Nanoscale mapping and spectroscopy of non-radiative hyperbolic modes in hexagonal boron nitride nanostructures.
Nano Lett. 2018 Feb 16;:
Authors: Brown LV, Davanco M, Sun Z, Kretinin AV, Chen Y, Matson JR, Vurgaftman I, Sharac N, Giles A, Fogler MM, Taniguchi T, Watanabe K, Novoselov KS, Maier SA, Centrone A, Caldwell JD
The inherent crystal anisotropy of hexagonal boron nitride (hBN) provides the ability to support hyperbolic phonon polaritons, i.e. polaritons that can propagate with very large wavevectors within the material volume, thereby enabling optical confinement to exceedingly small dimensions. Indeed, previous research has shown that nanometer-scale truncated nanocone hBN cavities, with deep subdiffractional dimensions, support three-dimensionally confined optical modes in the mid-infrared. Due to optical selection rules only a few of the many theoretically predicted modes have been observed experimentally via far-field reflection and scattering-type scanning near-field optical microscopy (s-SNOM). The photothermal induced resonance (PTIR) technique probes optical and vibrational resonances overcoming weak far-field emission by leveraging an atomic force microscope (AFM) probe to transduce local sample expansion caused by light absorption. Here we show that PTIR enables the direct observation of previously unobserved, dark hyperbolic modes of hBN nanostructures. Leveraging these optical modes and their wide range of angular and radial momenta could provide a new degree of control over the electromagnetic near-field concentration, polarization in nanophotonic applications.
PMID: 29451802 [PubMed - as supplied by publisher]
An upconversion nanoplatform with extracellular pH-driven tumor-targeting ability for improved photodynamic therapy.
Nanoscale. 2018 Feb 16;:
Authors: Ai F, Wang N, Zhang X, Sun T, Zhu Q, Kong W, Wang F, Zhu G
Upconversion nanoparticles (UCNPs) are widely utilized for photodynamic therapy (PDT) due to their specific upconverting luminescence that utilizes near infrared (NIR) light to excite photosensitizers (PSs) for PDT. The efficiency of UCNP-based PDT will be improved if the cancer-targeting property of nanomedicine is enhanced. Herein, we employed the pH low insertion peptide (pHLIP), a cancer-targeting moiety, to functionalize an 808 nm excited UCNP-based nanoplatform that has a minimized over-heating effect to perform PDT. pHLIP can bring cargo specifically into cancer cells under an acidic environment, realizing the effective active-targeting abilities to cancer cells or tumor due to acidosis. The pHLIP-functionalized nanoplatform was assembled and well characterized. The nanoplatform shows an efficient NIR-irradiated PDT effect in cancer cells, especially under a slightly acidic condition that mimics the tumor microenvironment, and this effectiveness is attributed to the targeting properties of pHLIP to cancer cells under acidic conditions that favor the entry of the nanoplatform. Furthermore, the pHLIP-functionalized nanoplatform shows a favorable safety profile in mice with a high maximum tolerated dose (MTD), which may broaden the availability of administration in vivo. The efficient in vivo antitumor activity is achieved through intratumor injection of the nanoplatform followed by NIR irradiation on the breast tumor. The nanoparticles are largely accumulated in the tumor site, revealing the excellent tumor-targeting properties of the pHLIP-functionalized nanoplatform, which ensures efficient PDT in vivo. Moreover, the nanoparticles have a long retention time in the bloodstream, indicating their stability in vivo. Overall, we provide an example of a UCNP-based nanosystem with tumor-targeting properties to perform efficient PDT both in vitro and in vivo.
PMID: 29451577 [PubMed - as supplied by publisher]
Upconversion in photodynamic therapy: plumbing the depths.
Dalton Trans. 2018 Feb 16;:
Authors: Hamblin MR
Photodynamic therapy (PDT) involves the combination of non-toxic dyes called photosensitizers (PS) and harmless visible light that interact with ambient oxygen to give reactive oxygen species (ROS) that can damage biomolecules and kill cells. PDT has mostly been developed as a cancer therapy but can also be used as an antimicrobial approach against localized infections. However even the longest wavelength used for exciting PS (in the 700 nm region) has relatively poor tissue penetration, and many PS are much better excited by blue and green light. Therefore upconversion nanoparticles (UCNPs) have been investigated in order to allow deeper-penetrating near-infrared light (980 nm or 810 nm) to be used for PDT. NaYF4 nanoparticles doped with Yb3+ and Er3+ or with Tm3+ and Er3+ have been attached to PS either by covalent conjugation, or by absorption to the coating or shell (used to render the UCNPs biocompatible). Forster resonance energy transfer to the PS then allows NIR light energy to be transduced into ROS leading to cell killing and tumor regression. Some studies have experimentally demonstrated the deep tissue advantage of UCNP-PDT. Recent advances have included dye-sensitized UCNPs and UCNPs coupled to PS, and other potentially synergistic drug molecules or techniques. A variety of bioimaging modalities have also been combined with upconversion PDT. Further studies are necessary to optimize the drug-delivery abilities of the UCNPs, improve the quantum yields, allow intravenous injection and tumor targeting, and ensure lack of toxicity at the required doses before potential clinical applications.
PMID: 29451568 [PubMed - as supplied by publisher]
Near-infrared bone densitometry: a feasibility study on distal radius measurement.
J Biophotonics. 2018 Feb 16;:
Authors: Chung C, Chen YP, Leu TH, Sun CW
Osteoporosis, defined as decreased bone mineral density (BMD), poses patients in dangers for fracture risk and has become a major public health problem worldwide because of is associated morbidity, mortality and costs. Without doubt, early detection and timely intervention are important to successfully manage osteoporosis and its associated complications. The dual-energy x-ray absorptiometry (DXA) is the most popular and standard method to measure BMD. However, limitations including radiation exposure and availability restrict its application for osteoporosis screening among general population. In this study, we developed a simple method to detect human distal radius bone density based on near infrared (NIR) image system. Among 10 volunteers (including five young and five elderly participants) receiving bone density measurement using our NIR image system at the ultradistal part of bilateral distal radius, we demonstrated a strong correlation between the optical attenuation and BMD measured with DXA, which may facilitate predicting bone density status. We hope our potential NIR image system may open a new avenue for development of osteoporosis screening facilities and help in prevention of osteoporosis related fracture and its associated complications in the near future. Pearson's correlations between BMD values from the DXA and light intensity of NIR system.
PMID: 29451366 [PubMed - as supplied by publisher]
Near infrared photoimmunotherapy with combined exposure of external and interstitial light sources.
Mol Pharm. 2018 Feb 16;:
Authors: Maruoka Y, Nagaya T, Sato K, Ogata F, Okuyama S, Choyke PL, Kobayashi H
Near infrared photoimmunotherapy (NIR-PIT) is a new target-cell specific cancer treatment that induces highly selective necrotic/immunogenic cell death after systemic administration of a photo-absorber antibody conjugate and subsequent NIR light exposure. However, the depth of NIR light penetration in tissue (approximately 2 centimeters) with external light sources, limits the therapeutic effects of NIR-PIT. Interstitial light exposure using cylindrical diffusing optical fibers can overcome this limitation. The purpose in this study was to compare three NIR light delivery methods for treating tumors with NIR-PIT using a NIR laser system at an identical light energy; external exposure alone, interstitial exposure alone, and the combination. Panitumumab conjugated with the photosensitizer, IRDye-700DX (pan-IR700) was intravenously administered to mice with A431-luc xenografts which are epithelial growth factor receptor (EGFR) positive. One and two days later, NIR light was administered to the tumors using one of three methods. Interstitial exposure alone and in combination with external sources showed the greatest decrease in bioluminescence signal intensity. Additionally, the combination of external and interstitial NIR light exposure showed significantly greater tumor size reduction and prolonged survival after NIR-PIT compared to external exposure alone. This result suggested that the combination of external and interstitial NIR light exposure was more effective than externally applied light alone. Although external exposure is the least invasive means of delivering light, the combination of external and interstitial exposures produces superior therapeutic efficacy in tumors greater than 2cm in depth from the tissue surface.
PMID: 29450993 [PubMed - as supplied by publisher]
MHI-148 Cyanine Dye Conjugated Chitosan Nanomicelle with NIR Light-Trigger Release Property as Cancer Targeting Theranostic Agent.
Mol Imaging Biol. 2018 Feb 15;:
Authors: Thomas RG, Moon MJ, Surendran SP, Park HJ, Park IK, Lee BI, Jeong YY
PURPOSE: Paclitaxel (PTX) loaded hydrophobically modified glycol chitosan (HGC) micelle is biocompatible in nature, but it requires cancer targeting ability and stimuli release property for better efficiency. To improve tumor retention and drug release characteristic of HGC-PTX nanomicelles, we conjugated cancer targeting heptamethine dye, MHI-148, which acts as an optical imaging agent, targeting moiety and also trigger on-demand drug release on application of NIR 808 nm laser.
PROCEDURES: The amine group of glycol chitosan modified with hydrophobic 5β-cholanic acid and the carboxyl group of MHI-148 were bonded by 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide/N-hydroxysuccinimide chemistry. Paclitaxel was loaded to MHI-HGC nanomicelle by an oil-in-water emulsion method, thereby forming MHI-HGC-PTX.
RESULTS: Comparison of near infrared (NIR) dyes, MHI-148, and Flamma-774 conjugated to HGC showed higher accumulation for MHI-HGC in 4T1 tumor and 4T1 tumor spheroid. In vitro studies showed high accumulation of MHI-HGC-PTX in 4T1 and SCC7 cancer cell lines compared to NIH3T3 cell line. In vivo fluorescence imaging of the 4T1 and SCC7 tumor showed peak accumulation of MHI-HGC-PTX at day 1 and elimination from the body at day 6. MHI-HGC-PTX showed good photothermal heating ability (50.3 °C), even at a low concentration of 33 μg/ml in 1 W/cm2 808 nm laser at 1 min time point. Tumor reduction studies in BALB/c nude mice with SCC7 tumor showed marked reduction in MHI-HGC-PTX in the PTT group combined with photothermal therapy compared to MHI-HGC-PTX in the group without PTT.
CONCLUSION: MHI-HGC-PTX is a cancer theranostic agent with cancer targeting and optical imaging capability. Our studies also showed that it has cancer targeting property independent of tumor type and tumor reduction property by combined photothermal and chemotherapeutic effects.
PMID: 29450802 [PubMed - as supplied by publisher]
Electrospun Conjugated Polymer/Fullerene Hybrid Fibers: Photoactive Blends, Conductivity through Tunneling-AFM, Light Scattering, and Perspective for Their Use in Bulk-Heterojunction Organic Solar Cells.
J Phys Chem C Nanomater Interfaces. 2018 Feb 08;122(5):3058-3067
Authors: Yang Z, Moffa M, Liu Y, Li H, Persano L, Camposeo A, Saija R, Iatì MA, Maragò OM, Pisignano D, Nam CY, Zussman E, Rafailovich M
Hybrid conjugated polymer/fullerene filaments based on MEH-PPV/PVP/PCBM were prepared by electrospinning, and their properties were assessed by scanning electron, atomic and lateral-force, tunneling, and confocal microscopies, as well as by attenuated-total-reflection Fourier transform infrared spectroscopy, photoluminescence quantum yield, and spatially resolved fluorescence. Highlighted features include the ribbon shape of the realized fibers and the persistence of a network serving as a template for heterogeneous active layers in solar cell devices. A set of favorable characteristics is evidenced in this way in terms of homogeneous charge-transport behavior and formation of effective interfaces for diffusion and dissociation of photogenerated excitons. The interaction of the organic filaments with light, exhibiting specific light-scattering properties of the nanofibrous mat, might also contribute to spreading incident radiation across the active layers, thus potentially enhancing photovoltaic performance. This method might be applied to other electron donor-electron acceptor material systems for the fabrication of solar cell devices enhanced by nanofibrillar morphologies embedding conjugated polymers and fullerene compounds.
PMID: 29449907 [PubMed]
Study on Strain Compensation for Multiple-Quantum Well in Infrared Light-Emitting Diode Using the InxGa1-xP Strain Barrier.
J Nanosci Nanotechnol. 2018 Mar 01;18(3):2014-2017
Authors: Kim DK, Lee HJ
Strain compensation for multiple-quantum wells (MQWs) relative to the efficiency improvement of infrared light-emitting diodes (IR-LEDs) was investigated through the use of an InxGa1-xP strain barrier. The InxGa1-xP barrier, which was inserted between the n-confinement and active regions, developed for the reduction of lattice-mismatched strains in GaAs/AlGaAs and InGaAs/GaAs MQWs. Through photoluminescence, improved intensity was displayed in InGaAs/GaAs MQWs having InxGa1-xP strain barriers, with a significant increase in the intensity observed at the In0.47GaP strain barrier. This result is attributed to strain compensation between the In0.47GaP tensile strain barrier used and the In0.07GaAs compressive strain in MQWs. Through results based on InGaAs/GaAs MQWs, the highest output power of 6 mW was obtained at the In0.47GaP strain barrier, which shows a relative increase of almost 20% as compared to conventional MQWs.
PMID: 29448702 [PubMed - in process]
Interface State Density and Series Resistance of n-Type Nanocrystalline FeSi₂/p-Type Si Heterojunctions Formed by Utilizing Facing-Target Direct-Current Sputtering.
J Nanosci Nanotechnol. 2018 Mar 01;18(3):1841-1846
Authors: Sittimart P, Duangrawa A, Onsee P, Teakchaicum S, Nopparuchikun A, Promros N
n-Type nanocrystalline FeSi2/p-type Si heterojunctions were formed by using facing-target direct- current sputtering at room temperature. The J-V characteristic results revealed that the reverse leakage current is large and the response under illumination of near-infrared light is very weak. The capacitance-voltage-frequency (C-V-f) and conductance-voltage-frequency (G-V-f) measurements were carried out at room temperature in order to estimate the series resistance (Rs) by using the Nicollian-Brews method and the density of interface state (Nss) by using the Hill-Coleman method. By estimation according to the Nicollian-Brews method, the Rs value increases with decreasing f value. The Rs values at zero bias voltage were 2.07 Ω at 60 kHz and 1.54 Ω at 2 MHz, which are consistent with those calculated by using the Cheung's and Norde's methods. The obtained Rs should be attributable to the Rs existing in the ohmic contact and neutral regions, which is the current-limiting factor for junctions. The nss values calculated by using the Hill-Coleman method were 2.70 × 1014 eV-1cm-2 at 60 kHz and 1.43 × 1013 eV-1cm-2 at 2 MHz. This result revealed the presence of interface states at the hetero-interface behaving as a leakage current center and a trap center of the photo-generated carrier, which degraded the junction properties at room temperature.
PMID: 29448669 [PubMed - in process]
Graphene-Pyrene Nanocomposites Obtained Using Azide Chemistry.
J Nanosci Nanotechnol. 2018 Feb 01;18(2):1290-1295
Authors: Xia Z, Kabe R, Liscio A, Kovtun A, Treossi E, Feng X, Palermo V
In this study we describe a simple and fast procedure for the covalent functionalization of pristine graphene with a pyrene-terminated alkylazide, transformed in a highly reactive radical by thermal activation. The functionalized graphene sheets showed enhanced dispersibility in organic solvents compared to the pristine ones, thus enhancing their solution processability and compatibility with solvents or polymers. The relative improvement of solubility estimated form the absorption spectra was ≈60% in CHCl3 and ≈1200% in THF. The obtained materials were characterized by optical absorption spectroscopy, photoemission spectroscopy, infrared spectroscopy and X-rays photoelectron spectroscopy. The presence of the pyrene photoemitting chromophore in the grafting unit allowed to monitor the successful grafting and to confirm the effectiveness of the alkylazide to improve graphene solubility even when present in small amounts on the graphene surface.
PMID: 29448576 [PubMed - in process]
Facile One-Pot Synthesis of Graphene Oxide by Sonication Assisted Mechanochemical Approach and Its Surface Chemistry.
J Nanosci Nanotechnol. 2018 Feb 01;18(2):902-912
Authors: Bera M, Gupta P, Maji PK
Facile one pot synthesis of graphene oxide (GO) by sonication assisted mechanochemical approach has been reported here. The amalgamation of ultrasonication and mechanical stirring has assisted the synthesis of GO in a short time duration of only 4 hours with good reaction yield. The structural characterization of GO was performed by X-ray diffraction spectroscopy (XRD), Fourier transform infrared spectroscopy (FTIR), UV-Visible spectroscopy and Raman spectroscopy. Atomic force microscopic (AFM) analysis manifested the flake like morphology of GO with average sheet thickness ~1.5 nm. AFM also provides important information about the surface roughness. Transmission electron microscope (TEM) analysis gave clear visualization of well exfoliated structure of GO in the form of thin flakes. The field emission scanning electron microscope (FESEM) analysis revealed a crimpling surface morphology of GO. The average size of GO flake as revealed through various morphological as well as light scattering techniques was around 3 μm. Moreover, important surface chemistry of the synthesized GO was well ascertained through contact angle analysis, AFM analysis and zeta potential analysis.
PMID: 29448514 [PubMed - in process]
Photocatalytic Degradation of Oxytetracycline by Ternary Mixed Catalyst and Toxicity Assessment Using Boar Sperm.
J Nanosci Nanotechnol. 2018 Feb 01;18(2):779-788
Authors: Zhou K, Xie XD, Hu XY, Chen MC, Chang CT
Response surface methodology was adopted to obtain ternary mixed catalysts of TiO2-loaded ZSM-5 zeolite and graphene. Oxytetracycline was used as challenged toxicant to evaluate the photocatalytic degradation efficiency of the composites. The optimal weight ratio of graphene, TiO2, and ZSM-5 was 1:8:1. The composites were characterized by ultraviolet-visible spectroscopy, X-ray diffraction, fourier transform infrared, N2 adsorption-desorption isotherms, and transmission electron microscope with an energy-dispersive spectroscopy system, etc. Synthesized samples showed high stability and strong visible-light absorption efficiency. The optimal operating conditions of oxytetracycline photocatalytic degradation were achieved over a wide range of pH and temperature. With 0.1 g/L of optimal ternary mixed composite, the photocatalytic degradation of oxytetracycline was nearly reached completion within 150 min at all treatment temperatures at pH 7. Toxicity of degraded oxytetracycline solution was assayed by a boar sperm quality model using fluorescent staining and flow cytometry. During 180 min of photocatalytic treatment, the degraded oxytetracycline solution showed increasing biotoxicity and changed the morphology and function of boar sperm, despite not killing them.
PMID: 29448494 [PubMed - in process]
Characterization of the Initial Intermediate Formed during Photoinduced Oxygenation of the Ruthenium(II) Bis(bipyridyl)flavonolate Complex.
Inorg Chem. 2016 Aug 01;55(15):7320-2
Authors: Han X, Klausmeyer KK, Farmer PJ
A ruthenium(II) flavonolate complex, [Ru(II)(bpy)2fla][BF4], was synthesized to model the reactivity of the flavonol dioxygenases. The treatment of dry CH3CN solutions of [Ru(II)(bpy)2fla][BF4] with dioxygen under light leads to the oxidative O-heterocyclic ring opening of the coordinated substrate flavonolate, resulting in the formation of [Ru(II)(bpy)2(carboxylate)][BF4] (carboxylate = O-benzoylsalicylate or benzoate) species, as determined by electrospray ionization mass spectrometry. Moderation of the excitation and temperature allowed isolation and characterization of an intermediate, [Ru(II)(bpy)2bpg][BF4] (bpg = 2-benzoyloxyphenylglyoxylate), generated by the 1,2-addition of dioxygen to the central flavonolate ring.
PMID: 27437831 [PubMed - indexed for MEDLINE]