Fluorescence Enhancement and End-to-End Assembly of Bisacridinedione–Gold Nanorods by Calcium Ions

X1134sciescopu

Femto-second laser beam with a low power density achieved a two-photon photodynamic cancer therapy with quantum dots

Focusing the femto-second (fs) laser beam on the target was the usual way to carry out a two-photon excitation (TPE) in previous photodynamic therapy (PDT) studies. However, focusing the laser deep inside the tissues of the tumor is unrealistic due to tissue scattering, so that this focusing manner seems unfit for practical TPE PDT applications. In this work, we prepared a conjugate of quantum dots (QDs) and sulfonated aluminum phthalocyanine (AlPcS) for TPE PDT, because QDs have a very high two-photon absorption cross section (TPACS) and thus QDs can be excited by an unfocused 800 nm fs laser beam with a low power density and then transfer the energy to a conjugated AlPcS via fluorescence resonance energy transfer (FRET). The FRET efficiency of the QD-AlPcS conjugate in water was as high as 90%, and the FRET process of the cellular QD-AlPcS was also observed in both KB and HeLa cells under TPE of a 800 nm fs laser. The singlet oxygen (O-1(2)) products were produced by the QD-AlPcS under the TPE of the unfocused 800 nm fs laser via FRET mediated PDT. Moreover, the QD-AlPcS can effectively destroy these cancer cells under the irradiation of the 800 nm unfocused fs laser beam with a power density of 92 mW mm(-2), and particularly the killing efficiency of the TPE is comparable to that of the commonly used one-photon excitation (OPE) at visible wavelengths. These results highlight the potential of QD-AlPcS for TPE PDT with a near infrared wavelength.open112019sciescopu

Imaging Depths of Near-Infrared Quantum Dots in First and Second Optical Windows

Potential advantages of quantum dot (QD) imaging in the second optical window (SOW) at 1,000 to 1,400 nm over the first optical window (FOW) at 700 to 900 nm have attracted much interest. QDs that emit at 800 nm (800QDs) and QDs that emit at 1,300 nm (1,300QDs) are used to investigate the imaging depths at the FOW and SOW. QD images in biologic tissues are processed binarized via global thresholding method, and the imaging depths are determined using the criteria of contrast to noise ratio and relative apparent size. Owing to the reduced scattering in the SOW, imaging depth in skin can be extended by approximately three times for 1,300QD/SOW over 800QD/FOW. In liver, excitation of 1,300QD/SOW can be shifted to longer wavelengths; thus, the imaging depth can be extended by 1.4 times. Effects of quantum yield (QY), concentration, incidence angle, polarization, and fluence rate F on imaging depth are comprehensively studied. Under F approved by the Food and Drug Administration, 1,300QDs with 50% QY can reach imaging depths of 29.7 mm in liver and 17.5 mm in skin. A time-gated excitation using 1,000 times higher F pulses can obtain the imaging depth of ≈ 5 cm. To validate our estimates, in vivo whole-body imaging experiments are performed using small-animal models

Quantum dot-aluminum phthalocyanine conjugates perform photodynamic reactions to kill cancer cells via fluorescence resonance energy transfer

Sulfonated aluminum phthalocyanines (AlPcSs), commonly used photosensitizers for photodynamic therapy of cancers (PDT), were conjugated with amine-dihydrolipoic acid-coated quantum dots (QDs) by electrostatic binding, achieving 70 AlPcSs per QD. The AlPcS-QD conjugates can utilize the intense light absorptions of conjugated QDs to indirectly excite AlPcSs producing singlet oxygen via fluorescence resonance energy transfer (FRET), demonstrating a new excitation model for PDT. The AlPcS-QD conjugates easily penetrated into human nasopharyngeal carcinoma cells and carried out the FRET in cells, with efficiency around 80%. Under the irradiation of a 532-nm laser, which is at the absorption region of QDs but not fit for the absorption of AlPcSs, the cellular AlPcS-QD conjugates can destroy most cancer cells via FRET-mediated PDT, showing the potential of this new strategy for PDT.open116045sciescopu

Imaging depths of near-infrared quantum dots in first and second optical windows

Potential advantages of quantum dot (QD) imaging in the second optical window (SOW) at 1,000 to 1,400 nm over the first optical window (FOW) at 700 to 900 nm have attracted much interest. QDs that emit at 800 nm (800QDs) and QDs that emit at 1,300 nm (1,300QDs) are used to investigate the imaging depths at the FOW and SOW. QD images in biologic tissues are processed binarized via global thresholding method, and the imaging depths are determined using the criteria of contrast to noise ratio and relative apparent size. Owing to the reduced scattering in the SOW, imaging depth in skin can be extended by approximately three times for 1,300QD/SOW over 800QD/FOW. In liver, excitation of 1,300QD/SOW can be shifted to longer wavelengths; thus, the imaging depth can be extended by 1.4 times. Effects of quantum yield (QY), concentration, incidence angle, polarization, and fluence rate F on imaging depth are comprehensively studied. Under F approved by the Food and Drug Administration, 1,300QDs with 50% QY can reach imaging depths of 29.7 mm in liver and 17.5 mm in skin. A time-gated excitation using 1,000 times higher F pulses can obtain the imaging depth of approximate to 5 cm. To validate our estimates, in vivo whole-body imaging experiments are performed using small-animal models.archiving status unknown114941sciescopu

Metal ion-induced dual fluorescent change for aza-crown ether acridinedione-functionalized gold nanorods and quantum dots

Aza-crown ether acridinedione-functionalized quantum dots (ACEADD-QDs) and aza-crown ether acridinedione-functionalized gold nanorods (ACEADD-GNRs) have been developed as a pair for a fluorescent chemosensor detecting metal ions. The ACEADD-QDs have dual emissions at a visible wavelength of similar to 430 nm from the acridinedione dye moiety and at a near-infrared (NIR) wavelength of similar to 775 nm from the CdTeSe QDs. In the presence of Ca2+ or Mg2+ ions, the ACEADD-QD and ACEADD-GNR pair can form a sandwich complex mediated by the metal ion. The ACEADD-QD and ACEADD-GNR complex pair shows visible fluorescence enhancement from the acridinedione dye and concurrent fluorescence quenching from the NIR QD. The aza-crown ether complex results in the suppression of photoinduced electron transfer from the aza-crown ether to the acridinedione dye moiety. At the same time, the QD fluorescence can be effectively quenched by the nanometal surface energy transfer from the QD to the GNR. This ACEADD-QD and ACEADD-GNR pair can effectively transduce the selective binding event of crown ethers with metal ions into the simultaneous modulation of the enhancement in dye fluorescence and the quenching of QD emission, which can open a new strategy for ratiometric sensors that are selective and robust against the environment conditions.open111315sciescopu

Surface engineering of inorganic nanoparticles for imaging and therapy

Many kinds of inorganic nanoparticles (NPs) including semiconductor, metal, metal oxide, and lanthanide-doped NPs have been developed for imaging and therapy applications. Their unique optical, magnetic, and electronic properties can be tailored by controlling the composition, size, shape, and structure. Interaction of such NPs with cells and/or in vivo compartments is critically determined by the surface properties, and sophisticated control over the NP surface is essential to control their fate in biological environments. We review NP surface coating strategies using the categories of small surface ligand, polymer, and lipid. Use of small ligand molecules has the advantage of maintaining the minimal hydrodynamic (HD) size. Polymers can be advantageous in NP anchoring by combining multiple affinity groups. Encapsulation of NPs in polymers, lipids or surfactants can preserve the as-synthesized NPs. NP surface properties and reaction conditions should be carefully considered to obtain a bioconjugate that maintains the physicochemical properties of NP and functionalities of the conjugated biomolecules. We highlight how the surface properties of NPs impact their interactions with cells and in vivo compartments, especially focused on the important surface design parameters such as HD size, surface charge, and targeting. Typically, maximal cellular uptake can take place in the intermediate NP size range of 40-60 nm. Clearance of NPs from blood circulation is largely dependent on the degree of uptake by reticuloendothelial system when they are larger than 10 nm. When the HD size is below 10 nm, NPs show broad distribution over many organs. Reduction of HD size below the limit of renal barrier can achieve fast clearance of NPs. For maximal tumor accumulation, NPs should have long blood circulation time and should be large enough to prevent rapid penetration. NPs are also desired to rapidly clear out from the body after the mission before they cause toxic side effects. However, efficient clearance from the body to avoid side effects may result in the reduction in residence time required for accumulation in target tissues. Smart design of NP surface coating that can meet the conflicting demands can open a new avenue of NP applications. Surface charge and hydrophobicity need to be carefully considered for NP surface design. Positively charged NPs more adsorb on cell membranes and consequently show higher level of internalizations when compared with negatively charged or neutral NPs. NPs encounter a large variety of biomolecules in vivo, where non-specific adsorptions can potentially alter the physicochemical properties of the NPs. For optimal performance, NPs are suggested to have neutral surface charge at physiological conditions, small HD size, and minimal non-specific adsorption levels. Zwitterionic NP surface coating by small surface ligands can be a promising approach. Toxicity is one of most critical issues, where proper control of the NP surface can significantly reduce the toxicities. (C) 2012 Elsevier B.V. All rights reserved.X11132124sciescopu

Quantum dot-engineered M13 virus layer-by-layer composite films for highly selective and sensitive turn-on TNT sensors

We developed quantum dot-engineered M13 virus layer-by-layer hybrid composite films with incorporated fluorescence quenchers. TNT is designed to displace the quenchers and turn on the quantum dot fluorescence. TNT was detected at the sub ppb level with a high selectivity.open111516sciescopu

Tanycytic TSPO Inhibition Induces Lipophagy to Regulate Lipid Metabolism and Improve Energy Balance

Hypothalamic glial cells named tanycytes, which line the 3rd ventricle (3V), are components of the hypothalamic network that regulates a diverse array of metabolic functions for energy homeostasis. Herein, we report that TSPO (translocator protein), an outer mitochondrial protein, is highly enriched in tanycytes and regulates homeostatic responses to nutrient excess as a potential target for an effective intervention in obesity. Administration of a TSPO ligand, PK11195, into the 3V, and tanycyte-specific deletion of Tspo reduced food intake and elevated energy expenditure, leading to negative energy balance in a high-fat diet challenge. Ablation of tanycytic Tspo elicited AMPK-dependent lipophagy, breaking down lipid droplets into free fatty acids, thereby elevating ATP in a lipid stimulus. Our findings suggest that tanycytic TSPO affects systemic energy balance through macroautophagy/autophagy-regulated lipid metabolism, and highlight the physiological significance of TSPO in hypothalamic lipid sensing and bioenergetics in response to overnutrition. Abbreviations: 3V: 3rd ventricle; ACAC: acetyl-Coenzyme A carboxylase; AGRP: agouti related neuropeptide; AIF1/IBA1: allograft inflammatory factor 1; AMPK: AMP-activated protein kinase; ARC: arcuate nucleus; Atg: autophagy related; Bafilo: bafilomycin A1; CAMKK2: calcium/calmodulin-dependent protein kinase kinase 2, beta; CCCP: carbonyl cyanide m-chlorophenylhydrazone; CNS: central nervous system; COX4I1: cytochrome c oxidase subunit 4I1; FFA: free fatty acid; GFAP: glial fibrillary acidic protein; HFD: high-fat diet; ICV: intracerebroventricular; LAMP2: lysosomal-associated membrane protein 2; LD: lipid droplet; MAP1LC3B/LC3B: microtubule-associated protein 1 light chain 3 beta; MBH: mediobasal hypothalamus; ME: median eminence; MEF: mouse embryonic fibroblast; NCD: normal chow diet; NEFM/NFM: neurofilament medium; NPY: neuropeptide Y; OL: oleic acid; POMC: pro-opiomelanocortin-alpha; PRKN/Parkin: parkin RBR E3 ubiquitin protein ligase; Rax: retina and anterior neural fold homeobox; RBFOX3/NeuN: RNA binding protein, fox-1 homolog (C. elegans) 3; RER: respiratory exchange ratio; siRNA: small interfering RNA; SQSTM1: sequestosome 1; TG: triglyceride; TSPO: translocator protein; ULK1: unc-51 like kinase 1; VCO2: carbon dioxide production; VMH: ventromedial hypothalamus; VO2: oxygen consumption. © 2019, © 2019 The Author(s). Published by Informa UK Limited, trading as Taylor & Francis Group.TRU