Two-Photon Absorption of Cationic Conjugated Polyelectrolytes: Effects of Aggregation and Application to 2-Photon-Sensitized Fluorescence from Green Fluorescent Protein

Wang, Shanshan; Li, Zhiliang; Liu, Xinglei; Phan, Samantha; Lv, Fengting; Belfield, Kevin D.; Wang, Shu; Schanze, Kirk S.

doi:10.1021/acs.chemmater.7b00676

Cited by 28 publications

(28 citation statements)

References 63 publications

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“…A majority of extant studies on 2PA properties of polymers has employed the Z-scan technique [32][33][34][35][36][37][38] and, to a lesser extent, the two-photon excited fluorescence (TPEF) [39][40][41][42] as optical characterization techniques. The former technique, in general, has grown to be the most frequently used method of the characterization of third-order (and higher-order) NLO properties of materials that are available in the form of solutions or that could be fabricated as amorphous, uniform films.…”

Section: Introductionmentioning

confidence: 99%

Nonlinear Optical Pigments. Two-Photon Absorption in Crosslinked Conjugated Polymers and Prospects for Remote Nonlinear Optical Thermometry

2020

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Nonlinear optical (NLO) pigments are compounds insoluble in solvents that exhibit phenomena related to nonlinear optical susceptibilities (χ(n) where n = 2,3,...), e.g., two-photon absorption (2PA) which is related to the imaginary part of χ(3). Determination of spectrally-resolved 2PA properties for NLO pigments of macromolecular nature, such as coordination polymers or crosslinked polymers, has long been a challenging issue due to their particulate form, precluding characterizations with standard techniques such as Z-scan. In this contribution, we investigate thus far unknown spectrally-resolved 2PA properties of a new subclass of NLO pigments—crosslinked conjugated polymers. The studied compounds are built up from electron-donating (triphenylamine) and electron-withdrawing (2,2’-bipyridine) structural fragments joined by vinylene (Pol1) or vinyl(4-ethynylphenyl) (Pol2) aromatic bridges. 2PA properties of these polymers have been characterized in broad spectral range by specially modified two-photon excited fluorescence (TPEF) techniques: solid state TPEF (SSTPEF) and internal standard TPEF (ISTPEF). The impact of self-aggregation of aromatic backbones on the 2PA properties of the polymers has been evaluated through extended comparisons of NLO parameters, i.e., 2PA cross sections (σ2) and molar-mass normalized 2PA merit factors (σ2/M) with those of small-molecular model compounds: Mod1 and Mod2. By doing this, we found that the 2PA response of Pol1 and Pol2 is improved 2–3 times versus respective model compounds in the solid state form. Further comparisons with 2PA results collected for diluted solutions of Mod1 and Mod2 supports the notion that self-aggregated structure contributes to the observed enhancement of 2PA response. On the other hand, it is clear that Pol1 and Pol2 suffer from aggregation-caused quenching phenomenon, well reflected in time-resolved fluorescence properties as well as in relatively low values of quantum yield of fluorescence. Accordingly, despite improved intrinsic 2PA response, the effective intensity of two-photon excited emission for Pol1 and Pol2 is slightly lower relative to Mod1 and Mod2. Finally, we explore temperature-resolved luminescence properties under one- (377 nm), two- (820 nm), and three-photon excitation (1020 nm) conditions of postsynthetically Eu3+-functionalized material, Pol1-Eu, and discuss its suitability for temperature sensing applications.

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Section: Introductionmentioning

confidence: 99%

Nonlinear Optical Pigments. Two-Photon Absorption in Crosslinked Conjugated Polymers and Prospects for Remote Nonlinear Optical Thermometry

2020

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“…The remarkable optical properties and low cytotoxicity of the PPE based CPEs make them a promising material for imaging, [23] cellular protein recognition, [24] cell types detection and differentiation, [13,25] and gene delivery applications [26] . Moreover, poly(phenylene ethynylene) (PPE)‐type CPEs exhibit two‐photon absorption that allows their application for two‐photon fluorescence imaging of mammalian cells [27,28] . Despite their interesting fluorescence imaging properties, an expanded study to understand the effect of CPE structure on cell imaging has not been performed.…”

Section: Introductionmentioning

confidence: 99%

Fluorescence Imaging of Mammalian Cells with Cationic Conjugated Polyelectrolytes

et al. 2020

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Fluorescence imaging using poly(phenylene ethynylene) (PPE) based conjugated polyelectrolytes (CPEs) has garnered considerable attention in the recent past due to their remarkable photophysical properties. In this report, we studied the fluorescence imaging properties of a set of six PPE‐based CPEs appended with side chains varying in structure and number of cationic charges. The photophysical and aggregation features of the CPEs depend on the overall charge density on the polymer in water. The cytotoxicity of the CPEs was evaluated against MCF‐7 mammalian cells, which revealed that polyelectrolytes with less cationic charge are less cytotoxic and vice versa. Confocal laser scanning microscopy (CLSM) studies showed that all the CPEs could efficiently penetrate into the MCF‐7 cells after 10 h of incubation. The transit of CPEs into the lysosomes was confirmed by comparison with the uptake of LysoTracker Red DND‐99 dye, which also revealed that the polyelectrolytes are highly photostable. We also demonstrated that the imidazolium‐functionalized CPEs could selectively stain bacteria over mammalian cells, suggesting the importance of CPEs for clinical applications.

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“…GFP is a 238-aa protein with a molecular weight of about 26.9 kDa. The core of GFP, 4-(4-hydroxybenzylidene)-1,2-dimethyl-imidazolinone (p-HOBDI), is enclosed at the centre of an 11-stranded β-barrel, and spontaneously forms a complex by binding to amino acid residues Ser65-Tyr66-Gly67 after a multistep reaction 6 . The remaining residues fold into a host scaffold or matrix, providing an intricate microenvironment which is essential for keeping the fluorophore HOBDI highly emissive 7 .…”

Section: Introductionmentioning

confidence: 99%

Role of Hydrogen Bonding in Green Fluorescent Protein-like Chromophore Emission

Yang

Nian

Zhang

et al. 2019

Sci Rep

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The fluorescence emission from green fluorescent protein (GFP) is known to be heavily influenced by hydrogen bonding between the core fluorophore and the surrounding side chains or water molecules. Yet how to utilize this feature for modulating the fluorescence of GFP chromophore or GFP-like fluorophore still remains elusive. Here we present theoretical calculations to predict how hydrogen bonding could influence the excited states of the GFP-like fluorophores. These studies provide both a new perspective for understanding the photophysical properties of GFP as well as a solid basis for the rational design of GFP-based fluorophores.

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Two-Photon Absorption of Cationic Conjugated Polyelectrolytes: Effects of Aggregation and Application to 2-Photon-Sensitized Fluorescence from Green Fluorescent Protein

Cited by 28 publications

References 63 publications

Nonlinear Optical Pigments. Two-Photon Absorption in Crosslinked Conjugated Polymers and Prospects for Remote Nonlinear Optical Thermometry

Nonlinear Optical Pigments. Two-Photon Absorption in Crosslinked Conjugated Polymers and Prospects for Remote Nonlinear Optical Thermometry

Fluorescence Imaging of Mammalian Cells with Cationic Conjugated Polyelectrolytes

Role of Hydrogen Bonding in Green Fluorescent Protein-like Chromophore Emission

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