Characterization and application of porous gold nanoparticles as 2‐photon luminescence imaging agents: 20‐fold brighter than gold nanorods

Two‐photon nonlinear microscopy with the aid of plasmonic contrast agents is an attractive bioimaging technique capable of generating high‐resolution images in 3 dimensions and facilitating targeted imaging with deep tissue penetration. In this work, physically synthesized gold nanoparticles containing multiple nanopores are used as 2‐photon contrast agents and are reported to emit a 20‐fold brighter 2‐photon luminescence as compared to typical contrast agents, that is, gold nanorods. A successful application of our porous gold nanoparticles is experimentally demonstrated by in vitro nonlinear optical imaging of adipocytes at subcellular level.      

Inside Front Cover: Enhanced volumetric imaging in 2‐photon microscopy via acoustic lens beam shaping (J. Biophotonics 2/2018)

Two‐photon microscopy is the tool of choice for fluorescence imaging of deep tissues with high resolution, but can be limited in three‐dimensional acquisition speed and penetration depth. In this work, these issues are addressed by using an acoustic optofluidic lens capable of ultrafast beam shaping on a pixel basis. Driving the lens with different phase profiles enables high‐speed volumetric imaging, or enhanced signal‐to‐background for deeper penetration. Further details can be found in the article by Simonluca Piazza et al. ( e201700050 )

     

Redox luminescence switch based on Mn2+‐doped NaYF4:Yb,Er upconversion nanorods

An redox luminescence switch was developed for the sensing of glutathione (GSH), l ‐cysteine (Cys) or l ‐ascorbic acid (AA) based on redox reaction. The Mn²⁺‐doped NaYF₄:Yb,Er upconversion nanorods (UCNRs) with an emission peak located in the red region were synthesized. The luminescence intensity of the UCNRs could be quenched due to the Mn²⁺ could be oxidized to MnO₂ by KMnO₄. Subsequently, when the AA, GSH or Cys was added into the MnO₂ modified upconversion nanosystem, which could reduced MnO₂ to Mn²⁺ and the luminescence intensity was recovered. The concentration ranges of the nanosystem are 0.500–3.375 mM (R² = 0.99) for AA, 0.6250–11.88 mM (R² = 0.99) for GSH and 0.6250–9.375 mM (R² = 0.99) for Cys, respectively.     

Inside Back Cover: In vivo full‐field functional optical hemocytometer (J. Biophotonics 2/2018)

Full‐field functional optical hemocytometer (FFOH), based on the absorption intensity fluctuation modulation (AIFM) effect, is in vivo label‐free image method for capillaries of near‐transparent live biological specimens. FFOH can provide a flow video, flow velocity measurement and RBC count, simultaneously. The zebrafish experimental result shows the potential to study the physiological mechanisms of the blood circulation systems. Further details can be found in the article by Fuli Zhang et al. ( e201700039 )

     

Back Cover: Joint tagging assisted fluctuation nanoscopy enables fast high‐density super‐resolution imaging (J. Biophotonics 9/2018)

Based on multicolor quantum dots (QDs) labeling, the joint tagging assisted super‐resolution radial fluctuation (JT‐SRRF) nanoscopy achieves high‐fidelity super‐resolution imaging of subcellular microtubules and fast live‐cell parallel tracking of cholera toxin subunit B (CTB) induced lipid clusters spatially distributed below the optical diffraction limit. This method paves the way for fast high‐density parallel tracking, which is especially beneficial for the investigation of the intensive dynamics in live‐cell applications. Further details can be found in the article by Zhiping Zeng, Jing Ma, Peng Xi, and Canhua Xu ( e201800020 ).

     

Inside Cover: Internalization kinetics and cytoplasmic localization of functionalized diatomite nanoparticles in cancer cells by Raman imaging (J. Biophotonics 4/2018)

The internalization kinetics and intracellular spatial distribution of functionalized diatomite nanoparticles in human lung epidermoid carcinoma cell line have been investigated by confocal fluorescence and Raman microscopy. In this context, Raman imaging due to its non‐destructive, chemically selective and label‐free working principle provides evidence that the nanovectors are internalized and co‐localize with lipid environments, suggesting an endocytic internalisation route. Nanoparticle uptakes and intracellular persistence are observed up to 72 hours, without damage to cell viability or morphology. Further details can be found in the article by Stefano Managò et al. ( e201700207 )

     

Interaction of glucose‐derived carbon quantum dots with silver and gold nanoparticles and its application for the fluorescence detection of 6‐thioguanine

The interaction of glucose‐derived carbon quantum dots (CQDs) with silver (Ag) and gold (Au) nanoparticles (NPs) was explored by fluorescence spectroscopy. Both metal NPs cause an efficient quenching of CQD fluorescence, which is likely due to the energy transfer process between CQDs as donors and metal NPs as acceptors. The Stern–Volmer plots were evaluated and corresponding quenching constants were found to be 1.9 × 10¹⁰ and 2.2 × 10⁸ M^?1 for AgNPs and AuNPs, respectively. The analytical applicability of these systems was demonstrated for turn‐on fluorescence detection of the anti‐cancer drug, 6‐thioguanine. Because the CQD–AgNP system had much higher sensitivity than the CQD–AuNP system, we used it as a selective fluorescence probe in a turn‐on assay of 6‐thioguanine. Under optimum conditions, the calibration graph was linear from 0.03 to 1.0 μM with a detection limit of 0.01 μM. The developed method was applied to the analysis of human plasma samples with satisfactory results.     

Inside Back Cover: The conformation of bovine serum albumin adsorbed to the surface of single all‐dielectric nanoparticles following light‐induced heating (J. Biophotonics 7/2018)

Germanium vs Silicon: All‐dielectric nanoparticles provides the heat resistance for proteins under light‐induced heating. Further details can be found in the article by Andrei A. Krasilin et al. ( e201700322 )

     

Front Cover: A high‐throughput all‐optical laser‐scanning imaging flow cytometer with biomolecular specificity and subcellular resolution (J. Biophotonics 2/2018)

A new type of high‐throughput imaging flow cytometer (>20 000 cells s^‐1) based upon an all‐optical ultrafast laser‐scanning imaging technique, called free‐space angular‐chirp‐enhanced delay (FACED) is reported. FACED imaging flow cytometers enables high‐throughput visualization of functional morphology of individual cells with subcellular resolution. It critically empowers largescale and deep characterization of single cells and their heterogeneity with high statistical power— an ability to become increasingly critical in single‐cell analysis adopted in a wide range of biomedical and life‐science applications. Further details can be found in the article by Wenwei Yan et al. ( e201700178 )

     

Back Cover: Non‐invasive optical method for real‐time assessment of intracorneal riboflavin concentration and efficacy of corneal cross‐linking (J. Biophotonics 7/2018)

We disclose a theranostic device for performing image‐guided riboflavin/UV‐A corneal cross‐linking. The device determines treatment efficacy by real time monitoring of riboflavin concentration in the corneal stroma. The study shows efficacy of the device in eye bank human donor tissues. Further details can be found in the article by Giuseppe Lombardo et al. ( e201800028 )

     

Assessment of the metabolism and morphology of the porcine cornea,lens and retina by 2‐photon imaging

Two‐photon imaging is a noninvasive imaging technique with increasing importance in the biological and medical fields since it allows intratissue cell imaging with high resolution. We demonstrate the feasibility of using a single 2‐photon instrument to evaluate the cornea, the crystalline lens and the retina based on their autofluorescence (AF). Image acquisition was performed using a custom‐built 2‐photon microscope for 5‐dimensional microscopy with a near infrared broadband sub‐15 femtosecond laser centered at 800 nanometers. Signals were detected using a spectral photomultiplier tube. The spectral ranges for the analysis of each tissue/layer AF were determined based on the spectra of each tissue as well as of pure endogenous fluorophores. The cornea, lens and retina are characterized at multiple depths with subcellular resolution based on their morphology and AF lifetime. Additionally, the AF lifetime of NAD(P)H was used to assess the metabolic activity of the cornea epithelium, endothelium and keratocytes. The feasibility to evaluate the metabolic activity of lens epithelial cells was also demonstrated, which may be used to further investigate the pathogenesis of cataracts. The results illustrate the potential of multimodal multiphoton imaging as a novel ophthalmologic technique as well as its potential as a diagnostic tool.      

Inside Cover: Optimized perfusion‐based CUBIC protocol for the efficient whole‐body clearing and imaging of rat organs (J. Biophotonics 5/2018)

Optical tissue clearing is a method allowing post‐mortem deep imaging of organs in three dimensions. By optimizing the CUBIC clearing protocol, the authors provide rapid and simple approach to clear the entire adult rat organism within as little as four days, which is accompanied by the variety of its staining and imaging techniques. The image was captured with polarizers and demonstrates transparent rodent heart with thread‐like crystals of clearing reagent. Further details can be found in the article by Pawe? Matryba et al. ( e201700248 ).

     

Biogenesis,characterization, and the effect of vicenin‐gold nanoparticles on glucose utilization in 3T3‐L1 adipocytes: A bioinformatic approach to illuminate its interaction with PTP 1B and AMPK

This study reported the synthesis of Vicenin‐2 gold nanoparticles (VN‐AuNPs) and evaluated their effect on the glucose utilization efficiency of 3T3‐L1 adipocytes. The VN‐AuNPs were characterized by microscopic, DLS and spectral analysis. The bio‐reducing efficiency of Vicenin‐2 (VN) was computed and confirmed by HPLC analysis. The stability of VN‐AuNPs in various physiological media was explored. The cytotoxicity and glucose uptake assays were performed in 3T3‐L1 adipocytes. The docking of VN with PTP1B and AMPK was also performed. The color change and UV absorption at 537 nm preliminarily confirmed the VN reduced gold nanoparticles. The VN‐AuNPs appeared as spherical particles (57 nm) and face centered cubic crystals under TEM and XRD analysis, respectively. Its zeta potential was found to be ?6.53 mV. The FT‐IR spectra of VN and its AuNPs confirmed its stability. The computed reducing potential of VN was similar to the extent of VN utilized during the synthesis of VN‐AuNPs. The VN‐AuNPs showed a remarkable stability in different physiological media. At 100 µM concentration, VN‐AuNPs displayed 78.21% cell viability. A concentration dependent increase in glucose uptake was noted in 3T3‐L1 adipocytes when incubated with VN‐AuNPs. The docking data revealed a strong interaction of VN with the binding pockets of PTP1B and AMPK. This demonstrates that the fabricated VN‐AuNPs might enhance the intracellular VN availability mediated cellular glucose utilization and this would serve as a novel nanodrug for the management of diabetes. © 2015 American Institute of Chemical Engineers Biotechnol. Prog., 31:1096–1106, 2015     

Front Cover: Spectrally encoded coherence tomography and reflectometry: Simultaneous en face and cross‐sectional imaging at 2 gigapixels per second (J. Biophotonics 4/2018)

SECTR is a novel multimodal imaging platform for combined volumetric optical coherence tomography (OCT) and en face spectrally encoded reflectometry (SER). The authors demonstrate three‐dimensional motion‐tracking with millisecond temporal and micron spatial resolution using complementary data from OCT and SER, and preliminary algorithms and results showing real‐time image aiming and multi‐volumetric mosaicking for reconstruction of wide‐field composites. The image shows a noninvasively imaged nine‐field mosaic of in vivo human retina and depth‐resolved visualization of tissue microstructures. Further details can be found in the article by Mohamed T. El‐Haddad, Ivan Bozic, and Yuankai K. Tao ( e201700268 )

     

β‐Amino acids containing peptides and click‐cyclized peptide as β‐turn mimics: a comparative study with ‘conventional’ lactam‐ and disulfide‐bridged hexapeptides

The increasing interest in click chemistry and its use to stabilize turn structures led us to compare the propensity for β‐turn stabilization of different analogs designed as mimics of the β‐turn structure found in tendamistat. The β‐turn conformation of linear β‐amino acid‐containing peptides and triazole‐cyclized analogs were compared to ‘conventional’ lactam‐ and disulfide‐bridged hexapeptide analogs. Their 3D structures and their propensity to fold in β‐turns in solution, and for those not structured in solution in the presence of α‐amylase, were analyzed by NMR spectroscopy and by restrained molecular dynamics with energy minimization. The linear tetrapeptide Ac‐Ser‐Trp‐Arg‐Tyr‐NH₂ and both the amide bond‐cyclized, c[Pro‐Ser‐Trp‐Arg‐Tyr‐D ‐Ala] and the disulfide‐bridged, Ac‐c[Cys‐Ser‐Trp‐Arg‐Tyr‐Cys]‐NH₂ hexapeptides adopt dominantly in solution a β‐turn conformation closely related to the one observed in tendamistat. On the contrary, the β‐amino acid‐containing peptides such as Ac‐(R)‐β³‐hSer‐(S)‐Trp‐(S)‐β³‐hArg‐(S)‐β³‐hTyr‐NH₂, and the triazole cyclic peptide, c[Lys‐Ser‐Trp‐Arg‐Tyr‐βtA]‐NH₂, both specifically designed to mimic this β‐turn, do not adopt stable structures in solution and do not show any characteristics of β‐turn conformation. However, these unstructured peptides specifically interact in the active site of α‐amylase, as shown by TrNOESY and saturation transfer difference NMR experiments performed in the presence of the enzyme, and are displaced by acarbose, a specific α‐amylase inhibitor. Thus, in contrast to amide‐cyclized or disulfide‐bridged hexapeptides, β‐amino acid‐containing peptides and click‐cyclized peptides may not be regarded as β‐turn stabilizers, but can be considered as potential β‐turn inducers. Copyright © 2011 European Peptide Society and John Wiley & Sons, Ltd.     

Front Cover: Photoluminescence intensity ratio of Eu‐conjugated lactates—A simple optical imaging technique for biomarker analysis for critical diseases (J. Biophotonics 5/2018)

Eu³⁺integrated photoluminescence intensity ratio (PLIR) approach for optical detection of lactates in blood serum, plasma and confocal imaging of brain tissues has very high potential for exploitation of this technique in both in vitro monitoring and in vivo bioimaging applications for the detection of biomarkers in various diseases states. This image is diagrammatic representation of fact that the overall PLIR is higher with more lactates conjugated with Eu³⁺ ions. Further details can be found in the article by Tarun Kakkar et al. ( e201700199 ).

     

Inside Cover: Noninvasive,high‐speed,near‐infrared imaging of the biomolecular distribution and molecular mechanism of embryonic development in fertilized fish eggs (J. Biophotonics 4/2018)

The biomaterial distribution and its molecular mechanism of embryonic development in Japanese medaka fish were visualized without staining using high‐speed near‐infrared imaging. It was a remarkable achievement to visualize the structures of eyes, lipid bilayer membranes, micelles, and water structural variations at the interface of different substances. Furthermore, insights on lipid metabolism and membrane functions were obtained from the biased distribution of lipoproteins and the presence of unsaturated fatty acids in the egg membrane. Further details can be found in the article by Mika Ishigaki ( e201700115 )

     

Inside Back Cover: Development of a 3‐dimensional tissue lung phantom of a preterm infant for optical measurements of oxygen—Laser‐detector position considerations (J. Biophotonics 3/2018)

The picture depicts the different 3d‐printed organs, thorax, lungs, heart and bone. Assembled it is used as an optical phantom of a preterm infant for performing percutaneous optical measurements of the gas content in the lungs. In order to simulate the optical properties of the tissue, the heart and thorax can be filled with liquid phantoms, a mixture of Intralipid and Indian Ink. Further details can be found in the article by Jim Larsson et al. ( e201700097 ).

     

Retraction: Zhong H,Lu L,Wang Y,Yang H. Single layer molybdenum disulfide as an optical nanoprobe for 2 photon luminescence and second harmonic generation cell imaging. J. Biophotonics. 2018;11:e201700354.

The above article from the Journal of Biophotonics, published online on 9 January 2018 in Wiley Online Library as Early View ( https://onlinelibrary.wiley.com/doi/abs/10.1002/jbio.201700354 ), and in Volume 11, e201700354, has been retracted by agreement between the authors (Hong Zhong, Lin Lu, Yuanhao Wang, Hongxing Yang), Prof. Sailing He, Prof. Jurgen Popp (Editor‐in‐Chief) and Wiley‐VCH GmbH & Co. KGaA. The retraction has been agreed because the submitting author Hong Zhong failed to acknowledge the true authorship of the presented study which was originally conducted by a group led by Prof. Sailing He in South China Normal University, Guangzhou of China. REFERENCE Zhong H, Lu L, Wang Y, Yang H. Single layer molybdenum disulfide as an optical nanoprobe for 2 photon luminescence and second harmonic generation cell imaging. J. Biophotonics  2018 ;11:e201700354. https://doi.org/10.1002/jbio.201700354