A new type of silica-coated Gd₂(CO₃)₃:Tb nanoparticle as a bifunctional agent for magnetic resonance imaging and fluorescent imaging

We report a new type of dual modal nanoprobe to combine optical and magnetic resonance bioimaging. A simple reverse microemulsion method and coating process was introduced to synthesize silica-coated Gd(2)(CO(3))(3):Tb nanoparticles, and the particles, with an average diameter of 16 nm, can be dispersed in water. As in vitro cell imaging of the nanoprobe shows, the nanoprobe accomplishes delivery to gastric SGC7901 cancer cells successfully in a short time, as well as NCI-H460 lung cancer cells. Furthermore, it presents no evidence of cell toxicity or adverse affect on kidney cell growth under high dose, which makes the nanoprobe's optical bioimaging modality available. The possibility of using the nanoprobe for magnetic resonance imaging is also demonstrated, and the nanoprobe displays a clear T(1)-weighted effect and could potentially serve as a bimodal T(1)-positive contrast agent. Therefore, the new nanoprobe formed from carbonate nanoprobe doped with rare earth ions provides the dual modality of optical and magnetic resonance imaging.     

Preoperative Detection and Intraoperative Visualization of Brain Tumors for More Precise Surgery: A New Dual‐Modality MRI and NIR Nanoprobe

In clinical practice, it is difficult to identify tumor margins during brain surgery due to its inherent infiltrative character. Herein, a unique dual‐modality nanoprobe (Gd‐DOTA‐Ag₂S QDs, referred as Gd‐Ag₂S nanoprobe) is reported, which integrates advantages of the deep tissue penetration of enhanced magnetic resonance (MR) imaging of Gd and the high signal‐to‐noise ratio and high spatiotemporal resolution of fluorescence imaging in the second near‐infrared window (NIR‐II) of Ag₂S quantum dots (QDs). Due to the abundant tumor angiogenesis and the enhanced permeability and retention effect in the tumor, a brain tumor (U87MG) in a mouse model is clearly delineated in situ with the help of the Gd assisted T1 MR imaging and the intraoperative resection of the tumor is precisely accomplished under the guidance of NIR‐II fluorescence imaging of Ag₂S QDs after intravenous injection of Gd‐Ag₂S nanoprobe. Additionally, no histologic changes are observed in the main organs of the mouse after administration of Gd‐Ag₂S nanoprobe for 1 month, indicating the high biocompatibility of the nanoprobe. We expect that such a novel “Detection and Operation” strategy based on Gd‐Ag₂S nanoprobe is promising in future clinical applications.     

Dual‐Modal NIR‐Fluorophore Conjugated Magnetic Nanoparticle for Imaging Amyloid‐β Species In Vivo

Senile plaques, the extracellular deposit of amyloid‐β (Aβ) peptides, are one of the neuropathological hallmarks found in Alzheimer's disease (AD) brain. The current method of brain imaging of amyloid plaques based on positron emission tomography (PET) is expensive and invasive with low spatial resolution. Thus, the development of sensitive and nonradiative amyloid‐β (Aβ)‐specific contrast agents is highly important and beneficial to achieve early AD detection, monitor the disease progression, and evaluate the effectiveness of potential AD drugs. Here a neuroprotective dual‐modal nanoprobe developed by integrating highly Aβ‐specific and turn‐on fluorescence cyanine sensors with superparamagnetic iron oxide nanoparticles as an effective near‐infrared imaging (NIRI)/magnetic resonance imaging (MRI) contrast agent for imaging of Aβ species in vivo is reported. This Aβ‐specific probe is found not only nontoxic and noninvasive, but also highly blood brain barrier permeable. It also shows a potent neuroprotective effect against Aβ‐induced toxicities. This nanoprobe is successfully applied for in vivo fluorescence imaging with high sensitivity and selectivity to Aβ species, and MRI with high spatial resolution in an APP/PS1 transgenic mice model. Its potential as a powerful in vivo dual‐modal imaging tool for early detection and diagnosis of AD in humans is affirmed.     

Optical and MRI multifunctional nanoprobe for targeting gliomas

A multifunctional nanoprobe capable of targeting glioma cells, detectable by both magnetic resonance imaging and fluorescence microscopy, was developed. The nanoprobe was synthesized by coating iron oxide nanoparticles with covalently bound bifunctional poly(ethylene glycol) (PEG) polymer, which were subsequently functionalized with chlorotoxin and the near-infrared fluorescing molecule Cy5.5. Both MR imaging and fluorescence microscopy showed significant preferential uptake of the nanoparticle conjugates by glioma cells. Such a nanoprobe could potentially be used to image resections of glioma brain tumors in real time and to correlate preoperative diagnostic images with intraoperative pathology at cellular-level resolution.     

Hyperbranched Conjugated Polyelectrolyte for Dual‐modality Fluorescence and Magnetic Resonance Cancer Imaging

Herein is reported the synthesis of gadolinium ion (Gd(III))‐chelated hyperbranched conjugated polyelectrolyte (HCPE‐Gd) and its application in fluorescence and magnetic resonance (MR) dual imaging in live animals. The synthesized HCPE‐Gd forms nanospheres with an average diameter of ～42 nm measured by laser light scattering and a quantum yield of 10% in aqueous solution. The absorption spectrum of HCPE‐Gd has two maxima at 318 and 417 nm, and its photoluminescence maximum centers at 591 nm. Confocal laser scanning microscopy studies indicate that the HCPE‐Gd is internalized in MCF‐7 cancer cell cytoplasm with good photostability and low cytotoxicity. Further fluorescence and MR imaging studies on hepatoma H₂₂ tumor‐bearing mouse model reveal that HCPE‐Gd can serve as an efficient optical/MR dual‐modal imaging nanoprobe for in vivo cancer diagnosis.     

Hierarchically Nanostructured Hybrid Platform for Tumor Delineation and Image‐Guided Surgery via NIR‐II Fluorescence and PET Bimodal Imaging

Bimodal imaging with fluorescence in the second near infrared window (NIR‐II) and positron emission tomography (PET) has important significance for tumor diagnosis and management because of complementary advantages. It remains challenging to develop NIR‐II/PET bimodal probes with high fluorescent brightness. Herein, bioinspired nanomaterials (melanin dot, mesoporous silica nanoparticle, and supported lipid bilayer), NIR‐II dye CH‐4T, and PET radionuclide ⁶⁴Cu are integrated into a hybrid NIR‐II/PET bimodal nanoprobe. The resultant nanoprobe exhibits attractive properties such as highly uniform tunable size, effective payload encapsulation, high stability, dispersibility, and biocompatibility. Interestingly, the incorporation of CH‐4T into the nanoparticle leads to 4.27‐fold fluorescence enhancement, resulting in brighter NIR‐II imaging for phantoms in vitro and in situ. Benefiting from the fluorescence enhancement, NIR‐II imaging with the nanoprobe is carried out to precisely delineate and resect tumors. Additionally, the nanoprobe is successfully applied in tumor PET imaging, showing the accumulation of the nanoprobe in a tumor with a clear contrast from 2 to 24 h postinjection. Overall, this hierarchically nanostructured platform is able to dramatically enhance fluorescent brightness of NIR‐II dye, detect tumors with NIR‐II/PET imaging, and guide intraoperative resection. The NIR‐II/PET bimodal nanoprobe has high potential for sensitive preoperative tumor diagnosis and precise intraoperative image‐guided surgery.     

Quantum dot-labeled aptamer nanoprobes specifically targeting glioma cells

Two new techniques, aptamer-based specific recognition and quantum dot (QD)-based fluorescence labeling, are becoming increasingly important in biosensing. In this study, these two techniques have been coupled together to construct a new kind of fluorescent QD-labeled aptamer (QD-Apt) nanoprobe by conjugating GBI-10 aptamer to the QD surface. GBI-10 is a single-stranded DNA (ssDNA) aptamer for tenascin-C, which distributes on the surface of glioma cells as a dominant extracellular matrix protein. The QD-Apt nanoprobe can recognize the tenascin-C on the human glioma cell surface, which will be helpful for the development of new convenient and sensitive in?vitro diagnostic assays for glioma. The QD-Apt nanoprobe has particular features such as strong fluorescence, stability, monodispersity and uniformity. In addition, this probe preparation method is universal, so it is expected to provide a new type of stable nanoprobe for high-throughput and fast biosensing detection and bioimaging. New methods for real-time and dynamic tracking and imaging can be accordingly developed.     

A Functional CT Contrast Agent for In Vivo Imaging of Tumor Hypoxia

Hypoxia, which has been well established as a key feature of the tumor microenvironment, significantly influences tumor behavior and treatment response. Therefore, imaging for tumor hypoxia in vivo is warranted. Although some imaging modalities for detecting tumor hypoxia have been developed, such as magnetic resonance imaging, positron emission tomography, and optical imaging, these technologies still have their own specific limitations. As computed tomography (CT) is one of the most useful imaging tools in terms of availability, efficiency, and convenience, the feasibility of using a hypoxia‐sensitive nanoprobe (Au@BSA‐NHA) for CT imaging of tumor hypoxia is investigated, with emphasis on identifying different levels of hypoxia in two xenografts. The nanoprobe is composed of Au nanoparticles and nitroimidazole moiety which can be electively reduced by nitroreductase under hypoxic condition. In vitro, Au@BSA‐NHA attain the higher cellular uptake under hypoxic condition. Attractively, after in vivo administration, Au@BSA‐NHA can not only monitor the tumor hypoxic environment with CT enhancement but also detect the hypoxic status by the degree of enhancement in two xenograft tumors with different hypoxic levels. The results demonstrate that Au@BSA‐NHA may potentially be used as a sensitive CT imaging agent for detecting tumor hypoxia.     

Ratiometric Nanoparticle Probe Based on FRET‐Amplified Phosphorescence for Oxygen Sensing with Minimal Phototoxicity

Luminescent oxygen probes enable direct imaging of hypoxic conditions in cells and tissues, which are associated with a variety of diseases, including cancer. Here, a nanoparticle probe that addresses key challenges in the field is developed, it: i) strongly amplifies room temperature phosphorescence of encapsulated oxygen‐sensitive dyes; ii) provides ratiometric response to oxygen; and iii) solves the fundamental problem of phototoxicity of phosphorescent sensors. The nanoprobe is based on 40 nm polymeric nanoparticles, encapsulating ≈2000 blue‐emitting cyanine dyes with fluorinated tetraphenylborate counterions, which are as bright as 70 quantum dots (QD525). It functions as a light‐harvesting nanoantenna that undergoes efficient Förster resonance energy transfer to ≈20 phosphorescent oxygen‐sensitive platinum octaethylporphyrin (PtOEP) acceptor dyes. The obtained nanoprobe emits stable blue fluorescence and oxygen‐sensitive red phosphorescence, providing ratiometric response to dissolved oxygen. The light harvesting leads to ≈60‐fold phosphorescence amplification and makes the single nanoprobe particle as bright as ≈1200 PtOEP dyes. This high brightness enables oxygen detection at a single‐particle level and in cells at ultra‐low nanoprobe concentration with no sign of phototoxicity, in contrast to PtOEP dye. The developed nanoprobe is successfully applied to the imaging of a microfluidics‐generated oxygen gradient in cancer cells. It constitutes a promising tool for bioimaging of hypoxia.     

Responsive Upconversion Nanoprobe for Background‐Free Hypochlorous Acid Detection and Bioimaging

Responsive nanoprobes play an important role in bioassay and bioimaging, early diagnosis of diseases and treatment monitoring. Herein, a upconversional nanoparticle (UCNP)‐based nanoprobe, Ru@UCNPs, for specific sensing and imaging of hypochlorous acid (HOCl) is reported. This Ru@UCNP nanoprobe consists of two functional components,, i.e., NaYF₄:Yb, Tm UCNPs that can convert near infrared light‐to‐visible light as the energy donor, and a HOCl‐responsive ruthenium(II) complex [Ru(bpy)₂(DNCH‐bpy)](PF₆)₂ (Ru‐DNPH) as the energy acceptor and also the upconversion luminescence (UCL) quencher. Within this luminescence resonance energy transfer nanoprobe system, the UCL OFF–ON emission is triggered specifically by HOCl. This triggering reaction enables the detection of HOCl in aqueous solution and biological systems. As an example of applications, the Ru@UCNPs nanoprobe is loaded onto test papers for semiquantitative HOCl detection without any interference from the background fluorescence. The application of Ru@UCNPs for background‐free detection and visualization of HOCl in cells and mice is successfully demonstrated. This research has thus shown that Ru@UCNPs is a selective HOCl‐responsive nanoprobe, providing a new way to detect HOCl and a new strategy to develop novel nanoprobes for in situ detection of various biomarkers in cells and early disgnosis of animal diseases.     

Multimodal imaging guided photothermal therapy using functionalized graphene nanosheets anchored with magnetic nanoparticles

In this work, a nanoscale reduced graphene oxide-iron oxide nanoparticle (RGO-IONP) complex is noncovalently functionalized with polyethylene glycol (PEG), obtaining a RGO-IONP-PEG nanocomposite with excellent physiological stability, strong NIR optical absorbance, and superparamagnetic properties. Using this theranostic nanoprobe, in-vivo triple modal fluorescence, photoacoustic, and magnetic resonance imaging are carried out, uncovering high passive tumor targeting, which is further used for effective photothermal ablation of tumors in mice.     

Design,Properties, and In Vivo Behavior of Super­paramagnetic Persistent Luminescence Nanohybrids

With the fast development of noninvasive diagnosis, the design of multimodal imaging probes has become a promising challenge. If many monofunctional nanocarriers have already proven their efficiency, only few multifunctional nanoprobes have been able to combine the advantages of diverse imaging modalities. An innovative nanoprobe called mesoporous persistent luminescence magnetic nanohybrids (MPNHs) is described that shows both optical and magnetic resonance imaging (MRI) properties intended for in vivo multimodal imaging in small animals. MPNHs are based on the assembly of chromium‐doped zinc gallate oxide and ultrasmall superparamagnetic iron oxide nanoparticles embedded in a mesoporous silica shell. MPNHs combine the optical advantages of persistent luminescence, such as real time imaging with highly sensitive and photostable detection, and MRI negative contrast properties that ensure in vivo imaging with rather high spatial resolution. In addition to their imaging capabilities, these MPNHs can be motioned in vitro with a magnet, which opens multiple perspectives in magnetic vectorization and cell therapy research.     

Layered Nanoprobe for Long‐Lasting Fluorescent Cell Label

A long‐lasting particle‐based fluorescent label is designed for extended cell imaging studies. This onion‐like nanoprobe is constructed through layer‐by‐layer fabrication technology. The nanoprobes are assembled with multiple layers of optically quenched polyelectrolytes, the fluorescence signal of which can be released later by intracellular proteolysis. Upon incubation with cells, the assembled nanoprobes are taken up efficiently. The tight packing and layered assembly of the quenched polyelectrolytes slow subsequent intracellular degradation, and then result in a prolonged intracellular fluorescence signal for up to 3 weeks with no noticeable toxicity.     

Sensitive chemiluminescent imaging for chemoselective analysis of glycan expression on living cells using a multifunctional nanoprobe

A novel sensitive chemiluminescent (CL) imaging method was developed for in situ monitoring of cell surface glycan expression through chemoselective labeling of carbohydrate motifs and then binding to a multifunctional nanoprobe. The nanoprobe was fabricated by assembling biotin-DNA and a large amount of horseradish peroxidase (HRP) on gold nanoparticles (AuNPs). The chemoselective labeling was performed by selective oxidization of the hydroxyl sites of sialyl and galactosyl groups on cell surfaces into aldehydes by periodate and galactose oxidase, respectively, and then aniline-catalyzed hydrazone ligation with biotin hydrazide for specific recognition to avidin. With the biotin-avidin system, the multifunctional nanoprobe could conveniently be bound to the glycan sites on the cell surface. The DNA chain presenting between the AuNPs and biotin assembled on the nanoprobe could obviate the steric effect, and HRP acted to trigger the CL emission of the luminal-H(2)O(2) system. Therefore the expression of both sialyl and galactosyl groups could be selectively monitored by CL imaging with high sensitivity due to the high amount of HRP. Using human liver cancer HCCC-9810 cells as a model, this CL imaging strategy could detect HCCC cells ranging from 6 × 10(2) to 1 × 10(7) cells mL(-1) with a detection limit down to 12 cells. More importantly, this method could be used for distinguishing cancer cells from normal cells and monitoring of dynamic carbohydrate expression on living cells, providing promising application in clinical diagnosis and treatment of cancer.     

Tumor‐Responsive Fluorescent Light‐up Probe Based on a Gold Nanoparticle/Conjugated Polyelectrolyte Hybrid

A tumor‐responsive nanoprobe based on a conjugated polyelectrolyte and gold nanoparticle (AuNP) hybrid was designed to response to the low pH extracellular microenvironment in tumor with light‐up fluorescence. AuNPs with positive surface charges were prepared by direct reducing Au salt with sodium borohydride and stabilized by cystamine. A pH triggered charge‐reversible polymer and a water‐soluble cationic conjugated polyelectrolyte (CPE) were sequentially deposited onto the AuNP surface through electrostatic interaction. The obtained hybrid probe is monodispersed with an average diameter of 68.3 nm by dynamic light scattering measurement. In physiological conditions (pH ≈ 7.4), the hybrid probe is almost non‐fluorescent due to the super‐quenching of CPE by AuNPs via energy/charge transfer and efficient exciton migration along the polymer backbone. When exposed to acidic extracellular microenvironments in tumor (pH_e ≈ 6.5), the acid‐labile amides hydrolyze into primary amines. The generated amine groups result in strong electrostatic repulsion between CPE and AuNPs, leading to recovered probe fluorescence. The fluorescence turn‐on is further utilized for tumor extracellular acidic microenvironment imaging. In addition, under in vivo conditions, the nanosized hybrid probe exhibits specific accumulation in tumor tissue with light‐up fluorescence, which provides new opportunities for easy tumor imaging and identification.     

A paramagnetic nanoprobe to detect tumor cell death using magnetic resonance imaging

A 110 kDa (ca. 5 nm in diameter) bivalent paramagnetic nanoprobe for detecting cell death using magnetic resonance imaging (MRI) is described, in which two biotinylated C2A domains of the protein synaptotagmin-I were complexed with a single avidin molecule, which had been labeled with gadolinium chelates. This nanoprobe bound with high affinity and specificity to the phosphatidylserine exposed by dying cells and was demonstrated to allow MRI detection of apoptotic tumor cells in vitro.     

Dual-emission fluorescent silica nanoparticle-based probe for ultrasensitive detection of Cu2+

An effective dual-emission fluorescent silica nanoparticle-based probe has been constructed for rapid and ultrasensitive detection of Cu(2+). In this nanoprobe, a dye-doped silica core served as a reference signal, thus providing a built-in correction for environmental effects. A response dye was covalently grafted on the surface of the silica nanoparticles through a chelating reagent for Cu(2+). The fluorescence of the response dye could be selectively quenched in the presence of Cu(2+), accompanied by a visual orange-to-green color switch of the nanoprobe. The nanoprobe provided an effective platform for reliable detection of Cu(2+) with a detection limit as low as 10 nM, which is nearly 2 × 10(3) times lower than the maximum level (～20 μM) of Cu(2+) in drinking water permitted by the U.S. Environmental Protection Agency (EPA). The high sensitivity was attributed to the strong chelation of Cu(2+) with polyethyleneimine (PEI) and a signal amplification effect. The nanoprobe constructed by this method was very stable, enabling the rapid detection of Cu(2+) in real water samples. Good linear correlations were obtained over the concentration range from 1 × 10(-7) to 8 × 10(-7) (R(2) = 0.99) with recoveries of 103.8-99.14% and 95.5-95.14% for industrial wastewater and lake water, respectively. Additionally, the long-wavelength emission of the response dye can avoid the interference of the autofluorescence of the biosystems, which facilitated their applications in monitoring Cu(2+) in cells. Furthermore, the nanoprobe showed a good reversibility; the fluorescence can be switched "off" and "on" by an addition of Cu(2+) and EDTA, respectively.     

Fluorescent magnetic hybrid nanoprobe for multimodal bioimaging

A fluorescent magnetic hybrid imaging nanoprobe (HINP) was fabricated by the conjugation of superparamagnetic Fe3O4 nanoparticles and visible light emitting (～600 nm) fluorescent CdTe/CdS quantum dots (QDs). The assembly strategy used the covalent linking of the oxidized dextran shell of magnetic particles to the glutathione ligands of QDs. The synthesized HINP formed stable water-soluble colloidal dispersions. The structure and properties of the particles were characterized by transmission electron and atomic force microscopy, energy dispersive x-ray analysis and inductively coupled plasma optical emission spectroscopy, dynamic light scattering analysis, optical absorption and photoluminescence spectroscopy, and fluorescent imaging. The luminescence imaging region of the nanoprobe was extended to the near-infrared (NIR) (～800 nm) by conjugation of the superparamagnetic nanoparticles with synthesized CdHgTe/CdS QDs. Cadmium, mercury based QDs in HINP can be easily replaced by novel water-soluble glutathione stabilized AgInS2/ZnS QDs to present a new class of cadmium-free multimodal imaging agents. The observed NIR photoluminescence of fluorescent magnetic nanocomposites supports their use for bioimaging. The developed HINP provides dual-imaging channels for simultaneous optical and magnetic resonance imaging.     

Ratiometric Photoacoustic Molecular Imaging for Methylmercury Detection in Living Subjects

Photoacoustic molecular imaging is an emerging and promising diagnostic tool for heavy metal ions detection. Methylmercury (MeHg⁺) is one of the most potent neurotoxins, which damages the brain and nervous system of human beings through fish consumption. The development of a selective and sensitive method for MeHg⁺ detection is highly desirable. In this Communication, we develope a chemoselective photoacoustic sensor (LP‐hCy7) composed of the liposome (LP) and MeHg⁺‐responsive near‐infrared (NIR) cyanine dye (hCy7) for MeHg⁺ detection within living subjects, such as zebrafish and mouse. The as‐prepared LP‐hCy7 nanoprobe displays unique dual‐shift NIR absorbance peaks and produces a normalized turn‐on response after the reaction of MeHg⁺ and hCy7 through a mercury‐promoted cyclization reaction. The absorbance intensities of LP‐hCy7 nanoprobe at 690 and 860 nm are decreased and increased, respectively. The ratiometric photoacoustic signal (PA860/PA690) is noticeably increased in the presence of MeHg⁺. These findings not only provide a ratiometric photoacoustic molecular imaging probe for the detection of metal ions in vivo, but also provides a tool for spectroscopic photoacoustic molecular imaging.     

In vivo MRI detection of gliomas by chlorotoxin-conjugated superparamagnetic nanoprobes

Converging advances in the development of nanoparticle-based imaging probes and improved understanding of the molecular biology of brain tumors offer the potential to provide physicians with new tools for the diagnosis and treatment of these deadly diseases. However, the effectiveness of promising nanoparticle technologies is currently limited by insufficient accumulation of these contrast agents within tumors. Here a biocompatible nanoprobe composed of a poly(ethylene glycol) (PEG) coated iron oxide nanoparticle that is capable of specifically targeting glioma tumors via the surface-bound targeting peptide, chlorotoxin (CTX), is presented. The preferential accumulation of the nanoprobe within gliomas and subsequent magnetic resonance imaging (MRI) contrast enhancement are demonstrated in vitro in 9L cells and in vivo in tumors of a xenograft mouse model. TEM imaging reveals that the nanoprobes are internalized into the cytoplasm of 9L cells and histological analysis of selected tissues indicates that there are no acute toxic effects of these nanoprobes. High targeting specificity and benign biological response establish this nanoprobe as a potential platform to aid in the diagnosis and treatment of gliomas and other tumors of neuroectodermal origin.