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Saucier MA, Kruse NA, Seidel BE, Hammer NI, Tschumper GS, Delcamp JH. Phospha-RosIndolizine Dye with Shortwave Infrared (SWIR) Absorption and Emission. J Org Chem 2024; 89:9092-9097. [PMID: 38841830 DOI: 10.1021/acs.joc.4c00741] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/07/2024]
Abstract
Shortwave infrared (SWIR, 1000-1700 nm) absorbing and emitting dyes are needed for infrared diodes and sensors used in a wide variety of industrial and medical applications. Herein, an electron-withdrawing phosphine oxide (P═O) substituted xanthene is coupled with strong indolizine donors to produce a SWIR absorbing (λabs = 1294 nm in DCM) and emitting (λemis = 1450 nm in DCM) dye called PRos1450. The unique properties of this dye are characterized via photophysical, electrochemical, and computational analyses.
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Affiliation(s)
- Matthew A Saucier
- Department of Chemistry and Biochemistry, University of Mississippi, Coulter Hall, University, Mississippi 38677, United States
| | - Nicholas A Kruse
- Department of Chemistry and Biochemistry, University of Mississippi, Coulter Hall, University, Mississippi 38677, United States
| | - Brennan E Seidel
- Department of Chemistry and Biochemistry, University of Mississippi, Coulter Hall, University, Mississippi 38677, United States
| | - Nathan I Hammer
- Department of Chemistry and Biochemistry, University of Mississippi, Coulter Hall, University, Mississippi 38677, United States
| | - Gregory S Tschumper
- Department of Chemistry and Biochemistry, University of Mississippi, Coulter Hall, University, Mississippi 38677, United States
| | - Jared H Delcamp
- Department of Chemistry and Biochemistry, University of Mississippi, Coulter Hall, University, Mississippi 38677, United States
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2
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Meador WE, Lin EY, Lim I, Friedman HC, Ndaleh D, Shaik AK, Hammer NI, Yang B, Caram JR, Sletten EM, Delcamp JH. Silicon-RosIndolizine fluorophores with shortwave infrared absorption and emission profiles enable in vivo fluorescence imaging. Nat Chem 2024; 16:970-978. [PMID: 38528102 DOI: 10.1038/s41557-024-01464-6] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/06/2022] [Accepted: 01/29/2024] [Indexed: 03/27/2024]
Abstract
In vivo fluorescence imaging in the shortwave infrared (SWIR, 1,000-1,700 nm) and extended SWIR (ESWIR, 1,700-2,700 nm) regions has tremendous potential for diagnostic imaging. Although image contrast has been shown to improve as longer wavelengths are accessed, the design and synthesis of organic fluorophores that emit in these regions is challenging. Here we synthesize a series of silicon-RosIndolizine (SiRos) fluorophores that exhibit peak emission wavelengths from 1,300-1,700 nm and emission onsets of 1,800-2,200 nm. We characterize the fluorophores photophysically (both steady-state and time-resolved), electrochemically and computationally using time-dependent density functional theory. Using two of the fluorophores (SiRos1300 and SiRos1550), we formulate nanoemulsions and use them for general systemic circulatory SWIR fluorescence imaging of the cardiovascular system in mice. These studies resulted in high-resolution SWIR images with well-defined vasculature visible throughout the entire circulatory system. This SiRos scaffold establishes design principles for generating long-wavelength emitting SWIR and ESWIR fluorophores.
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Affiliation(s)
- William E Meador
- University of Mississippi, Department of Chemistry and Biochemistry, Oxford, MS, USA
| | - Eric Y Lin
- University of California Los Angeles, Department of Chemistry and Biochemistry, Los Angeles, CA, USA
| | - Irene Lim
- University of California Los Angeles, Department of Chemistry and Biochemistry, Los Angeles, CA, USA
| | - Hannah C Friedman
- University of California Los Angeles, Department of Chemistry and Biochemistry, Los Angeles, CA, USA
| | - David Ndaleh
- University of Mississippi, Department of Chemistry and Biochemistry, Oxford, MS, USA
| | - Abdul K Shaik
- University of Mississippi, Department of Chemistry and Biochemistry, Oxford, MS, USA
| | - Nathan I Hammer
- University of Mississippi, Department of Chemistry and Biochemistry, Oxford, MS, USA
| | | | - Justin R Caram
- University of California Los Angeles, Department of Chemistry and Biochemistry, Los Angeles, CA, USA
| | - Ellen M Sletten
- University of California Los Angeles, Department of Chemistry and Biochemistry, Los Angeles, CA, USA.
| | - Jared H Delcamp
- University of Mississippi, Department of Chemistry and Biochemistry, Oxford, MS, USA.
- Air Force Research Laboratory, Materials and Manufacturing Directorate (RXNC), Wright-Patterson AFB, Dayton, OH, USA.
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3
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Brøndsted F, Stains CI. Xanthene-Based Dyes for Photoacoustic Imaging and their Use as Analyte-Responsive Probes. Chemistry 2024:e202400598. [PMID: 38662806 DOI: 10.1002/chem.202400598] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/13/2024] [Indexed: 06/15/2024]
Abstract
Developing imaging tools that can report on the presence of disease-relevant analytes in multicellular organisms can provide insight into fundamental disease mechanisms as well as provide diagnostic tools for the clinic. Photoacoustic imaging (PAI) is a light-in, sound-out imaging technique that allows for high resolution, deep-tissue imaging with applications in pre-clinical and point-of-care settings. The continued development of near-infrared (NIR) absorbing small-molecule dyes promises to improve the capabilities of this emerging imaging modality. For example, new dye scaffolds bearing chemoselective functionalities are enabling the detection and quantification of disease-relevant analytes through activity-based sensing (ABS) approaches. Recently described strategies to engineer NIR absorbing xanthenes have enabled development of analyte-responsive PAI probes using this classic dye scaffold. Herein, we present current strategies for red-shifting the spectral properties of xanthenes via bridging heteroatom or auxochrome modifications. Additionally, we explore how these strategies, coupled with chemoselective spiroring-opening approaches, have been employed to create ABS probes for in vivo detection of hypochlorous acid, nitric oxide, copper (II), human NAD(P)H: quinone oxidoreductase isozyme 1, and carbon monoxide. Given the versatility of the xanthene scaffold, we anticipate continued growth and development of analyte-responsive PAI imaging probes based on this dye class.
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Affiliation(s)
- Frederik Brøndsted
- Department of Chemistry, University of Virginia, 22904, Charlottesville, VA, USA
| | - Cliff I Stains
- Department of Chemistry, University of Virginia, 22904, Charlottesville, VA, USA
- University of Virginia Cancer Center, University of Virginia, 22908, Charlottesville, VA, USA
- Virginia Drug Discovery Consortium, 24061, Blacksburg, VA, USA
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4
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Zeng Y, Qu J, Wu G, Zhao Y, Hao J, Dong Y, Li Z, Shi J, Francisco JS, Zheng X. Two Key Descriptors for Designing Second Near-Infrared Dyes and Experimental Validation. J Am Chem Soc 2024; 146:9888-9896. [PMID: 38546165 DOI: 10.1021/jacs.3c14805] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 04/11/2024]
Abstract
Second near-infrared (NIR-II) optical imaging technology has emerged as a powerful tool for diagnostic and image-guided surgery due to its higher imaging contrast. However, a general strategy for efficiently designing NIR-II organic molecules is still lacking, because NIR-II dyes are usually difficult to synthesize, which has impeded the rapid development of NIR-II bioprobes. Herein, based on the theoretical calculations on 62 multiaryl-pyrrole (MAP) systems with spectra ranging from the visible to the NIR-II region, a continuous red shift of the spectra toward the NIR-II region could be achieved by adjusting the type and site of substituents on the MAPs. Two descriptors (ΔEgs and μgs) were identified as exhibiting strong correlations with the maximum absorption/emission wavelengths, and the descriptors could be used to predict the emission spectrum in the NIR-II region only if ΔEgs ≤ 2.5 eV and μgs ≤ 22.55 D. The experimental absorption and emission spectra of ten MAPs fully confirmed the theoretical predictions, and biological imaging in vivo of newly designed MAP23-BBT showed high spatial resolution in the NIR-II region in deep tissue angiography. More importantly, both descriptors of ΔEgs and μgs have shown general applicability to most of the reported donor-acceptor-donor-type non-MAP NIR-II dyes. These results have broad implications for the efficient design of NIR-II dyes.
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Affiliation(s)
- Yi Zeng
- Key Laboratory of Cluster Science of Ministry of Education, Key Laboratory of Medicinal Molecule Science and Pharmaceutics Engineering of Ministry of Industry and Information Technology, Beijing Key Laboratory of Photoelectroic/Electro-Photonic Conversion Materials, School of Chemistry and Chemical Engineering, Beijing Institute of Technology, Beijing 100081, China
| | - Jiamin Qu
- Beijing Key Laboratory of Construction Tailorable Advanced Functional Materials and Green Applications, School of Materials Science and Engineering, Beijing Institute of Technology, Beijing 100081, China
| | - Guanghao Wu
- Beijing Key Laboratory of Construction Tailorable Advanced Functional Materials and Green Applications, School of Materials Science and Engineering, Beijing Institute of Technology, Beijing 100081, China
| | - Yeyun Zhao
- Beijing Key Laboratory of Construction Tailorable Advanced Functional Materials and Green Applications, School of Materials Science and Engineering, Beijing Institute of Technology, Beijing 100081, China
| | - Jiaman Hao
- Key Laboratory of Cluster Science of Ministry of Education, Key Laboratory of Medicinal Molecule Science and Pharmaceutics Engineering of Ministry of Industry and Information Technology, Beijing Key Laboratory of Photoelectroic/Electro-Photonic Conversion Materials, School of Chemistry and Chemical Engineering, Beijing Institute of Technology, Beijing 100081, China
| | - Yuping Dong
- Beijing Key Laboratory of Construction Tailorable Advanced Functional Materials and Green Applications, School of Materials Science and Engineering, Beijing Institute of Technology, Beijing 100081, China
| | - Zesheng Li
- Key Laboratory of Cluster Science of Ministry of Education, Key Laboratory of Medicinal Molecule Science and Pharmaceutics Engineering of Ministry of Industry and Information Technology, Beijing Key Laboratory of Photoelectroic/Electro-Photonic Conversion Materials, School of Chemistry and Chemical Engineering, Beijing Institute of Technology, Beijing 100081, China
| | - Jianbing Shi
- Beijing Key Laboratory of Construction Tailorable Advanced Functional Materials and Green Applications, School of Materials Science and Engineering, Beijing Institute of Technology, Beijing 100081, China
| | - Joseph S Francisco
- Department of Earth and Environmental Science and Department of Chemistry, University of Pennsylvania, Philadelphia, Pennsylvania 19104-6316, United States
| | - Xiaoyan Zheng
- Key Laboratory of Cluster Science of Ministry of Education, Key Laboratory of Medicinal Molecule Science and Pharmaceutics Engineering of Ministry of Industry and Information Technology, Beijing Key Laboratory of Photoelectroic/Electro-Photonic Conversion Materials, School of Chemistry and Chemical Engineering, Beijing Institute of Technology, Beijing 100081, China
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Meador WE, Lewis TA, Shaik AK, Wijesinghe KH, Yang B, Dass A, Hammer NI, Delcamp JH. Molecular Engineering of Stabilized Silicon-Rosindolizine Shortwave Infrared Fluorophores. J Org Chem 2024; 89:2825-2839. [PMID: 38334085 DOI: 10.1021/acs.joc.3c01917] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/10/2024]
Abstract
Fluorescence-based biological imaging in the shortwave infrared (SWIR, 1000-1700 nm) is an attractive replacement for modern in vivo imaging techniques currently employed in both medical and research settings. Xanthene-based fluorophores containing heterocycle donors have recently emerged as a way to access deep SWIR emitting fluorophores. A concern for xanthene-based SWIR fluorophores though is chemical stability toward ambient nucleophiles due to the high electrophilicity of the cationic fluorophore core. Herein, a series of SWIR emitting silicon-rosindolizine (SiRos) fluorophores with emission maxima >1300 nm (up to 1550 nm) are synthesized. The SiRos fluorophore photophysical properties and chemical stability toward nucleophiles are examined through systematic derivatization of the silicon-core alkyl groups, indolizine donor substitution, and the use of o-tolyl or o-xylyl groups appended to the fluorophore core. The dyes are studied via absorption spectroscopy, steady-state emission spectroscopy, solution-based cyclic voltammetry, time-dependent density functional theory (TD-DFT) computational analysis, X-ray diffraction crystallography, and relative chemical stability over time. Optimal chemical stability is observed via the incorporation of the 2-ethylhexyl silicon substituent and the o-xylyl group to protect the core of the fluorophore.
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Affiliation(s)
- William E Meador
- Department of Chemistry and Biochemistry, University of Mississippi, 322 Coulter Hall, University, Mississippi 38677, United States
| | - Timothy A Lewis
- Department of Chemistry and Biochemistry, University of Mississippi, 322 Coulter Hall, University, Mississippi 38677, United States
| | - Abdul K Shaik
- Department of Chemistry and Biochemistry, University of Mississippi, 322 Coulter Hall, University, Mississippi 38677, United States
| | - Kalpani Hirunika Wijesinghe
- Department of Chemistry and Biochemistry, University of Mississippi, 322 Coulter Hall, University, Mississippi 38677, United States
| | - Boqian Yang
- HORIBA Scientific, 20 Knightsbridge Rd, Piscataway, New Jersey 08854, United States
| | - Amala Dass
- Department of Chemistry and Biochemistry, University of Mississippi, 322 Coulter Hall, University, Mississippi 38677, United States
| | - Nathan I Hammer
- Department of Chemistry and Biochemistry, University of Mississippi, 322 Coulter Hall, University, Mississippi 38677, United States
| | - Jared H Delcamp
- Department of Chemistry and Biochemistry, University of Mississippi, 322 Coulter Hall, University, Mississippi 38677, United States
- Materials and Manufacturing Directorate (RXNC), Air Force Research Laboratory, 2230 Tenth Street B655, Wright-Patterson AFB, Ohio 45433, United States
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Khan Z, Sekar N. Deep Red to NIR Emitting Xanthene Hybrids: Xanthene‐Hemicyanine Hybrids and Xanthene‐Coumarin Hybrids. ChemistrySelect 2023. [DOI: 10.1002/slct.202203377] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Affiliation(s)
- Zeba Khan
- Department of Dyestuff Technology (Currently named as Department of Specialty Chemicals Technology) Institute of Chemical Technology, Matunga (E) Mumbai Maharashtra India, PIN 400019
| | - Nagaiyan Sekar
- Department of Dyestuff Technology (Currently named as Department of Specialty Chemicals Technology) Institute of Chemical Technology, Matunga (E) Mumbai Maharashtra India, PIN 400019
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Saucier MA, Smith C, Kruse NA, Hammer NI, Delcamp JH. Acid-Triggered Switchable Near-Infrared/Shortwave Infrared Absorption and Emission of Indolizine-BODIPY Dyes. Molecules 2023; 28:molecules28031287. [PMID: 36770954 PMCID: PMC9919721 DOI: 10.3390/molecules28031287] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/14/2022] [Revised: 01/19/2023] [Accepted: 01/23/2023] [Indexed: 01/31/2023] Open
Abstract
Fluorescent organic dyes that absorb and emit in the near-infrared (NIR, 700-1000 nm) and shortwave infrared (SWIR, 1000-1700 nm) regions have the potential to produce noninvasive high-contrast biological images and videos. BODIPY dyes are well known for their high quantum yields in the visible energy region. To tune these chromophores to the NIR region, fused nitrogen-based heterocyclic indolizine donors were added to a BODIPY scaffold. The indolizine BODIPY dyes were synthesized via microwave-assisted Knoevenagel condensation with indolizine aldehydes. The non-protonated dyes showed NIR absorption and emission at longer wavelengths than an aniline benchmark. Protonation of the dyes produced a dramatic 0.35 eV bathochromic shift (230 nm shift from 797 nm to 1027 nm) to give a SWIR absorption and emission (λmaxemis = 1061 nm). Deprotonation demonstrates that material emission is reversibly switchable between the NIR and SWIR.
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Affiliation(s)
- Matthew A. Saucier
- Department of Chemistry and Biochemistry, University of Mississippi, University, MI 38677, USA
| | - Cameron Smith
- Department of Chemistry and Biochemistry, University of Mississippi, University, MI 38677, USA
| | - Nicholas A. Kruse
- Department of Chemistry and Biochemistry, University of Mississippi, University, MI 38677, USA
| | - Nathan I. Hammer
- Department of Chemistry and Biochemistry, University of Mississippi, University, MI 38677, USA
| | - Jared H. Delcamp
- Department of Chemistry and Biochemistry, University of Mississippi, University, MI 38677, USA
- Materials and Manufacturing Directorate, Air Force Research Laboratory, 2230 Tenth Street Area B Building 655, Wright-Patterson AFB, Dayton, OH 45433, USA
- UES, Inc., 4401 Dayton Xenia Rd, Dayton, OH 45432, USA
- Correspondence: or
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The pursuit of xanthenoid fluorophores with near-infrared-II emission for in vivo applications. Anal Bioanal Chem 2022:10.1007/s00216-022-04463-z. [PMID: 36445453 DOI: 10.1007/s00216-022-04463-z] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/21/2022] [Revised: 11/19/2022] [Accepted: 11/23/2022] [Indexed: 11/30/2022]
Abstract
As fluorescence imaging in the second near-infrared window (NIR-II, 1000-1700 nm) has gained increasing attention, it is inevitable that NIR-II fluorophores, the cornerstone of NIR-II imaging, have come to the middle of the stage. NIR-II xanthenoid fluorophores with good stability, high brightness, and fluorescence adjustability are becoming popular. We here reviewed the recent progress of xanthenoid fluorophores with NIR-II emission for in vivo applications. Especially, we focus on the strategies used for longer wavelength and fluorescence regulation to construct OFF-ON or ratiometric NIR-II fluorescent probes.
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East AK, Lee MC, Smaga LP, Jiang C, Mallojjala SC, Hirschi JS, Chan J. Synthesis of Silicon-Substituted Hemicyanines for Multimodal SWIR Imaging. Org Lett 2022; 24:8509-8513. [PMID: 36374323 PMCID: PMC10112353 DOI: 10.1021/acs.orglett.2c03382] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
SWIR dyes offer many advantages over their more common NIR congeners; however, the available options are limited. New SWIR imaging agents can be accessed by remodeling existing NIR molecules (i.e., hemicyanines (HDs)). In this study, we synthesized SWIR-HD, a modified HD featuring dimethylsilicon and benzo[cd]indolium groups that are designed to red-shift the absorbance and emission to 988 and 1126 nm, respectively. SWIR-HD was employed to visualize the liver and tumors via multimodal SWIR imaging.
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Affiliation(s)
- Amanda K. East
- Department of Chemistry, Beckman Institute for Advanced Science and Technology, and Cancer Center at Illinois, University of Illinois at Urbana−Champaign, Urbana, Illinois 61801, United States
| | - Michael C. Lee
- Department of Chemistry, Beckman Institute for Advanced Science and Technology, and Cancer Center at Illinois, University of Illinois at Urbana−Champaign, Urbana, Illinois 61801, United States
| | - Lukas P. Smaga
- Department of Chemistry, Beckman Institute for Advanced Science and Technology, and Cancer Center at Illinois, University of Illinois at Urbana−Champaign, Urbana, Illinois 61801, United States
| | - Chang Jiang
- Department of Chemistry, Beckman Institute for Advanced Science and Technology, and Cancer Center at Illinois, University of Illinois at Urbana−Champaign, Urbana, Illinois 61801, United States
| | - Sharath C. Mallojjala
- Department of Chemistry, Binghamton University, Binghamton, New York 13902, United States
| | - Jennifer S. Hirschi
- Department of Chemistry, Binghamton University, Binghamton, New York 13902, United States
| | - Jefferson Chan
- Department of Chemistry, Beckman Institute for Advanced Science and Technology, and Cancer Center at Illinois, University of Illinois at Urbana−Champaign, Urbana, Illinois 61801, United States
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Chatterjee S, Shaik AK, Wijesinghe KH, Ndaleh D, Dass A, Hammer NI, Delcamp JH. Design and Synthesis of RhodIndolizine Dyes with Improved Stability and Shortwave Infrared Emission up to 1250 nm. J Org Chem 2022; 87:11319-11328. [PMID: 35984405 DOI: 10.1021/acs.joc.2c00678] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
The design of shortwave infrared (SWIR) emissive small molecules with good stability in water remains an important challenge for fluorescence biological imaging applications. A series of four SWIR emissive rhodindolizine (RI) dyes were rationally designed and synthesized to probe the effects of nonconjugated substituents, conjugated donor groups, and nanoencapsulation in a water-soluble polymer on the stability and optical properties of the dyes. Steric protecting groups were added at the site of a significant LUMO presence to probe the effects on stability. Indolizine donor groups with added dimethylaniline groups were added to reduce the electrophilicity of the dyes toward nucleophiles such as water. All of the dyes were found to absorb (920-1096 nm peak values) and emit (1082-1256 nm peak values) within the SWIR region. Among xanthene-based emissive dyes, emission values >1200 nm are exceptional with 1256 nm peak emission being a longer emission than the recent record setting VIX-4 xanthene-based dye. Half-lives were improved from ∼5 to >24 h through the incorporation of either steric-based core protection groups or donors with increased donation strength. Importantly, the nanoencapsulation of the dyes in a water-soluble surfactant (Triton-X) allows for the use of these dyes in biological imaging applications.
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Affiliation(s)
- Satadru Chatterjee
- Department of Chemistry and Biochemistry, University of Mississippi, Coulter Hall, University, Mississippi 38677, United States
| | - Abdul Kalam Shaik
- Department of Chemistry and Biochemistry, University of Mississippi, Coulter Hall, University, Mississippi 38677, United States
| | - Kalpani Hirunika Wijesinghe
- Department of Chemistry and Biochemistry, University of Mississippi, Coulter Hall, University, Mississippi 38677, United States
| | - David Ndaleh
- Department of Chemistry and Biochemistry, University of Mississippi, Coulter Hall, University, Mississippi 38677, United States
| | - Amala Dass
- Department of Chemistry and Biochemistry, University of Mississippi, Coulter Hall, University, Mississippi 38677, United States
| | - Nathan I Hammer
- Department of Chemistry and Biochemistry, University of Mississippi, Coulter Hall, University, Mississippi 38677, United States
| | - Jared H Delcamp
- Department of Chemistry and Biochemistry, University of Mississippi, Coulter Hall, University, Mississippi 38677, United States
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Piwoński H, Nozue S, Habuchi S. The Pursuit of Shortwave Infrared-Emitting Nanoparticles with Bright Fluorescence through Molecular Design and Excited-State Engineering of Molecular Aggregates. ACS NANOSCIENCE AU 2022; 2:253-283. [PMID: 37102065 PMCID: PMC10125152 DOI: 10.1021/acsnanoscienceau.1c00038] [Citation(s) in RCA: 7] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Indexed: 04/28/2023]
Abstract
Shortwave infrared (SWIR) fluorescence detection gradually becomes a pivotal real-time imaging modality, allowing one to elucidate biological complexity in deep tissues with subcellular resolution. The key challenge for the further growth of this imaging modality is the design of new brighter biocompatible fluorescent probes. This review summarizes the recent progress in the development of organic-based nanomaterials with an emphasis on new strategies that extend the fluorescence wavelength from the near-infrared to the SWIR spectral range and amplify the fluorescence brightness. We first introduce the most representative molecular design strategies to obtain near-infrared-SWIR wavelength fluorescence emission from small organic molecules. We then discuss how the formation of nanoparticles based on small organic molecules contributes to the improvement of fluorescence brightness and the shift of fluorescence to SWIR, with a special emphasis on the excited-state engineering of molecular probes in an aggregate state and spatial packing of the molecules in nanoparticles. We build our discussion based on a historical perspective on the photophysics of molecular aggregates. We extend this discussion to nanoparticles made of conjugated polymers and discuss how fluorescence characteristics could be improved by molecular design and chain conformation of the polymer molecules in nanoparticles. We conclude the article with future directions necessary to expand this imaging modality to wider bioimaging applications including single-particle deep tissue imaging. Issues related to the characterization of SWIR fluorophores, including fluorescence quantum yield unification, are also mentioned.
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