title: Carbon nanodots featuring efficient FRET for two-photon photodynamic cancer therapy with a low fs laser power density.
abstract: The 5,10,15,20-tetrakis(1-methyl 4-pyridinio) porphyrins (TMPyP), a photosensitizer used for photodynamic therapy of cancers (PDT), were linked to carbon dots (CDots) to form the conjugates of CDot-TMPyP by the electrostatic force. The 415 nm emission band of CDots was well overlapped with the absorption band of TMPyP, so that the Cdots in conjugates can work as donor to transfer the energy to TMPyP moiety by fluorescence resonance energy transfer (FRET) with an FRET efficiency of 45%, determined by the fluorescence lifetime change between the free CDots and conjugated CDots. The two-photon absorption cross section (TPACS) of TMPyP is as low as 110 GM and the TMPyP thus be not suitable for two-photon PDT. Whereas the CDots have high TPACS, and their TPACS are excitation wavelength dependent with the maximum value of 15000 GM at 700 nm. Therefore, the conjugates of CDot-TMPyP were explored for two-photon excitation (TPE) PDT. The two-photon image of CDot-TMPyP in Hela cells was clearly seen under the excitation of a 700 nm femto-second (fs) laser. The singlet oxygen production of CDot-TMPyP was also much higher than that of TMPyP alone under TPE of a 700 nm fs laser. The in vitro PDT killing was further achieved with CDot-TMPyP by TPE of the 700 nm fs laser. Particularly herein the low power density of fs laser from unfocused laser beam was successfully used to carry out the TPE PDT, because of the high TPACS of CDots. These results demonstrate that the CDot-TMPyP conjugates are promising for TPE PDT and needed to investigate further.
authors.affiliation: State Key Laboratory of Surface Physics and Department of Physics, and Key Laboratory of Micro and Nano Photonic Structures (Ministry of Education), Fudan University, Shanghai 200433, China.
authors.forename: Jing
authors.initials: J
authors.lastname: Wang
authors.affiliation: State Key Laboratory of Molecular Engineering of Polymers, Department of Macromolecular Science, Fudan University, Shanghai 200433 PR China.
authors.forename: Zehui
authors.initials: Z
authors.lastname: Zhang
authors.affiliation: State Key Laboratory of Surface Physics and Department of Physics, and Key Laboratory of Micro and Nano Photonic Structures (Ministry of Education), Fudan University, Shanghai 200433, China.
authors.forename: Shuai
authors.initials: S
authors.lastname: Zha
authors.affiliation: State Key Laboratory of Surface Physics and Department of Physics, and Key Laboratory of Micro and Nano Photonic Structures (Ministry of Education), Fudan University, Shanghai 200433, China.
authors.forename: Yinyan
authors.initials: Y
authors.lastname: Zhu
authors.affiliation: State Key Laboratory of Molecular Engineering of Polymers, Department of Macromolecular Science, Fudan University, Shanghai 200433 PR China.
authors.forename: Peiyi
authors.initials: P
authors.lastname: Wu
authors.affiliation: Department of Physics and Institure of Nanotechnology, Bar Ilan University, Ramat Gan 52900, Israel.
authors.forename: Benjamin
authors.initials: B
authors.lastname: Ehrenberg
authors.affiliation: State Key Laboratory of Surface Physics and Department of Physics, and Key Laboratory of Micro and Nano Photonic Structures (Ministry of Education), Fudan University, Shanghai 200433, China. Electronic address: jychen@fudan.edu.cn.
authors.forename: Ji-Yao
authors.initials: JY
authors.lastname: Chen
mesh_terms: D002244:Carbon / Q000737:chemistry*; D031541:Fluorescence Resonance Energy Transfer / Q000379:methods*; D006367:HeLa Cells; D006801:Humans; D007834:Lasers; D046529:Microscopy, Electron, Transmission; D049329:Nanostructures / Q000737:chemistry*; D010778:Photochemotherapy / Q000379:methods; D017785:Photons; D017319:Photosensitizing Agents / Q000494:pharmacology; D011166:Porphyrins / Q000494:pharmacology; D026082:Singlet Oxygen / Q000737:chemistry
chemical_list: D017319:Photosensitizing Agents; D011166:Porphyrins; D026082:Singlet Oxygen; C021096:tetra(4-N-methylpyridyl)porphine; D002244:Carbon
keywords: Carbon dots; Fluorescence resonance energy transfer; Photodynamic therapy of cancers; Two-photon absorption cross section