Metastructure “Trap” Coating by Acoustic Confinement Effect for Antibacterial Sonothermal Therapy

Abstract

Antibacterial sonothermal therapy (ASTT) is attractive for treating implant‐associated infection, which addresses the limitations of poor penetration of photothermal therapy. However, achieving implant surface‐specific ultrasound heating is incredibly challenging. Inspired by the porous acoustic metastructure in noise reduction, the acoustic metastructure would be a new strategy for attaining ASTT. Herein, an “acoustic confinement effect” is proposed to “trap” ultrasound for the metastructure TiO2 porous coating on titanium implants. The metastructure coating accomplishes specific acoustic absorption and efficient acoustic‐to‐thermal conversion, surpassing the non‐specific heating of conventional coatings. The theoretical calculation and experiment of metastructure porous coating prove the acoustic‐to‐thermal conversion mechanism, which is also validated in metastructure porous coatings on medical polyetheretherketone, indicating it is universal. Excitingly, this acoustic metastructure “trap” can capture bacteria and local sonothermal enhancement, exhibiting superior ASTT antibacterial rates (S. aureus, 99.69%; E. coil, 99.58%) at low‐power ultrasound. In addition, the metastructure TiO2 coating mimics human bone and demonstrates outstanding osseointegration. This study sheds substantial light on developing the acoustic responsive surface, broadening a new direction of acoustic metamaterials in medical applications.

Biofunctionalisation strategies of material surface and the inspired biological effects for bone repair

“…(c) Schematic diagram of the synthesis of MION-RGD/Agarose (MRA) hydrogels, and its mechanism of osteogenesis, biomineralisation, and angiogenesis in the bone defect site under mild magnetic hyperthermia [68]. (d) Schematic depiction of TiO2 metastructure coating design and its antibacterial sonothermal therapy mechanism [81].…”

“…Guan Shiwei et al constructed a porous TiO 2 coating on the surface of titanium by micro-arc oxidation. This porous acoustic metastructure coating has an excellent antibacterial sonothermal therapy effect, which provides a new idea for the development of the antibacterial sonothermal therapy (Figure 6d) [81].…”

Metainterface Heterostructure Enhances Sonodynamic Therapy for Disrupting Secondary Biofilms

“…14−16 Acoustic metastructures focus on developing artificial structures capable of manipulating and controlling sound waves. 17,18 Metasurfaces have produced exciting optical manipulation, biosensing, and flexible electronics. 19,20 As we know, interfaces are the sites of catalytic reactions, and interfacial electron transfer properties determine the catalytic activity.…”

“…Notably, the "honeycomb-like" metastructure of HTO/VG exhibited an exceptional acoustic-to-thermal effect, which was explored in depth in previous work. 18 HTO/ VG effectively eradicated secondary biofilm infections through synergistic SDT and sonothermal therapy (STT). This strategy explores metainterfacial heterostructure sonosensitive implants and leads the way in the synergy between SDT and STT.…”

“…The metamaterial is an emerging design and breaks the existing shackles as a revolutionary strategy. − Metamaterials include the metastructure and metainterface, which are rooted in the collective properties of a single cell’s engineered structure (shape and arrangement) rather than the constituents’ intrinsic properties . Actually, researchers have mainly focused on the development of the metastructure and metasurface, with more limited research on the metainterface. − Acoustic metastructures focus on developing artificial structures capable of manipulating and controlling sound waves. , Metasurfaces have produced exciting optical manipulation, biosensing, and flexible electronics. , As we know, interfaces are the sites of catalytic reactions, and interfacial electron transfer properties determine the catalytic activity. The metainterface is a periodic arrangement of individual heterointerfacial cells that can amplify catalytic effects.…”