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Poly(lactic acid) (PLA) is the most utilized biodegradable polymer in orthopedic implant applications because of its ability to replace regenerated bone tissue via continuous degradation over time. However, the poor osteoblast affinity for PLA results in a high risk of early implant failure, and this issue remains one of the most difficult challenges with this technology. In this study, we demonstrate the use of a new technique in which plasma immersion ion implantation (PIII) is combined with a conventional DC magnetron sputtering. This technique, referred to as sputtering-based PIII (S-PIII), makes it possible to produce a tantalum (Ta)-implanted PLA surface within 30 s without any tangible degradation or deformation of the PLA substrate. Compared to a Ta-coated PLA surface, the Ta-implanted PLA showed twice the surface roughness and substantially enhanced adhesion stability in dry and wet conditions. The strong hydrophobic surface properties and biologically relatively inert chemical structure of PLA were ameliorated by Ta S-PIII treatment, which produced a moderate hydrophilic surface and enhanced cell−material interactions. Furthermore, in an in vivo evaluation in a rabbit distal femur implantation model, Ta-implanted PLA demonstrated significantly enhanced osseointegration and osteogenesis compared with bare PLA. These results indicate that the Ta-implanted PLA has great potential for orthopedic implant applications.

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Titanium (Ti)-based dental implants with multiscale surface topography have attracted great attention as a promising approach to enhance fixation and long-term stability of the implants, through the synergistic effect of nano- and microscale surface roughness, for accelerated bone regeneration and improved mechanical interlocking. However, structural integrity and mechanical stability of the multiscale roughened Ti surface under deformation need to be considered because significant deformation of dental implants is often induced during the surgical operation. Therefore, in this study, a well-defined nanoporous structure was directly introduced onto micro-roughened Ti surfaces through target-ion induced plasma sputtering (TIPS) with a tantalum (Ta) target, following sand-blasted, large-grit and acid-etching (SLA). This two-step etching process successfully created multiscale surface roughness on Ti with a minimal change of the pre-formed microscale roughness. Moreover, TIPS allowed the Ti surface to possess good mechanical stability under deformation and improved hydrophilicity, through altering the surface chemistry of brittle and hydrophobic SLA-treated Ti without formation of the interface between nanoporous and microporous structures. The in vitro and in vivo tests confirmed that multiscale roughened Ti significantly enhanced osteoblast attachment, proliferation and differentiation, which eventually led to improved bone regeneration and osseointegration, compared to smooth and micro-roughened Ti.

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