MoS2/Cu-MOF heterojunction-engineered smart scaffold: Dual-mode chemo-sonodynamic synergy and sonocurrent-driven osteogenic integration for bone regeneration.

Molybdenum disulfide (MoS2), a typical piezoelectric sonosensitive material, holds great promise in ultrasound-activated catalytic antibacterial applications and osteogenic differentiation promotion. However, it has two key limitations: rapid carrier recombination leading to insufficient antibacterial activity; and difficulty in forming stable interfaces with biopolymers as an inorganic compound, which impairs effective sonocurrent transmission in heterojunction scaffolds for osteogenesis induction. To address these issues, we proposed a multi-beneficial strategy: anchoring Cu-MOF to MoS2 via CuS chemical bonds to construct a Type-II MoS2/Cu-MOF heterojunction. Under ultrasonic stimulation, this heterojunction undergoes polarization to form a built-in electric field, accelerating carrier separation and enhancing catalytic efficiency. Additionally, Cu-MOF releases Cu+ and Cu2+ ions, which undergo Fenton-like reactions with bacterial endogenous H2O2 and glutathione to generate hydroxyl radicals via chemodynamic effects, increasing reactive oxygen species (ROS) production; the resultant oxygen further boosts sonodynamic efficiency. Furthermore, Cu2+ in MoS2/Cu-MOF forms metal coordination bonds with carboxyl groups in poly-l-lactic acid (PLLA) macromolecules, constructing an interfacial "Line-Point-Plane" ternary structure that enhances interfacial electron transfer efficiency, facilitates sonocurrent transmission, and thus effectively realizes electrical stimulation for osteogenic differentiation. Specifically, we incorporated the heterojunction into PLLA matrix powder and fabricated MoS2/Cu-MOF/PLLA heterojunction scaffolds via selective laser sintering (SLS). Under ultrasonic stimulation, these scaffolds achieve synergistic sono/chemodynamic antibacterial activity, while ultrasound-activated sonocurrents transmit through the ternary interfacial structure of the heterojunction scaffolds to effectively induce osteogenic differentiation. Results showed that compared to pure MoS2 scaffolds, the heterojunction scaffold exhibited a 0.4 eV narrower band gap and a 350 Ω lower impedance, with antibacterial rates of 97.3 % and 98 % against Staphylococcus (S.aureus) and Escherichia coli (E.coli), respectively. Notably, under ultrasonic irradiation, the upregulation of osteogenic factors such as Wnt-10b is induced, and osteoblast differentiation is promoted simultaneously; the results indicate that osteogenic factors like Wnt-10b have a potential role in promoting osteoblast differentiation under ultrasonic conditions.