Near-infrared Signals Research Articles

A nanoscale optical biosensor based on peptide encapsulated SWCNTs for detection of acetic acid in the gaseous phase

Biosensors play a key role in almost every field of human activity – ranging from biomedical diagnosis and point-of-care health monitoring to environmental monitoring and forensics. Single-walled carbon nanotubes (SWCNTs) are one of the most promising materials for near-infrared (NIR) fluorescence-based biosensing. Herein, we develop a reusable, drop-casted, real-time optical biosensor based on peptide-encapsulated SWCNTs for the detection of low concentrations of acetic acid in the air, at room temperature. While detection of NIR signal usually requires expensive and bulky equipment, here we use the (6,5) SWCNTs chirality whose peak fluorescence lies within the range of 970 nm – 1050 nm, enabling the usage of low cost and compact silicon-based detectors. We demonstrate the detection of wine spoilage based on excess gaseous acetic acid using peptide-wrapped SWCNT sensors down to 0.05% (v/v) acetic acid concentrations. Our results open new avenues for gas phase detection using NIR fluorescent SWCNT nanosensors.

The Efficiency of DNA Labeling with Near-Infrared Fluorescent Dyes

The efficiency of DNA labeling was assessed for 2'-deoxyuridine 5'-triphosphate (dUTP) derivatives containing the Cy7 cyanine dye as a fluorophore. Two fluorescent Cy7-labeled dUTP analogs differed in the chemical structure of the linker between the fluorophore and nucleotide moieties. The efficiency of the polymerase chain reaction (PCR) and inhibition with modified nucleotides were estimated by real-time PCR. The efficiency of labeled nucleotide incorporation in PCR products was measured by quantitative electrophoresis. The efficiency of target DNA labeling was evaluated by binding the fluorescently labeled PCR products to a microarray of oligonucleotide probes immobilized in hydrogel drops (a biochip). The near-infrared hybridization signal was detected by digital luminescence microscopy. An increase in linker length was found to provide more efficient incorporation of the labeled nucleotide. Both of the compounds provided high sensitivity and high specificity of DNA testing via allele-specific hybridization on a biochip.

Encoding the complete electric field of an ultraviolet ultrashort laser pulse in a near-infrared nonlinear-optical signal.

We introduce a variation on the cross-correlation frequency-resolved optical gating (XFROG) technique that uses a near-infrared (NIR) nonlinear-optical signal to characterize pulses in the ultraviolet (UV). Using a transient-grating XFROG beam geometry, we create a grating using two copies of the unknown UV pulse and diffract a NIR reference pulse from it. We show that, by varying the delay between the UV pulses creating the grating, the UV pulse intensity-and-phase information can be encoded into a NIR signal. We also implemented a modified generalized-projections phase-retrieval algorithm for retrieving the UV pulses from these spectrograms. We performed proof-of-principle measurements of chirped pulses and double pulses, all at 400 nm. This approach should be extendable deeper into the UV and potentially even into the extreme UV or x-ray range.

Targeted NIRF/MR dual-mode imaging of breast cancer brain metastasis using BRBP1-functionalized ultra-small iron oxide nanoparticles.

Tumor metastasis to brain is the main clinical manifestation of patients with advanced breast cancer, leading to poor survival prognosis. In order to detect the early incidence of brain metastasis, it is urgent to develop hypersensitive contrast agents for multimode imaging. In this study, PEG-phospholipids coated, a phage play derived peptide, BRBP1 peptide modified ultra-small iron oxide nanoparticles were prepared for targeted NIRF and MR imaging of breast cancer brain metastasis. The nanoparticles showed 10nm core-shell, high relaxivity values and photon emission efficiency in vitro. The nanoparticles offered a T2 contrast imaging effect and near-infrared fluorescent signal enhancement. Compared with control peptide modified nanoparticles, the MR/NIRF imaging signal of BRBP1-modified nanoparticles in tumor tissue was significantly enhanced, which should be induced by the targeting ability of BRBP1 peptide. These results indicated that BRBP1-SPIO@mPEG (DiR) nanoparticles could be applied as an effective targeted delivery system for diagnosis of breast cancer brain metastasis.

(Invited) Evolution of Synthetic Molecular Recognition on Single Walled Carbon Nanotubes

Molecular recognition is fundamental to the design of therapeutics, diagnostics, and sensors. Many of these sensor technologies rely on natural or synthetic molecular recognition elements such as antibodies and aptamers, which have evolved to be highly selective for their molecular targets. However, there are numerous applications for which existing approaches to molecular recognition have been unable to generate optical probes, particularly for neuromodulators and neuropeptides. Herein, we describe a polymer evolution-based platform, in which 10^12 unique polynucleotide polymers are adsorbed to single-walled carbon nanotubes (SWNT). The SWNT-pinned polynucleotide polymers can be screened for their ability to bind a target analyte and provide a selective near-infrared fluorescence signal. Iterative selection of analyte-binding polymers that form a SWNT-surface-adsorbed phase for target recognition are identified through ionic desorption of sub-optimal polymers, and exponential amplification of synthetic polymers that recognize the target analyte. Next-generation sequencing identifies SWNT-polynucleotide conjugates with sequences selective and sensitive for the desired analyte. We demonstrate the utility of this platform for the evolution of SWNT-polymer nanosensors for neuromodulators [1] and neuropeptides, and discuss its potential for identification of chirality-specific SWNT separation. Our results suggest our platform is fundamentally generic in enabling the evolution of nanosensors from synthetic polymer-nanoparticle conjugates for any desired analyte. 1. Jeong, S., Yang, D., Beyene, A.G., O’Donnell, J.T.D., Gest, A. M., Navarro, N., Sun, X., Landry, M.P. High Throughput Evolution of Near Infrared Serotonin Nanosensors. Science Advances (2019). DOI: 10.1101/673152

An Integrated Enhancement Solution for 24-Hour Colorful Imaging

The current industry practice for 24-hour outdoor imaging is to use a silicon camera supplemented with near-infrared (NIR) illumination. This will result in color images with poor contrast at daytime and absence of chrominance at nighttime. For this dilemma, all existing solutions try to capture RGB and NIR images separately. However, they need additional hardware support and suffer from various drawbacks, including short service life, high price, specific usage scenario, etc. In this paper, we propose a novel and integrated enhancement solution that produces clear color images, whether at abundant sunlight daytime or extremely low-light nighttime. Our key idea is to separate the VIS and NIR information from mixed signals, and enhance the VIS signal adaptively with the NIR signal as assistance. To this end, we build an optical system to collect a new VIS-NIR-MIX dataset and present a physically meaningful image processing algorithm based on CNN. Extensive experiments show outstanding results, which demonstrate the effectiveness of our solution.

Evaluation of Lung Quality by Near-Infrared Fluorescent Imaging during Ex Vivo Lung Perfusion

Improved real-time assessment of donor lung quality during Ex Vivo Lung Perfusion (EVLP) could enhance safe utilization of lungs for transplantation. Near-infrared (NIR) fluorescent imaging with indocyanine green (ICG) has been used in various clinical intraoperative applications to evaluate tissue perfusion. We investigated the feasibility of NIR imaging during EVLP and aimed to detect and quantify lung perfusion and permeability. Pig lungs with extended 24-hour cold ischemia (n=4) and human lungs rejected from clinical transplantation (n=2) were assessed with NIR imaging during EVLP. Serial NIR imaging was performed with SPY Elite imaging system after ICG (0.3, 0.6 or 1.0 mg) administration through pulmonary artery (Fig A). Tissue perfusion was quantified using SPYQ analysis software, and tissue ICG accumulation was correlated with lung damage. Strong NIR signal was detected immediately after ICG administration with 0.6 mg (pig lungs) or 1.0 mg (human lungs) doses resulting in optimal fluorescence for tissue perfusion evaluation. In contrast to the transient kinetics and fast liver metabolism during clinical in vivo ICG administration, a single ICG dose during EVLP resulted in stable NIR signal for over 10 hours. Perfusion quantification of pig lungs with extended cold preservation revealed peripheral areas with compromised tissue perfusion that gradually recovered over time with recruitment of additional pulmonary vascular beds (Fig B). ICG accumulation was detected in sites with damage and increased vascular permeability in pig and human lungs (Fig C and D). NIR imaging with a clinically-approved intravascularly-delivered ICG fluorescent probe can dynamically quantify tissue perfusion and detect damage-induced vascular permeability. This novel and promising imaging modality could be used during EVLP to assess lung quality, or to determine effects of therapeutics that target tissue perfusion and vascular permeability.

Fluoro-Photoacoustic Polymeric Renal Reporter for Real-Time Dual Imaging of Acute Kidney Injury.

Photoacoustic (PA) imaging agents detect disease tissues and biomarkers with increased penetration depth and enhanced spatial resolution relative to traditional optical imaging, and thus hold great promise for clinical applications. However, existing PA imaging agents often encounter the issues of slow body excretion and low-signal specificity, which compromise their capability for in vivo detection. Herein, a fluoro-photoacoustic polymeric renal reporter (FPRR) is synthesized for real-time imaging of drug-induced acute kidney injury (AKI). FPRR simultaneously turns on both near-infrared fluorescence (NIRF) and PA signals in response to an AKI biomarker (γ-glutamyl transferase) with high sensitivity and specificity. In association with its high renal clearance efficiency (78% at 24 h post-injection), FPRR can detect cisplatin-induced AKI at 24 h post-drug treatment through both real-time imaging and optical urinalysis, which is 48 h earlier than serum biomarker elevation and histological changes. More importantly, the deep-tissue penetration capability of PA imaging results in a signal-to-background ratio that is 2.3-fold higher than NIRF imaging. Thus, the study not only demonstrates the first activatable PA probe for real-time sensitive imaging of kidney function at molecular level, but also highlights the polymeric probe structure with high renal clearance.

The Valsalva maneuver: an indispensable physiological tool to differentiate intra versus extracranial near-infrared signal.

Developing near-infrared spectroscopy (NIRS) parameter recovery techniques to more specifically resolve brain physiology from that of the overlying tissue is an important part of improving the clinical utility of the technology. The Valsalva maneuver (VM) involves forced expiration against a closed glottis causing widespread venous congestion within the context of a fall in cardiac output. Due to the specific anatomical confines and metabolic demands of the brain we believe a properly executed VM has the ability to separate haemodynamic activity of brain tissue from that of the overlying scalp as observed by NIRS, and confirmed by functional magnetic resonance imaging (fMRI). Healthy individuals performed a series of standing maximum effort VMs under separate observation by frequency domain near-infrared spectroscopy (FD-NIRS) and fMRI. Nine individuals completed the clinical protocol (6 males, age 21-40). During the VMs, brain and extracranial tissue targeted signal were significantly different (opposite direction of change) in both fMRI and NIRS (p=0.00025 and 0.00115 respectively), with robust cross correlation of parameters between modalities. Four of these individuals performed further VMs after infiltrating 2% xylocaine/1:100,000 epinephrine (vasoconstrictor) into scalp tissue beneath the probes. No significant difference in the cerebrally derived parameters was observed. The maximum effort VM has the ability to separate NIRS observable physiology of the brain from the overlying extracranial tissue. Observations made by this FD cerebral NIRS device are comparable with fMRI in this context.

Artificial Synapses: Near‐Infrared‐Irradiation‐Mediated Synaptic Behavior from Tunable Charge‐Trapping Dynamics (Adv. Electron. Mater. 2/2020)

In article number 1900765, Vellaisamy A. L. Roy, Ye Zhou, Su-Ting Han, and co-workers demonstrate a photonic synaptic transistor based on a tunable charge-trapping medium. The device senses and responds to near-infrared light signals, and can mimic memorization and dynamic forgetting processes, enabling device-level synaptic evolution from short-term to long-term neuroplasticity.

Self-powered, superior high gain silicon-based near-infrared photosensing for low-power light communication

Although Silicon (Si) is the cornerstone of state-of-the-art integrated circuit, Si photonics still suffer many challenges regarding low-power consumption, high-integrated and miniaturization. Herein, by combining the pyro-phototronic effect and quantum tunneling effect, we develop a self-powered Si-based near-infrared (NIR) photodetector (PD) with ultrafast response-speed, high gain and excellent wavelength selectivity. The fabricated p-Si/Al2O3/n-ZnO NWs heterojuncted NIR PD exhibits a superior photoresponsivity up to 0.41 A W−1 and detectivity higher than 3.68 × 1012 Jones, with the photoresponse time as low as 15 μs. These results are much better than most of the previously reported NIR PDs based on semiconductor nanowires and even other emerging two-dimensional (2D) materials. Furthermore, the fabricated NIR PD is then used as a self-powered signal receiver to construct a low-power NIR light communication system that can decode and transmit the encoded NIR signals from a commercial remote controller. This work not only provides in-depth understandings about the pyro-phototronic effect and quantum tunneling effect in Si-based heterojuncted structures, but also indicates their potential applications in low-power communication systems.

Health Monitoring of Human Multiple Physiological Parameters Based on Wireless Remote Medical System

Telemedicine, as a new technical means and medical model, can truly realize the sharing and monitoring of telemedicine information, and ultimately ensure that everyone has equal access to medical and health resources. Based on the research on the status of telemedicine application and wireless communication technology, this paper proposes a multi-physical parameter wireless telemedicine health monitoring system solution, and analyzes the overall structure and functional requirements of the system. Human physiological parameters of the wireless remote medical system for health monitoring include body temperature, respiration, blood oxygen saturation, pulse, blood pressure, and electrocardiogram. In this paper, fabric electrodes are used to extract human bioimpedance signals, discrete Fourier transform algorithm is used to detect human respiratory signals, and respiratory rate is detected based on dynamic differential threshold peak detection technology. The reflection type photoelectric sensor is used to realize the reflection of the human pulse signal, and the continuous measurement of the cuff-free blood pressure based on the pulse wave conduction time is combined with the ECG (Electrocardiogram) data. A self-learning threshold algorithm based on near-infrared photo plethysmo graphy signal trough detection is designed on the reflective blood oxygen saturation calculation algorithm. The difference threshold method is used to extract the QRS band feature points. We tested the overall operation of the system. The results show that the collected human physiological signal data is accurate. After a series of tests, the validity and reliability of the collected physiological signals have been proven.

Cascaded Multiresponsive Self-Assembled 19F MRI Nanoprobes with Redox-Triggered Activation and NIR-Induced Amplification.

Molecular probes featuring promising capabilities including specific targeting, high signal-to-noise ratio, and in situ visualization of deep tissues are in great demand for tumor diagnosis and therapy. 19F magnetic resonance imaging (MRI) techniques incorporating stimuli-responsive probes are anticipated to be highly beneficial for specific detection and imaging of tumors because of negligible background and deep tissue penetration. Herein, we report a cascaded multiresponsive self-assembled nanoprobe, which enables sequential redox-triggered and near-infrared (NIR) irradiation-induced 19F MR signal activation/amplification for sensing and imaging. Specifically, we designed and synthesized a cascaded multiresponsive 19F-bearing nanoprobe based on the self-assembly of amphiphilic redox-responsive 19F-containing polymers and NIR-absorbing indocyanine green (ICG) molecules. It could realize the activation of 19F signals in the reducing tumor microenvironment and subsequent signal amplification via the photothermal process. This stepwise two-stage activation/amplification of 19F signals was validated by 19F NMR and MRI both in vitro and in vivo. The multiresponsive 19F nanoprobes capable of cascaded 19F signal activation/amplification and photothermal effect exertion can provide accurate sensing and imaging of tumors.

High performance one-for-all phototheranostics: NIR-II fluorescence imaging guided mitochondria-targeting phototherapy with a single-dose injection and 808 nm laser irradiation

Current phototheranostics is still encountering various impediments, which causes complicated and prolonged therapy, and increases unnecessary side effects and systemic toxicity to patients. Herein, mitochondria-targeting one-for-all phototheranostic nanoparticles based on single-component organic molecule were designed and fabricated. After being irradiated with a single 808 nm laser, outstanding second near-infrared (NIR-II) fluorescence signals (with a high fluorescence quantum yield of 2.2% in water) were obtained for NIR-II fluorescence imaging, which could efficiently locate tumor and real-time monitor the therapeutic process. Moreover, such nanoparticles also presented superb photothermal conversion efficiency (39.6%) and singlet oxygen yield (2.3%, almost 12 times higher than clinical NIR dye indocyanine green) under 808 nm laser illumination, which could produce both potent hyperthermia and abundant singlet oxygen, resultantly leading to the mitochondrial dysfunction and further cell apoptosis. Both in vitro and in vivo investigations demonstrated that such nanoagents displayed significantly tumor theranostic efficacy, resulting from single 808 nm laser triggered high performance NIR-II fluorescence imaging guided mitochondria-targeting phototherapy. It was noteworthy that only a single-dose injection and 808 nm laser irradiation were employed during in vivo treatment. We believe that the phototheranostic nanoparticles developed in this work will open up a new dimension in cancer theranostics.

Comparison of Satellite-Derived Precipitable Water Vapor Through Near-Infrared Remote Sensing Channels

The retrieval accuracies of three typical near-infrared (NIR) precipitable water vapor (PWV) products are thoroughly discussed in this article. The NIR PWV data are obtained from three satellite sensors: the Moderate-Resolution Imaging Spectroradiometer (MODIS)/Terra, the medium-resolution imaging spectrometer (MERIS)/Envisat, and the medium-resolution spectral imager (MERSI)/FY-3A. Collocated Global Positioning System (GPS) PWV data from GPS network are employed as the reference data set because of its high precision in water vapor measurement. Relative difference and root-mean-square (rms) difference are computed for “Clear,” “Cloudy,” and “All Weather” categories for each NIR water vapor product. The results reveal that PWV derived from NIR sensors tend to underestimate the water vapor values with the existence of cloud, as NIR signals cannot penetrate the cloud. Under “Clear” condition, the overall rms for remote sensors are close to the expected goal accuracies, namely, with root-mean-square-error (RMSE) of 5.480 mm for MODIS/Terra, 3.708 mm for MERIS/Envisat, 8.644 mm for MERSI/FY-3A. MERIS/Envisat has the highest PWV retrieval accuracy, while the MODIS/Terra PWV product has the best correlation with GPS PWV ( $R^{2}$ is 0.951). The MODIS/Terra tends to overestimate PWV value, while MERSI/FY-3A tends to underestimate the PWV value. Moreover, a comprehensive comparison of seasonal variation and wet/dry variation for each NIR PWV product is also performed in this study. The results indicate that the RMSE increases significantly under wet conditions (PWV larger than 20 mm) than under dry conditions (PWV smaller than 20 mm) for all remote sensing PWV products.

Imaging of X-Ray-Excited Emissions from Quantum Dots and Biological Tissue in Whole Mouse

Optical imaging in clinical and preclinical settings can provide a wealth of biological information, particularly when coupled with targetted nanoparticles, but optical scattering and absorption limit the depth and resolution in both animal and human subjects. Two new hybrid approaches are presented, using the penetrating power of X-rays to increase the depth of optical imaging. Foremost, we demonstrate the excitation by X-rays of quantum-dots (QD) emitting in the near-infrared (NIR), using a clinical X-ray system to map the distribution of QDs at depth in whole mouse. We elicit a clear, spatially-resolved NIR signal from deep organs (brain, liver and kidney) with short (1 second) exposures and tolerable radiation doses that will permit future in vivo applications. Furthermore, X-ray-excited endogenous emission is also detected from whole mouse. The use of keV X-rays to excite emission from QDs and tissue represent novel biomedical imaging technologies, and exploit emerging QDs as optical probes for spatial-temporal molecular imaging at greater depth than previously possible.

Naked-Eye Readout of Analyte-Induced NIR Fluorescence Responses by an Initiation-Input-Transduction Nanoplatform.

Fluorescence visualization (FV) in the near-infrared (NIR) window promises to break through the signal-to-background ratio (SBR) bottleneck of traditional visible-light-driven FV methods. However, straightforward NIR-FV has not been realized, owing to the lack of methods to readily transduce NIR responses into instrument-free, naked eye-recognizable outputs. Now, an initiation-input-transduction platform comprising a well-designed NIR fluorophore as the signal initiator and lanthanide-doped nanocrystals as the transducer for facile NIR-FV is presented. The analyte-induced off-on NIR signal serves as a sensitizing switch of transducer visible luminescence for naked-eye readout. The design is demonstrated for portable, quantitative detection of phosgene with significantly improved SBR and sensitivity. By further exploration of initiators, this strategy holds promise to create advanced NIR-FV probes for broad sensing applications.

Naked‐Eye Readout of Analyte‐Induced NIR Fluorescence Responses by an Initiation–Input–Transduction Nanoplatform

AbstractFluorescence visualization (FV) in the near‐infrared (NIR) window promises to break through the signal‐to‐background ratio (SBR) bottleneck of traditional visible‐light‐driven FV methods. However, straightforward NIR‐FV has not been realized, owing to the lack of methods to readily transduce NIR responses into instrument‐free, naked eye‐recognizable outputs. Now, an initiation–input–transduction platform comprising a well‐designed NIR fluorophore as the signal initiator and lanthanide‐doped nanocrystals as the transducer for facile NIR‐FV is presented. The analyte‐induced off–on NIR signal serves as a sensitizing switch of transducer visible luminescence for naked‐eye readout. The design is demonstrated for portable, quantitative detection of phosgene with significantly improved SBR and sensitivity. By further exploration of initiators, this strategy holds promise to create advanced NIR‐FV probes for broad sensing applications.

Near‐Infrared‐Irradiation‐Mediated Synaptic Behavior from Tunable Charge‐Trapping Dynamics

AbstractParallel information storage coupled with storage density is a major focus for non‐volatile memory devices to achieve neuromorphic computing that can work at low power. In this regard, a photoactive charge‐trapping medium consisting of inorganic heteronanosheets for the fabrication of a synaptic transistor is demonstrated. This synaptic device senses and responds to near‐infrared (NIR) light signals and mimics the memorization and dynamic forgetting process due to the reversible nature of photogenerated charge interaction. Device‐level synaptic evolutions from short‐term plasticity to long‐term plasticity, paired pulse facilitation, and paired pulse depression are realized with light modulation on the weight update terminal. To understand the underlying mechanism of the synaptic behavior under NIR signals, systematic analysis is carried out using in situ atomic force microscopy based electrical techniques. With its photoactive architecture, this information processing analogue is validated for visual object recognition, which paves the way for implementing NIR‐controlled neuromorphic computing.

Near-Infrared Imaging with Second-Window Indocyanine Green in Newly Diagnosed High-Grade Gliomas Predicts Gadolinium Enhancement on Postoperative Magnetic Resonance Imaging.

Intraoperative molecular imaging with tumor-targeting fluorophores offers real-time detection of neoplastic tissue. The second window indocyanine green (SWIG) technique relies on passive accumulation of indocyanine green (ICG), a near-infrared fluorophore, in neoplastic tissues. In this study, we explore the ability of SWIG to detect neoplastic tissue and to predict postoperative magnetic resonance imaging (MRI) findings intraoperatively. Retrospective data were collected from 36 patients with primary high-grade gliomas (HGG) enrolled as part of a larger trial between October 2014 and October 2018. Patients received systemic ICG infusions at 2.5-5 mg/kg 24 h preoperatively. Near-infrared fluorescence was recorded throughout the case and from biopsy specimens. The presence/location of residual SWIG signal after resection was compared to the presence/location of residual gadolinium enhancement on postoperative MRI. The extent of resection was not changed based on near-infrared imaging. All 36 lesions demonstrated strong near-infrared fluorescence (signal-to-background = 6.8 ± 2.2) and 100 % of tumors reaching the cortex were visualized before durotomy. In 78 biopsy specimens, near-infrared imaging demonstrated higher sensitivity and accuracy than white light for diagnosing neoplastic tissue intraoperatively. Furthermore, near-infrared imaging predicted gadolinium enhancement on postoperative MRI with 91 % accuracy, with visualization of residual enhancement as small as 0.3 cm3. Patients with no residual near-infrared signal after resection were significantly more likely to have complete resection on postoperative MRI (p value < 0.0001). Intraoperative imaging with SWIG demonstrates highly sensitive detection of HGG tissue in real time. Furthermore, post-resection near-infrared imaging correlates with postoperative MRI. Overall, our findings suggest that SWIG can provide surgeons with MRI-like results in real time, potentially increasing resection rates.