Targeting-specific Nanoprobes in the Second Near-infrared Window for Biomedical Applications

Fluorescence imaging with high spatiotemporal resolution and sensitivity is employed for in vivo visualization and detection applications. Compared with visible light and the first near-infrared window (700–900 nm), the second near-infrared window (1 000–1 700 nm) imaging has a lower auto-background fluorescence, deeper tissue penetration, and a higher signal-to-noise ratio, thus highlighting its broad prospects in the biomedical field. Currently, reported second near-infrared region probes include single-walled carbon nanotubes, rare-earth nanoparticles, quantum dots, metal materials, and organic molecular dyes. Multimodal imaging can overcome the limitations of single imaging and provide more comprehensive information on the anatomical structure, tissue composition, and cellular and molecular quantification of lesions to achieve multi-level visualization. Therefore, second near-infrared window nanoprobes must be engineered for multimodal imaging. Moreover, these nanoprobes can be actively targeted by modification with antibodies, peptides, nucleotides, or biofilms to obtain detailed and accurate information on biological systems. This review describes the active targeting capabilities of various second near-infrared window nanoprobes in multimodal imaging, diagnosis, and treatment of different diseases by carrying different ligands and the common features and future application prospects of second near-infrared window fluorescent nanoprobes with targeting ability

Superparamagnetic nanoparticles with efficient near-infrared photothermal effect at the second biological window

Superparamagnetic nanoparticles (iron oxide nanoparticles¿IONs) are suitable for hyperthermia after irradiating with radiofrequency radiation. Concerning the suitability for laser ablation, IONs present a low molar absorption coefficient in the near-infrared region close to 800 nm. For this reason, they are combined with other photothermal agents into a hybrid composite. Here, we show that IONs absorb and convert into heat the infrared radiation characteristic of the so-called second-biological window (1000-1350 nm) and, in consequence, they can be used for thermal ablation in such wavelengths. To the known excellent water solubility, colloidal stability and biocompatibility exhibited by IONs, an outstanding photothermal performance must be added. For instance, a temperature increase of 36 °C was obtained after irradiating at 8.7 W cm−2 for 10 min a suspension of IONs at iron concentration of 255 mg L−1. The photothermal conversion efficiency was ~72%. Furthermore, IONs showed high thermogenic stability during the whole process of heating/cooling. To sum up, while the use of IONs in the first bio-window (700-950 nm) presents some concerns, they appear to be good photothermal agents in the second biological window

新規蛍光プローブ探索のための C2C12 細胞を用いた機能性組織の再構築

The second near-infrared window ranged between 900 and 1400 nm, namely NIR-II, has advantages for deep tissue imaging with extrinsic fluorophores due to lacking autofluorescence, low light absorption, and reduced scattering. Most of the proposed probes were used for labeling with antibodies. As a new application, we plan to monitor electrical activity in a living tissue noninvasively using membrane potential dye with NIR-II fluorescence. So we need the excitable cell culture system to screen candidates of such dyes. C2C12 skeletal myoblasts were morphologically differentiated to myotubes under the optimal conditions, and the electrical stimulation-induced contraction of the myotubes was monitored optically. This myotube system would permit screening membrane potential dyes in NIR-II

第二近赤外光の生体内挙動を検討するための モンテカルロシミュレーション

The second near-infrared window, namely NIR-II, ranges between 1000 and 1600 nm and is suitable for the deep tissue imaging with extrinsic fluorophores because of the lack of autofluorescence, low light absorption, and reduced scattering. NIR-II has the advantages over the first near-infrared region used previously in noninvasive measurement, 700-900 nm. Nevertheless there were few reports on the photon behaviors of this wavelength range with living tissues. Here we first outlined optical parameters such as absorption coefficient, scattering coefficient, anisotropy of scatter, refractive index of the tissues. Next we described the Monte Carlo method for simulating photon behaviors in living tissues in brief. Finally, using this model, we analyzed the behaviors within the media having optical parameters specific to the tissues

Tuning Electroluminescence from Functionalized SWCNT Networks further into the Near-Infrared

Near-infrared electroluminescence from carbon-based emitters, especially in the second biological window (NIR-II) or at telecommunication wavelengths, is difficult to achieve. Single-walled carbon nanotubes (SWCNTs) have been proposed as a possible solution due to their tunable and narrowband emission in the near-infrared and high charge carrier mobilities. Furthermore, the covalent functionalization of SWCNTs with a controlled number of luminescent sp$^{3}$ defects leads to even more red-shifted photoluminescence with enhanced quantum yields. Here, we demonstrate that by tailoring the binding configuration of the introduced sp$^{3}$ defects and hence tuning their optical trap depth we can generate emission from polymer-sorted (6,5) and (7,5) nanotubes that is mainly occurring in the telecommunication O-band (1260-1360 nm). Networks of these functionalized nanotubes are integrated in ambipolar, light-emitting field-effect transistors to yield the corresponding narrowband near-infrared electroluminescence. Further investigation of the current and carrier density-dependent electro- and photoluminescence spectra enable insights into the impact of different sp$^{3}$ defects on charge transport in networks of functionalized SWCNTs

Near to short wave infrared light generation through AlGaAs-on-insulator nanoantennas

AlGaAs-on-insulator (AlGaAs-OI) has recently emerged as a novel promising platform for nonlinear optics at the nanoscale. Among the most remarkable outcomes, second harmonic generation (SHG) in the visible/near infrared spectral region has been demonstrated in AlGaAs-OI nanoantennas (NA). In order to extend the nonlinear frequency generation towards the short wave infrared window, in this work we propose and demonstrate via numerical simulations difference frequency generation (DFG) in AlGaAs-OI NAs. The NA geometry is finely adjusted in order to obtain simultaneous optical resonances at the pump, signal and idler wavelengths, which results in an efficient DFG with conversion efficiencies up to 0.01%. Our investigation includes the study of the robustness against random variations of the NA geometry that may occur at fabrication stage. Overall, these outcomes identify a new potential and yet unexplored application of AlGaAs-OI NAs as compact devices for the generation and control of the radiation pattern in the near to short infrared spectral region

Near to short wave infrared light generation through AlGaAs-on-insulator nanoantennas

AlGaAs-on-insulator (AlGaAs-OI) has recently emerged as a promising platform for nonlinear optics at the nanoscale. Among the most remarkable outcomes, second-harmonic generation (SHG) in the visible/near infrared spectral region has been demonstrated in AlGaAs-OI nanoantennas (NAs). In order to extend the nonlinear frequency generation towards the short wave infrared window, in this work we propose and demonstrate via numerical simulations difference frequency generation (DFG) in AlGaAs-OI NAs. The NA geometry is finely adjusted in order to obtain simultaneous optical resonances at the pump, signal and idler wavelengths, which results in an efficient DFG with conversion efficiencies up to 0.01%. Our investigation includes the study of the robustness against random variations of the NA geometry that may occur at fabrication stage. Overall, these outcomes identify what we believe to be a new potential and yet unexplored application of AlGaAs-OI NAs as compact devices for the generation and control of the radiation pattern in the near to short infrared spectral region

Deep-Tissue Anatomical Imaging of Mice Using Carbon Nanotube Fluorophores in the Second Near Infrared Window

Fluorescent imaging in the second near infrared window (NIR II, 1-1.4 {\mu}m) holds much promise due to minimal autofluorescence and tissue scattering. Here, using well functionalized biocompatible single-walled carbon nanotubes (SWNTs) as NIR II fluorescent imaging agents, we performed high frame rate video imaging of mice during intravenous injection of SWNTs and investigated the path of SWNTs through the mouse anatomy. We observed in real-time SWNT circulation through the lungs and kidneys several seconds post-injection, and spleen and liver at slightly later time points. Dynamic contrast enhanced imaging through principal component analysis (PCA) was performed and found to greatly increase the anatomical resolution of organs as a function of time post-injection. Importantly, PCA was able to discriminate organs such as the pancreas which could not be resolved from real-time raw images. Tissue phantom studies were performed to compare imaging in the NIR II region to the traditional NIR I biological transparency window (700- 900 nm). Examination of the feature sizes of a common NIR I dye (indocyanine green, ICG) showed a more rapid loss of feature contrast and integrity with increasing feature depth as compared to SWNTs in the NIR II region. The effects of increased scattering in the NIR I versus NIR II region were confirmed by Monte Carlo simulation. In vivo fluorescence imaging in the NIR II region combined with PCA analysis may represent a powerful approach to high resolution optical imaging through deep tissues, useful for a wide range of applications from biomedical research to disease diagnostics.Comment: Proceedings of the National Academy of Sciences (PNAS), 201