Down-conversion Nanoparticles Research Articles

Selective Twin NIR‐IIb Ratiometric Luminescence Nanoprobes Enable the Accurate Visualization of MPO‐Mediated Oxidative Stress in Acute Liver Injury

AbstractOxidative stress, orchestrated by myeloperoxidase (MPO), plays crucial roles in the progression of many diseases. Nonetheless, the role of MPO‐mediated oxidative stress in distinct factor‐induced acute liver injuries (ALI) is still up for dispute, mainly due to the lack of probes for in vivo monitoring of MPO releases. Here, a highly selective MPO probe (CSQ) based on the epoxidation biochemical reaction within the MPO‐H2O2‐Cl− system is screened to construct dual near infrared‐IIb (NIR‐IIb) ratiometric (F1550Em, 808Ex/F1550Em, 980Ex) luminescence nanoprobes by integrating CSQ onto down conversion nanoparticles (DCNPs) with and without liver‐targeting moiety (twin NIR‐IIb nanoprobes). Liver‐targeting probes are employed to monitor MPO release, whereas non‐liver‐targeting probes are utilized to assess MPO activity across all cell types. Using twin NIR‐IIb nanoprobes, the MPO‐mediated oxidative stress progressively increased are observed in carbon tetrachloride (CCl4)‐induced ALI over 12 h. In contrast, the MPO‐mediated oxidative stress in acetaminophen (APAP)‐induced ALI initially increased, peaked within 3 h, and then rapidly weakened to normal levels within 12 h. Importantly, the differential release of MPO from neutrophils/Kupfer cells to extracellular fluids in the two types of ALI is revealed. This work reveals significant differences in MPO distribution and the role of MPO‐mediated oxidative stress in CCl4 and APAP‐induced ALI.

Remarkable Plasmonic Enhanced Luminescence of Ce3+doped Lanthanide Downconversion Nanoparticles in NIR‐II Window by Silver Hole‐Cap Nanoarrays

AbstractLanthanide downconversion nanoparticles (DCNPs) have huge potential in biosensing and imaging applications in the NIR‐II window. However, DCNPs inherently suffer from low quantum efficiency, due to low absorption cross‐section and the restricted doping concentration of lanthanide ions. In this work, a combined strategy for downconversion luminescence in the NIR‐II window is investigated by the integration of Ce3+ ions into the conventional NaYF4: Yb3+, Er3+ DCNPs and incorporation of periodic silver hole‐cap coupled Nanoarrays (Ag‐HCNAs) simultaneously. Over two orders of magnitude, luminescence enhancement is achieved by the combination of optimized Ce3+ doping and plasmonic effects, compared to NaYF4: Yb3+, Er3+ DCNPs immobilized on the glass substrate. Moreover, 3D Finite‐Difference Time‐Domain (FDTD) simulations and time‐resolved luminescence measurements are combined to gain important insights into the mechanism of downconversion luminescence enhancement. The results show that there is a large electric field enhancement between the Ag nanoholes and the Ag hemisphere cap at 980 nm (excitation enhancement), while the lifetime shortening at 1525 nm revealed an increased radiative decay rate and enhanced quantum yield (emission rate enhancement). The strategy for downconversion luminescence enhancement demonstrated in this work holds a significant potential for advancing the next generation biosensing and bioimaging based on DCNPs in the NIR‐II window.

Quantitative Imaging of MicroRNA‐21 In Vivo for Real‐Time Monitoring of the Cancer Initiation and Progression

AbstractMicroRNA‐21 (MiR‐21) has been confirmed to be upregulated in tumors, and its abnormal expression is closely associated with tumor occurrence. However, the traditional imaging methods are limited to qualitative imaging of miR‐21, and no effective strategy has been developed for monitoring its concentration in vivo during cancer initiation and progression. Herein, a biosensor is created utilizing a NIR‐II ratiometric fluorescent nanoprobe to quantitatively monitor dynamic alterations in miR‐21 levels in vivo. The nanoprobe (termed DCNP@DNA2@IR806) is constructed by introducing IR806 as a donor and down‐conversion nanoparticles (DCNP) as the acceptor, using DNA as linkers. Upon miR‐21‐responsive initiation of the nanoprobe, the 1550 nm fluorescent signal of DCNP stimulated by a 808 nm laser (F1550, 808Ex) increased because of the close proximity of IR806 to the DCNP and the subsequent non‐radiative energy transfer (NRET). Meanwhile, the 1550 nm fluorescent signal of DCNP stimulated by a 980 nm laser (F1550, 980Ex) remained stable because of the absence of NRET. This ratiometric NIR‐II fluorescent signal has been confirmed to be a reliable indicator of miR‐21 concentration in vivo. The strategy holds promise for further enhancing the understanding of microRNAs‐based molecular mechanisms underlying cancer progression, laying a foundation for the early diagnosis of microRNAs‐related diseases.

A Room-Temperature Strategy to Synthesize Ce/Tb-Codoped NaYF4 Nanoparticles with a Photoluminescence Quantum Yield Exceeding 50.

NaYF4:Ce3+,Tb3+ down-conversion nanoparticles with a photoluminescence quantum yield (PLQY) of 54.8% are synthesized by using a ligand-assisted coprecipitation method in this study. The reaction is completed within 1 min at room temperature, and short-chain hexanoic acid and hexylamine serve as the binary ligands, which enable us to synthesize highly luminescent NaYF4:Ce3+,Tb3+ nanoparticles at room temperature. X-ray diffraction (XRD) and transmission electron microscopy (TEM) are used to characterize the as-prepared nanocrystals. The results reveal that the NaYF4:Ce3+,Tb3+ nanocrystals exhibit excellent dispersion and have a particle size of 2.7 nm. Our NaYF4:Ce3+,Tb3+ nanocrystals possess the advantages of room-temperature preparation, high PLQY, and ultrasmall particle size. These results reveal that the NaYF4:Ce3+,Tb3+ nanocrystals might have a high potential in the applications of lighting, display devices, and bioimaging.

Activatable Nanoprobes for Dual‐Modal NIR‐II Photoacoustic and Fluorescence Imaging of Hydrogen Sulfide in Colon Cancer

AbstractHigh hydrogen sulfide (H2S) expression has been shown to play a crucial role in tumor growth and proliferation in colon cancer. So far, most probes used for monitoring H2S offer single‐modal imaging, which makes the collection of accurate information for tumor diagnosis difficult. In the present study, a novel dual‐modal imaging probe in the second near‐infrared (NIR‐II, 950‐1700) window is proposed and constructed by coating a uniform shell of polydopamine (PDA) on the surface of cuprous oxide (Cu2O)‐conjugated downconversion nanoparticles (DCNPs). Of note, DCNP‐Cu2O@PDA is in the “on” state, with emission centered at 1550 nm (irradiation using a 980nm laser) in non‐neoplastic tissues. Colon tumors with endogenous H2S overexpression can induce the in situ transformation of Cu2O to copper sulfide (Cu2‐XS）. Owing to the competitive absorption between Cu2‐XS and DCNPs at a wavelength of 980 nm, the generated DCNP‐Cu2‐XS@PDA exhibits a quenched NIR‐II fluorescence (FL) signal. Meanwhile, Cu2‐XS exhibits a strong absorbance at 1250 nm, enhancing the NIR‐II photoacoustic (PA) signal accompanied by NIR‐II FL attenuation. The switching in PA and FL signals at the tumor site offered “double assurances” for the accurate monitoring of H2S.

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.

Plasmonic‐Enhanced NIR‐II Downconversion Fluorescence beyond 1500 nm from Core–Shell–Shell Lanthanide Nanoparticles

AbstractThis paper reports on the light amplification of NaGdF4:Yb,Er,Ce@NaGdF4:Yb,Nd@NaGdF4 core–shell–shell downconversion nanoparticles (CSS‐DCNPs) in the near‐infrared second biological window (NIR‐II: 1000–1700 nm) by plasmonic nanostructures. Through a precisely controlled plasmonic metallic nanostructure, fluorescence from Yb3+ induced 1000 nm emission, Nd3+ induced 1060 nm emission, and Er3+ induced 1527 nm emission are enhanced 1.6‐fold, 1.7‐fold, and 2.2‐fold, respectively, under an 808 nm laser excitation for the CSS‐DCNPs coupled with a gold hole‐cap nanoarray (Au‐HCNA), while the Er3+ induced 1527 nm emission under a 980 nm laser excitation is enhanced up to 6‐fold. To gain insight into the enhancement mechanism, the plasmonic modulation of Er3+ induced NIR‐II emission at 1550 nm under 980 nm excitation is studied by FDTD simulation and lifetime measurements, showing the observed fluorescence enhancement can be attributed to a combination of enhanced excitation and an increased radiative decay rate.

Handheld NIR-to-NIR Platform for on-site evaluating protective neutralizing antibody against SARS-CoV-2 ancestral strain and Omicron variant after vaccination or infection

Lateral flow assays (LFAs) are promising points-of-care tests, playing a vital role in diseases screening, diagnosis and surveillance. However, development of portable, cheap, and smart LFAs platform for sensitive and accurate quantification of disease biomarkers in complex media is challenging. Here, a cheap handheld device was developed to realize on-site detection of disease biomarkers by Nd3+/Yb3+ co-doped near-infrared (NIR)-to-NIR downconversion nanoparticles (DCNPs) based LFA. Its sensitivity is at least 8-fold higher for detecting NIR light signal from Nd3+/Yb3+ co-doped nanoparticles than conventional expensive InGaAs camera based detection platform. Additionally, we enhance NIR quantum yield of Nd3+/Yb3+ co-doped nanoparticles up to 35.5% via simultaneous high dopant of sensitizer ions Nd3+ and emitter ions Yb3+. Combination of NIR-to-NIR handheld detection device and ultra-bright NIR emitting NaNbF4:Yb60%@NaLuF4 nanoparticle probe allows the detection sensitivity of SARS-CoV-2 ancestral strain and Omicron variants specific neutralizing antibodies LFA up to the level of commercial enzyme linked immunosorbent assay kit. Furthermore, by this robust method, enhanced neutralizing antibodies against SARS-CoV-2 ancestral strain and Omicron variants are observed in healthy participants with Ad5-nCoV booster on top of two doses of inactivated vaccine. This NIR-to-NIR handheld platform provides a promising strategy for on-site evaluating protective humoral immunity after SARS-CoV-2 vaccination or infection.

Near-Infrared Persistent Luminescence Nanoprobe for Ultrasensitive Image-Guided Tumor Resection.

Near-infrared (NIR) fluorescence imaging poses significant superiority over traditional medical imaging for tumor resection, thus having attracted widely attention. However, for tiny tumor residues, it requires relative high sensitivity to determine. Here, based on persistent luminescence nanoparticles (PLNPs), an ultrasensitive nanoprobe with extraordinary tumor imaging result is developed to guide surgical removal. Persistent luminescence (PersL) is quenched in normal tissue by the outer layer of MnO2 , and is recovered due to the degradation of MnO2 in tumor microenvironment, significantly improving the sensitivity of tumor imaging. Combined with the absence of background fluorescence in imaging of PLNPs, ultrahigh sensitivity is achieved. In orthotopic breast cancer model, the intraoperative tumor-to-normal tissue (T/NT) signal ratio of the nanoprobe is 58.8, about 9 times that of downconversion nanoparticles. The T/NT ratio of residual tumor (<2mm) remains 12.4, considerably high to distinguish tumor tissue from normal tissue. Besides, multiple-microtumor, 4T1 liver-implanted tumor and lung metastasis models are built to prove that this ultrasensitive nanoprobe is feasible to recognize tumor residues. Notably, PersL imaging takes only 1.5min, appropriate to be applied for intraoperative imaging. Overall, an ultrasensitive and convenient imaging for recognizing residual tumor tissue is introduced, holding promise for complete surgical removal.

NIR-IIb fluorescence-image guided synergistic surgery/starvation/chemodynamic therapy: an innovative treatment paradigm for malignant non-small cell lung cancers.

Background: Currently, the prognosis and survival rate for patients bearing non-small cell lung cancer (NSCLC) is still quite poor, mainly due to lack of efficient theranostic paradigms to exert in time diagnostics and therapeutics. Methods: Herein, for NSCLC treatment, we offer a customized theranostic paradigm, termed NIR-IIb fluorescence diagnosis and synergistic surgery/starvation/chemodynamic therapeutics, with a newly designed theranostic nanoplatform PEG/MnCuDCNPs@GOx. The nanoplatform is composed of brightly NIR-II emissive downconversion nanoparticles (DCNPs)-core and Mn/Cu-silica shell loaded with glucose oxidase (GOx) to achieve synergistic starvation and chemodynamic therapy (CDT). Results: It is found that 10% Ce3+ doped in the core and 100% Yb3+ doped in the middle shell greatly improves the NIR-IIb emission up to even 20.3 times as compared to the core-shell DCNPs without Ce3+ doping and middle shell. The bright NIR-IIb emission of the nanoplatform contributes to sensitive margin delineation of early-stage NSCLC (diameter < 1 mm) with a signal-to-background ratio (SBR) of 2.18, and further assists in visualizing drug distribution and guiding surgery/starvation/chemodynamic therapy. Notably, the starvation therapy mediated by GOx-driven oxidation reaction efficiently depletes intratumoral glucose, and supplies H2O2 to boost the CDT mediated by the Mn2+ and Cu2+, which consequently realized a highly effective synergistic treatment for NSCLC. Conclusion: This research demonstrates an efficient treatment paradigm for NSCLC with NIR-IIb fluorescence diganosis and image-guided synergistic surgery/starvation/chemodynamic therapeutics.

Microenvironment‐Tailored Catalytic Nanoprobe for Ratiometric NIR‐II Fluorescence/Photoacoustic Imaging of H2O2 in Tumor and Lymphatic Metastasis

AbstractIn vivo H2O2 visualization is crucial for disease diagnosis. Catalytic reaction‐based probes show potential in H2O2 detection, yet their in vivo application remains challenging because catalysts always require a specific pH to function and cellular glutathione (GSH) may suppress signaling by depletion of hydroxyl radicals and oxidized substrates. Here, a microenvironment‐tailored catalytic nanoprobe (MTCN) comprising Fe2+, citric acid (CA), 2,2′‐azino‐bis(3‐ethylbenzothiazoline‐6‐sulfonic acid) diammonium salt (ABTS), and downconversion nanoparticles in the liposomal cavity as well as a reference dye in the lipid membrane is reported, which utilizes the selective permeability of the liposomal membrane to offer a favorable pH for Fe2+ catalyst with the aid of CA and to avoid GSH‐triggered signal loss by preventing entry of GSH into the cavity. The MTCN displays a large NIR‐II fluorescence (FL) ratio between 1550 and 1080 nm (FL1550Em,808Ex/FL1080Em,980Ex), but a small photoacoustic (PA) ratio between 808 and 1048 nm (PA808/PA1048). Upon exposure of MTCN to H2O2, catalytic conversion of ABTS into its oxidized form ABTS·+ with 808 nm absorption causes a noticeable increment in PA808/PA1048 accompanied by an apparent decrement in FL1550Em,808Ex/FL1080Em,980Ex, enabling bimodal ratiometric imaging of H2O2 in the tumor and lymphatic metastasis.

Lanthanide/Cu2-xSe Nanoparticles for Bacteria-Activated NIR-II Fluorescence Imaging of Infection.

A material system enabling specific NIR-II fluorescence imaging of Gram-positive bacteria is described. The material system is based on the electrostatic binding of Cu2-xSe and vancomycin-modified NaGdF4:Nd,Yb@NaGdF4 downconversion nanoparticles (DCNPs), the fluorescence of which is weak owing to the spectral overlap of Cu2-xSe absorption with the DCNP NIR emission. The presence of Gram-positive bacteria precisely disconnects the bond between vancomycin-modified DCNPs and Cu2-xSe, thus enabling a strong fluorescent signal. In vivo studies show that the material system can be specifically activated at the site of Gram-positive bacterial infection but is essentially nonfluorescent in the area of Gram-negative bacterial infection.

Tracking Cell Viability for Adipose-Derived Mesenchymal Stem Cell-Based Therapy by Quantitative Fluorescence Imaging in the Second Near-Infrared Window.

Cell survival rate determines engraftment efficiency in adipose-derived mesenchymal stem cell (ADSC)-based regenerative medicine. In vivo monitoring of ADSC viability to achieve effective tissue regeneration is a major challenge for ADSC therapy. Here, we developed an activated near-infrared II (NIR-II) fluorescent nanoparticle consisting of lanthanide-based down-conversion nanoparticles (DCNPs) and IR786s (DCNP@IR786s) for cell labeling and real-time tracking of ADSC viability in vivo. In dying ADSCs due to excessive ROS generation, absorption competition-induced emission of IR786s was destroyed, which could turn on the NIR-II fluorescent intensity of DCNPs at 1550 nm by 808 nm laser excitation. In contrast, the NIR-II fluorescent intensity of DCNPs was stable at 1550 nm by 980 nm laser excitation. This ratiometric fluorescent signal was precise and sensitive for tracking ADSC viability in vivo. Significantly, the nanoparticle could be applied to quantitively evaluate stem cell viability in real-time in vivo. Using this method, we successfully sought two small molecules including glutathione and dexamethasone that could improve stem cell engraftment efficiency and enhance ADSC therapy in a liver fibrotic mouse model. Therefore, we provide a potential strategy for real-time in vivo quantitative tracking of stem cell viability in ADSC therapy.

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

Acquired brain injury (ABI), which is the umbrella term for all brain injuries, is one of the most dangerous diseases resulting in high morbidity and mortality, making it extremely significant to early diagnosis of ABI. Current methods, which are mainly composed of X-ray computed tomography and magnetic resonance angiography, remain limited in diagnosis of ABI with respect to limited spatial resolution and long scanning times. Here, we reported through-skull fluorescence imaging of mouse cerebral vasculature without craniotomy, utilizing the fluorescence of down-conversion nanoparticles (DCNPs) in the 1.3 - 1.7 μm near-infrared window (NIR-II window). Due to its high spatial resolution of 22.79 μm, the NIR-II fluorescence imaging method could quickly distinguish the brain injury region of mice after performing the stab wound injury (traumatic brain injury) and ischemic stroke (non-traumatic brain injury), enabling it a powerful tool in the noninvasive and early diagnosis of ABI.

NaGdF4:Nd@NaGdF4 Core-Shell Down-Conversion Nanoparticles as NIR-II Fluorescent Probes for Targeted Imaging of Bacteria

Bacterial infections are a serious ongoing threat to human health. As such, within the context of modern technology, there is an urgent need to develop fluorescent probes suitable for diagnosing bacterial infections in vivo. Herein, we synthesize NaGdF4:Nd@NaGdF4 core-shell down-conversion nanoparticles (DCNPs) demonstrating excellent emission intensity in the second near-infrared (NIR-II) window for use as fluorescent probes to enable high-quality imaging of pathogenic infections. The fluorescent probe is covalently linked with vancomycin (Van), which specifically binds to Gram-positive bacteria such as S. aureus. Both in vitro detection and in vivo imaging results show that the Van-modified NIR-II fluorescent probe can distinguish Gram-positive from Gram-negative bacteria with a high degree of selectivity. Biocompatibility is verified by MTT assay and histological analyses.

In Vivo Tracking of Cell Viability for Adoptive Natural Killer Cell‐Based Immunotherapy by Ratiometric NIR‐II Fluorescence Imaging

AbstractThe therapeutic efficacy of natural killer (NK) cells‐based immunotherapy is greatly related with the survival of transplanted NK cells. However, no effective strategy was reported to monitor NK cell viability in adoptive immunotherapy in vivo. Herein, we develop a ratiometric NIR‐II fluorescence imaging strategy to quantitively track and visualize the adoptive NK cell viability in vivo in real‐time. The nanoprobe consists of lanthanide‐based down‐conversion nanoparticles (DCNP) coated with IR786s, a reactive oxygen species (ROS) sensitive to NIR dye, which was directly labeled with NK cells. Upon cell death, the excessive ROS generation occurred within NK cells, along with IR786s degradation, turning on NIR‐II fluorescent signal at 1550 nm of DCNP under 808‐nm excitation, while the fluorescent signal at 1550 nm of DCNP under 980‐nm excitation was stable. Such an intracellular ROS‐induced ratiometric NIR‐II fluorescent signal was validated to correlate well with NK cell viability in vivo. Using this nanoreporter, we further demonstrated that co‐treatment with IL‐2, IL‐15, and IL‐21 could improve NK cell viability in vivo, achieving enhanced immunotherapy for orthotopic hepatocellular carcinoma. Overall, this strategy allows for longitudinal and quantitative tracking of NK cell viability in NK cell‐based immunotherapy.

In Vivo Tracking of Cell Viability for Adoptive Natural Killer Cell-Based Immunotherapy by Ratiometric NIR-II Fluorescence Imaging.

The therapeutic efficacy of natural killer (NK) cells-based immunotherapy is greatly related with the survival of transplanted NK cells. However, no effective strategy was reported to monitor NK cell viability in adoptive immunotherapy in vivo. Herein, we develop a ratiometric NIR-II fluorescence imaging strategy to quantitively track and visualize the adoptive NK cell viability in vivo in real-time. The nanoprobe consists of lanthanide-based down-conversion nanoparticles (DCNP) coated with IR786s, a reactive oxygen species (ROS) sensitive to NIR dye, which was directly labeled with NK cells. Upon cell death, the excessive ROS generation occurred within NK cells, along with IR786s degradation, turning on NIR-II fluorescent signal at 1550 nm of DCNP under 808-nm excitation, while the fluorescent signal at 1550 nm of DCNP under 980-nm excitation was stable. Such an intracellular ROS-induced ratiometric NIR-II fluorescent signal was validated to correlate well with NK cell viability in vivo. Using this nanoreporter, we further demonstrated that co-treatment with IL-2, IL-15, and IL-21 could improve NK cell viability in vivo, achieving enhanced immunotherapy for orthotopic hepatocellular carcinoma. Overall, this strategy allows for longitudinal and quantitative tracking of NK cell viability in NK cell-based immunotherapy.

Progress in Light‐Responsive Lanthanide Nanoparticles toward Deep Tumor Theranostics

AbstractRecently, lanthanide nanoparticles have aroused widespread interest in cancer theranostics by virtue of their excellent photoresponsive performance in deep‐seated tumors. The abundant ladder‐like energy levels, controllable emission profiles, and unique photoluminescence properties make lanthanide nanoparticles highly efficient for deep skin‐penetration of near‐infrared (NIR) light, concentrating light energy in tumors with negligible scattering and minimal autofluorescence from biological tissues. High‐Z radio‐sensitization of lanthanide elements endows lanthanide nanoparticles with a high X‐ray attenuation coefficient, making them effective nanoprobes for X‐ray‐excited bioimaging and synchronous radiotherapy‐related treatments. In this review, comprehensive progressions including the synthesis, structural characteristics of lanthanide nanoparticles, and distinct optical excitation mechanisms with NIR and X‐ray triggers, are summarized. Advances in NIR‐excited and X‐ray‐triggered cancer imaging methods and therapies are described in detail, wherein NIR‐induced luminescence from upconversion nanoparticles and downconversion nanoparticles are introduced separately based on some typical sensitization. Finally, the challenges and opportunities of lanthanide nanoparticles as light‐triggered cancer theranostic candidates are discussed, whose translation from bench to bedside still has a long journey to go.

Dye‐Sensitized Downconversion Nanoprobes with Emission Beyond 1500 nm for Ratiometric Visualization of Cancer Redox State

AbstractDetection of glutathione (GSH) in the body is essential to accurately map the redox state of cells and real‐time visualization of physiological and pathological conditions in vivo. However, traditional fluorescence (FL) imaging in the near‐infrared I region (NIR‐I, 650–900 nm) is difficult to quantitively visualize GSH in vivo due to the tissue autofluorescence background and disastrous photon scattering. Herein, a NIR‐IIb (1500–1700 nm) nanoprobe consisting of 4‐nitrophenol‐Cy7 (NPh) conjugated lanthanide‐based downconversion nanoparticles (DCNP@NPh‐PEG) is developed for in vivo ratiometric imaging of GSH. In the presence of GSH, NPh shows responsively enhanced FL emission at 808 nm, thus enhancing FL signal at 1550 nm of DCNPs excited by 808 nm (F1550, 808Ex) through non‐radiative energy transfer (NRET) effect, while the fluorescence of DCNP at 1550 nm excited by 980 nm laser (F1550, 980Ex) is stable because no NRET occurred. The ratiometric F1550, 980Ex/F1550, 808Ex value exhibits a linearship with GSH concentration ranged from 0–24 mm with detection limit of 0.3 mm. The NIR‐IIb nanoprobe has excellent performance in detecting and imaging GSH in both subcutaneous tumor and orthotopic colon tumor in vivo with high accuracy and resolution. The design strategy of the ratiometric NIR‐II FL nanoprobe based on the activated FERT effect provides a reliable tool for the development of NIR‐II nanoprobes for accurate biosensing in vivo.

A Feasible and Facile Method for the Anticounterfeiting of Down Fiber

In order to prevent counterfeiting of down fiber from consumers, rare earth fluorescent materials are developed in the field of material identification and anticounterfeiting. Herein, the development of verifiable down fiber based on infrared excitation‐infrared emission was described. A novel method was approached to prepare security down fiber, which involved modification of down‐conversion nanoparticles (DCNPs) by sulfonic groups and self‐assembly onto down fiber through electrostatic force. DCNPs were successfully prepared from ytterbium‐deposited NaYF4 nanoparticles using a complexation precipitation approach, in which the trivalent ytterbium ions served as the luminescent center. Sulfonic down‐conversion nanoparticles (SO3‐SiO2@DCNPs) were fabricated by the hydrolysis of 3‐mercaptopropyl triethoxysilane (MPTES) and next oxidation to enhance the combination of the DCNPs with down fiber. The synthesis of DCNPs and SO3‐SiO2@DCNPs and its pendant to down were confirmed by XRD, SEM, XPS, FT‐IR, Zeta potential meter, and PL, which revealed the presence of DCNPs in the size average 86 nm. The obtained DCNPs and security down fiber were launching an invisible red‐shifted emission of 930∼1080 nm (corresponding to the 2F5/2 ⟶ 2F7/2 transitions in Yb3+). After washing, the infrared emission of security down fiber was evaluated and proved to be effective with fine results, which showed its potential application in the field of security.