Ultrabright NIR-II Nanoprobe for Image-Guided Accurate Resection of Tiny Metastatic Lesions.

Fluorescence imaging is a vital way to delineate the tumor boundaries. Here, we achieve a NIR-II aggregation-induced emission luminogen (AIEgen) with a fluorescence quantum yield (QY) of 12.6% in water through straightforward alkyl side chain modification. After loading of NIR-II AIEgen into polystyrene (PS) nanospheres, the thermal deactivation pathway is extremely limited, thereby concentrating absorption excitation on fluorescence emission. The fluorescence intensity is further enhanced by 5.4 times, the QY increases to 21.1%, and the NIR-II imaging signal is accordingly enhanced by 8.7 times, surpassing conventional DSPE-PEG carriers. The NIR-II@PS nanoprobe showcases superior resolution and tissue penetration depth compared to indocyanine green (ICG) and short-range near-infrared AIEgens. In vivo investigations underscore its tumor-to-normal tissue ratio (3.9) at 24 h post intravenous injection, enabling complete resection of ≤1 mm metastases under NIR-II bioimaging guidance. Additionally, the PS carrier-nanoparticles exhibit low toxicity in vivo, laying a promising foundation for the future design of medical nanomaterials.

A Contrast-Enhanced Tri-Modal MRI Technique for High-Performance Hypoxia Imaging of Breast Cancer.

Personalized radiotherapy strategies enabled by the construction of hypoxia-guided biological target volumes (BTVs) can overcome hypoxia-induced radioresistance by delivering high-dose radiotherapy to targeted hypoxic areas of the tumor. However, the construction of hypoxia-guided BTVs is difficult owing to lack of precise visualization of hypoxic areas. This study synthesizes a hypoxia-responsive T1, T2, T2 mapping tri-modal MRI molecular nanoprobe (SPION@ND) and provides precise imaging of hypoxic tumor areas by utilizing the advantageous features of tri-modal magnetic resonance imaging (MRI). SPION@ND exhibits hypoxia-triggered dispersion-aggregation structural transformation. Dispersed SPION@ND can be used for routine clinical BTV construction using T1-contrast MRI. Conversely, aggregated SPION@ND can be used for tumor hypoxia imaging assessment using T2-contrast MRI. Moreover, by introducing T2 mapping, this work designs a novel method (adjustable threshold-based hypoxia assessment) for the precise assessment of tumor hypoxia confidence area and hypoxia level. Eventually this work successfully obtains hypoxia tumor target and accurates hypoxia tumor target, and achieves a one-stop hypoxia-guided BTV construction. Compared to the positron emission tomography-based hypoxia assessment, SPION@ND provides a new method that allows safe and convenient imaging of hypoxic tumor areas in clinical settings.

Rational Design of Activatable Lanthanide NIR-IIb Emissive Nanoprobe for In Situ Specific Imaging of HOCl In Vivo.

Hypochlorous acid (HOCl), as an indispensable signaling molecule in organisms, is one of the key members of reactive oxygen species (ROS). However, in vivo, real-time dynamic near-infrared fluorescence imaging of HOCl levels in the 1400-1700 nm sub-window (NIR-IIb) remains a major challenge due to the lack of suitable detection methods. Herein, a general design of HOCl-responsive NIR-IIb fluorescence nanoprobe is proposed by integrating NaLuF4Yb/Er@NaLuF4 downshift nanoparticles (DSNPs) and HOCl recognition/NIR-IIb emissive modulation unit of M2-xS (M = Cu, Co, Pb) nanodots for real-time monitoring of HOCl levels. The fluorescence modulation unit of M2-xS nanodots presents remarkably enhanced absorption than Yb sensitizer at 980 nm and greatly inhibits the NIR-IIb fluorescence emission via competitive absorption mechanism. While, the M2-xS nanodots are easily degraded after triggering by HOCl, resulting in HOCl responsive turn-on (≈ten folds) NIR-IIb emission at 1532 nm. More importantly, in vivo highly precise and specific monitoring of inflammatory with abnormal HOCl expression is successfully achieved. Thus, the explored competitive absorption mediated quenching-activation mechanism provides a new general strategy of designing HOCl-responsive NIR-IIb fluorescence nanoprobe for highly specific and sensitive HOCl detection.

Intelligent Reconfiguration-Promoted Cellular Internalization of Core-Shell DNA Nanoprobe Equipped with Successive Dual Stimuli-Responsive Protective Satellites for Amplification Fluorescence Imaging of Tumor Cells.

Although DNA probes have attracted increasing interest for precise tumor cell identification by imaging intracellular biomarkers, the requirement of commercial transfection reagents, limited targeting ligands, and/or non-biocompatible inorganic nanostructures has hampered the clinic translation. To circumvent these shortcomings, a reconfigurable ES-NC (Na+-dependent DNAzyme (E)-based substrate (S) cleavage core/shell DNA nanocluster (NC)) entirely from DNA strands is assembled for precise imaging of cancerous cells in a successive dual-stimuli-responsive manner. This nanoprobe is composed of a strung DNA tetrahedral satellites-based protective (DTP) shell, parallelly aligned target-responsive sensing (PTS) interlayer, and hydrophobic cholesterol-packed innermost layer (HCI core). Tetrahedral axial rotation-activated reconfiguration of DTP shell promotes the exposure of interior hydrophobic moieties, enabling cholesterol-mediated cellular internalization without auxiliary elements. Within cells, over-expressed glutathione triggers the disassembly of the DTP protective shell (first stimulus), facilitating target-stimulated signal transduction/amplification process (second stimuli). Target miRNA-21 is detected down to 10.6 fM without interference from coexisting miRNAs. Compared with transfection reagent-mediated counterpart, ES-NC displays a higher imaging ability, resists nuclease degradation, and has no detectable damage to healthy cells. The blind test demonstrates that the ES-NC is suitable for the identification of cancerous cells from healthy cells, indicating a promising tool for early diagnosis and prediction of cancer.

Combination of XEOL, TR-XEOL and HB-T interferometer at the TPS 23A X-ray nanoprobe for exploring quantum materials.

In this study, a combination of X-ray excited optical luminescence (XEOL), time-resolved XEOL (TR-XEOL) and the Hanbury-Brown and Twiss (HB-T) interferometer at the Taiwan Photon Source (TPS) 23A X-ray nanoprobe beamline for exploring quantum materials is demonstrated. On the basis of the excellent spatial resolution rendered using a nano-focused beam, emission distributions of artificial micro-diamonds can be obtained by XEOL maps, and featured emission peaks of a selected local area can be obtained by XEOL spectra. The hybrid bunch mode of the TPS not only provides a sufficiently high peak power density for experiments at each beamline but also permits high-quality temporal domain (∼200 ns) measurements for investigating luminescence dynamics. From TR-XEOL measurements, the decay lifetime of micro-diamonds is determined to be approximately 16 ns. Furthermore, the XEOL spectra of artificial micro-diamonds can be investigated by the HB-T interferometer to identify properties of single-photon sources. The unprecedented strategy of combining XEOL, TR-XEOL and the HB-T interferometer at the X-ray nanoprobe beamline will open new avenues with significant characterization abilities for unraveling the emission mechanisms of single-photon sources for quantum materials.

A new two-dimensional, spiropyran-based polymer fluorescent nanoprobe with quantitative-fluorescent and photochromic properties for multi-substance detection.

One challenge of the structural design of a fluorescent probe is how to improve the detection performance on trace target analytes in complex samples. Herein a new polymer fluorescent nanoprobe (2DSP-C28) has been synthesized, by adopting a two-dimensional (2D), spiropyran (SP)-based nanosheet structure with hydrophobic long-chain alkanes (C28). Unlike a traditional SP-based small molecule probe, the 2DSP-C28probe can exhibit quantitative-fluorescent and photochromic properties. Under the detection of metal-ions, the nanoprobe in dimethyl sulfoxide aqueous solution is selectively fluorescent-quenched-responsive for Fe-ions (∼100µM), with a characteristic stoichiometric ratio of <10, a high sensitivity (limit of detection: ∼0.2µM). When the nanoprobe is incorporated into electrospun polyethylene oxide, it can be used for gas detection, and display a color-change with acid-base gas and identify the HF gas. It is expected that this new polymer fluorescent nanoprobe can be promisingly applied for rapidly environmental monitoring on the ion or gas pollution.

Fluorescent MnO2@DEHP Nanoprobe for Rapid and Selective Detection of Fe(III) ions.

Particle extraction via the liquid-liquid interface (PELLI) method has been utilized to produce Di-(2-ethylhexyl) phosphate (DEHP) coated MnO2 fluorescent nanoprobe denoted as MnO2@DEHP for the selective detection of Fe3+ ions. The synthesized MnO2@DEHP nanoprobe was characterized by various instrumental techniques such as FT-IR, PXRD, TEM, EDAX, HRTEM, DLS, and XPS. Since the high concentration of Fe3+ in waste water leads to water pollution, which in turn affects the ecosystem, and causes severe health hazards. Therefore, accurate detection of Fe3+ ions in the aqueous systems is essential as they are involved in various chemical and biological processes in living things. Here, the synthesized MnO2@DEHP nanoprobe selectively detects Fe3+ ions in the presence of various metal ions in an aqueous media by fluorescence quenching (turn-off) mechanism. The limit of detection (LOD) of MnO2@DEHP nanoprobe for Fe3+ was found to be 0.49 µM. The test-strip method and real water sample analysis were also used to demonstrate the viability of MnO2@DEHP as a fluorescent nanoprobe to detect Fe3+ ions visually and in environment monitoring applications.

Development of europium(III) complex functionalized silica nanoprobe for luminescence detection of tetracycline.

Increasing awareness of the health and environment impacts of the antibiotics misuse or overuse, such as tetracycline (TC) in treatment or prevention of infections and diseases, has driven the development of robust methods for their detection in biological, environmental and food systems. In this work, we report the development of a new europium(III) complex functionalized silica nanoprobe (SiNPs-Eu3+) for highly sensitive and selective detection of TC residue in aqueous solution and food samples (milk and meat). The nanoprobe is developed by immobilization of Eu3+ ion onto the surface of silica nanoparticles (SiNPs) as the emitter and TC recognition unit. The ß-diketone configuration of TC can further coordinate with Eu3+ steadily on the surface of nanoprobe, facilitating the absorption of light excitation for Eu3+ emitter activation and luminescence "off-on" response. The dose-dependent luminescence enhancement of SiNPs-Eu3+ nanoprobe exhibits good linearities, allowing the quantitative detection of TC. The SiNPs-Eu3+ nanoprobe shows high sensitivity and selectivity for TC detection in buffer solution. Time resolved luminescence analysis enables the elimination of autofluorescence and light scattering for highly sensitive detection of TC in milk and pork mince with high accuracy and precision. The successful development of SiNPs-Eu3+ nanoprobe is anticipated to provide a rapid, economic, and robust approach for TC detection in real world samples.

Enhancing intracellular mRNA precise imaging-guided photothermal therapy with a nucleic acid-based polydopamine nanoprobe.

Despite significant advancements in cancer research, real-time monitoring and effective treatment of cancer through non-invasive techniques remain a challenge. Herein, a novel polydopamine (PDA) nucleic acid nanoprobe has been developed for imaging signal amplification of intracellular mRNA and precise photothermal therapy guidance in cancer cells. The PDA nucleic acid nanoprobe (PDA@DNA) is constructed by assembling an aptamer hairpin (H1) labeled with the Cy5 fluorophore and another nucleic acid recognition hairpin (H2) onto PDA nanoparticles (PDA NPs), which have exceptionally high fluorescence quenching ability and excellent photothermal conversion properties. The nanoprobe could facilitate cellular uptake of DNA molecules and their protection from nuclease degradation. Upon recognition and binding to the intracellular mRNA target, a catalytic hairpin assembly (CHA) reaction occurs. The stem of H1 unfolds upon binding, allowing the exposed H1 to hybridize with H2, forming a flat and sturdy DNA double-stranded structure that detaches from the surface of PDA NPs. At the same time, the target mRNA is displaced and engages in a new cyclic reaction, resulting in the recovery and significant amplification of Cy5 fluorescence. Using thymidine kinase1 (TK1) mRNA as a model mRNA, this nanoprobe enables the analysis of TK1 mRNA with a detection limit of 9.34 pM, which is at least two orders of magnitude lower than that of a non-amplifying imaging nucleic acid probe. Moreover, with its outstanding performance for in vitro detection, this nanoprobe excels in precisely imaging tumor cells. Through live-cell TK1 mRNA imaging, it can accurately distinguish between tumor cells and normal cells. Furthermore, when exposed to 808-nm laser irradiation, the nanoprobe fully harnesses exceptional photothermal conversion properties of PDA NPs. This results in a localized temperature increase within tumor cells, which ultimately triggers apoptosis in these tumor cells. The integration of PDA@DNA presents innovative prospects for tumor diagnosis and image-guided tumor therapy, offering the potential for high-precision diagnosis and treatment of tumors.

Dual-mode nanoprobe strategy integrating ultrasound and near-infrared light for targeted and synergistic arterial thrombolysis.

Efficient thrombolysis in time is crucial for prognostic improvement of patients with acute arterial thromboembolic disease, while limitations and complications still exist in conventional thrombolytic treatment methods. Herein, our study sought to investigate a novel dual-mode strategy that integrated ultrasound (US) and near-infrared light (NIR) with establishment of hollow mesoporous silica nanoprobe (HMSN) which contains Arginine-glycine-aspartate (RGD) peptide (thrombus targeting), perfluoropentane (PFP) (thrombolysis with phase-change and stable cavitation) and indocyanine green (ICG) (thrombolysis with photothermal conversion). HMSN is used as the carrier, the surface is coupled with targeted RGD to achieve high targeting and permeability of thrombus, PFP and ICG are loaded to achieve the collaborative diagnosis and treatment of thrombus by US and NIR, so as to provide a new strategy for the integration of diagnosis and treatment of arterial thrombus. From the in vitro and in vivo evaluation, RGD/ICG/PFP@HMSN can aggregate and penetrate at the site of thrombus, and finally establish the dual-mode directional development and thrombolytic treatment under the synergistic effect of US and NIR, providing strong technical support for the accurate diagnosis and treatment of arterial thrombosis.

Magnetic resonance imaging with upconversion nanoprobes capable of crossing the blood-cerebrospinal fluid barrier.

The central nervous system (CNS) maintains homeostasis with its surrounding environment by restricting the ingress of large hydrophilic molecules, immune cells, pathogens, and other external harmful substances to the brain. This function relies heavily on the blood-cerebrospinal fluid (B-CSF) and blood-brain barrier (BBB). Although considerable research has examined the structure and function of the BBB, the B-CSF barrier has received little attention. Therapies for disorders associated with the central nervous system have the potential to benefit from targeting the B-CSF barrier to enhance medication penetration into the brain. In this study, we synthesized a nanoprobe ANG-PEG-UCNP capable of crossing the B-CSF barrier with high targeting specificity using a hydrocephalus model for noninvasive magnetic resonance ventriculography to understand the mechanism by which the CSF barrier may be crossed and identify therapeutic targets of CNS diseases. This magnetic resonance nanoprobe ANG-PEG-UCNP holds promising potential as a safe and effective means for accurately defining the ventricular anatomy and correctly locating sites of CSF obstruction.

Surface ligand-regulated renal clearance of MRI/SPECT dual-modality nanoprobes for tumor imaging.

BACKGROUND: The general sluggish clearance kinetics of functional inorganic nanoparticles tend to raise potential biosafety concerns for in vivo applications. Renal clearance is a possible elimination pathway for functional inorganic nanoparticles delivered through intravenous injection, but largely depending on the surface physical chemical properties of a given particle apart from its size and shape. RESULTS: In this study, three small-molecule ligands that bear a diphosphonate (DP) group, but different terminal groups on the other side, i.e., anionic, cationic, and zwitterionic groups, were synthesized and used to modify ultrasmall Fe3O4 nanoparticles for evaluating the surface structure-dependent renal clearance behaviors. Systematic studies suggested that the variation of the surface ligands did not significantly increase the hydrodynamic diameter of ultrasmall Fe3O4 nanoparticles, nor influence their magnetic resonance imaging (MRI) contrast enhancement effects. Among the three particle samples, Fe3O4 nanoparticle coated with zwitterionic ligands, i.e., Fe3O4@DMSA, exhibited optimal renal clearance efficiency and reduced reticuloendothelial uptake. Therefore, this sample was further labeled with 99mTc through the DP moieties to achieve a renal-clearable MRI/single-photon emission computed tomography (SPECT) dual-modality imaging nanoprobe. The resulting nanoprobe showed satisfactory imaging capacities in a 4T1 xenograft tumor mouse model. Furthermore, the biocompatibility of Fe3O4@DMSA was evaluated both in vitro and in vivo through safety assessment experiments. CONCLUSIONS: We believe that the current investigations offer a simple and effective strategy for constructing renal-clearable nanoparticles for precise disease diagnosis.

"All in one" nanoprobe Au-TTF-1 for target FL/CT bioimaging, machine learning technology and imaging-guided photothermal therapy against lung adenocarcinoma.

The accurate preoperative diagnosis and tracking of lung adenocarcinoma is hindered by non-targeting and diffusion of dyes used for marking tumors. Hence, there is an urgent need to develop a practical nanoprobe for tracing lung adenocarcinoma precisely even treating them noninvasively. Herein, Gold nanoclusters (AuNCs) conjugate with thyroid transcription factor-1 (TTF-1) antibody, then multifunctional nanoprobe Au-TTF-1 is designed and synthesized, which underscores the paramount importance of advancing the machine learning diagnosis and bioimaging-guided treatment of lung adenocarcinoma. Bright fluorescence (FL) and strong CT signal of Au-TTF-1 set the stage for tracking. Furthermore, the high specificity of TTF-1 antibody facilitates selective targeting of lung adenocarcinoma cells as compared to common lung epithelial cells, so machine learning software Lung adenocarcinoma auxiliary detection system was designed, which combined with Au-TTF-1 to assist the intelligent recognition of lung adenocarcinoma jointly. Besides, Au-TTF-1 not only contributes to intuitive and targeted visualization, but also guides the following noninvasive photothermal treatment. The boundaries of tumor are light up by Au-TTF-1 for navigation, it penetrates into tumor and implements noninvasive photothermal treatment, resulting in ablating tumors in vivo locally. Above all, Au-TTF-1 serves as a key platform for target bio-imaging navigation, machine learning diagnosis and synergistic PTT as a single nanoprobe, which demonstrates attractive performance on lung adenocarcinoma.

Turn-off fluorescent nanoprobe based on carbon dots synthesised by UV/H2O2 advanced oxidation for the detection of bisphenol A in canned foods.

A novel assay was developed based on a turn-off fluorescent probe using the in situ generation of carbon dots (CDs) by means of UV/H2O2 advanced oxidation of carbohydrates for the detection of bisphenol A (BPA) in food. Different parameters involved in the synthesis of CDs for the direct recognition of BPA have been optimised and a sensing mechanism is outlined. The presence of H2O2 during CD synthesis causes a fluorescence enhancement due to the action of highly oxidant HO· radicals formed throughout the photochemical reaction. Phenolic compounds such as BPA can be easily degraded by the UV/H2O2 oxidation process, acting as a HO· free radical scavengers. This results in a decrease in the fluorescence that can be related to the BPA concentration. Under optimal conditions, a detection limit of 15 µg/kg of BPA and a quantification limit of 46 µg/kg of BPA in food samples were obtained. The repeatability and reproducibility, expressed as relative standard deviation and obtained for two concentration levels (30 µg/kg and 200 µg/kg, n = 5), were less than 2.0% and 6.4%, respectively. The proposed procedure was applied to the analysis of five samples of canned foods (sweet corn, peas, mushrooms, cockles and natural tuna), obtaining concentrations in the range 29.8-49.9 µg/kg of sample. Recovery studies were conducted at two concentration levels (100 and 400 µg BPA/kg of sample), resulting in recoveries in the range 99-101%. Method validation against two certified reference materials was also successfully performed. The experimental results demonstrate that the novel approach is suitable for the detection and quantification of BPA in canned foods.

Reusable fluorescence nanoprobe based on DNA-functionalized metal-organic framework for ratiometric detection of mercury (II) ions.

A reusable fluorescent nanoprobe was developed using DNA-functionalized metal-organic framework (MOF) for ratiometric detection of Hg2+. We utilized a zirconium-based MOF (UiO-66) to encapsulate tris(bipyridine) ruthenium(II) chloride (Ru(bpy)32+), resulting in Ru(bpy)32+@UiO-66 (RU) with red fluorescence. The unsaturated metal sites in UiO-66 facilitate the attachment of thymine-rich single-strand DNA (T-ssDNA) through Zr-O-P bond, producing T-ssDNA-functionalized RU complex (RUT). The T-ssDNA selectively binds to Hg2+, forming stable T-Hg2+-T base pairs and folding into double-stranded DNA, which permits the intercalation of SYBR Green I (SGI) and activates its green fluorescence. In the presence of Hg2+, SGI fluorescence increases in a dose-dependent manner, while Ru(bpy)32+ fluorescence remains constant. This fluorescence contrast enables RUT to serve as an effective ratiometric nanoprobe for Hg2+ detection, with a detection limit of 3.37 nM. Additionally, RUT demonstrates exceptional reusability due to the ability of cysteine to remove Hg2+, given its stronger affinity for thiol groups. The RUT was successfully applied to detect Hg2+ in real water samples. This work advances the development of ratiometric fluorescence nanoprobe based on DNA-functionalized MOFs.

Aptamer-functionalized gold nanoparticles for mercury ion detection in a colorimetric assay based on color change time as signal readout.

A universal strategy for a rapid colorimetric method for Hg2+ in an aqueous solution is described. The specific binding of Hg2+ (thymine-Hg2+-thymine) with thiolated DNA-functionalized gold nanoparticles (AuNPs) via Au-S bonds increases the spatial hindrance of the AuNP surface, resulting in a weakened catalytic ability of AuNPs to catalyze the reaction between p-nitrophenol and NaBH4. Therefore, the color change time (CCT) of the solution from yellow to colorless becomes longer. Based on the kinetic curve of absorbance over time measured by a UV spectrometer, the level of Hg2+ in aqueous solutions can be easily quantified. A linear relationship between CCT and Hg2+ concentration was obtained in the 10-600-nM range with a detection limit of 0.20 nM, which is much lower than the limit value (10 nM) defined by the US Environmental Protection Agency for Hg2+ in drinking water. The excellent sensitivity comes from CCT as the signal output of the probe, rather than the absorbance or wavelength change used in traditional colorimetric probes as the signal output.

A sequential dual-locked luminescent copper nanocluster probe for tumor cell imaging and killing.

A sequential dual-locked luminescent copper nanoclusters (CuNCs) probe was designed and synthesized for the specific imaging and selective killing of tumor cells. This nanoprobe was prepared by first forming a Fe3+-coupled tannic acid (TA)-stabilized CuNCs (CuNCs-FeIII), which is in quenching state due to the electron transfer between CuNCs and Fe3+, and then coating a protectable layer of hyaluronic acid (HA) on the surface of CuNCs-FeIII to form the final dual-locked nanoprobe (CuNCs-FeIII@HA). When the nanoprobe of CuNCs-FeIII@HA target enter the tumor cells through CD44-HA receptor, HAase will first digest the HA layer of the nanoprobes, and then, GSH over-expressed in tumor cells will reduce Fe3+ to Fe2+, thus restoring the fluorescence emission of CuNCs and at the same time killing the tumor cells with the hydroxyl free radicals (∙OH) produced by the Fenton reaction between Fe2+ and H2O2. This sequential dual-locked luminescent nanoprobe of CuNCs-FeIII@HA has been successfully used for the specific imaging and selective killing of tumor cells.

Ultrasensitive Urinary Diagnosis of Organ Injuries Using Time-Resolved Luminescent Lanthanide Nano-bioprobes.

Urinary sensing of synthetic biomarkers that are released into urine after specific activation in an in vivo disease environment is an emerging diagnosis strategy to overcome the insensitivity of a previous biomarker assay. However, it remains a great challenge to achieve sensitive and a specific urinary photoluminescence (PL) diagnosis. Herein, we report a novel urinary time-resolved PL (TRPL) diagnosis strategy by exploiting europium complexes of diethylenetriaminepentaacetic acid (Eu-DTPA) as synthetic biomarkers and designing the activatable nanoprobes. Notably, TRPL of Eu-DTPA in the enhancer can eliminate the urinary background PL for ultrasensitive detection. We achieved sensitive urinary TRPL diagnosis of mice kidney and liver injuries by using simple Eu-DTPA and Eu-DTPA-integrated nanoprobes, respectively, which cannot be realized by traditional blood assays. This work demonstrates the exploration of lanthanide nanoprobes for in vivo disease-activated urinary TRPL diagnosis for the first time, which might advance the noninvasive diagnosis of diverse diseases via tailorable nanoprobe designs.

Probing Spin-Dependent Ballistic Charge Transport at Single-Nanometer Length Scales.

The coherent transport of charge and spin is a key requirement of future devices for quantum computing and communication. Scattering at defects or impurities may significantly reduce the coherence of quantum-mechanical states, thereby affecting the device functionality. While numerous methods exist to experimentally assess charge transport, the real-space detection of a material's ballistic spin transport properties with nanometer resolution remains a challenge. Here we report on a novel approach that utilizes a combination of spin-polarized scanning tunneling microscopy (SP-STM) and the recently introduced molecular nanoprobe (MONA) technique. It relies on the local injection of spin-polarized charge carriers from a magnetic STM tip and their detection by a single surface-deposited phthalocyanine molecule via reversible electron-induced tautomerization events. Based on the particular electronic structure of the Rashba alloy BiAg2, which is governed by a spin-momentum-locked surface state, we prove that the current direction inverses upon tip magnetization reversal.

An Indocyanine Green-Based Nanoprobe for In Vivo Detection of Cellular Senescence.

There is an urgent need to improve conventional cancer-treatments by preventing detrimental side effects, cancer recurrence and metastases. Recent studies have shown that presence of senescent cells in tissues treated with chemo- or radiotherapy can be used to predict the effectiveness of cancer treatment. However, although the accumulation of senescent cells is one of the hallmarks of cancer, surprisingly little progress has been made in development of strategies for their detection in vivo. To address a lack of detection tools, we developed a biocompatible, injectable organic nanoprobe (NanoJagg), which is selectively taken up by senescent cells and accumulates in the lysosomes. The NanoJagg probe is obtained by self-assembly of indocyanine green (ICG) dimers using a scalable manufacturing process and characterized by a unique spectral signature suitable for both photoacoustic tomography (PAT) and fluorescence imaging. In vitro, ex vivo and in vivo studies all indicate that NanoJaggs are a clinically translatable probe for detection of senescence and their PAT signal makes them suitable for longitudinal monitoring of the senescence burden in solid tumors after chemotherapy or radiotherapy.