Infectious bone defects, characterised by persistent an infection and bone loss, are thought of a significant problem in medical orthopedics, typically resulting in limb dysfunction and even life-threatening situations for sufferers [1], [2], [3]. Inside the infectious microenvironment, bacterial invasion triggers inflammatory responses, disrupts bone metabolism, and elevates reactive oxygen species (ROS) ranges, resulting in necrosis of newly shaped bone tissue [4], [5]. Moreover, bacterial adhesion and colonization on implant surfaces not solely severely impede bone regeneration but additionally promote biofilm formation, stopping osseointegration between the implant and host bone, which frequently ends in implant loosening and eventual failure [6], [7]. At present, debridement of the contaminated website and systemic antibiotic remedy are the first medical methods for managing contaminated bone defects [8], [9], [10], [11]. Nevertheless, antibiotics wrestle to fight complicated infections attributable to drug-resistant micro organism and should disrupt the human microbial ecosystem, impairing the osteoinductive capability of implant supplies and exacerbating the chance of implant loosening and failure [12], [13]. Consequently, the event of practical bone implants that concurrently exhibit potent antibacterial properties and tissue-regenerative capabilities has emerged as an pressing medical want [14], [15].
In organic methods, vitality exists in varied kinds and undergoes intricate biochemical interconversion via pathways similar to adenosine triphosphate (ATP) technology, redox reactions, and oxidative phosphorylation [16], [17], [18]. These pure vitality transformations critically affect the differentiation destiny of various cell populations and play a pivotal function in tissue regeneration [19], [20]. Impressed by these pure pathways, researchers have begun exploring the conversion of exogenous vitality sources, similar to mechanical, electrical, optical, and thermal vitality, into localized bioactive indicators or antibacterial results, providing novel methods for tissue regeneration and anti-infection remedy [21], [22]. For example, piezoelectric supplies like barium titanate can transduce mechanical stress into electrical indicators, activating oxidative phosphorylation in macrophages and modulating their immune response to shift from the pro-inflammatory M1 phenotype to the regenerative M2 phenotype, thereby selling tissue restore [1]. Equally, ultrasound-driven mechanical vibrations from implant scaffolds can convert acoustic vitality into mechanical stimuli, opening voltage-gated calcium channels on cell membranes and stimulating the proliferation and osteogenic differentiation of bone marrow mesenchymal stem cells (BMSCs) [23].
Within the context of antibacterial remedy, photothermal and photodynamic therapies have been extensively investigated. These approaches make use of nanomaterials (e.g., black phosphorus) or photosensitizers to transform mild vitality into warmth or ROS, rising bacterial membrane permeability and subsequently killing micro organism through hyperthermia or oxidative stress [24], [25], [26], [27], [28]. Moreover, magnetothermal sterilization has been achieved utilizing iron oxide (Fe₃O₄)-based microneedles that penetrate bacterial biofilms and generate localized warmth below magnetic fields [29]. Regardless of their efficacy, these therapies typically depend on exogenous supplies (nanomaterials or photosensitizers) coated on or composited with implants, involving complicated fabrication processes and exhibiting poor long-term stability [30]. Furthermore, most of those methods lack the capability to induce osteogenesis throughout implant integration, and the extreme warmth or ROS generated throughout remedy could harm surrounding bone tissue [31], [32].
To deal with these limitations, we suggest leveraging the intrinsic property modulation of implants together with photothermal and photodynamic remedies to attain multimodal vitality conversion for the efficient administration of contaminated bone defects. Our earlier analysis demonstrated that exactly managed micro/nanostructures on implant surfaces can stretch mobile microtubules, transducing extracellular mechanical stimuli into intracellular ATP manufacturing to induce bone regeneration [33]. On this research, we chosen polyetheretherketone (PEEK), a clinically prevalent orthopedic implant materials, because the substrate and constructed a micro/nano-carbonized floor layer with graphene-like buildings through a easy laser etching. Underneath extended near-infrared (NIR) irradiation, the graphene-like construction converts photonic vitality into thermal vitality through electron-phonon coupling, enabling bactericidal results via localized hyperthermia [34], [35]. Concurrently, valence-band holes within the graphene-like layer catalyze the transformation of ambient H₂O into hydroxyl radicals (·OH), reaching potent antibacterial efficacy via chemically pushed oxidative stress [36], [37]. Following bacterial eradication across the implant, transient NIR irradiation generates gentle thermal vitality to reinforce membrane permeability of BMSCs [38]. This thermal stimulus synergizes with the micro/nanostructure-induced cytoskeletal pressure to facilitate mechano-bioenergy conversion, whereby mechanical and thermal vitality are reworked into biochemical vitality via ATP manufacturing, finally selling osteogenic differentiation of stem cells. These processes represent a hierarchical multimodal vitality conversion pathway. On this system, NIR irradiation first triggers photothermal and photodynamic results as the first vitality conversion processes, producing thermal vitality and reactive oxygen species. Subsequently, secondary vitality conversion arises from the hierarchical porous buildings in addition to the organic responses induced by these main results. After implantation into contaminated bone defects, the graphene-like functionalized PEEK implant can successfully kill micro organism whereas inducing osteogenic differentiation of cells, reaching fast interfacial osseointegration (Fig. 1).
