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Jiang S, He Y, Brandt JH, Zhao L, Chen J. Sensing Mechanism and Excited-State Dynamics of a Widely Used Intracellular Fluorescent pH Probe: pHrodo. J Phys Chem Lett 2023; 14:10482-10488. [PMID: 37967406 PMCID: PMC10683063 DOI: 10.1021/acs.jpclett.3c02653] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/20/2023] [Revised: 11/07/2023] [Accepted: 11/10/2023] [Indexed: 11/17/2023]
Abstract
The pHrodo with an "off-on" response to the changes of pH has been widely used as a fluorescent pH probe for bioimaging. The fluorescence off-on mechanism is fundamentally important for its application and further development. Herein, the sensing mechanism, especially the relevant excited-state dynamics, of pHrodo is investigated by steady-state and time-resolved spectroscopy as well as quantum chemical calculations, showing that pHrodo is best understood using the bichromophore model. Its first excited state (S1) is a charge transfer state between two chromophores. From S1, pHrodo relaxes to its ground state (S0) via an ultrafast nonradiative process (∼0.5 ps), which causes its fluorescence to be "off". After protonation, S1 becomes a localized excited state, which accounts for the fluorescence being turned "on". Our work provides photophysical insight into the sensing mechanism of pHrodo and indicates the bichromophore model might be relevant to a wide range of fluorescent probes.
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Affiliation(s)
- Simin Jiang
- Nano-Science
Center & Department of Chemistry, University
of Copenhagen, Universitetsparken 5, DK-2100 Copenhagen, Denmark
| | - Yanmei He
- Nano-Science
Center & Department of Chemistry, University
of Copenhagen, Universitetsparken 5, DK-2100 Copenhagen, Denmark
- Division
of Chemical Physics and NanoLund, Lund University, P.O. Box 124, 22100 Lund, Sweden
| | - Jonas Højberg Brandt
- Nano-Science
Center & Department of Chemistry, University
of Copenhagen, Universitetsparken 5, DK-2100 Copenhagen, Denmark
| | - Li Zhao
- College
of Science, China University of Petroleum
(East China), Qingdao 266580, Shandong, China
| | - Junsheng Chen
- Nano-Science
Center & Department of Chemistry, University
of Copenhagen, Universitetsparken 5, DK-2100 Copenhagen, Denmark
- Division
of Chemical Physics and NanoLund, Lund University, P.O. Box 124, 22100 Lund, Sweden
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Zhang W, Zhao L, Laursen BW, Chen J. Revealing the sensing mechanism of a fluorescent pH probe based on a bichromophore approach. Phys Chem Chem Phys 2022; 24:26731-26737. [DOI: 10.1039/d2cp04339d] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
Abstract
The pH sensing mechanism of TMARh is investigated by femtosecond transient absorption spectroscopy and quantum chemistry calculations, showing that this new type of sensor can be better understood using the bichromophore model.
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Affiliation(s)
- Wei Zhang
- Hefei National Research Center for Physical Sciences at the Microscale, Department of Chemical Physics, University of Science and Technology of China, Hefei, Anhui 230026, China
- Division of Chemical Physics and NanoLund, Lund University, Box 124, Lund 22100, Sweden
| | - Li Zhao
- College of Science, China University of Petroleum (East China), Qingdao 266580, Shandong, China
| | - Bo W. Laursen
- Nano-Science Center & Department of Chemistry, University of Copenhagen, Universitetsparken 5, 2100 Copenhagen, Denmark
| | - Junsheng Chen
- Division of Chemical Physics and NanoLund, Lund University, Box 124, Lund 22100, Sweden
- Nano-Science Center & Department of Chemistry, University of Copenhagen, Universitetsparken 5, 2100 Copenhagen, Denmark
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3
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Santella M, Della Pia E, Sørensen JK, Laursen BW. Synthesis and properties of sulfur-functionalized triarylmethylium, acridinium and triangulenium dyes. Beilstein J Org Chem 2019; 15:2133-2141. [PMID: 31579076 PMCID: PMC6753677 DOI: 10.3762/bjoc.15.210] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/28/2019] [Accepted: 08/23/2019] [Indexed: 12/14/2022] Open
Abstract
Triangulenium dyes functionalized with one, two or three ethylthiol functionalities were synthesized and their optical properties were studied. The sulfur functionalities were introduced by aromatic nucleophilic substitution of methoxy groups in triarylmethylium cations with ethanethiol followed by partial or full ring closure of the ortho positions with nitrogen or oxygen bridges leading to sulfur-functionalized acridinium, xanthenium or triangulenium dyes. For all the dye classes the sulfur functionalities are found to lead to intensely absorbing dyes in the visible range (470 to 515 nm), quite similar to known analogous dye systems with dialkylamino donor groups in place of the ethylthiol substituents. For the triangulenium derivatives significant fluorescence was observed (Φf = 0.1 to Φf = 0.3).
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Affiliation(s)
- Marco Santella
- Nano-Science Center and Department of Chemistry, University of Copenhagen, Universitetsparken 5, 2100 Copenhagen Ø, Denmark
| | - Eduardo Della Pia
- Nano-Science Center and Department of Chemistry, University of Copenhagen, Universitetsparken 5, 2100 Copenhagen Ø, Denmark
| | - Jakob Kryger Sørensen
- Nano-Science Center and Department of Chemistry, University of Copenhagen, Universitetsparken 5, 2100 Copenhagen Ø, Denmark
| | - Bo W Laursen
- Nano-Science Center and Department of Chemistry, University of Copenhagen, Universitetsparken 5, 2100 Copenhagen Ø, Denmark
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Frankær CG, Hussain KJ, Dörge TC, Sørensen TJ. Optical Chemical Sensor Using Intensity Ratiometric Fluorescence Signals for Fast and Reliable pH Determination. ACS Sens 2019; 4:26-31. [PMID: 30592615 DOI: 10.1021/acssensors.8b01485] [Citation(s) in RCA: 27] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Optical pH sensors enable noninvasive monitoring of pH, yet in pure sensing terms, the potentiometric method of measuring pH is still vastly superior. Here, we report a full spectrometer-based optical pH sensor system consisting of sensor chemistry, hardware, and software that for the first time is capable of challenging the performance of an electrode-based pH meter in specific applications such as biopharmaceutical process monitoring and in single-use bioproduction. A highly photostable triangulenium fluorophore emitting at 590 nm was immobilized in an organically modified silicon matrix that allows for fast time-response by rapid diffusion of water in and out of the resulting composite polymer deposited on a polycarbonate substrate. Fluctuations from the fiber optical sensor hardware have been reduced by including a highly photostable terrylene-based reference dye emitting at 660 nm, thus enabling intensity-based ratiometric readouts. The dyes were excited by 505 nm light from a light emitting diode. The sensor was operational within a pH range of 4.6-7.6, and was characterized and demonstrated to have properties that are comparable to those of commercial pH electrodes considering time-response ( t90 < 90 s), precision (0.03 pH-units), and drift.
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Affiliation(s)
- Christian G. Frankær
- Nano-Science Center and Department of Chemistry, University of Copenhagen, Universitetsparken 5, 2100 Copenhagen Ø, Denmark
- FRS-systems ApS, Hovedgaden 20, 4621 Gadstrup, Denmark
| | | | - Tommy C. Dörge
- Nano-Science Center and Department of Chemistry, University of Copenhagen, Universitetsparken 5, 2100 Copenhagen Ø, Denmark
| | - Thomas J. Sørensen
- Nano-Science Center and Department of Chemistry, University of Copenhagen, Universitetsparken 5, 2100 Copenhagen Ø, Denmark
- FRS-systems ApS, Hovedgaden 20, 4621 Gadstrup, Denmark
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Ishi-i T, Nakanishi T. pH-Responsive Fluorescence Change Based on Dynamic Exchange between Emitting Aggregates and Quenching Monomers in Donor-Acceptor Dyes Bearing Carboxylic Acid Groups. European J Org Chem 2018. [DOI: 10.1002/ejoc.201800025] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/13/2023]
Affiliation(s)
- Tsutomu Ishi-i
- Department of Biochemistry and Applied Chemistry; National Institute of Technology; Kurume College; 1-1-1 Komorino 8555 Kurume 830- Japan
| | - Taishi Nakanishi
- Department of Biochemistry and Applied Chemistry; National Institute of Technology; Kurume College; 1-1-1 Komorino 8555 Kurume 830- Japan
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Junker AKR, Sørensen TJ. Rationalizing substituent effects in 1-azathioxanthone photophysics. Methods Appl Fluoresc 2017; 6:014002. [PMID: 29160773 DOI: 10.1088/2050-6120/aa9c16] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
The influence of an electron donating substituent on the photophysical properties of 1-azathioxanthone dyes has been investigated using optical spectroscopy and theoretical models. The motivation behind the study is based on the fact that thioxanthones are efficient triplet sensitizers, and thus promising sensitizers for lanthanide centered emission. By adding an aza group to one of the phenyl ring systems, direct coordination to a lanthanide center becomes possible, which makes azathoixanthones great candidates as antenna chromophores in lanthanide(III) based dyes. Here, three 1-azathioxanthone derivatives have been synthesized targeting efficient triplet formation following absorption in the visible range of the spectrum. This is achieved by adding methoxy groups to the 1-azathioxanthone core. The derivatives were characterized using absorption, emission, and time-gated emission spectroscopy, where fluorescent quantum yields, singlet and triplet excited states lifetimes were determined. The experimentally determined photophysical properties of the three 1-azathioxanthone compounds are contrasted to those of the parent thioxanthone and is rationalized using the Strickler-Berg equation, Hückel MO theory, and Dewar's rules in combination with computational chemistry. We find that the transition energies follow predictions, but that the overall photophysical properties are determined by the relative energies as well as the nature of the involved states in both the singlet and the triplet excited state manifolds.
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Affiliation(s)
- Anne Kathrine R Junker
- Nano-Science Center & Department of Chemistry, University of Copenhagen, Universitetsparken 5, DK-2100 København Ø, Denmark
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