The NIR-IIb (1500-1700 nm) window is ideal for deep-tissue optical imaging in mammals, but lacks bright and biocompatible probes. Here, we developed biocompatible cubic-phase (α-phase) erbium-based rare-earth nanoparticles (ErNPs) exhibiting bright downconversion luminescence at ~ 1600 nm for dynamic imaging of cancer immune-therapy in mice. We used ErNPs functionalized with cross-linked hydrophilic polymer layers attached to anti-PD-L1 antibody for molecular imaging of PD-L1 in a mouse model of colon cancer and achieved tumor to normal tissue signal ratios of ~ 40. The long luminescence lifetime of ErNPs (~ 4.6 ms) enabled simultaneous imaging of ErNPs and lead sulfide quantum dots (PbS QDs) emitting in the same ~ 1600 nm window. In vivo NIR-IIb molecular imaging of PD-L1 and CD8 revealed cytotoxic T *
Deep-tissue three-dimensional (3D) optical imaging of live mammals with high spatiotemporal resolution in non-invasive manners has been challenging due to light scattering. Here, we developed near-infrared II (NIR-II, 1000–1700 nm) light sheet microscopy (LSM) with excitation and emission up to ~ 1320 nm and ~ 1700 nm respectively for optical sectioning through live tissues at ~ 750-μm penetration depth without any invasive surgery. Suppressed light scattering allowed imaging at ~ 2 mm depth in glycerol-cleared brain tissues. NIR-II LSM in normal and oblique configurations enabled
in vivo
imaging of live mice through intact tissue, revealing abnormal blood flow and T cell motion in tumor microcirculation and mapping out programmed-death ligand 1 (PD-L1) and programmed cell death protein 1 (PD-1) in tumors with cellular resolution. 3D imaging through intact mouse head resolved vascular channels between skull and brain cortex, and monitored recruitment of macrophages/microglia to traumatic brain injury site post injury.
In the past decade, noticeable progress has been achieved regarding fluorescence imaging in the second near-infrared (NIR-II) window. Fluorescence imaging in the NIR-II window demonstrates superiorities of deep tissue penetration and high spatial and temporal resolution, which are beneficial for profiling physiological processes. Meanwhile, molecular imaging has emerged as an efficient tool to decipher biological activities on the molecular and cellular level. Extending molecular imaging into the NIR-II window would enhance the imaging performance, providing more detailed and accurate information of the biological system. In this progress report, selected achievements made in NIR-II molecular imaging are summarized. The organization of this report is based on strategies underlying rational designs of NIR-II imaging probes and their applications in molecular imaging are highlighted. This progress report may provide guidance and reference for further development of functional NIR-II probes designed for high-performance molecular imaging.
Highly sensitive capacitive-type pressure sensor has been achieved by fabricating reliefs on solution-processable hydrogel electrodes. Hybrid PVA/PANI hydrogels (PVA, poly-(vinyl alcohol); PANI, polyaniline) with a fully physically crosslinked binary network are selected as the electrodes of the pressure sensors. On the basis of the solution processability, reliefs are fabricated on the surface of PVA/PANI hydrogel electrodes by a template method. The gauge factor (GF) is enhanced by introducing reliefs and regulated by controlling the composition and relief dimension of hydrogel electrodes. The optimized pressure sensor containing reliefs achieves the highest GF of 7.70 kPa −1 and a sensing range of 0−7.4 kPa. Furthermore, the freezing and drying problems of the hydrogel sensors are overcome by introducing a binary solvent of water/glycerol and the pressure sensing ability at −18 °C has been achieved. Finally, monitoring of various pressures in daily life, such as joint bending, blowing, and brush writing, is demonstrated using such pressure sensors.
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