Near-infrared Fluorescent Nanoprobes Research Articles

Near-Infrared Fluorescent Nanoprobes for Revealing the Role of Dopamine in Drug Addiction.

Brain imaging techniques enable visualizing the activity of central nervous system without invasive neurosurgery. Dopamine is an important neurotransmitter. Its fluctuation in brain leads to a wide range of diseases and disorders, like drug addiction, depression, and Parkinson's disease. We designed near-infrared fluorescence dopamine-responsive nanoprobes (DRNs) for brain activity imaging during drug abuse and addiction process. On the basis of light-induced electron transfer between DRNs and dopamine and molecular wire effect of the DRNs, we can track the dynamical change of the neurotransmitter level in the physiological environment and the releasing of the neurotransmitter in living dopaminergic neurons in response to nicotine stimulation. The functional near-infrared fluorescence imaging can dynamically track the dopamine level in the mice midbrain under normal or drug-activated condition and evaluate the long-term effect of addictive substances to the brain. This strategy has the potential for studying neural activity under physiological condition.

Amplification of near-infrared fluorescence in semiconducting polymer nanoprobe for grasping the behaviors of systemically administered endothelial cells in ischemia treatment.

To date, there have been few studies on using fluorescent cell trackers for non-invasively monitoring the invivo fate of systemically administered cells. This is because only a relatively small number of cells can reach the disease site post systemic infusion, and thus achieving ideal invivo cell tracking requires that the fluorescent cell trackers should hold combined merits of ultrahigh near-infrared (NIR) fluorescence, negligible interference on cell behavior and function, excellent retention within cells, as well as accurate long-term cell tracking ability. To address this challenge, we herein developed a highly NIR fluorescent nanoprobe (SPN) based on semiconducting π-conjugated polymers (SPs), by synthesis of a NIR SP-emitter, employment of fluorescence resonance energy transfer (FRET) strategy, and optimization of different FRET donor SPs. Due to the 53.7-fold intra-particle amplification of NIR fluorescence, the SPN could track as few as 2000 endothelial cells (ECs) upon intra-arterial injection into critical limb ischemia (CLI)-bearing mice, showing much higher sensitivity in ECs tracking compared with the most popular commercial cell trackers. What's more, the SPN could provide precise information on the behaviors of systemically injected ECs in CLI treatment including the invivo fate and regenerative contribution of ECs for at least 21 days.

Contrast agents based on switchable near-infrared fluorescent nanoprobes for highly sensitive optical imaging

We have synthesized and characterized photophysical properties of a novel contrast agent based on switchable near-infrared (NIR) fluorescent nanoprobes that enables optical imaging with a higher sensitivity than conventional contrast agents allow. The high sensitivity was a result not only of the intrinsically high signal-to-background ratio that could be obtained in the NIR spectral region, but also from the increased signal intensity that was provided by using activatable nanoprobes. The NIR fluorescent nanoprobes were synthesized by encapsulating indocyanine green (ICG) into pH-responsive polymer nanoparticles. The intensity of the NIR fluorescence signal from the nanoparticles increased about 11-fold in acidic solution, due to the release of ICG molecules from the nanoparticles. The efficacy of fluorescence recovery from the quenched state to the de-quenched state could be modulated by controlling the relative concentrations between pH-responsive polymer and ICG. The fluorescence recovery properties of switchable NIR nanoprobes were also evaluated by cellular uptake experiments. Our experimental results support the use of pH-responsive nanoparticles with incorporated contrast agents as activatable molecular imaging nanoprobes.

Abstract 225: Anti-atherosclerotic Effects of Plaque Macrophage Targetable Nanoparticle-mediated PPAR-γ Agonist Delivery in Atherogenic Mice

Introduction: Atherosclerosis is a process of lipid accumulation and inflammation. In particular, plaque macrophages are associated with fibrous cap destabilization and rupture. We hypothesized that the specific delivery of a PPAR-γ agonist to inflamed plaques via nanoprobe (NP) targeting macrophage mannose receptors could reduce plaque burden and inflammation. Methods and Results: Macrophage mannose receptor targetable nanoprobe (MMR-NP) was fabricated by chemically conjugating thiolated glycol chitosan with mannose-PEG-maleimide, followed by incorporating PPAR-γ agonist (lobeglitazone) into this nanoscale delivery system (MMR-Lobe). For in vivo monitoring of therapeutic response, near-infrared fluorescence NP was prepared by conjugation of Cy5.5 (ext/emi 675/694 nm) with MMR-NP. In cellular uptake study, the MMR-NP showed high affinity to mannose receptors on macrophages. MMR-Lobe attenuated LPS-induced inflammatory cytokines such as TNF-α, IL-6, and MMP-9 in RAW264.7 cells. Additionally, MMR-Lobe increased expression of ABCA1, ABCG1 and LXR-α, known as PPAR-γ regulator genes involved in cholesterol efflux, in RAW264.7 cells. Using a customized high-resolution intravital fluorescence microscope, the in vivo serial imaging of carotid atheroma in apoE-/- mice injected with MMR-Lobe (7 mg/kg, twice weekly for 4 weeks) revealed a significant decrease in plaque burden and inflammation (Figure) as compared to baseline, or non-treated controls, or p.o. Lobe treated mice (p<0.01 respectively, 6 mice in each group). En face imaging, FM, and immunostainings corroborated the in vivo findings. Conclusions: MMR-Lobe was able to selectively target atheroma macrophages, and effectively reduce both plaque burden and inflammation as assessed by serial intravital optical imaging. We suggest that nanoprobe-mediated PPAR-γ agonist delivery targeting plaque macrophages holds a promising theranostic approach for high-risk atheromata.

Near-infrared fluorescence nanoprobe for enzyme-substrate system sensing and in vitro imaging

Herein we report a simple and sensitive fluorescent sensing platform for phenol and enzyme activity detection based on 3-aminobenzeneboronic acid functionalized CuInS2 QDs (APBA-CuInS2 QDs). APBA were covalently linked to CuInS2 QDs surface to form the APBA-CuInS2 QDs which had a fairly symmetric fluorescence emission peak at 736nm in the near-infrared spectral region. In the presence of tyrosinase, phenol can be catalyzed the oxidization into catechol, which could reactive toward the boronic acid functional groups of APBA-CuInS2 QDs to form five-membered cyclic esters, leading to the fluorescence quenching of the QDs. The effective fluorescence quenching of APBA-CuInS2 QDs by phenol enabled this proposed nanosensor to sensitively detect the phenol product-related enzyme system, such as acid phosphatase-catalyzed hydrolysis of phenyl phosphate. Thus, the proposed biosensor was utilized for facile, sensitive, and selective detection phenol, tyrosinase and acid phosphatase. The detection limits of phenol, tyrosinase and acid phosphatase reached 0.05μmolL−1, 0.03UmL−1 and 6nUmL−1 for, respectively. The feasibility of the proposed nanosensor in real samples assay was also studied and satisfactory results were obtained. Meanwhile, using the APBA-CuInS2 QDs fluorescence probe, we successfully performed in vitro imaging of human prostate cancer cells, suggesting the biocompatible sensor has potentially extensive application clinic diagnoses assays.

Facile Construction of Near Infrared Fluorescence Nanoprobe with Amphiphilic Protein-Polymer Bioconjugate for Targeted Cell Imaging.

A simple, straightforward, and reproducible strategy for the construction of a near-infrared (NIR) fluorescence nanoprobe was developed by coating CuInS2/ZnS quantum dots (CIS/ZnS QDs) with a novel amphiphilic bioconjugate. The amphiphilic bioconjugate with a tailor-designed structure of bovine serum albumin (BSA) as the hydrophilic segment and poly(ε-caprolactone) (PCL) as the hydrophobic part was fabricated by chemical coupling the hydrophobic polymer chain to BSA via the maleimide-sulfhydryl reaction. By incorporating CIS/ZnS QDs into the hydrophobic cores of the self-assembly of BSA-PCL conjugate, the constructed NIR fluorescence nanoprobe exhibited excellent fluorescent properties over a wide pH range (pH 3-10) and a good colloidal stability in PBS buffer (pH = 7.4) with or without 10% fetal bovine serum. The presence of the outer BSA shell effectively reduced the nonspecific cellular binding and imparted high biocompatibility and low-toxicity to the probe. Moreover, the NIR fluorescence nanoprobe could be functionalized by conjugating cyclic Arg-Gly-Asp (cRGD) peptide, and the decorated nanoprobe was shown to be highly selective for targeted integrin αvβ3-overexpressed tumor cell imaging. The feasibility of the constructed NIR fluorescence probe in vivo application was further investigated and the results demonstrated its great potential for in vivo imaging. This developed protocol for phase transfer of the CIS/ZnS QDs was universal and applicable to other nanoparticles stabilized with hydrophobic ligands.

PHe-induced charge-reversible NIR fluorescence nanoprobe for tumor-specific imaging.

Inspired by the specificity of acid tumor microenvironment, we constructed a flexible charge-reversible near-infrared (NIR) fluorescence nanoprobe in response to tumor extracellular pH (pHe) for effective tumor-specific imaging. The nanoprobe consists of an NIR-emitted CuInS2/ZnS quantum dot (CIS/ZS QDs) core and a tailored lauric acid and 2,3-dimethylmaleic anhydride modified ε-polylysine (ε-PL-g-LA/DMA) shell, which provides not only a dense protective layer for the QDs but also the ability of pHe-induced positive charge-mediated endocytosis into tumor cells. The results showed that the QDs@ε-PL-g-LA/DMA nanoprobe with a uniform size of 40 nm had high chemical stability at pH 7.4 and excellent optical properties. Especially, it swiftly reversed its surface charge to positive in 20 min when exposed to pHe due to the cleavage of the β-carboxyl amide bond of ε-PL-g-LA/DMA. Moreover, the cell uptake of the pHe-sensitive QDs nanoprobe exposed at pH 6.8 into HeLa cells is much more significant than that at pH 7.4, which further verified the availability of the electrostatic adsorptive endocytosis facilitated targeting ability. The pHe-induced targeting imparted the QDs nanoprobe a broad targeting ability in a variety of solid tumors. Furthermore, as an effective alternative mechanism for tumor targeting, responsive charge reversion is also universally applicable to other cancer theranostics agent.

Bilayered near-infrared fluorescent nanoparticles based on low molecular weight PEI for tumor-targeted in vivo imaging

To improve the tumor fluorescent imaging results in vivo, bilayered nanoparticles encapsulating a lipophilic near-infrared (NIR) fluorescent dye 1,1′-dioctadecyl-3,3,3′,3′-tetramethylindotri-carbocyanine iodide (DiR) were prepared using low molecular weight stearic acid-grafted polyethyleneimine and hyaluronic acid (DiR-PgSHA nanoparticles), which were investigated as a novel NIR fluorescent nano-probe for in vivo tumor-targeted optical imaging. These nanoparticles were characterized by transmission electron microscopy (TEM), infrared (IR) spectra, UV-visual absorption, and fluorescent emission spectra. Their cytotoxicity in vitro and hepatotoxicity in vivo were tested by MTT assay and histological study, respectively. In vivo NIR fluorescence imaging of the DiR-PgSHA nanoparticles was performed using a Carestream imaging system. The DiR-PgSHA nanoparticles were sphere shaped with a diameter of approximately 50 nm according to the TEM images. The DiR-PgSHA nanoparticles had a low cytotoxicity in vitro according to the MTT assay and low hepatotoxicity in vivo as determined in histological studies. The fluorescent emission of DiR-PgSHA nanoparticles was stable in pH values of 5–9 in solution, with only slight blue-shifts of the emission maxima at the basic pH range. The DiR-PgSHA nanoparticles exhibited a substantial tumor-targeting ability in the optical imaging with the use of tumor-bearing mice. These results demonstrated that the DiR-PgSHA nanoparticle is an excellent biocompatible nano-probe for in vivo tumor-targeted NIR fluorescence imaging with a potential for clinical applications.

Biocompatible near-infrared fluorescent nanoparticles for macro and microscopic in vivo functional bioimaging.

Near-infrared (NIR) imaging technology has been widely used for biomedical research and applications, since it can achieve deep penetration in biological tissues due to less absorption and scattering of NIR light. In our research, polymer nanoparticles with NIR fluorophores doped were synthesized. The morphology, absorption/emission features and chemical stability of the fluorescent nanoparticles were characterized, separately. NIR fluorescent nanoparticles were then utilized as bright optical probes for macro in vivo imaging of mice, including sentinel lymph node (SLN) mapping, as well as distribution and excretion monitoring of nanoparticles in animal body. Furthermore, we applied the NIR fluorescent nanoparticles in in vivo microscopic bioimaging via a confocal microscope. Under the 635 nm-CW excitation, the blood vessel architecture in the ear and the brain of mice, which were administered with nanoparticles, was visualized very clearly. The imaging depth of our one-photon microscopy, which was assisted with NIR fluorescent nanoprobes, can reach as deep as 500 μm. Our experiments show that NIR fluorescent nanoparticles have great potentials in various deep-tissue imaging applications.

Self-assembly-induced near-infrared fluorescent nanoprobes for effective tumor molecular imaging.

Fabrication of near-infrared (NIR) fluorescent nanoprobes (NPs) has drawn great attention due to their potential as highly sensitive optical probes for in vivo tumor molecular imaging. Herein, a facile strategy has been reported for the preparation of ultrasmall (<20 nm) indocyanine green (ICG)-containing NIR fluorescent NPs using self-assembly chemistry between folate (FA) modified water-soluble chitosan (WCS) and ICG. The ICG-containing NPs exhibit characteristics of crystalline solid, good photostability, low cytotoxicity and high tumor targeting ability for in vitro cell imaging. We also explored this system for in vivo tumor molecular imaging. Significant tumor accumulation was observed for both in vitro and in vivo tumor imaging in HeLa tumor cell imaging and xenograft-bearing mice model (2 μmol kg-1 at 48 and 72 h time points). The availability of these self-assembled NIR NPs provides a convenient tool for tumor imaging and detection.

PH-responsive near-infrared nanoprobe imaging metastases by sensing acidic microenvironment

A pH responsive near-infrared fluorescence nanoprobe was developed and visualized pulmonary metastases in a mouse model with a volume as small as 0.5 mm3 by sensing the acidic tumor microenvironment.

An individually coated near-infrared fluorescent protein as a safe and robust nanoprobe for in vivo imaging

A prerequisite for in vivo fluorescence imaging is the safety of fluorescent probes. Among all fluorescent probes, fluorescent proteins (FPs) might be the safest ones, which have been widely used in biological sciences at the gene level. But FPs have not been used in vivo in the purified form yet due to the instability of proteins. Here, we individually coat near-infrared (NIR) FPs (NIRFPs) with a silica nanoshell, resulting in NIRFP@silica, one of the safest and brightest NIR fluorescent nanoprobes with a quantum yield of 0.33 for in vivo imaging. The silica shell not only protects NIRFPs from denaturation and metabolic digestion, but also enhances the quantum yield and photostability of the coated NIRFPs. When injected via the tail vein, NIRFP@silica NPs can distribute all over the mouse body, and then can be efficiently eliminated through urine in 24 h, demonstrating its potential applications as a safe and robust NIR fluorescence probe for whole body imaging.

Upconverting and NIR emitting rare earth based nanostructures for NIR-bioimaging

In recent years, significant progress was achieved in the field of nanomedicine and bioimaging, but the development of new biomarkers for reliable detection of diseases at an early stage, molecular imaging, targeting and therapy remains crucial. The disadvantages of commonly used organic dyes include photobleaching, autofluorescence, phototoxicity and scattering when UV (ultraviolet) or visible light is used for excitation. The limited penetration depth of the excitation light and the visible emission into and from the biological tissue is a further drawback with regard to in vivo bioimaging. Lanthanide containing inorganic nanostructures emitting in the near-infrared (NIR) range under NIR excitation may overcome those problems. Due to the outstanding optical and magnetic properties of lanthanide ions (Ln(3+)), nanoscopic host materials doped with Ln(3+), e.g. Y2O3:Er(3+),Yb(3+), are promising candidates for NIR-NIR bioimaging. Ln(3+)-doped gadolinium-based inorganic nanostructures, such as Gd2O3:Er(3+),Yb(3+), have a high potential as opto-magnetic markers allowing the combination of time-resolved optical imaging and magnetic resonance imaging (MRI) of high spatial resolution. Recent progress in our research on over-1000 nm NIR fluorescent nanoprobes for in vivo NIR-NIR bioimaging will be discussed in this review.

Near-Infrared Fluorescent Nanoprobes for in Vivo Optical Imaging.

Near-infrared (NIR) fluorescent probes offer advantages of high photon penetration, reduced light scattering and minimal autofluorescence from living tissues, rendering them valuable for noninvasive mapping of molecular events, assessment of therapeutic efficacy, and monitoring of disease progression in animal models. This review provides an overview of the recent development of the design and optical property of the different classes of NIR fluorescent nanoprobes associated with in vivo imaging applications.

Near-infrared fluorescent nanoprobes for cancer molecular imaging: status and challenges

Near-infrared fluorescence (NIRF) imaging promises to improve cancer imaging and management; advances in nanomaterials allow scientists to combine new nanoparticles with NIRF imaging techniques, thereby fulfilling this promise. Here, we present a synopsis of current developments in NIRF nanoprobes, their use in imaging small living subjects, their pharmacokinetics and toxicity, and finally their integration into multimodal imaging strategies. We also discuss challenges impeding the clinical translation of NIRF nanoprobes for molecular imaging of cancer. Whereas utilization of most NIRF nanoprobes remains at a proof-of-principle stage, optimizing the impact of nanomedicine in cancer patient diagnosis and management will probably be realized through persistent interdisciplinary amalgamation of diverse research fields.

Dextran based pH-activated near-infrared fluorescence nanoprobe imaging the acidic compartments in cancer cells

A novel dextran-based nanoprobe was synthesized and demonstrated the pH-activated near-infrared (NIR) fluorescence in the physiologically acidic aqueous solutions and acidic compartments in human glioblastoma cancer cells.