Near-infrared Spectral Window Research Articles

Band Edge Excitons and Amplified Spontaneous Emission of Mercury Chalcogenide Nanoplatelets

AbstractColloidal nanoplatelets of HgSe and HgTe prepared indirectly through cation exchange reactions can transfer many of the advantageous properties of atomically precise, 2D cadmium chalcogenides to the near‐infrared (NIR) spectral window. In this work, HgSe and HgTe nanoplatelets are studied to understand their fundamental photophysical properties, particularly those areas of similarity and difference from cadmium‐based NPLs, and to examine their potential as optical gain media. Similar to cadmium chalcogenide NPLs, low‐temperature photoluminescence of HgTe NPLs displays two‐color emission that depends on temperature, sample, fluence, excitation frequency, and irradiation time. Both HgTe and HgSe show nanosecond emission dynamics at temperatures as low as 2.5 K, with no indication that bright‐dark excitonic splitting governs the low‐temperature photoluminescence. Collectively, experimental data is most consistent with emission from a negative trion state at low temperature. Although the mercury chalcogenide nanoplatelets are shown to have broadened optical resonances compared to the cadmium chalcogenides from which they are derived, they retain slow Auger recombination and can display low‐threshold amplified spontaneous emission in the NIR spectral window. Optical pumping thresholds for HgTe NPLs are observed as low as 4.4 µJ cm−2 and highlight the potential 2D nanoplatelets as gain medium in the near‐infrared.

Shortwave-infrared-light-emitting probes for the in vivo tracking of cancer vaccines and the elicited immune responses

Tracking and imaging immune cells in vivo non-invasively would offer insights into the immune responses induced by vaccination. Here we report a cancer vaccine consisting of polymer-coated NaErF4/NaYF4 core–shell down-conversion nanoparticles emitting luminescence in the near-infrared spectral window IIb (1,500–1,700 nm in wavelength) and with surface-conjugated antigen (ovalbumin) and electrostatically complexed adjuvant (class-B cytosine–phosphate–guanine). Whole-body wide-field imaging of the subcutaneously injected vaccine in tumour-bearing mice revealed rapid migration of the nanoparticles to lymph nodes through lymphatic vessels, with two doses of the vaccine leading to the complete eradication of pre-existing tumours and to the prophylactic inhibition of tumour growth. The abundance of antigen-specific CD8+ T lymphocytes in the tumour microenvironment correlated with vaccine efficacy, as we show via continuous-wave imaging and lifetime imaging of two intravenously injected near-infrared-emitting probes (CD8+-T-cell-targeted NaYbF4/NaYF4 nanoparticles and H-2Kb/ovalbumin257-264 tetramer/PbS/CdS quantum dots) excited at different wavelengths, and by volumetrically visualizing the three nanoparticles via light-sheet microscopy with structured illumination. Nanoparticle-based vaccines and imaging probes emitting infrared light may facilitate the design and optimization of immunotherapies.

Spiral volumetric optoacoustic tomography for imaging whole-body biodynamics in small animals.

Fast tracking of biological dynamics across multiple murine organs using the currently commercially available whole-body preclinical imaging systems is hindered by their limited contrast, sensitivity and spatial or temporal resolution. Spiral volumetric optoacoustic tomography (SVOT) provides optical contrast, with an unprecedented level of spatial and temporal resolution, by rapidly scanning a mouse using spherical arrays, thus overcoming the current limitations in whole-body imaging. The method enables the visualization of deep-seated structures in living mammalian tissues in the near-infrared spectral window, while further providing unrivalled image quality and rich spectroscopic optical contrast. Here, we describe the detailed procedures for SVOT imaging of mice and provide specific details on how to implement a SVOT system, including component selection, system arrangement and alignment, as well as the image processing methods. The step-by-step guide for the rapid panoramic (360°) head-to-tail whole-body imaging of a mouse includes the rapid visualization of contrast agent perfusion and biodistribution. The isotropic spatial resolution possible with SVOT can reach 90 µm in 3D, while alternative steps enable whole-body scans in less than 2 s, unattainable with other preclinical imaging modalities. The method further allows the real-time (100 frames per second) imaging of biodynamics at the whole-organ level. The multiscale imaging capacity provided by SVOT can be used for visualizing rapid biodynamics, monitoring responses to treatments and stimuli, tracking perfusion, and quantifying total body accumulation and clearance dynamics of molecular agents and drugs. Depending on the imaging procedure, the protocol requires 1-2 h to complete by users trained in animal handling and biomedical imaging.

Optical focusing inside scattering media with iterative time-reversed ultrasonically encoded near-infrared light.

Focusing light inside scattering media is a long-sought goal in optics. Time-reversed ultrasonically encoded (TRUE) focusing, which combines the advantages of biological transparency of the ultrasound and the high efficiency of digital optical phase conjugation (DOPC) based wavefront shaping, has been proposed to tackle this problem. By invoking repeated acousto-optic interactions, iterative TRUE (iTRUE) focusing can further break the resolution barrier imposed by the acoustic diffraction limit, showing great potential for deep-tissue biomedical applications. However, stringent requirements on system alignment prohibit the practical use of iTRUE focusing, especially for biomedical applications at the near-infrared spectral window. In this work, we fill this blank by developing an alignment protocol that is suitable for iTRUE focusing with a near-infrared light source. This protocol mainly contains three steps, including rough alignment with manual adjustment, fine-tuning with a high-precision motorized stage, and digital compensation through Zernike polynomials. Using this protocol, an optical focus with a peak-to-background ratio (PBR) of up to 70% of the theoretical value can be achieved. By using a 5-MHz ultrasonic transducer, we demonstrated the first iTRUE focusing using near-infrared light at 1053 nm, enabling the formation of an optical focus inside a scattering medium composed of stacked scattering films and a mirror. Quantitatively, the size of the focus decreased from roughly 1 mm to 160 µm within a few consecutive iterations and a PBR up to 70 was finally achieved. We anticipate that the capability of focusing near-infrared light inside scattering media, along with the reported alignment protocol, can be beneficial to a variety of applications in biomedical optics.

Green Synthesis of Near-Infrared Plasmonic Gold Nanostructures by Pomegranate Extract and Their Supramolecular Assembling with Chemo- and Photo-Therapeutics.

Au nanostructures exhibiting a localized surface plasmon resonance in the near-infrared spectral window are obtained in a single, green step at room temperature by pomegranate extract in the presence of a highly biocompatible β-cyclodextrin branched polymer, without the need of preformed seeds, external reducing and sacrificial agents, and conventional surfactants. The polymeric component makes the Au nanostructures dispersible in water, stable for weeks and permits their supramolecular assembling with the chemotherapeutic sorafenib and a nitric oxide (NO) photodonor (NOPD), chosen as representative for chemo- and photo-therapeutics. Irradiation of the plasmonic Au nanostructures in the therapeutic window with 808 nm laser light results in a good photothermal response, which (i) is not affected by the presence of either the chemo- or the phototherapeutic guests and (ii) does not lead to their photoinduced decomposition. Besides, irradiation of the hybrid Au nanoassembly with the highly biocompatible green light results in the NO release from the NOPD with efficiency similar to that observed for the free guest. Preliminary biological experiments against Hep-G2 hepatocarcinoma cell lines are also reported.

Tether-free photothermal deep-brain stimulation in freely behaving mice via wide-field illumination in the near-infrared-II window.

Invasive brain implants and tethered optical fibres are typically used in restrained or motion-impaired animals, limiting the control and the decoding of the neural circuitry in freely behaving ones. Here we report the implant- and tether-free optical neurostimulation of deep brain regions by locally injected and untargeted photothermal transducers. The macromolecular transducers, comprising a semiconducting polymer core and an amphiphilic polymer shell, have an average diameter of 40 nanometres and achieve a photothermal conversion of 71% (at 1064 nm), activating the transient receptor potential cation channel subfamily V member 1 (TRPV1) ectopically expressed by an adeno-associated virus in dopaminergic neurons of tyrosine hydroxylase-driven Cre recombinase transgenic mice. The near-transparency of biological tissue in the second near-infrared window enabled the light source to be placed at 50 centimetres above the mouse, at a low incident power density of 10 milliwatt/square millimetre, resulting in the activation, through the scalp and skull, of the dopaminergic neurons in the ventral tegmental area, with minimal thermal damage. The approach is suitable for the neurostimulation of socially interacting mice.

Tumor-Associated Immune-Cell-Mediated Tumor-Targeting Mechanism with NIR-II Fluorescence Imaging.

The strategy of structure-inherent tumor targeting (SITT) with cyanine-based fluorophores is receiving more attention because no chemical conjugation of targeting moieties is required. However, the targeting mechanism behind SITT has not yet been well explained. Here, it is demonstrated that heptamethine-cyanine-based fluorophores possess not only targetability of tumor microenvironments without the need for additional targeting ligands but also second near-infrared spectral window (NIR-II) imaging capabilities, i.e., minimum scattering and ultralow autofluorescence. The new SITT mechanism suggests that bone-marrow-derived and/or tissue-resident/tumor-associated immune cells can be a principal target for cancer detection due to their abundance in tumoral tissues. Among the tested, SH1 provides ubiquitous tumor targetability and a high tumor-to-background ratio (TBR) ranging from 9.5 to 47 in pancreatic, breast, and lung cancer mouse models upon a single bolus intravenous injection. Furthermore, SH1 can be used to detect small cancerous tissues smaller than 2 mm in diameter in orthotopic lung cancer models. Thus, SH1 could be a promising cancer-targeting agent and have a bright future for intraoperative optical imaging and image-guided cancer surgery.

Near-infrared benzodiazoles as small molecule environmentally-sensitive fluorophores

The development of fluorophores emitting in the near-infrared spectral window has gained increased attention given their suitable features for biological imaging. In this work, we have optimised a general and straightforward synthetic approach to prepare a small library of near-infrared-emitting C-bridged nitrobenzodiazoles using commercial precursors. C-bridged benzodiazoles have low molecular weight and neutral character as important features that are not common in most near-infrared dyes. We have investigated their fluorescence response in the presence of a wide array of 60 different biomolecules and identified compound 3i as a potential chemosensor to discriminate between Fe2+ and Fe3+ ions in aqueous media.

A phosphorescent probe for in vivo imaging in the second near-infrared window.

In the second near-infrared spectral window (NIR-II; with wavelengths of 1,000-1,700 nm), in vivo fluorescence imaging can take advantage of reduced tissue autofluorescence and lower light absorption and scattering by tissue. Here, we report the development and in vivo application of a NIR-II phosphorescent probe that has lifetimes of hundreds of microseconds and a Stokes shift of 430 nm. The probe is made of glutathione-capped copper-indium-selenium nanotubes, and in acidic environments (pH 5.5-6.5) switches from displaying fluorescence to phosphorescence. In xenograft models of osteosarcoma and breast cancer, intravenous or intratumoral injections of the probe enabled phosphorescence imaging at signal-to-background ratios, spatial resolutions and sensitivities higher than NIR-II fluorescence imaging with polymer-stabilized copper-indium-sulfide nanorods. Phosphorescence imaging may offer superior imaging performance for a range of biomedical uses.

Helicene-Based Ligands Enable Strong Magneto-Chiral Dichroism in a Chiral Ytterbium Complex.

Here we report the first experimental observation of magneto-chiral dichroism (MChD) detected through light absorption in an enantiopure lanthanide complex. The P and M enantiomers of [YbIII((X)-L)(hfac)3] (X = P, M; L = 3-(2-pyridyl)-4-aza[6]-helicene; hfac = 1,1,1,5,5,5-hexafluoroacetylacetonate), where the chirality is held by the helicene-based ligand, were studied in the near-infrared spectral window. When irradiated with unpolarized light in a magnetic field, these chiral complexes exhibit a strong MChD signal (gMChD ca. 0.12 T-1) associated with the 2F5/2 ← 2F7/2 electronic transition of YbIII. The low temperature absorption and MChD spectra reveal a fine structure associated with crystal field splitting and vibronic coupling. The temperature dependence of the main dichroic signal detected up to 150 K allowed, for the first time, the disentanglement of the two main microscopic contributions to the dichroic signal predicted by the MChD theory. These findings pave the way toward probing MChD in chiral lanthanide-based single-molecule magnets.

Giant nonlinear optical responses from photon-avalanching nanoparticles.

Avalanche phenomena use steeply nonlinear dynamics to generate disproportionately large responses from small perturbations, and are found in a multitude of events and materials1. Photon avalanching enables technologies such as optical phase-conjugate imaging2, infrared quantum counting3 and efficient upconverted lasing4-6. However, the photon-avalanching mechanism underlying these optical applications has been observed only in bulk materials and aggregates6,7, limiting its utility and impact. Here we report the realization of photon avalanching at room temperature in single nanostructures-small, Tm3+-doped upconverting nanocrystals-and demonstrate their use in super-resolution imaging in near-infrared spectral windows of maximal biological transparency. Avalanching nanoparticles (ANPs) can be pumped by continuous-wave lasers, and exhibit all of the defining features of photon avalanching, including clear excitation-power thresholds, exceptionally long rise time at threshold, and a dominant excited-state absorption that is more than 10,000 times larger than ground-state absorption. Beyond the avalanching threshold, ANP emission scales nonlinearly with the 26th power of the pump intensity, owing to induced positive optical feedback in each nanocrystal. This enables the experimental realization of photon-avalanche single-beam super-resolution imaging7 with sub-70-nanometre spatial resolution, achieved by using only simple scanning confocal microscopy and without any computational analysis. Pairing their steep nonlinearity with existing super-resolution techniques and computational methods8-10, ANPs enable imaging with higher resolution and at excitation intensities about 100 times lower than other probes. The low photon-avalanching threshold and excellent photostability of ANPs also suggest their utility in a diverse array of applications, including sub-wavelength imaging7,11,12 and optical and environmental sensing13-15.

Multi-Wavelength Photo-Magnetic Imaging System for Photothermal Therapy Guidance.

In photothermal therapy, cancerous tissue is treated by the heat generated from absorbed light energy. For effective photothermal therapy, the parameters affecting the induced temperature should be determined before the treatment by modeling the increase in temperature via numerical simulations. However, accurate simulations can only be achieved when utilizing the accurate optical, thermal, and physiological properties of the treated tissue. Here, we propose a multi-wavelength photo-magnetic imaging (PMI) technique that provides quantitative and spatially resolved tissue optical absorption maps at any wavelength within the near-infrared (NIR) window to assist accurate photothermal therapy planning. The study was conducted using our recently developed multi-wavelength PMI system, which operates at four laser wavelengths (760, 808, 860, and 980 nm). An agar tissue-simulating phantom containing water, lipid, and ink was illuminated using these wavelengths, and the slight internal laser-induced temperature rise was measured using magnetic resonance thermometry (MRT). The phantom optical absorption was recovered at the used wavelengths using our dedicated PMI image reconstruction algorithm. These absorption maps were then used to resolve the concentration of the tissue chromophores, and thus deduce its optical absorption spectrum in the NIR region based on the Beer-Lambert law. The optical absorption of the phantom was successfully recovered at the used four wavelengths with an average error of ~1.9%. The recovered absorption coefficient was then used to simulate temperature variations inside the phantom. A comparison between the modeled temperature maps and the MRT measured ones showed that these maps are in a good agreement with an average pseudo R2 statistic of 0.992. These absorption values were used to successfully recover the concentration of the used chromophores. Finally, these concentrations are used to accurately calculate the total absorption spectrum of the phantom in the NIR spectral window with an average error as low as ~2.3%. Multi-wavelength PMI demonstrated a great ability to assess the distribution of tissue chromophores, thus providing its total absorption at any wavelength within the NIR spectral range. Therefore, applications of photothermal therapy applied at NIR wavelengths can benefit from the absorption spectrum recovered by PMI to determine important parameters such as laser power as well as the laser exposure time needed to attain a specific increase in temperature prior to treatment. Lasers Surg. Med. 00:00-00, 2020. © 2020 Wiley Periodicals LLC.

Design, synthesis and photocytotoxicity of upconversion nanoparticles: Potential applications for near-infrared photodynamic and photothermal therapy.

Photodynamic therapy (PDT) and photothermal therapy (PTT) are emerging modalities for the treatment of tumors and nonmalignant conditions, based on the use of photosensitizers to generate singlet oxygen or heat, respectively, upon light (laser) irradiation. They have potential advantages over conventional treatments, being minimally invasive with precise spatial-temporal selectivity and reduced side effects. However, most clinically employed PDT agents are activated at visible (vis) wavelengths for which the tissue penetration and, hence, effective treatment depth are compromised. In addition, the lipophilicity of near-infrared (NIR) photothermal agents limits their use and efficiency. To achieve combined PDT/PTT effects, both excitation wavelengths need to be tuned into the NIR spectral window of biological tissues. This paper reports the synthesis of neodymium-doped upconversion nanoparticles (NaYF4 :Yb,Er,Nd@NaYF4 :Nd) that convert 800 nm light into vis wavelengths, which can then activate conventional photosensitizers on the nanoparticle surface for PDT. Covalently bonded IR-780 dyes can readily be activated by 800 nm laser irradiation. The PEGylated nanoplatform exhibited a narrow size distribution, good stability and efficient generation of singlet oxygen under laser irradiation. The in vitro photocytotoxicity of this engineered nanoplatform as either a PDT or PTT agent in HeLa cells is demonstrated, while fluorescence microscopy in nanoplatform-incubated cells highlights its potential for bioimaging.

Achromatic nanostructured gradient index microlenses.

We present a development of microlenses achromatically corrected in near-infrared spectral windows. We show that the standard fiber drawing technology can be successfully applied to the development achromatic gradient index microlenses by means of internal nanostructurization. These gradient index microlenses can achieve similar performance to standard aspheric doublets, while utilizing a simpler, singlet element geometry with flat surfaces. A nanostructured lens with a parabolic profile was designed using a combination of the simulated annealing method and the effective medium approximation theory. Measurements on the fabricated lenses show that the microlenses have a nearly wavelength-independent focal plane at a distance of about 35 μm from the lens facet over the wavelength range of 600-1550 nm. The successful design and fabrication of achromatic flat-parallel rod microlenses opens new perspectives for micro-imaging systems and wavelength-independent coupling into optical fibers.

Subcellular distribution and cellular self-repair ability of fluorescent quantum dots emitting in the visible to near-infrared region

Semiconductor II-VI quantum dots (QDs), as high-performance fluorescent biological probes, have garnered significant attention due to their superior optical properties. To enable QDs for wide-ranging bioapplications, concerns about their in vitro behavior need to be fully addressed. Herein, for the first time, cellular behaviors of aqueous synthesized-QDs (aqQDs), whose maximum emission wavelength (λ emission) covers the visible to near-infrared spectral window, are systematically investigated. Our results demonstrate that three different sized aqQDs feature distinct cellular distributions, i.e. aqQD530 (aqQDs whose λ emission is 530 nm) and aqQD620 (aqQDs whose λ emission is 620 nm) mainly distribute in the cytoplasm and nucleus, while aqQD730 (aqQDs whose λ emission is 730 nm) mainly accumulates in the cytoplasm. Most significantly, the phenomenon that cellular self-repair ability is dependent on diameters of aqQDs is revealed for the first time. In particular, small-sized QDs (e.g. aqQD530 and aqQD620) severely deteriorate cellular self-repair ability, leading to an irreversible decrease in cell viability. In striking contrast, large-sized QDs (e.g. aqQD730) have little effect on cellular self-repair ability, and the cell viability is restored after removal of aqQD730 from the culture medium. Our results provide invaluable information for QD-relevant biosafety analysis, as well as suggest available guidance for the design of biocompatible QDs for wide utilization in biological and biomedical studies.

Highly Fluorescent Polycaprolactones with Tunable Light Emission Wavelengths across Visible to NIR Spectral Window

Polycaprolactone (PCL) has been widely used in biomedical applications such as tissue engineering due to its promising biodegradability, biocompatibility, and mechanical processability. However, commercially available PCL without any fluorescence does not meet the increasing demand in biomedical applications, for example, to monitor noninvasively the fate of implanted scaffolds in tissue engineering. To that end, exploration of new fluorescent PCL polymers plays an essential role in tracking their degradation under physiological conditions and distinguishing PCL scaffolds at the interface with biological systems such as cells and tissues. Herein, this study reports a series of tailor‐made fluorescent PCL polymers with various light emission wavelengths ranging from visible to near‐infrared (NIR) region in solid states. These fluorescent PCL polymers are amenable to be processed into nanofibers using electrospinning, as well as waterborne nanoparticle ink for macroscale stamping, brush writing, and microcontact printing. Finally, the application of the NIR fluorescent PCL for in vitro imaging and monitoring of scaffold degradation is demonstrated.

Assessment of Gate Width Size on Lifetime-Based Förster Resonance Energy Transfer Parameter Estimation

Förster Resonance Energy Transfer (FRET) enables the observation of interactions at the nanoscale level through the use of fluorescence optical imaging techniques. In FRET, fluorescence lifetime imaging can be used to quantify the fluorescence lifetime changes of the donor molecule, which are associated with proximity between acceptor and donor molecules. Among the FRET parameters derived from fluorescence lifetime imaging, the percentage of donor that interacts with the acceptor (in proximity) can be estimated via model-based fitting. However, estimation of the lifetime parameters can be affected by the acquisition parameters such as the temporal characteristics of the imaging system. Herein, we investigate the effect of various gate widths on the accuracy of estimation of FRET parameters with focus on the near-infrared spectral window. Experiments were performed in silico, in vitro, and in vivo with gate width sizes ranging from 300 ps to 1000 ps in intervals of 100 ps. For all cases, the FRET parameters were retrieved accurately and the imaging acquisition time was decreased three-fold. These results indicate that increasing the gate width up to 1000 ps still allows for accurate quantification of FRET interactions even in the case of short lifetimes such as those encountered with near-infrared FRET pairs.

Detection limits for blood on four fabric types using infrared diffuse reflection spectroscopy in mid- and near-infrared spectral windows.

Detection limits (DL) for blood on four fabric types were estimated for calibrations derived using partial least squares regression applied to infrared (IR) diffuse reflection spectra. Samples were prepared by dip-coating acrylic, cotton, nylon, and polyester fabrics from solutions of diluted rat blood. While DLs often appear in terms of dilution factor in the forensic community, mass percentage, coverage (mass per unit area), or film thickness are often more relevant when comparing experimental methods. These alternate DL units are related to one another and presented here. The best IR diffuse reflection DLs for blood on acrylic and cotton fabrics were in the mid-IR spectral window corresponding to the protein Amide I/II absorption bands. These DLs were dilution by a factor of 2300 (0.019% w/w blood solids) for acrylic and a factor of 610 (0.055% w/w blood solids) for cotton. The best DL for blood on polyester was found in the mid-IR spectral window corresponding to the protein Amide A absorption band at dilution by a factor of 900 (0.034% w/w blood solids). Because of the similarity between the IR spectra of blood solids and nylon fabrics, no satisfactory IR DLs were determined for the calibration of blood on nylon. We compare our values to DLs reported for blood detection using the standard luminol method. The most commonly reported luminol DLs are of the order of 1000-fold dilution, which we estimate are a factor of 2-7 lower than our reported IR DLs on a coverage basis.

Highlights From The Latest Articles in Gold Nanoparticles for Theranostics

2014 Cancer theranostics using gold-nanorods: photoacoustic imaging & photothermal therapy Evaluation of: Kim S, Chen YS, Luke GP, Emelianov SY. In-vivo ultrasound and photoacoustic image guided photothermal cancer therapy using silica-coated gold nanorods. IEEE Trans. Ultrasonics Ferroelectrics Freq. Control 5, 891–897 (2014). Gold nanoparticles have been intensively explored as photothermal transducers based on excessive optical absorption for cancer diagnosis and treatment [1,2]. By controlling the shape and size of gold nanoparticles, their localized plasmon resonance peaks can be tuned to a near-infrared spectral region in which optical light can penetrate deeper into biological tissues. Photoacoustic imaging is a hybrid biomedical imaging tool that can sensitively map the distribution of optical absorbers and local temperatures in biological tissues. Therefore, plasmonic gold nanoparticles have been widely utilized in order to maximize the photoacoustic detection sensitivity in cancer physiopathologic studies. In a recent issue of IEEE Transactions on Ultrasonics, Ferroelectrics and Frequency Control, Kim et al. demonstrated photoacoustic and ultrasound image-guided photothermal cancer therapy using silica-coated plasmonic gold nanorods in small animals in vivo. The silica-coated gold nanorods with an average length and width of 63 ± 7 nm and 35 ± 5 nm, respectively, were synthesized from cetyltrimethylammonium bromidestabilized gold nanorods [3]. Then, the biocompatibility was enhanced by switching cetyltrimethylammonium bromide with mPEG-thiol, and the mPEG polymers were used for silica coating. The plasmonic peak of the silica-coated gold nanorods was at 805 nm within the near-infrared spectral window. A xenograft tumor model was induced by subcutaneous injection of human epithelial cancer cells to the right flank of a nude mouse. A total of 200 μl of silica-coated gold nanorod solution (40 μg of gold) was intravenously injected via the tail vein. The concentrations of oxygenated hemoglobin, deoxygenated hemoglobin and silica-coated gold nanorods within the tumor site were measured by a spectroscopic photoacoustic imaging scanner. Then, photothermal therapy was performed by irradiating with continuous-wave laser beams with an average laser power of 1 W at 808 nm, and the temperature elevation was monitored by the photoacoustic imaging scanner. The temperature reached up to 16°C above the body temperature. Therefore, this paper clearly proves that silica-coated gold nanorods can be used as theranostic photoacoustic and photothermal agents for cancer studies.

Spatially resolved measurements of H2O, HCl, CO, OCS, SO2, cloud opacity, and acid concentration in the Venus near-infrared spectral windows

We observed Venus with the Apache Point Observatory 3.5 m telescope TripleSpec spectrograph (R = 3500, λ = 0.96–2.47 µm) on 1–3 March 2009 and on 25, 27, and 30 November and 2–4 December 2010. With these observations and synthetic spectra generated with the Spectral Mapping and Atmospheric Radiative Transfer model, we produce the first simultaneous maps of cloud opacity, acid concentration, water vapor (H2O), hydrogen chloride (HCl), carbon dioxide (CO), carbonyl sulfide (OCS), and sulfur dioxide (SO2) abundances in the Venusian lower atmosphere. Water measured at wavelengths near 1.18 µm (near-surface) averages 29 ± 2ppm (2009) and 27 ± 2 ppm (2010) and measured near 1.74 µm (15–30 km) averages 33 ± 2 ppm (2009) and 32 ± 2 ppm (2010). Water in both these altitude ranges is spatially homogeneous. Water measured near 2.4 µm (30–45 km) averages 34 ± 2 ppm (2009) and 33 ± 3 ppm (2010) and is spatially inhomogeneous and variable. HCl is measured near 1.74 µm to be 0.41 ± 0.04 ppm (2009) and 0.42 ± 0.05 ppm (2010). CO and OCS (2.3–2.5 µm; 30–45 km in altitude) are spatially inhomogeneous and show anticorrelation. CO (35 km) averages 25 ± 3 ppm (2009) and 22 ± 2 ppm (2010). OCS (36 km) averages 0.44 ± 0.10 ppm (2009) and 0.57 ± 0.12 ppm (2010). SO2 measurements average 140 ± 37 ppm (2009) and 126 ± 32 ppm (2010). Many species display a hemispherical dichotomy in their distribution. We find considerable spatial variability suggesting active processes with conservation between species. The most variable regions are just below the Venus cloud deck, and these may be related to changes in atmospheric circulation or virga events.