Dual-modality Probe Research Articles

Real-time tracking and dual-mode imaging of hypochlorous acid in vivo by a small-sized fluorescence probe

Endogenous hypochlorous acid (HOCl), an ROS of particular interest, is like a double-edged sword, which has dual influence on both the maintenance of normal physiological functions and the occurrence of many diseases. Methods to track minimal changes of biological HOCl in both multi-modes and real time are essential for precisely tracking this biomolecule with high oxidation activity. However, the methods are still limited due to the difficulty in combining the two functions into one. To resolve this issue, we herein introduced a small-sized fluorescence probe KSQT with two sites which are sensitive to HOCl at nanomolar and micromolar concentrations. With this novel design, our probe achieved real-time and distinct detection of both physiological and pathogenic concentrations of HOCl via turn-on and ratiometric responses in turn, which enables it to effectively avoid the fluorescence cross-talk through simultaneous use of multiple probes and to solve the problem of transmembrane trafficking of previous dual-mode HOCl probes with large size or high positive charges. Together with its marvelous response to HOCl, high biomembrane permeability and biocompatibility, the real-time and dual-mode fluorescence imaging of endogenous HOCl in living HepG2 cells and living zebrafish were accomplished.

Activatable photoacoustic/fluorescent dual-modal probe for monitoring of drug-induced liver hypoxia in vivo.

Effective monitoring of liver hypoxia status is crucial for the detection and treatment of drug-induced liver injury. Here, a novel photoacoustic and fluorescent dual-modal probe (NO2-CS) was rationally developed and applied to image isoniazid-induced liver hypoxia through detecting the over-expressed nitroreductase.

An ethanethioate functionalized polythiophene as an optical probe for sensitive and fast detection of water content in organic solvents.

A new polythiophene-based optical probe, namely PTS, was designed and prepared for detection and quantification of the water present in organic solvents. PTS exhibited sensitive and fast absorption and fluorescence signaling response to the changes of water content in tetrahydrofuran (THF), N,N-dimethylformamide (DMF) and N,N-dimethylacetamide (DMAc) due to the water-induced interpolymer-stacking aggregation as demonstrated by dynamic light scattering (DLS) analysis. The fluorescence intensity of PTS at 550 nm linearly reduced as a function of the water content in detection ranges of 0-30% (v/v) in THF, 0-10% in DMF and 0-10% in DMAc with the limit of detection (LOD) for water being 0.034% (v/v) in THF, 0.013% (v/v) in DMF, and 0.014% (v/v) in DMAc, respectively. Additionally, PTS-incorporated test paper was fabricated to successfully achieve naked-eye detection of water in DMF and DMAc. PTS was further applied to estimate the water content in real samples, convincingly demonstrating that our method was comparable with the standard Karl Fischer titration.

Novel water-dispersible silicon nanoparticles as a fluorescent and colorimetric dual-mode probe for emodin detection

A novel fluorescent and colorimetric dual-mode sensing method based on water-dispersible SiNPs was constructed for the sensitive detection of emodin.

Synthesis and application of a 19F-labeled fluorescent nucleoside as a dual-mode probe for i-motif DNAs.

Because of their stable orientations and their minimal interference with native DNA interactions and folding, emissive isomorphic nucleoside analogues are versatile tools for the accurate analysis of DNA structural heterogeneity. Here, we report on a bifunctional trifluoromethylphenylpyrrolocytidine derivative (FPdC) that displays an unprecedented quantum yield and highly sensitive 19F NMR signal. This is the first report of a cytosine-based dual-purpose probe for both fluorescence and 19F NMR spectroscopic DNA analysis. FPdC and FPdC-containing DNA were synthesized and characterized; our robust dual probe was successfully used to investigate the noncanonical DNA structure, i-motifs, through changes in fluorescence intensity and 19F chemical shift in response to i-motif formation. The utility of FPdC was exemplified through reversible fluorescence switching of an FPdC-containing i-motif oligonucleotide in the presence of Ag(i) and cysteine.

Synthesis of deep red emitting Cu–In–Zn–Se/ZnSe quantum dots for dual-modal fluorescence and photoacoustic imaging

CuInSe2 quantum dots (QDs) are one of the most important Cd-free fluorescent probes; they usually exhibited low fluorescence intensity, suggesting that a considerable amount of absorbed photon energy was lost as heat. In this study we aimed to improve the fluorescence intensity of CuInSe2 QDs and investigate their photoacoustic (PA) signal resulting from the heat dissipation, which was previously rarely reported. Cu–In–Zn–Se/ZnSe QDs were synthesized by adopting two strategies of Zn doping and ZnSe shell growth. It was found that there was an upper limit for Zn concentration beyond which the fluorescence intensity began to decrease. In addition, a blue shift of the emission peak of Cu–In–Zn–Se/ZnSe QDs was observed at high concentrations of ZnSe precursor due to the diffusion of excessive Zn. To prepare the dual-modal fluorescence and PA imaging probe, poly(maleic anhydride-alt-1-octadecene) (PMAO) modified with polyethylene glycol (PEG) was coated on the QDs, which led to a slight reduction in fluorescence. Cellular labeling on HeLa cells was performed to demonstrate the utility of these probes for fluorescence imaging. We further studied the in vitro PA imaging capabilities of the Cu–In–Zn–Se/ZnSe/PMAO-g-PEG nanoparticles, which showed a distinct PA signal beyond 1.0 mg ml−1. The current work demonstrated that a moderate amount of Zn doping is necessary for enhancing fluorescence and there is a limit beyond which the fluorescence will be diminished. We also demonstrated the proof of concept that Cu–In–Zn–Se/ZnSe QDs are able to serve as a potential PA imaging contrast agent.

Self-Assembly Fabrication of Honeycomb-like Magnetic-Fluorescent Fe3O4-QDs Nanocomposites for Bimodal Imaging.

Magnetic-fluorescent nanocomposites have a tremendous potential in biomedicine realms as a revolutionary dual-modality probe tool for more accurate medical detection. However, complicated and inefficient postprocesses pose obstacles to obtaining high-quality magnetic-fluorescent nanocomposites. Thus, the fabrication of magnetic-fluorescent functional nanocomposites via a simple, effective, and ideal method remains a challenge and is still waiting to be tapped. The new synthesis approaches are becoming impending demands and probably enable us to address these above-mentioned problems. In this contribution, we present a novel self-assembly synthesis route for the construction of magnetic-fluorescent bimodal imaging nanocomposites rather than adopting sophisticated postpreparative processes. The Fe3O4 and quatum dots (QDs) nanocomposites were cross-linked fleetly by cerium(III) ion driven coordination bonds in which the cerium(III) ions served as the cross-connecting node and the carboxylate groups acted as bridging ligands. The potential application for dual-modality imaging capability was validated on tumor-bearing mice. This ingenious strategy was extremely efficient and handy for the magnetic-fluorescent Fe3O4-QDs nanocomposite construction. Significantly, our cerium(III) ion driven self-assembly method probably has a wide applicability for nanoparticles and organic molecules containing carboxyl groups but extensive explorations are still necessary.

A highly selective and sensitive “off-on” fluorescent probe for the detection of nerve agent mimic DCNP in solution and vapor phase

Chemical warfare agents (CWAs) are the most feared and unpredictable terrorist weapon that threaten global security. For the issue of human security, it is highly demanded to establish rapid and reliable methods for the detection of CWAs. In this work, a hemicyanine-based colorimetric and off-on fluorescent dual-modal probe for the detection of a nerve agent mimic diethyl cyanophosphonate (DCNP) has been developed. The probe exhibits fast response (<3 min), high selectivity, and excellent sensitivity with a low limit of detection (4.5 nM). More importantly, test strips loaded with the probe can sense DCNP vapor in low concentration and distinguish DCNP vapor from other nerve agent mimics by both naked eyes and fluorescence.

Miniaturized all fiber probe for optical coherence tomography and pH detection of biological tissue.

We present a novel all-fiber probe with 710-μm outside diameter for combined optical coherence tomography and pH detection. In cancer surgery, a significant challenge is how to completely remove the malignant tumor without cutting too much normal tissue. The difference between cancer tissue and normal tissue not only lies in morphology and structure but also in tissue pH, where malignant tissue has a lower pH. This dual-modality probe combined optical coherence tomography and pH detection of biological tissue, is expected to determine whether the tissue is cancerous quickly and accurately. The probe utilizes a typical three-segment structure (double-clad fiber - no-core fiber - graded-index fiber). We obtained a lateral resolution of ~10.6 μm, a working distance of ~506 μm and a pH measurement accuracy of 0.01 pH unit for the probe. The performance of the all-fiber probe was verified through an ex vivo experiment using the porcine brain specimen.

An Activatable and Switchable Nanoaggregate Probe for Detecting H2 S and Its Application in Mice Brains.

Employing a sequentially activated probe design method, an activatable, switchable and dual-mode probe was designed. This nanoprobe, HSDPP, could be effectively activated by H2 S to form H-type aggregates with green emission; subsequently, the aggregates could bind to mtDNA to form monomers and the emIssion color switched from green to deep-red. We exploited HSDPP to image exogenous and endogenous H2 S in living cells. Of note, for the first time, this novel nanoprobe with an optimal partition coefficient value (LogP=1.269) was successfully applied for tracking the endogenous H2 S upregulation stimulated by cystathionase activator S-adenosyl-L-methionine (SAM) in mice brains. Finally, our work provides an invaluable chemical tool for probing endogenous H2 S upregulation in vitro/vivo and, importantly, affords a prospective design strategy for developing switchable chemosensors to unveil the relationship between biomolecules and DNA in mitochondria in many promising areas.

Hollow magnetic-fluorescent nanoparticles for dual-modality virus detection

Combination of magnetic nanomaterials with multifunctionality is an emerging class of materials that exhibit tremendous potential in advanced applications. Synthesizing such novel nanocomposites without compromising magnetic behavior and introducing added functional properties is proven challenging. In this study, an optically active quantum dot (QD) (core) encapsulated inside iron oxide (hollow shell) is prepared as the first electrochemical/fluorescence dual-modality probe. Presence of magnetic layer on the surface enables excellent magnetic property and the encapsulating of QDs on the hollow shell structure maintains the fluorescence with minimal quenching effect, endowing for potential application with fluorescence modality readout. We successfully demonstrate dual-modality sensing utilizing of QD-encapsulated magnetic hollow sphere nanoparticles (QD@MHS NPs) with magnetic separation ability and highly integrated multimodal sensing for the detection of various viruses including hepatitis E virus (HEV), HEV-like particles (HEV-LPs), norovirus-like particles (NoV-LPs), and norovirus (NoV) from clinical specimens. Most importantly, fecal samples of HEV-infected monkey are successfully diagnosed with sensitivity similar to gold standard real-time quantitative reverse transcription-polymerase chain reaction (RT-qPCR). This well-defined QD@MHS NPs-based nanoplatform intelligently integrates dual-modality sensing and magnetic bio-separation, which open a gateway to provide an efficient point-of care testing for virus diagnostics.

Molecular imaging and deep learning analysis of uMUC1 expression in response to chemotherapy in an orthotopic model of ovarian cancer

Artificial Intelligence (AI) algorithms including deep learning have recently demonstrated remarkable progress in image-recognition tasks. Here, we utilized AI for monitoring the expression of underglycosylated mucin 1 (uMUC1) tumor antigen, a biomarker for ovarian cancer progression and response to therapy, using contrast-enhanced in vivo imaging. This was done using a dual-modal (magnetic resonance and near infrared optical imaging) uMUC1-specific probe (termed MN-EPPT) consisted of iron-oxide magnetic nanoparticles (MN) conjugated to a uMUC1-specific peptide (EPPT) and labeled with a near-infrared fluorescent dye, Cy5.5. In vitro studies performed in uMUC1-expressing human ovarian cancer cell line SKOV3/Luc and control uMUC1low ES-2 cells showed preferential uptake on the probe by the high expressor (n = 3, p < .05). A decrease in MN-EPPT uptake by SKOV3/Luc cells in vitro due to uMUC1 downregulation after docetaxel therapy was paralleled by in vivo imaging studies that showed a reduction in probe accumulation in the docetaxel treated group (n = 5, p < .05). The imaging data were analyzed using deep learning-enabled segmentation and quantification of the tumor region of interest (ROI) from raw input MRI sequences by applying AI algorithms including a blend of Convolutional Neural Networks (CNN) and Fully Connected Neural Networks. We believe that the algorithms used in this study have the potential to improve studying and monitoring cancer progression, amongst other diseases.

Intravascular Photoacoustic and Autofluorescence Imaging for Detecting Intraplaque Hemorrhage: A Feasibility Study

Intraplaque hemorrhage (IPH), which is a trigger and conveys all blood components into the plaque, influencing the cholesterol crystal formation and retention, haemoglobin and oxidative enzymes, and blood-borne proteolytic activity. IPH is one of the key determinants for plaque vulnerability. In this paper, we proposed a dual-modality endoscope probe with a diameter of 1 mm for simultaneously detecting the lipid core and IPH, our system was composed of photoacoustic imaging (PAI) and near-infrared auto-fluorescence imaging (NIRAFI). The lipid as endogenous marker of intravascular PAI could visualize the lipid distribution of atherosclerotic plaque, and bilirubin as the marker of intravascular NIRAFI was used to locate and quantify the IPH. The phantom and ex vivo rabbit aorta experiments had proved the feasibility and capability of the dual-mode probe for imaging IPH and lipid core expansion. And the results indicated that the dual-mode intravascular endoscope had the potential for accurately detecting IPH in atherosclerotic plaques.

Development of a fluorine-18 radiolabelled fluorescent chalcone: evaluated for detecting glycogen

BackgroundGlycogen is a multibranched polysaccharide of glucose produced by cells to store energy and plays a key role in cancer. A previously reported fluorescent probe (CDg4) was shown to selectively bind glycogen in mouse embryonic stem cells, however the molecule was not evaluated in cancer cells. We report the synthesis and biological evaluation of a dual-modality imaging probe based on CDg4, for positron emission tomography (PET) and fluorescence microscopy.ResultsA fluorine-18 radiolabelled derivative of CDg4, ([18F]5) for in vivo quantification of total glycogen levels in cancer cells was developed and synthesised in 170 min with a non-decay corrected radiochemical yield (RCY n.d.c) of 5.1 ± 0.9% (n = 4) in > 98% radiochemical purity. Compound 5 and [18F]5 were evaluated in vitro for their potential to bind glycogen, but only 5 showed accumulation by fluorescence microscopy. The accumulation of 5 was determined to be specific as fluorescent signal diminished upon the digestion of carbohydrate polymers with α-amylase. PET imaging in non-tumour bearing mice highlighted rapid hepato-biliary-intestinal elimination of [18F]5 and almost complete metabolic degradation after 60 min in the liver, plasma and urine, confirmed by radioactive metabolite analysis.ConclusionsFluorescent compound 5 selectively accumulated in glycogen containing cancer cells, identified by fluorescence microscopy; however, rapid in vivo metabolic degradation precludes further investigation of [18F]5 as a PET radiopharmaceutical.

Controllable Cleavage of C-N Bond-Based Fluorescent and Photoacoustic Dual-Modal Probes for the Detection of H2S in Living Mice.

Hydrogen sulfide (H2S) has been recognized to influence a wide range of physiological and pathological processes. Its underlying molecular events, however, are still poorly understood. An activatable H2S probe for photoacoustic (PA) imaging is desirable to further explore the role of H2S in vivo. Nevertheless, only a few activatable PA probes for H2S detection have been reported. In particular, examples of dual-modal H2S probes with the combined advantages of fluorescence (high sensitivity and resolution) and PA imaging (deep penetration) are very rare. Herein the controllable cleavage of the C-N bond in nitrobenzoxadiazole (NBD) amine derivatives by H2S is presented for the first time. The cleavage reactivity was found to be accelerated by the introduction of an electron-withdrawing group. Through this strategy, a series of fluorescent and PA dual-modal probes (1-3) were developed for H2S detection. Among them, probe 3 shows a high fluorescence on-off response rate (k2 = 4.04 M-1 s-1) and excellent selectivity for H2S over other biothiols. Moreover, probe 3 can also work as an activatable PA H2S probe because of the significant shift of its absorption peak from 468 to 532 nm in the H2S reaction. Importantly, probe 3 demonstrates its capability for fluorescence and PA imaging of H2S in living cells and mice. These results indicate that the controllable cleavage of the C-N bond can serve as an efficient strategy for designing fluorescent and PA dual-modal H2S probes.

Magnetic-Photoacoustic Dual-Mode Probe for the Visualization of H2S in Colorectal Cancer.

Techniques for the qualitative and quantitative detection of H2S in vivo have attracted considerable attention due to the key role of H2S in various physiological and pathological processes. However, in vivo detection strategies for H2S are mainly based on fluorescence imaging, which is limited by its poor tissue penetration. Moreover, the limitations of single-mode probes are amplified in complex physiological environments. Herein, a core-shell Fe3O4@Cu2O nanoparticle was constructed as a magnetic-photoacoustic dual-mode probe for H2S detection in vitro and in vivo based on the in situ response of Cu2O to endogenous H2S in colon tumors. This probe is expected to greatly improve the accuracy of H2S detection in vivo because it employs two detection methods with complementary advantages. The new probe was experimentally applied to the in vivo and in vitro visualization of H2S in mice with colorectal cancer, validating the in situ reaction-activated dual-detection method. This work establishes a simple and efficient dual-mode imaging method based on a novel trigger mechanism. The findings provide a new strategy for colon cancer detection based on the in situ reactions at tumor sites.

A new strategy for determination of trace PO43− using CNDAu as resonance Rayleigh scattering and fluorescence dual-mode probe

The hydrophilic carbon nitride dots (CNDs) and gold-carbon nitride dots (CNDAu) were prepared by microwave digestion instrument with citric acid, thiourea and chloroauric acid as precursors. The morphology and properties of the nanomaterial were characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), resonance Rayleigh scattering (RRS), fluorescence (FL), Fourier transform infrared spectrometer (FTIR) and particle size analysis. The acidified ammonium molybdate and CNDs are combined to form complex by intermolecular forces, the system's fluorescence and RRS signals are decreased. After adding PO43−, the ammonium molybdate and PO43− form stable phosphomolybdate heteropoly acid (PMo) with hydrophobic properties, the PMo particles are separated from CNDs, and the released CNDs lead to the increase of FL signal. At the same time, PMo particles are simultaneously aggregate forming large particles, which are manifested by an increase in the RRS signal. We can establish a sensitive, rapid, selective method for the determination of trace PO43− by combining RRS and FL signals. Within a certain range, the signals of the two methods show a linear relationship with the concentration of PO43−. The linear range of dual-mode determination method is 1.4–21 nmol/L PO43−, with a detection limit of 0.60 nmol/L.

SimPET: a Preclinical PET Insert for Simultaneous PET/MR Imaging.

SimPET/M7 system is a small-animal dedicated simultaneous positron emission tomography and magnetic resonance imaging (PET/MRI) scanner. The SimPET insert has been upgraded from its prototype with a focus on count rate performance and sensitivity. The M7 scanner is a 1-T permanent magnet-based compact MRI system without any cryogens. Here, we present performance evaluation results of SimPET along with the results of mutual interference evaluation and simultaneously acquired PET/MR imaging. Following NEMA NU 4-2008 standard, we evaluated the performance of the SimPET system. The M7 MRI compatibility of SimPET was also assessed by analyzing MRI images of a uniform phantom under different PET conditions and PET count rates with different MRI pulse sequences. Mouse imaging was performed including a whole-body 18F-NaF PET scan and a simultaneous PET/MRI scan with 64Cu-NOTA-ironoxide. The spatial resolution at center based on 3D OSEM without and with warm background was 0.7mm and 1.45mm, respectively. Peak sensitivity was 4.21% (energy window = 250-750keV). The peak noise equivalent count rate with the same energy window was 151kcps at 38.4MBq. The uniformity was 4.42%, and the spillover ratios in water- and air-filled chambers were 14.6% and 12.7%, respectively. In the hot rod phantom image, 0.75-mm-diameter rods were distinguishable. There were no remarkable differences in the SNR and uniformity of MRI images and PET count rates with different PET conditions and MRI pulse sequences. In the whole-body 18F-NaF PET images, fine skeletal structures were well resolved. In the simultaneous PET/MRI study with 64Cu-NOTA-ironoxide, both PET and MRI signals changed before and after injection of the dual-modal imaging probe, which was evident with the exact spatiotemporal correlation. We demonstrated that the SimPET scanner has a high count rate performance and excellent spatial resolution. The combined SimPET/M7 enabled simultaneous PET/MR imaging studies with no remarkable mutual interference between the two imaging modalities.

A dual-modal probe for NIR fluorogenic and ratiometric photoacoustic imaging of Cys/Hcy in vivo

Biothiols, such as cysteine (Cys) and homocysteine (Hcy), play vital roles in biological homeostasis and are closely related to various pathological and physiological processes in the living systems. Therefore, the in vivo detection of biothiols is of great importance for early diagnosis of diseases and assessment of disease progression. In this work, we developed a near-infrared (NIR) fluorescence and photoacoustic dual-modal molecular probe ( NIR-S ) that can be specifically activated by Cys or Hcy. The aryl-thioether substituted cyanine probe can undergo nucleophilic substitution and Smiles rearrangement reaction, resulting in specific turn-on NIR fluorescence and ratiometric photoacoustic responses for Hcy/Cys. Thus, NIR-S not only realizes the specific NIR fluorescence and photoacoustic dual mode imaging to detect Hcy/Cys in solution, but also can be applied to living cells and mice to detect Hcy/Cys. This work provided a practical tool to detect Hcy/Cys levels in vivo , which would be beneficial for the early diagnosis and progress of diseases.

Controlled synthesis and upconversion luminescence properties of Yb3+/Er3+ co-doped Bi2O3 nanospheres for optical and X-ray computed tomography imaging

Bi2O3 nanospheres co-doped with Yb3+/Er3+ upconverting ions pair have been successfully synthesized via a facile hydrothermal method followed by a heat treatment. The resulting Bi2O3:Yb3+,Er3+ nanospheres show a monodisperse spherical morphology with narrow size distribution (~180 nm) and display intense upconversion luminescence under 980 nm laser excitation. It is found that the crystal structure, morphology and upconversion luminescence properties of nanospheres have a direct relationship with the doping concentration of Yb3+ and the subsequent calcination temperature. These Bi2O3:Yb3+,Er3+ nanospheres can be prepared in large quantities and can be easily modified with a layer of biocompatible polyethyleneimine (PEI) molecules. The yielded nanospheres could not only maintain uniform size and morphological characteristics, but also show good water dispersibility and biocompatibility. Remarkably, these Bi2O3:Yb3+,Er3+ upconversion nanophosphors could also act as an effective contrast agent for X-ray computed tomography (CT) imaging, which show higher contrast efficacy than commercial iodine-based contrast agent. The proposed facile synthetic route and inexpensive matrix materials pave the way for broad use of these Bi2O3:Yb3+,Er3+ nanospheres as ideal dual-mode bioimaging probes in biomedical field.