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Agrohia DK, Goswami R, Jantarat T, Çiçek YA, Thongsukh K, Jeon T, Bell JM, Rotello VM, Vachet RW. Suborgan Level Quantitation of Proteins in Tissues Delivered by Polymeric Nanocarriers. ACS NANO 2024; 18:16808-16818. [PMID: 38870478 DOI: 10.1021/acsnano.4c02344] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/15/2024]
Abstract
Amidst the rapid growth of protein therapeutics as a drug class, there is an increased focus on designing systems to effectively deliver proteins to target organs. Quantitative monitoring of protein distributions in tissues is essential for optimal development of delivery systems; however, existing strategies can have limited accuracy, making it difficult to assess suborgan dosing. Here, we describe a quantitative imaging approach that utilizes metal-coded mass tags and laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) to quantify the suborgan distributions of proteins in tissues that have been delivered by polymeric nanocarriers. Using this approach, we measure nanomole per gram levels of proteins as delivered by guanidinium-functionalized poly(oxanorborneneimide) (PONI) polymers to various tissues, including the alveolar region of the lung. Due to the multiplexing capability of the LA-ICP-MS imaging, we are also able to simultaneously quantify protein and polymer distributions, obtaining valuable information about the relative excretion pathways of the protein cargo and carrier. This imaging approach will facilitate quantitative correlations between nanocarrier properties and protein cargo biodistributions.
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Affiliation(s)
- Dheeraj K Agrohia
- Department of Chemistry, University of Massachusetts Amherst, Amherst, Massachusetts 01003, United States
| | - Ritabrita Goswami
- Department of Chemistry, University of Massachusetts Amherst, Amherst, Massachusetts 01003, United States
| | - Teerapong Jantarat
- Department of Chemistry, University of Massachusetts Amherst, Amherst, Massachusetts 01003, United States
| | - Yağız Anil Çiçek
- Department of Chemistry, University of Massachusetts Amherst, Amherst, Massachusetts 01003, United States
| | - Korndanai Thongsukh
- Department of Chemistry, University of Massachusetts Amherst, Amherst, Massachusetts 01003, United States
| | - Taewon Jeon
- Molecular and Cellular Biology Program, University of Massachusetts Amherst, Amherst, Massachusetts 01003, United States
| | - Jonathan M Bell
- Department of Chemistry, University of Massachusetts Amherst, Amherst, Massachusetts 01003, United States
| | - Vincent M Rotello
- Department of Chemistry, University of Massachusetts Amherst, Amherst, Massachusetts 01003, United States
- Molecular and Cellular Biology Program, University of Massachusetts Amherst, Amherst, Massachusetts 01003, United States
| | - Richard W Vachet
- Department of Chemistry, University of Massachusetts Amherst, Amherst, Massachusetts 01003, United States
- Molecular and Cellular Biology Program, University of Massachusetts Amherst, Amherst, Massachusetts 01003, United States
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Design and construction of a microfluidics workstation for high-throughput multi-wavelength fluorescence and transmittance activated droplet analysis and sorting. Nat Protoc 2023; 18:1090-1136. [PMID: 36707723 DOI: 10.1038/s41596-022-00796-2] [Citation(s) in RCA: 6] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/18/2021] [Accepted: 11/09/2022] [Indexed: 01/28/2023]
Abstract
Droplet microfluidics has revolutionized quantitative high-throughput bioassays and screening, especially in the field of single-cell analysis where applications include cell characterization, antibody discovery and directed evolution. However, droplet microfluidic platforms capable of phenotypic, fluorescence-based readouts and sorting are still mostly found in specialized labs, because their setup is complex. Complementary to conventional FACS, microfluidic droplet sorters allow the screening of cell libraries for secreted factors, or even for the effects of secreted or surface-displayed factors on a second cell type. Furthermore, they also enable PCR-activated droplet sorting for the isolation of genetic material harboring specific markers. In this protocol, we provide a detailed step-by-step guide for the construction of a high-throughput droplet analyzer and sorter, which can be accomplished in ~45 working hours by nonspecialists. The resulting instrument is equipped with three lasers to excite the fluorophores in droplets and photosensors that acquire fluorescence signals in the blue (425-465 nm), green (505-545 nm) and red (580-630 nm) spectrum. This instrument also allows transmittance-activated droplet sorting by analyzing the brightfield light intensity transmitting through the droplets. The setup is validated by sorting droplets containing fluorescent beads at 200 Hz with 99.4% accuracy. We show results from an experiment where droplets hosting single cells were sorted on the basis of increased matrix metalloprotease activity as an application of our workstation in single-cell molecular biology, e.g., to analyze molecular determinants of cancer metastasis.
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Meklef RA, Siemers F, Rein S. Development of a 3D-immunofluorescence analysis for sensory nerve endings in human ligaments. J Neurosci Methods 2022; 382:109724. [PMID: 36207004 DOI: 10.1016/j.jneumeth.2022.109724] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/30/2022] [Revised: 09/29/2022] [Accepted: 10/01/2022] [Indexed: 11/05/2022]
Abstract
BACKGROUND The analysis of ligamentous mechanoreceptors is difficult due to a high amount of unclassifiable mechanoreceptors, which result from incomplete visualization through limited microscopic techniques. NEW METHOD The method was developed using dorsal intercarpal ligaments and dorsal regions of the scapholunate interosseous ligament from human cadaver wrists. Consecutive 70 µm thick cryosections were stained with immunofluorescence markers for protein S100B, neurotrophin receptor p75 (p75), protein gene product 9.5 (PGP 9.5) and 4',6-diamidino-2-phenylindole (DAPI). 3D images of sensory nerve endings were obtained using a confocal laser scanning microscope. Experimental point spread functions (PSF) were used to deconvolve images. Sensory nerve endings were localised in each section plane and classified according to Freeman and Wyke. Finally, confocal data was visualized as 3D-images. RESULTS The method produced excellent image quality, revealing detailed three-dimensional structures. The created 3D-model of sensory nerve endings could be analyzed in all three dimensions, augmenting visualization of the form and immunoreactive pattern of sensory nerve endings. Deconvolution with experimentally measured PSFs aided in enhancing image quality. COMPARISON WITH EXISTING METHODS Using a triple immunofluorescent staining method allows to visualize the structure of sensory nerve endings more precisely than techniques with serial analysis of different monostaining of neural markers. Imaging in three dimensions enhances morphologic details, which are limited in 2D-microscopy. CONCLUSION 3D-triple immunofluorescence produces high quality visualization of mechanoreceptors, thereby improving their analysis. As an elaborate technique, it is ideal for defined research questions concerning the microstructure of sensory nerve endings.
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Affiliation(s)
- Rami Al Meklef
- Department of Plastic and Hand Surgery, Burn Unit, Klinikum Sankt Georg, Delitzscher Straße 141, 04129 Leipzig, Germany; Martin-Luther-University Halle-Wittenberg, Germany
| | - Frank Siemers
- Martin-Luther-University Halle-Wittenberg, Germany; Department of Plastic and Hand Surgery with Burn Unit, Trauma Center Bergmannstrost, 06112 Halle, Germany
| | - Susanne Rein
- Department of Plastic and Hand Surgery, Burn Unit, Klinikum Sankt Georg, Delitzscher Straße 141, 04129 Leipzig, Germany; Martin-Luther-University Halle-Wittenberg, Germany.
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Cao Y, Wu J, Zheng X, Lu Y, Piper JA, Lu Y, Packer NH. Assessing the activity of antibodies conjugated to upconversion nanoparticles for immunolabeling. Anal Chim Acta 2022; 1209:339863. [DOI: 10.1016/j.aca.2022.339863] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/10/2021] [Revised: 04/08/2022] [Accepted: 04/19/2022] [Indexed: 11/01/2022]
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Liu H, Kim C, Haldiman T, Sigurdson CJ, Nyström S, Nilsson KPR, Cohen ML, Wisniewski T, Hammarström P, Safar JG. Distinct conformers of amyloid beta accumulate in the neocortex of patients with rapidly progressive Alzheimer's disease. J Biol Chem 2021; 297:101267. [PMID: 34599965 PMCID: PMC8531671 DOI: 10.1016/j.jbc.2021.101267] [Citation(s) in RCA: 24] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/11/2021] [Revised: 09/27/2021] [Accepted: 09/28/2021] [Indexed: 12/03/2022] Open
Abstract
Amyloid beta (Aβ) deposition in the neocortex is a major hallmark of Alzheimer's disease (AD), but the extent of deposition does not readily explain phenotypic diversity and rate of disease progression. The prion strain-like model of disease heterogeneity suggests the existence of different conformers of Aβ. We explored this paradigm using conformation-dependent immunoassay (CDI) for Aβ and conformation-sensitive luminescent conjugated oligothiophenes (LCOs) in AD cases with variable progression rates. Mapping the Aβ conformations in the frontal, occipital, and temporal regions in 20 AD patients with CDI revealed extensive interindividual and anatomical diversity in the structural organization of Aβ with the most significant differences in the temporal cortex of rapidly progressive AD. The fluorescence emission spectra collected in situ from Aβ plaques in the same regions demonstrated considerable diversity of spectral characteristics of two LCOs-quatroformylthiophene acetic acid and heptaformylthiophene acetic acid. Heptaformylthiophene acetic acid detected a wider range of Aβ deposits, and both LCOs revealed distinct spectral attributes of diffuse and cored plaques in the temporal cortex of rapidly and slowly progressive AD and less frequent and discernible differences in the frontal and occipital cortex. These and CDI findings indicate a major conformational diversity of Aβ accumulating in the neocortex, with the most notable differences in temporal cortex of cases with shorter disease duration, and implicate distinct Aβ conformers (strains) in the rapid progression of AD.
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Affiliation(s)
- He Liu
- Department of Pathology, Case Western Reserve University, Cleveland, Ohio, USA
| | - Chae Kim
- Department of Pathology, Case Western Reserve University, Cleveland, Ohio, USA
| | - Tracy Haldiman
- Department of Pathology, Case Western Reserve University, Cleveland, Ohio, USA
| | - Christina J Sigurdson
- Department of Pathology, University of California, San Diego, La Jolla, California, USA; Department of Medicine, University of California, San Diego, La Jolla, California, USA
| | - Sofie Nyström
- Department of Physics, Chemistry, and Biology, Linköping University, Linköping, Sweden
| | - K Peter R Nilsson
- Department of Physics, Chemistry, and Biology, Linköping University, Linköping, Sweden
| | - Mark L Cohen
- Department of Pathology, Case Western Reserve University, Cleveland, Ohio, USA; National Prion Disease Pathology Surveillance Center, Case Western Reserve University, Cleveland, Ohio, USA
| | - Thomas Wisniewski
- Centre for Cognitive Neurology, Department of Neurology, New York University School of Medicine, New York, New York, USA; Department of Psychiatry, New York University School of Medicine, New York, New York, USA
| | - Per Hammarström
- Department of Physics, Chemistry, and Biology, Linköping University, Linköping, Sweden
| | - Jiri G Safar
- Department of Pathology, Case Western Reserve University, Cleveland, Ohio, USA; Department of Neurology, Case Western Reserve University, Cleveland, Ohio, USA.
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Laberiano-Fernández C, Hernández-Ruiz S, Rojas F, Parra ER. Best Practices for Technical Reproducibility Assessment of Multiplex Immunofluorescence. Front Mol Biosci 2021; 8:660202. [PMID: 34532339 PMCID: PMC8438151 DOI: 10.3389/fmolb.2021.660202] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/29/2021] [Accepted: 08/11/2021] [Indexed: 11/22/2022] Open
Abstract
Multiplex immunofluorescence (mIF) tyramide signal amplification is a new and useful tool for the study of cancer that combines the staining of multiple markers in a single slide. Several technical requirements are important to performing high-quality staining and analysis and to obtaining high internal and external reproducibility of the results. This review manuscript aimed to describe the mIF panel workflow and discuss the challenges and solutions for ensuring that mIF panels have the highest reproducibility possible. Although this platform has shown high flexibility in cancer studies, it presents several challenges in pre-analytic, analytic, and post-analytic evaluation, as well as with external comparisons. Adequate antibody selection, antibody optimization and validation, panel design, staining optimization and validation, analysis strategies, and correct data generation are important for reproducibility and to minimize or identify possible issues during the mIF staining process that sometimes are not completely under our control, such as the tissue fixation process, storage, and cutting procedures.
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Affiliation(s)
- Caddie Laberiano-Fernández
- Department of Translational Molecular Pathology, The University of Texas MD Anderson Cancer Center, Houston, TX, United States
| | - Sharia Hernández-Ruiz
- Department of Translational Molecular Pathology, The University of Texas MD Anderson Cancer Center, Houston, TX, United States
| | - Frank Rojas
- Department of Translational Molecular Pathology, The University of Texas MD Anderson Cancer Center, Houston, TX, United States
| | - Edwin Roger Parra
- Department of Translational Molecular Pathology, The University of Texas MD Anderson Cancer Center, Houston, TX, United States
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Gupta D, Sasmal R, Singh A, Joseph JP, Miglani C, Agasti SS, Pal A. Enzyme-responsive chiral self-sorting in amyloid-inspired minimalistic peptide amphiphiles. NANOSCALE 2020; 12:18692-18700. [PMID: 32970093 DOI: 10.1039/d0nr04581k] [Citation(s) in RCA: 21] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/11/2023]
Abstract
Self-sorting is a spontaneous phenomenon that ensures the formation of complex yet ordered multicomponent systems and conceptualizes the design of artificial and orthogonally functional compartments. In the present study, we envisage chirality-mediated self-sorting in β-amyloid-inspired minimalistic peptide amphiphile (C10-l/d-VFFAKK)-based nanofibers. The fidelity and stereoselectivity of chiral self-sorting was ascertained by Förster resonance energy transfer (FRET) by the judicious choice of a pyrene (Py)-hydroxy coumarin (HOCou) donor-acceptor pair tethered to the peptide sequences. Seed-promoted elongation of the homochiral peptide amphiphiles investigated by AFM image analyses and Thioflavin-T (ThT) binding study further validated the chiral recognition of the l/d peptide nanofibers. Moreover, direct visualization of the chirality-driven self-sorted nanofibers is reported using super-resolution microscopy that exhibits enantioselective enzymatic degradation for l-peptide fibers. Such enantioselective weakening of the hydrogels may be used for designing stimuli-responsive orthogonal compartments for delivery applications.
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Affiliation(s)
- Deepika Gupta
- Chemical Biology Unit, Institute of Nano Science and Technology, Sector 64, Mohali, Punjab 160062, India.
| | - Ranjan Sasmal
- Jawaharlal Nehru Centre for Advanced Scientific Research (JNCASR), Jakkur, Bangalore 560064, India
| | - Ashmeet Singh
- Chemical Biology Unit, Institute of Nano Science and Technology, Sector 64, Mohali, Punjab 160062, India.
| | - Jojo P Joseph
- Chemical Biology Unit, Institute of Nano Science and Technology, Sector 64, Mohali, Punjab 160062, India.
| | - Chirag Miglani
- Chemical Biology Unit, Institute of Nano Science and Technology, Sector 64, Mohali, Punjab 160062, India.
| | - Sarit S Agasti
- Jawaharlal Nehru Centre for Advanced Scientific Research (JNCASR), Jakkur, Bangalore 560064, India
| | - Asish Pal
- Chemical Biology Unit, Institute of Nano Science and Technology, Sector 64, Mohali, Punjab 160062, India.
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Ahmed MU, Velkov T, Zhou QT, Fulcher AJ, Callaghan J, Zhou F, Chan K, Azad MAK, Li J. Intracellular localization of polymyxins in human alveolar epithelial cells. J Antimicrob Chemother 2020; 74:48-57. [PMID: 30357331 DOI: 10.1093/jac/dky409] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/24/2018] [Accepted: 09/06/2018] [Indexed: 01/05/2023] Open
Abstract
Background Current inhaled polymyxin therapy is empirical and often large doses are administered, which can lead to pulmonary adverse effects. There is a dearth of information on the mechanisms of polymyxin-induced lung toxicity and their intracellular localization in lung epithelial cells. Objectives To investigate the intracellular localization of polymyxins in human lung epithelial A549 cells. Methods A549 cells were treated with polymyxin B and intracellular organelles (early and late endosomes, endoplasmic reticulum, mitochondria, lysosomes and autophagosomes), ubiquitin protein and polymyxin B were visualized using immunostaining and confocal microscopy. Fluorescence intensities of the organelles and polymyxin B were quantified and correlated for co-localization using ImageJ and Imaris platforms. Results Polymyxin B co-localized with early endosomes, lysosomes and ubiquitin at 24 h. Significantly increased lysosomal activity and the autophagic protein LC3A were observed after 0.5 and 1.0 mM polymyxin B treatment at 24 h. Polymyxin B also significantly co-localized with mitochondria (Pearson's R = 0.45) and led to the alteration of mitochondrial morphology from filamentous to fragmented form (n = 3, P < 0.001). These results are in line with the polymyxin-induced activation of the mitochondrial apoptotic pathway observed in A549 cells. Conclusions Accumulation of polymyxins on mitochondria probably caused mitochondrial toxicity, resulting in increased oxidative stress and cell death. The formation of autophagosomes and lysosomes was likely a cellular response to the polymyxin-induced stress and played a defensive role by disassembling dysfunctional organelles and proteins. Our study provides new mechanistic information on polymyxin-induced lung toxicity, which is vital for optimizing inhaled polymyxins in the clinic.
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Affiliation(s)
- Maizbha U Ahmed
- Drug Delivery, Disposition and Dynamics, Monash Institute of Pharmaceutical Sciences, Monash University, Parkville, Victoria, Australia.,Monash Biomedicine Discovery Institute, Department of Microbiology, Monash University, Victoria, Australia
| | - Tony Velkov
- Drug Delivery, Disposition and Dynamics, Monash Institute of Pharmaceutical Sciences, Monash University, Parkville, Victoria, Australia
| | - Qi Tony Zhou
- Department of Industrial and Physical Pharmacy, College of Pharmacy, Purdue University, West Lafayette, IN, USA
| | - Alex J Fulcher
- Monash Micro Imaging, Monash University, Victoria, Australia
| | - Judy Callaghan
- Monash Micro Imaging, Monash University, Victoria, Australia
| | - Fanfan Zhou
- School of Pharmacy, The University of Sydney, Camperdown, NSW, Australia
| | - Kim Chan
- School of Pharmacy, The University of Sydney, Camperdown, NSW, Australia
| | - Mohammad A K Azad
- Monash Biomedicine Discovery Institute, Department of Microbiology, Monash University, Victoria, Australia
| | - Jian Li
- Monash Biomedicine Discovery Institute, Department of Microbiology, Monash University, Victoria, Australia
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Jenko Bizjan B, Katsila T, Tesovnik T, Šket R, Debeljak M, Matsoukas MT, Kovač J. Challenges in identifying large germline structural variants for clinical use by long read sequencing. Comput Struct Biotechnol J 2019; 18:83-92. [PMID: 32099591 PMCID: PMC7026727 DOI: 10.1016/j.csbj.2019.11.008] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/01/2019] [Revised: 11/07/2019] [Accepted: 11/21/2019] [Indexed: 12/30/2022] Open
Abstract
Genomic structural variations, previously considered rare events, are widely recognized as a major source of inter-individual variability and hence, a major hurdle in optimum patient stratification and disease management. Herein, we focus on large complex germline structural variations and present challenges towards target treatment via the synergy of state-of-the-art approaches and information technology tools. A complex structural variation detection remains challenging, as there is no gold standard for identifying such genomic variations with long reads, especially when the chromosomal rearrangement in question is a few Mb in length. A clinical case with a large complex chromosomal rearrangement serves as a paradigm. We feel that functional validation and data interpretation are of outmost importance for information growth to be translated into knowledge growth and hence, new working practices are highlighted.
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Affiliation(s)
- Barbara Jenko Bizjan
- Clinical Institute of Special Laboratory Diagnostics, University Children’s Hospital, UMC, Ljubljana, Slovenia
| | - Theodora Katsila
- Institute of Chemical Biology, National Hellenic Research Centre, Athens, Greece
| | - Tine Tesovnik
- Clinical Institute of Special Laboratory Diagnostics, University Children’s Hospital, UMC, Ljubljana, Slovenia
| | - Robert Šket
- Clinical Institute of Special Laboratory Diagnostics, University Children’s Hospital, UMC, Ljubljana, Slovenia
| | - Maruša Debeljak
- Clinical Institute of Special Laboratory Diagnostics, University Children’s Hospital, UMC, Ljubljana, Slovenia
| | | | - Jernej Kovač
- Clinical Institute of Special Laboratory Diagnostics, University Children’s Hospital, UMC, Ljubljana, Slovenia
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Carro-Temboury MR, Arppe R, Hempel C, Vosch T, Just Sørensen T. Creating infinite contrast in fluorescence microscopy by using lanthanide centered emission. PLoS One 2017; 12:e0189529. [PMID: 29236769 PMCID: PMC5728579 DOI: 10.1371/journal.pone.0189529] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/10/2017] [Accepted: 11/27/2017] [Indexed: 11/18/2022] Open
Abstract
The popularity of fluorescence microscopy arises from the inherent mode of action, where the fluorescence emission from probes is used to visualize selected features on a presumed dark background. However, the background is rarely truly dark, and image processing and analysis is needed to enhance the fluorescent signal that is ascribed to the selected feature. The image acquisition is facilitated by using considerable illumination, bright probes at a relatively high concentration in order to make the fluorescent signal significantly more intense than the background signal. Here, we present two methods for completely removing the background signal in spectrally resolved fluorescence microscopy. The methodology is applicable for all probes with narrow and well-defined emission bands (Full width half-maximum < 20 nm). Here, we use two lanthanide based probes exploiting the narrow emission lines of europium(III) and terbium(III) ions. We used a model system with zeolites doped with lanthanides immobilized in a polymer stained with several fluorescent dyes regularly used in bioimaging. After smoothing the spectral data recorded in each pixel, they are differentiated. Method I is based on the direct sum of the gradient, while method II resolves the fluorescent signal by subtracting a background calculated via the gradient. Both methods improve signal-to-background ratio significantly and we suggest that spectral imaging of lanthanide-centered emission can be used as a tool to obtain absolute contrast in bioimaging.
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Affiliation(s)
| | - Riikka Arppe
- Nano-Science Center & Department of Chemistry, University of Copenhagen, Copenhagen, Denmark
| | - Casper Hempel
- Department of Micro- and Nanotechnology, Technical University of Denmark, Kgs Lyngby, Denmark
| | - Tom Vosch
- Nano-Science Center & Department of Chemistry, University of Copenhagen, Copenhagen, Denmark
| | - Thomas Just Sørensen
- Nano-Science Center & Department of Chemistry, University of Copenhagen, Copenhagen, Denmark
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