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Gong X, Kwak SY, Cho SY, Lundberg D, Liu AT, McGee MK, Strano MS. Single-Molecule Methane Sensing Using Palladium-Functionalized nIR Fluorescent Single-Walled Carbon Nanotubes. ACS Sens 2023; 8:4207-4215. [PMID: 37874627 DOI: 10.1021/acssensors.3c01542] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/25/2023]
Abstract
There has been considerable interest in detecting atmospheric and process-associated methane (CH4) at low concentrations due to its potency as a greenhouse gas. Nanosensor technology, particularly fluorescent single-walled carbon nanotube (SWCNT) arrays, is promising for such applications because of their chemical sensitivities at single-molecule detection limits. However, the methodologies for connecting the stochastic molecular fluctuations from gas impingement on such sensors require further development. In this work, we synthesize Pd-conjugated ss(GT)15-DNA-wrapped SWCNTas near-infrared (nIR) fluorescent, single-molecule sensors of CH4. The complexes are characterized using X-ray photoelectron spectroscopy (XPS) and spectrophotometry, demonstrating spectral changes between the Pd2+ and Pd0 oxidation states. The nIR fluctuations generated upon exposure from 8 to 26 ppb of CH4 were separated into high- and low-frequency components. Aggregating the low-frequency components for an array of sensors showed the most consistent levels of detection with a limit of 0.7 ppb. These results advance the hardware and computational methods necessary to apply this approach to the challenge of environmental methane sensing.
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Affiliation(s)
- Xun Gong
- Department of Chemical Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, United States
| | - Seon-Yeong Kwak
- Department of Agriculture, Forestry and Bioresources, College of Agriculture and Life Sciences, Seoul National University, Seoul 08826, Republic of Korea
| | - Soo-Yeon Cho
- School of Chemical Engineering, Sungkyunkwan University, Suwon 16419, Republic of Korea
| | - Daniel Lundberg
- Department of Chemical Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, United States
| | - Albert Tianxiang Liu
- Department of Chemical Engineering, University of Michigan, Ann Arbor, Michigan 48109, United States
| | - Melissa Keiko McGee
- Department of Chemical Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, United States
| | - Michael S Strano
- Department of Chemical Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, United States
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2
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Ma C, Schrage CA, Gretz J, Akhtar A, Sistemich L, Schnitzler L, Li H, Tschulik K, Flavel BS, Kruss S. Stochastic Formation of Quantum Defects in Carbon Nanotubes. ACS NANO 2023; 17:15989-15998. [PMID: 37527201 DOI: 10.1021/acsnano.3c04314] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 08/03/2023]
Abstract
Small perturbations in the structure of materials significantly affect their properties. One example is single wall carbon nanotubes (SWCNTs), which exhibit chirality-dependent near-infrared (NIR) fluorescence. They can be modified with quantum defects through the reaction with diazonium salts, and the number or distribution of these defects determines their photophysics. However, the presence of multiple chiralities in typical SWCNT samples complicates the identification of defect-related emission features. Here, we show that quantum defects do not affect aqueous two-phase extraction (ATPE) of different SWCNT chiralities into different phases, which suggests low numbers of defects. For bulk samples, the bandgap emission (E11) of monochiral (6,5)-SWCNTs decreases, and the defect-related emission feature (E11*) increases with diazonium salt concentration and represents a proxy for the defect number. The high purity of monochiral samples from ATPE allows us to image NIR fluorescence contributions (E11 = 986 nm and E11* = 1140 nm) on the single SWCNT level. Interestingly, we observe a stochastic (Poisson) distribution of quantum defects. SWCNTs have most likely one to three defects (for low to high (bulk) quantum defect densities). Additionally, we verify this number by following single reaction events that appear as discrete steps in the temporal fluorescence traces. We thereby count single reactions via NIR imaging and demonstrate that stochasticity plays a crucial role in the optical properties of SWCNTs. These results show that there can be a large discrepancy between ensemble and single particle experiments/properties of nanomaterials.
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Affiliation(s)
- Chen Ma
- Department of Chemistry, Ruhr-University Bochum, Bochum 44801, Germany
| | | | - Juliana Gretz
- Department of Chemistry, Ruhr-University Bochum, Bochum 44801, Germany
| | - Anas Akhtar
- Analytical Chemistry II, Faculty of Chemistry and Biochemistry, Ruhr-University Bochum, Bochum 44801, Germany
| | - Linda Sistemich
- Department of Chemistry, Ruhr-University Bochum, Bochum 44801, Germany
| | - Lena Schnitzler
- Department of Chemistry, Ruhr-University Bochum, Bochum 44801, Germany
| | - Han Li
- Institute of Nanotechnology, Karlsruhe Institute of Technology (KIT), Karlsruhe 76344, Germany
| | - Kristina Tschulik
- Analytical Chemistry II, Faculty of Chemistry and Biochemistry, Ruhr-University Bochum, Bochum 44801, Germany
| | - Benjamin S Flavel
- Institute of Nanotechnology, Karlsruhe Institute of Technology (KIT), Karlsruhe 76344, Germany
| | - Sebastian Kruss
- Department of Chemistry, Ruhr-University Bochum, Bochum 44801, Germany
- Fraunhofer Institute for Microelectronic Circuits and Systems, Duisburg 47057, Germany
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3
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Kallmyer NE, Musielewicz J, Sutter J, Reuel NF. Substrate-Wrapped, Single-Walled Carbon Nanotube Probes for Hydrolytic Enzyme Characterization. Anal Chem 2018; 90:5209-5216. [DOI: 10.1021/acs.analchem.7b05444] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Affiliation(s)
- Nathaniel E. Kallmyer
- Iowa State University, 2114 Sweeney Hall, 618 Bissell Road, Ames, Iowa 50011, United States
| | - Joseph Musielewicz
- Iowa State University, 2114 Sweeney Hall, 618 Bissell Road, Ames, Iowa 50011, United States
| | - Joel Sutter
- Iowa State University, 2114 Sweeney Hall, 618 Bissell Road, Ames, Iowa 50011, United States
| | - Nigel F. Reuel
- Iowa State University, 2114 Sweeney Hall, 618 Bissell Road, Ames, Iowa 50011, United States
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4
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Djokić DM, Goswami A. Quantum yield in polymer wrapped single walled carbon nanotubes: a computational model. NANOTECHNOLOGY 2017; 28:465204. [PMID: 29059055 DOI: 10.1088/1361-6528/aa8f38] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/07/2023]
Abstract
Quantum yield in polymer wrapped single walled carbon nanotubes (SWCNTs) has been computationally investigated using a 2D model of exciton decay with non-radiative channels due to the diffusive motion across the nanotube surface. Beside the role of SWCNT's ends as the exciton quenchers, we have considered the influence of the wrapping polymer through its chemistry and wrapping angle. The model has been solved exactly for zero-angle wrapping, a particular case when the polymer interfaces the nanotube along its axis. The general case has been treated numerically and it has been concluded that the wrapping angle has no relevant influence upon the quantum yield values which are of experimental interest. A wide range of quantum yield values computed in the present contribution can be helpful in understanding potentially available photoluminescence data of SWCNTs wrapped with a variety of polymer families.
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Affiliation(s)
- Dejan M Djokić
- Institute of Chemical Sciences and Engineering, Ecole Polytechnique Fédérale de Lausanne (EPFL), CH-1015 Lausanne, Switzerland. Center for Solid State Physics and New Materials, Institute of Physics Belgrade, University of Belgrade, Pregrevica 118, 11 080 Belgrade, Serbia
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5
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Kwak SY, Wong MH, Lew TTS, Bisker G, Lee MA, Kaplan A, Dong J, Liu AT, Koman VB, Sinclair R, Hamann C, Strano MS. Nanosensor Technology Applied to Living Plant Systems. ANNUAL REVIEW OF ANALYTICAL CHEMISTRY (PALO ALTO, CALIF.) 2017; 10:113-140. [PMID: 28605605 DOI: 10.1146/annurev-anchem-061516-045310] [Citation(s) in RCA: 34] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/07/2023]
Abstract
An understanding of plant biology is essential to solving many long-standing global challenges, including sustainable and secure food production and the generation of renewable fuel sources. Nanosensor platforms, sensors with a characteristic dimension that is nanometer in scale, have emerged as important tools for monitoring plant signaling pathways and metabolism that are nondestructive, minimally invasive, and capable of real-time analysis. This review outlines the recent advances in nanotechnology that enable these platforms, including the measurement of chemical fluxes even at the single-molecule level. Applications of nanosensors to plant biology are discussed in the context of nutrient management, disease assessment, food production, detection of DNA proteins, and the regulation of plant hormones. Current trends and future needs are discussed with respect to the emerging trends of precision agriculture, urban farming, and plant nanobionics.
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Affiliation(s)
- Seon-Yeong Kwak
- Department of Chemical Engineering, Massachusetts Institute of Technology, Cambridge, Massachussetts 02139;
| | - Min Hao Wong
- Department of Chemical Engineering, Massachusetts Institute of Technology, Cambridge, Massachussetts 02139;
| | - Tedrick Thomas Salim Lew
- Department of Chemical Engineering, Massachusetts Institute of Technology, Cambridge, Massachussetts 02139;
| | - Gili Bisker
- Department of Chemical Engineering, Massachusetts Institute of Technology, Cambridge, Massachussetts 02139;
| | - Michael A Lee
- Department of Chemical Engineering, Massachusetts Institute of Technology, Cambridge, Massachussetts 02139;
| | - Amir Kaplan
- Department of Chemical Engineering, Massachusetts Institute of Technology, Cambridge, Massachussetts 02139;
| | - Juyao Dong
- Department of Chemical Engineering, Massachusetts Institute of Technology, Cambridge, Massachussetts 02139;
| | - Albert Tianxiang Liu
- Department of Chemical Engineering, Massachusetts Institute of Technology, Cambridge, Massachussetts 02139;
| | - Volodymyr B Koman
- Department of Chemical Engineering, Massachusetts Institute of Technology, Cambridge, Massachussetts 02139;
| | - Rosalie Sinclair
- Department of Chemical Engineering, Massachusetts Institute of Technology, Cambridge, Massachussetts 02139;
| | - Catherine Hamann
- Department of Chemical Engineering, Massachusetts Institute of Technology, Cambridge, Massachussetts 02139;
| | - Michael S Strano
- Department of Chemical Engineering, Massachusetts Institute of Technology, Cambridge, Massachussetts 02139;
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6
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Meyer D, Hagemann A, Kruss S. Kinetic Requirements for Spatiotemporal Chemical Imaging with Fluorescent Nanosensors. ACS NANO 2017; 11:4017-4027. [PMID: 28379687 DOI: 10.1021/acsnano.7b00569] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/07/2023]
Abstract
Fluorescent nanosensors are powerful tools for basic research and bioanalytical applications. Individual nanosensors are able to detect single molecules, while ensembles of nanosensors can be used to measure the bulk concentration of an analyte. Collective imaging of multiple nanosensors could provide both spatial and temporal chemical information from the nano- to the microscale. This type of chemical imaging with nanosensors would be very attractive to study processes such as chemical signaling between cells (e.g., neurons). So far, it is not understood what processes are resolvable (concentration, time, space) and how optimal sensors should be designed. Here, we develop a theoretical framework to simulate the fluorescence image of arrays of nanosensors in response to a concentration gradient. For that purpose, binding and unbinding of the analyte is simulated for each single nanosensor by using a Monte Carlo simulation and varying rate constants (kon, koff). Multiple nanosensors are arranged on a surface and exposed to a concentration pattern cA(x,y,t) of an analyte. We account for the resolution limit of light microscopy (Abbe limit) and the acquisition speed and resolution of optical setups and determine the resulting response images ΔI(x,y,t). Consequently, we introduce terms for the spatial and temporal resolution and simulate phase diagrams for different rate constants that allow us to predict how a sensor should be designed to provide a desired spatial and temporal resolution. Our results show, for example, that imaging of neurotransmitter release requires rate constants of kon = 106 M-1 s-1and koff = 102 s-1 in many scenarios, which corresponds to high dissociation constants of Kd > 100 μM. This work predicts if a given fluorescent nanosensor array (rate constants, size, shape, geometry, density) is able to resolve fast concentration changes such as neurotransmitter release from cells. Additionally, we provide rational design principles to engineer nanosensors for chemical imaging.
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Affiliation(s)
- Daniel Meyer
- Institute of Physical Chemistry, Göttingen University , Tammannstrasse 6, Goettingen 37077, Germany
- Center for Nanoscale Microscopy and Molecular Physiology of the Brain (CNMPB) , Göttingen 37073, Germany
| | - Annika Hagemann
- Institute of Physical Chemistry, Göttingen University , Tammannstrasse 6, Goettingen 37077, Germany
- Center for Nanoscale Microscopy and Molecular Physiology of the Brain (CNMPB) , Göttingen 37073, Germany
| | - Sebastian Kruss
- Institute of Physical Chemistry, Göttingen University , Tammannstrasse 6, Goettingen 37077, Germany
- Center for Nanoscale Microscopy and Molecular Physiology of the Brain (CNMPB) , Göttingen 37073, Germany
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7
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Jang H, Lee JH, Braatz RD. Estimation of local concentration from measurements of stochastic adsorption dynamics using carbon nanotube-based sensors. KOREAN J CHEM ENG 2016. [DOI: 10.1007/s11814-015-0124-9] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/23/2022]
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8
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Jang H, Lee JH, Braatz RD. State Estimation of the Time-Varying and Spatially Localized Concentration of Signal Molecules from the Stochastic Adsorption Dynamics on the Carbon Nanotube-Based Sensors and Its Application to Tumor Cell Detection. PLoS One 2015; 10:e0141930. [PMID: 26528927 PMCID: PMC4631460 DOI: 10.1371/journal.pone.0141930] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/26/2015] [Accepted: 10/14/2015] [Indexed: 11/25/2022] Open
Abstract
This paper addresses a problem of estimating time-varying, local concentrations of signal molecules with a carbon-nanotube (CNT)-based sensor array system, which sends signals triggered by monomolecular adsorption/desorption events of proximate molecules on the surfaces of the sensors. Such sensors work on nano-scale phenomena and show inherently stochastic non-Gaussian behavior, which is best represented by the chemical master equation (CME) describing the time evolution of the probabilities for all the possible number of adsorbed molecules. In the CME, the adsorption rate on each sensor is linearly proportional to the local concentration in the bulk phase. State estimators are proposed for these types of sensors that fully address their stochastic nature. For CNT-based sensors motivated by tumor cell detection, the particle filter, which is nonparametric and can handle non-Gaussian distributions, is compared to a Kalman filter that approximates the underlying distributions by Gaussians. In addition, the second-order generalized pseudo Bayesian estimation (GPB2) algorithm and the Markov chain Monte Carlo (MCMC) algorithm are incorporated into KF and PF respectively, for detecting latent drift in the concentration affected by different states of a cell.
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Affiliation(s)
- Hong Jang
- Department of Chemical and Biomolecular Engineering, Korea Advanced Institute of Science and Technology, Daejeon, Korea
| | - Jay H. Lee
- Department of Chemical and Biomolecular Engineering, Korea Advanced Institute of Science and Technology, Daejeon, Korea
| | - Richard D. Braatz
- Department of Chemical Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts, United States of America
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9
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Ulissi Z, Sen F, Gong X, Sen S, Iverson N, Boghossian A, Godoy LC, Wogan GN, Mukhopadhyay D, Strano MS. Spatiotemporal intracellular nitric oxide signaling captured using internalized, near-infrared fluorescent carbon nanotube nanosensors. NANO LETTERS 2014; 14:4887-94. [PMID: 25029087 PMCID: PMC4134139 DOI: 10.1021/nl502338y] [Citation(s) in RCA: 42] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/21/2014] [Indexed: 05/04/2023]
Abstract
Fluorescent nanosensor probes have suffered from limited molecular recognition and a dearth of strategies for spatial-temporal operation in cell culture. In this work, we spatially imaged the dynamics of nitric oxide (NO) signaling, important in numerous pathologies and physiological functions, using intracellular near-infrared fluorescent single-walled carbon nanotubes. The observed spatial-temporal NO signaling gradients clarify and refine the existing paradigm of NO signaling based on averaged local concentrations. This work enables the study of transient intracellular phenomena associated with signaling and therapeutics.
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Affiliation(s)
- Zachary
W. Ulissi
- Department
of Chemical Engineering, Massachusetts Institute
of Technology, Cambridge, Massachusetts 02139, United States
| | - Fatih Sen
- Department
of Chemical Engineering, Massachusetts Institute
of Technology, Cambridge, Massachusetts 02139, United States
- Department
of Biochemistry, Dumlupinar University, Kutahya, 43100, Turkey
| | - Xun Gong
- Department
of Biomedical Engineering and Physiology, Mayo College of Medicine, Rochester, Minnesota 55905, United States
| | - Selda Sen
- Department
of Chemical Engineering, Massachusetts Institute
of Technology, Cambridge, Massachusetts 02139, United States
| | - Nicole Iverson
- Department
of Chemical Engineering, Massachusetts Institute
of Technology, Cambridge, Massachusetts 02139, United States
| | - Ardemis
A. Boghossian
- Department
of Chemical Engineering, Massachusetts Institute
of Technology, Cambridge, Massachusetts 02139, United States
| | - Luiz C. Godoy
- Department
of Biological Engineering, Massachusetts
Institute of Technology, Cambridge, Massachusetts 02139, United States
| | - Gerald N. Wogan
- Department
of Biological Engineering, Massachusetts
Institute of Technology, Cambridge, Massachusetts 02139, United States
| | - Debabrata Mukhopadhyay
- Department
of Biomedical Engineering and Physiology, Mayo College of Medicine, Rochester, Minnesota 55905, United States
- Department
of Biochemistry and Molecular Biology, Mayo
College of Medicine, Rochester, Minnesota 55905, United States
| | - Michael S. Strano
- Department
of Chemical Engineering, Massachusetts Institute
of Technology, Cambridge, Massachusetts 02139, United States
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10
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Assessment of the oxidative stability of lubricant oil using fiber-coupled fluorescence excitation–emission matrix spectroscopy. Anal Chim Acta 2014; 811:1-12. [DOI: 10.1016/j.aca.2013.10.019] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/01/2013] [Revised: 10/09/2013] [Accepted: 10/10/2013] [Indexed: 11/24/2022]
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11
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Kruss S, Hilmer AJ, Zhang J, Reuel NF, Mu B, Strano MS. Carbon nanotubes as optical biomedical sensors. Adv Drug Deliv Rev 2013; 65:1933-50. [PMID: 23906934 DOI: 10.1016/j.addr.2013.07.015] [Citation(s) in RCA: 202] [Impact Index Per Article: 18.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/18/2013] [Revised: 07/16/2013] [Accepted: 07/18/2013] [Indexed: 01/11/2023]
Abstract
Biosensors are important tools in biomedical research. Moreover, they are becoming an essential part of modern healthcare. In the future, biosensor development will become even more crucial due to the demand for personalized-medicine, point-of care devices and cheaper diagnostic tools. Substantial advances in sensor technology are often fueled by the advent of new materials. Therefore, nanomaterials have motivated a large body of research and such materials have been implemented into biosensor devices. Among these new materials carbon nanotubes (CNTs) are especially promising building blocks for biosensors due to their unique electronic and optical properties. Carbon nanotubes are rolled-up cylinders of carbon monolayers (graphene). They can be chemically modified in such a way that biologically relevant molecules can be detected with high sensitivity and selectivity. In this review article we will discuss how carbon nanotubes can be used to create biosensors. We review the latest advancements of optical carbon nanotube based biosensors with a special focus on near-infrared (NIR)-fluorescence, Raman-scattering and fluorescence quenching.
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Affiliation(s)
- Sebastian Kruss
- Department of Chemical Engineering, Massachusetts Institute of Technology, Cambridge, MA 02139, United States
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13
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Lente G. Stochastic mapping of first order reaction networks: a systematic comparison of the stochastic and deterministic kinetic approaches. J Chem Phys 2012; 137:164101. [PMID: 23126689 DOI: 10.1063/1.4758458] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
Stochastic maps are developed and used for first order reaction networks to decide whether the deterministic kinetic approach is appropriate for a certain evaluation problem or the use of the computationally more demanding stochastic approach is inevitable. On these maps, the decision between the two approaches is based on the standard deviation of the expectation of detected variables: when the relative standard deviation is larger than 1%, the use of the stochastic method is necessary. Four different systems are considered as examples: the irreversible first order reaction, the reversible first order reaction, two consecutive irreversible first order reactions, and the unidirectional triangle reaction. Experimental examples are used to illustrate the practical use of the theoretical results. It is shown that the maps do not only depend on particle numbers, but the influence of parameters such as time, rate constants, and the identity of the detected target variable is also an important factor.
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Affiliation(s)
- Gábor Lente
- Department of Inorganic and Analytical Chemistry, University of Debrecen, Debrecen, Hungary.
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14
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Reuel NF, Dupont A, Thouvenin O, Lamb DC, Strano MS. Three-dimensional tracking of carbon nanotubes within living cells. ACS NANO 2012; 6:5420-5428. [PMID: 22624495 DOI: 10.1021/nn301298e] [Citation(s) in RCA: 37] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/28/2023]
Abstract
Three-dimensional tracking of single-walled carbon nanotubes (SWNT) with an orbital tracking microscope is demonstrated. We determine the viscosity regime (above 250 cP) at which the rotational diffusion coefficient can be used for length estimation. We also demonstrate SWNT tracking within live HeLa cells and use these findings to spatially map corral volumes (0.27-1.32 μm(3)), determine an active transport velocity (455 nm/s), and calculate local viscosities (54-179 cP) within the cell. With respect to the future use of SWNTs as sensors in living cells, we conclude that the sensor must change the fluorescence signal by at least 4-13% to allow separation of the sensor signal from fluctuations due to rotation of the SWNT when measuring with a time resolution of 32 ms.
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Affiliation(s)
- Nigel F Reuel
- Department of Chemical Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA
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