieved by mixing Ti powder with given amounts of spacer NaCl particles (vol % equal to 30%, 40%, 50%, 60%, and 70%), compacted and sintered, and combined with DIS to generate a porous Ti with bone‐like mechanical properties and hierarchical topography to enhance Ti osseointegration. The porosity percentages range between 25% and 30% using 30 vol % NaCl space‐holder (SH) volume percentages to porosity rates of 63%–68% with SH volume of 70 vol % NaCl. Stable and reproducible nanopatterning on the flat surface between pores, inside pits, and along the internal pore walls are achieved, for the first time on any porous biomaterial. Nanoscale features were observed in the form of nanowalls and nanopeaks of lengths between 100 and 500 nm, thicknesses of 35‐nm and heights between 100 and 200 nm on average. Bulk mechanical properties that mimic bone‐like structures were observed along with increased wettability (by reducing contact values). Nano features were cell biocompatible and enhanced in vitro pre‐osteoblast differentiation and mineralization. Higher alkaline phosphatase levels and increased calcium deposits were observed on irradiated 50 vol % NaCl samples at 7 and 14 days. After 24 h, nanopatterned porous samples decreased the number of attached macrophages and the formation of foreign body giant cells, confirming nanoscale tunability of M1–M2 immuno‐activation with enhanced osseointegration.

Ion Bombardment-Induced Nanoarchitectonics on Polyetheretherketone Surfaces for Enhanced Nanoporous Bioactive Implants

“…The DPNS technique circumscribes all the modifications caused by momentum deposition of low energy incident ions, which produces a cascade of effect on the material surface, disrupting the surface equilibrium and crystal lattice for a few nanometers of the surface. The surface modifications caused by the specified irradiation parameters corroborate to the surface erosion, chemical modifications, lattice defects, mass redistribution, surface diffusion, preferential sputtering, shift of grain boundaries, surface stress, etc. − This approach directly addresses the challenges present in enhancing PEEK’s properties, circumventing the limitations of other methods. We hypothesize that the physical modifications induced by DPNS foster a more conducive environment for bone cells to attach, spread, and proliferate, the crucial step toward improved osseointegration.…”