Editorial: Metallic biomaterials for medical applications - volume II

Metallic biomaterials underpin many of the devices that clinicians use every day: titanium hip and knee prostheses, spinal fixation systems, dental implants, and cobalt-chromium or nitinol vascular stents. These alloys enable millions of arthroplasties, spinal fusions and endovascular procedures annually, yet their clinical success is still limited by stiffness mismatch and stress shielding, periprosthetic infection, corrosion and wear in harsh physiological environments, and by the largely passive role that implants play in modulating local inflammation and tissue regeneration. This Research Topic, Metallic biomaterials for medical applications -volume II, brings together four original contributions that address these challenges through surface nano-texturing, compositionally tailored 3D-printed alloys, mechanically informed porous architectures and bioresorbable neurovascular implants. In total, 40 authors from institutions in Germany, Italy, China and the United States contribute to this Research Topic, reflecting the global nature of metallic biomaterials research and its clinical relevance across diverse healthcare systems.

Schweitzer et al. employ ultraviolet laser-induced periodic surface structures (UV-LIPSS) on Ti6Al7Nb to interrogate how controlled nanotopography modulates osteoblast function and bacterial colonization. Using ultra-short-pulse ultraviolet laser machining, they generate well-defined nano-periodic topographies with spatial periodicities in the 200–300 nm range on arthroplasty-grade alloys. Primary human osteoblasts cultured on these UV-LIPSS surfaces show preserved viability, enhanced osteogenic function—evidenced by increased alkaline phosphatase activity—and a shift toward a less pro-inflammatory cytokine profile, compared with polished controls. In parallel, Staphylococcus aureus biofilm formation, quantified by wheat germ agglutinin staining, is reduced on UV-LIPSS Ti6Al7Nb. Together, these results support a design strategy in which surface nano-patterning alone, without altering bulk alloy chemistry, can both promote osseointegration and reduce bacterial colonisation on orthopaedic implants.

Luo et al. extended the design freedom from the surface to the whole by combining alloys with additive manufacturing used for guided bone regeneration (GBR). Luo et al. use selective laser melting to fabricate Ti–xCu meshes (x = 0, 4, 6, 8 wt%) tailored for personalized GBR in dental implantology. Increasing Cu content promotes Ti₂Cu precipitation in the α-Ti matrix and increases copper ion release, but without sacrificing corrosion resistance in physiological media. Alloys containing more than 4 wt% Cu achieve over 90% reduction of S. aureus and E. coli, while Ti–6Cu, in particular, balances high antibacterial efficacy with favourable osteoblast proliferation, upregulation of osteogenic genes, and an anti-inflammatory shift in macrophage-related markers. This work exemplifies how composition–microstructure design can be leveraged to integrate antibacterial and immunomodulatory functions into load-bearing metallic meshes for complex maxillofacial defects.

Stress shielding at the bone–implant interface remains a central concern in orthopaedics, especially as porous, lattice-like designs become mainstream. Ramagali Amadasi et al. address this issue with an integrated experimental and analytical framework that quantifies how porous metal scaffolds share load with cortical bone. Using bovine cortical bone blocks with machined cavities housing CoCrMo or Ti6Al4V scaffolds (porous or full-density), the authors combine axial compression tests, digital image correlation, finite element analysis, and a spring-based analytical model to resolve strain distributions in the bone. Porous scaffolds drive bone strain patterns closer to those of intact bone than full-density inserts, confirming their potential to mitigate stress shielding. Within this space, Ti6Al4V scaffolds provide more favourable reaction forces and strain transfer than CoCrMo, and scaffolds with 1,000 μm pores outperform 500 μm pores in restoring physiologic load transfer. These insights offer practical guidance for selecting both material and pore architecture in next-generation joint and spine implants.

The Research Topic also highlights the opportunities and pitfalls of degradable metallic devices in the vascular system. Oliver et al. report a brief research study on braided bioresorbable flow diverters (BRFDs) fabricated from an iron–manganese–nitrogen (FeMnN) alloy, evaluated in the rabbit elastase-induced aneurysm model. In a rabbit elastase-induced aneurysm model, FeMnN BRFDs are deployed and followed for 3 months. Despite earlier benchtop data showing adequate radial strength, flow diversion and MRI compatibility, most aneurysms remain incompletely occluded at the study endpoint. Angiography, gross inspection and histology reveal that the FeMnN wires resorb and fragment too rapidly at the aneurysm neck, so that the braid loses mechanical continuity before a stable neointimal layer can fully seal the aneurysm. Importantly, where FeMnN wires persist they are well integrated into neotissue, indicating that the alloy is biologically acceptable and that the limitation is primarily a resorption–mechanics mismatch rather than a failure of tissue healing. As such, this “negative” in vivo outcome is a constructive boundary condition for future designs, emphasising that wire diameter, braid architecture and corrosion kinetics must be co-optimised to align scaffold persistence with the 6–12-month time window typically required for intracranial aneurysm occlusion.

Taken together, the four contributions in Metallic biomaterials for medical applications–volume II illustrate a coherent design philosophy for metallic implants. UV-LIPSS surface engineering offers a purely physical, contamination-free route to improve bone–implant integration and reduce biofilm formation on established titanium alloys. Compositionally tailored, 3D-printed Ti–Cu meshes demonstrate how additive manufacturing can encode antibacterial and immunomodulatory behaviour into patient-specific dental devices. Mechanically informed studies of porous Ti6Al4V and CoCrMo scaffolds clarify how pore size, porosity and alloy stiffness govern load transfer and strain fields in cortical bone, with direct implications for long-term bone preservation. Finally, the FeMnN BRFD work illustrates that degradability per se is not an advantage unless the degradation profile is carefully matched to the biomechanics and healing timelines of the target vascular bed.

Although the authors contributing to this Research Topic work in Germany, Italy, China and the United States, the clinical questions they address are truly global. For example, ageing populations and high rates of osteoporosis-related fragility fractures in Latin America are expected to increase the demand for joint replacement and fracture fixation, often in health systems with constrained resources. In such settings, robust metallic implants that resist infection, preserve bone stock and avoid costly revision surgery are particularly valuable. Similarly, dental implantology in regions such as Brazil and other parts of Latin America must contend with population-specific bone density distributions and variable access to advanced imaging and customised devices, reinforcing the importance of designs that are both biofunctional and cost-effective. Collaborations that link centres with strong biomaterials research capabilities in Europe, Asia, North America and Latin America will therefore be essential to translate the concepts showcased in this Research Topic into widely accessible clinical solutions.

Looking ahead, several concrete directions emerge. First, there is a need for multi-objective optimisation frameworks that treat alloy composition, processing parameters, pore architecture and surface state as jointly tunable variables rather than as independent design knobs. Machine-learning models trained on curated datasets could integrate, for example, corrosion and degradation rates in simulated body fluids, ion release profiles, mechanical properties of lattice libraries (elastic modulus, yield strength, fatigue life), in vitro cell viability and differentiation metrics, and small-animal implantation outcomes. Such models could be used to rapidly screen candidate alloys and architectures, identify Pareto-optimal designs, and prioritise only the most promising combinations for large-animal studies, thereby reducing the overall animal burden.

Second, translational studies should be conducted in clearly defined, clinically relevant environments. For orthopaedic load-bearing devices, ovine or caprine long-bone and large-joint models, which reproduce cortical thickness and loading patterns similar to human bone, are particularly informative. For cardiovascular and neurovascular implants, porcine coronary and carotid models, or rabbit elastase-induced aneurysm models as used by Oliver et al., provide complementary information on device deployment, haemodynamics and healing. Explicitly matching animal model, anatomical site, loading regime and follow-up duration to the intended clinical indication will make preclinical datasets more comparable and more predictive of human outcomes.

Third, as advanced surface modification and texturing (including UV-LIPSS, laser remelting, plasma treatments and bio-inspired coatings) and additive manufacturing/3D printing become routine in both academic laboratories and industry, standardisation of descriptors and testing protocols becomes critical. For surfaces, parameters such as arithmetic roughness (Ra), root-mean-square roughness (Rq), feature periodicity and wettability (contact angle) should be reported alongside chemistry. For porous structures, global porosity (e.g., 60–80 vol%), pore size distributions, strut thickness, connectivity density and anisotropy metrics (such as directional stiffness ratios) should be routinely quantified. Harmonised reporting of these metrics, together with fatigue performance and degradation profiles where applicable, will allow more meaningful comparison across studies and facilitate regulatory evaluation of new devices.

Finally, the pathway from laboratory innovation to clinical impact will require a balanced dialogue between academic researchers, clinicians and industry. European titanium producers and additive manufacturing companies, North American stent and guidewire manufacturers, and rapidly growing medtech sectors in Asia and Latin America are all exploring novel alloys, textures and lattice architectures. Early engagement with such industrial partners can help ensure that promising concepts—such as UV-LIPSS-textured joint components, antibacterial Ti–Cu GBR meshes or functionally graded porous hip stems—are scalable, economically viable and compatible with existing manufacturing and quality-assurance frameworks.

From our perspective, the central take-home message of Metallic biomaterials for medical applications – volume II is that successful metallic implants will no longer be defined solely by their bulk mechanical properties. Instead, future devices must integrate: i. rational alloy design that controls corrosion and ion release; ii. precisely engineered surface and interfacial structures that steer cell behaviour and biofilm formation; iii. architected porosity that balances load transfer with bone ingrowth; and iv. data-driven, application-specific tuning of degradation or long-term stability. By embracing these principles, and by consciously addressing diverse regional clinical needs, metallic biomaterials can evolve from “strong and inert” supports to truly bioactive, context-aware technologies for orthopaedic, dental and cardiovascular care worldwide.

We would like to thank all contributing authors to the Research Topic, and the editorial staff of Frontiers in Materials for making this Research Topic possible.

Author contributions

DJ: Writing – original draft. LX: Writing – review and editing. CL: Writing – review and editing. LW: Conceptualization, Writing – review and editing.

Funding

The author(s) declared that financial support was not received for this work and/or its publication.

Conflict of interest

The author(s) declared that this work was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.

LW is the associate editor of Frontiers in Materials, Frontiers in Bioengineering and Biotechnology.

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Editorial on the Research Topic Metallic biomaterials for medical applications - volume II