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Open AccessArticle

Amino-Functionalized Nitrogen-Doped Graphene-Quantum-Dot-Based Nanomaterials with Nitrogen and Amino-Functionalized Group Content Dependence for Highly Efficient Two-Photon Bioimaging

1
School of Chemistry and Materials Science, Nanjing University of Information Science and Technology, Nanjing 210044, China
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Allergy & Clinical Immunology Research Center, National Cheng Kung University Hospital, College of Medicine, National Cheng Kung University, Tainan 701, Taiwan
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Department of Mechanical Engineering, National Cheng Kung University, Tainan 701, Taiwan
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The School of Chinese Medicine for Post-Baccalaureate, I-Shou University, Kaohsiung 840, Taiwan
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Department of Biochemistry and Molecular Biology, National Cheng Kung University Hospital, College of Medicine, National Cheng Kung University, Tainan 701, Taiwan
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Department of Microbiology & Immunology, National Cheng Kung University Hospital, College of Medicine, National Cheng Kung University, Tainan 701, Taiwan
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Department of Biological Science and Technology, I-Shou University, Kaohsiung 840, Taiwan
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Pharmacy Department of E-Da Hospital, Kaohsiung 824, Taiwan
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Taiwan Instrument Research Institute, National Applied Research Laboratories, Hsinchu City 300, Taiwan
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Department of Biomedical Engineering, National Cheng Kung University, Tainan 701, Taiwan
*
Authors to whom correspondence should be addressed.
Int. J. Mol. Sci. 2020, 21(8), 2939; https://doi.org/10.3390/ijms21082939
Received: 16 March 2020 / Revised: 16 April 2020 / Accepted: 16 April 2020 / Published: 22 April 2020
We fabricated nanomaterials comprising amino-functionalized and nitrogen-doped graphene quantum dots (amino-N-GQDs) and investigated their photostability and intrinsic luminescence in the near-infrared spectrum to determine their suitability as contrast agents in two-photon imaging (TPI). We observed that amino-N-GQDs with a higher amount of bonded nitrogen and amino-functionalized groups (6.2%) exhibited superior two-photon properties to those with a lower amount of such nitrogen and groups (4.9%). These materials were conjugated with polymers containing sulfur (polystyrene sulfonate, PSS) and nitrogen atoms (polyethylenimine, PEI), forming amino-N-GQD–PSS–PEI specimens (amino-N-GQD-polymers). The polymers exhibited a high quantum yield, remarkable stability, and notable two-photon properties and generated no reactive oxygen species, rendering them excellent two-photon contrast agents for bioimaging. An antiepidermal growth factor receptor (AbEGFR) was used for labeling to increase specificity. Two-photon imaging (TPI) of amino-N-GQD (6.2%)-polymer-AbEGFR-treated A431 cancer cells revealed remarkable brightness, intensity, and signal-to-noise ratios for each observation at a two-photon excitation power of 16.9 nJ pixel−1 under 30 scans and a three-dimensional (3D) depth of 105 µm, indicating that amino-N-GQD (6.2%)-polymer-AbEGFR-treated cells can achieve two-photon luminescence with 71 times less power required for two-photon autofluorescence (1322.8 nJ pixel−1 with 500 scans) of similar intensity. This economy can minimize photodamage to cells, rendering amino-N-GQD-polymers suitable for noninvasive 3D bioimaging. View Full-Text
Keywords: graphene quantum dot; two-photon photoproperties; ultralow two-photon excitation power; two-photon autofluorescence; noninvasive three-dimensional imaging graphene quantum dot; two-photon photoproperties; ultralow two-photon excitation power; two-photon autofluorescence; noninvasive three-dimensional imaging
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Kuo, W.-S.; Chang, C.-Y.; Huang, K.-S.; Liu, J.-C.; Shao, Y.-T.; Yang, C.-H.; Wu, P.-C. Amino-Functionalized Nitrogen-Doped Graphene-Quantum-Dot-Based Nanomaterials with Nitrogen and Amino-Functionalized Group Content Dependence for Highly Efficient Two-Photon Bioimaging. Int. J. Mol. Sci. 2020, 21, 2939.

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