Bioactive mesoporous silica nanoparticle-functionalized titanium implants with controllable antimicrobial peptide release potentiate the regulation of inflammation and osseointegration.

Bacterial infection and delayed osseointegration are two major challenges for titanium-based orthopedic implants. In the present study, we developed a functionalized titanium implant Ti-M@A by immobilizing antimicrobial peptide (AMP) HHC36-loaded diselenide-bridged mesoporous silica nanoparticles (MSNs) on the surface, which showed good long-term and mechanical stability. The functionalized implants can realize the sustained release of AMP over 30 days and exhibit over 95.71 % antimicrobial activity against four types of clinical bacteria (S. aureus, E. coli, P. aeruginosa and MRSA), which arose from the capability to destroy the bacterial membranes. Moreover, Ti-M@A can efficiently inhibit the biofilm formation of the bacteria. The functionalized implants can also significantly promote the osteogenic differentiation of mouse bone marrow-derived mesenchymal stem cells (mBMSCs) because of the Se in MSNs. Notably, it can trigger macrophages toward M2 polarization in vitro by scavenging ROS in LPS-activated macrophages. Consequently, in vivo assays with infection and non-infection bone defect models demonstrated that such bioactive implants can not only kill over 98.82 % of S. aureus, but also promote osseointegration. Hence, this study provides a combined strategy to resolve bacterial infection and delayed osseointegration for titanium implants.

Atomic-Scale Observation of Reversible Thermally Driven Phase Transformation in 2D In2Se3.

Phase transformation in emerging two-dimensional (2D) materials is crucial for understanding and controlling the interplay between structure and electronic properties. In this work, we investigate 2D In2Se3 synthesized via chemical vapor deposition, a recently discovered 2D ferroelectric material. We observed that In2Se3 layers with thickness ranging from a single layer to ∼20 layers stabilized at the ß phase with a superstructure at room temperature. At around 180 K, the ß phase converted to a more stable ß' phase that was distinct from previously reported phases in 2D In2Se3. The kinetics of the reversible thermally driven ß-to-ß' phase transformation was investigated by temperature-dependent transmission electron microscopy and Raman spectroscopy, corroborated with the expected minimum-energy pathways obtained from our first-principles calculations. Furthermore, density functional theory calculations reveal in-plane ferroelectricity in the ß' phase. Scanning tunneling spectroscopy measurements show that the indirect bandgap of monolayer ß' In2Se3 is 2.50 eV, which is larger than that of the multilayer form with a measured value of 2.05 eV. Our results on the reversible thermally driven phase transformation in 2D In2Se3 with thickness down to the monolayer limit and the associated electronic properties will provide insights to tune the functionalities of 2D In2Se3 and other emerging 2D ferroelectric materials and shed light on their numerous potential applications (e.g., nonvolatile memory devices).