Noninvasive and early diagnosis of acquired brain injury using fluorescence imaging in the NIR-II window

Inhibiting concentration quenching in Yb3+-Tm3+ upconversion nanoparticles by suppressing back energy transfer

Lanthanide-doped upconversion nanoparticles are promising for applications ranging from biosensing, bioimaging to solid-state lasing. However, their brightness remains limited by the concentration quenching effect of lanthanide activator ions, which greatly restricts their utility. Here, we develop a heterogeneous core-shell-shell nanostructure based on hexagonal NaYF4, in which Tm3+ activator and Yb3+ sensitizer are separated into the core and inner shell, while the outmost shell is used to suppress surface quenching effects. We show that this design can alleviate the activator concentration quenching effect, resulting in optimal Tm3+ concentration increasing from 1% to 8% at sub-100 W/cm2 irradiance, compared with the canonical core-only NaYF4:Yb3+/Tm3+. Moreover, under high excitation irradiance (20 MW/cm2), the optimal Tm3+ concentration could be further increased to 50%. Mechanistic investigations reveal that the spatial separation of sensitizer and activator effectively suppresses the back energy transfer from Tm3+ to Yb3+, driving the increase of optimal activator concentration. These findings enhance our understanding of lanthanide concentration quenching effect, unleashing opportunities for developing bright upconverting materials.

Luminescence Fingerprint of Intracellular NIR-II Gold Nanocluster Transformation: Implications for Sensing and Imaging

Gold nanoclusters emitting in the second biological window (NIR-II-AuNCs) have gained significant interest for their potential in deep-tissue bioimaging and biosensing applications due to the partial transparency and reduced autofluorescence of tissues in this spectral range. However, the limited understanding of how the biological environment affects their luminescent properties might hinder their use in bioimaging and biosensing. In this study, we investigated the emission properties of NIR-II-AuNCs when interacting and internalizing into live cells including macrophages, fibroblasts, and cancer cell lines, revealing substantial alterations in their luminescence. A systematic comparison between control and in vitro experiments concluded that the disruption of surface ligands is the main factor responsible for these alterations. NIR-II-AuNCs within cellular environments may also be influenced by other interactions, including aggregation or complexation with proteins. Furthermore, we also corroborated these spectroscopic modifications at the in vivo level, providing additional evidence of the environmental sensitivity of NIR-II-AuNCs. The results obtained in this study contribute to a deeper understanding of the luminescence mechanisms of NIR-II-AuNCs in biological environments in cells and in living tissues and are crucial for their optimization as reliable tools in biological environment for in vitro and in vivo imaging and diagnostics.

UCF-101 ameliorates traumatic brain injury by promoting microglia M2 polarization via AMPK/NF-κB pathways in LPS-induced BV2 cells

Traumatic brain injury (TBI) is a common neurosurgical emergency. As a macrophage in brain, microglia involves in secondary TBI injury. UCF-101, an Omi/HtrA2 inhibitor, protects against neurological disorders. This study aims to investigate the effects of UCF-101 in TBI and its mechanism. Mouse microglia cell BV2 cells were exposed to 1 µg/mL LPS to construct TBI in vitro models. Following CCK8 assay, cells were treated with LPS + UCF-101 (2, 5, 10 µM), LPS + Compound C (AMPK inhibitor, 20 µM), and LPS + UCF-101 + Compound C groups. With lactate dehydrogenase (LDH) content detection, ELISA and qRT-PCR assays were used to measure proinflammatory factors. Biomarkers of M1 (CD16/32 and iNOS) and M2 phenotypes (CD206), as well as AMPK/NF-κB pathway-related protein expression were assessed by flow cytometry, immunofluorescence, and Western blot methods. There was a decrease in M1 phenotype biomarkers and an increase in M2 phenotype biomarkers after UCF-101 treatment. UCF-101 exposure reduced TNF-α, LDH, IL-1β, IL-6, IL-8, p-NF-κB p65/NF-κB p65, and activated p-AMPK α (T172)/AMPK α (T172) expression. Importantly, further Compound C treatment counteracted these effects of UCF-101. In conclusion, UCF-101 ameliorates TBI by promoting microglia M2 polarization via AMPK/NF-κB pathways in LPS-induced BV2 cells, providing solid scientific foundation for clinical application of UCF-101 in TBI treatment.

Changes in the Secondary Structure and Assembly of Proteins on Fluoride Ceramic (CeF3) Nanoparticle Surfaces

Fluoride nanoparticles (NPs) are materials utilized in the biomedical field for applications including imaging of the brain. Their interactions with biological systems and molecules are being investigated, but the mechanism underlying these interactions remains unclear. We focused on possible changes in the secondary structure and aggregation state of proteins on the surface of NPs and investigated the principle underlying the changes using the amyloid β peptide (Aβ16-20) based on infrared spectrometry. CeF3 NPs (diameter 80 nm) were synthesized via thermal decomposition. Infrared spectrometry showed that the presence of CeF3 NPs promotes the formation of the β-sheet structure of Aβ16-20. This phenomenon was attributed to the hydrophobic interaction between NPs and Aβ peptides in aqueous environments, which causes the Aβ peptides to approach each other on the NP surface and form ordered hydrogen bonds. Because of the coexisting salts on the secondary structure and assembly of Aβ peptides, the formation of the β-sheet structure of Aβ peptides on the NP surface was suppressed in the presence of NH4+ and NO3- ions, suggesting the possibility that Aβ peptides were adsorbed and bound to the NP surface. The formation of the β-sheet structure of Aβ peptides was promoted in the presence of NH4+, whereas it was suppressed in the presence of NO3- because of the electrostatic interaction between the lysine residue of the Aβ peptide and the ions. Our findings will contribute to comparative studies on the effect of different NPs with different physicochemical properties on the molecular state of proteins.