Singlet Oxygen Generation from Watersoluble Quantum Dot Organic
Singlet Oxygen Generation from Water-soluble Quantum Dot. Organic Dye Nanocomposites Lixin Shi, Ana Gamboa, Billy Hernandez, Araceli B. Dasalla, and Matthias Selke* Department of Chemistry and Biochemistry, California State University, Los Angeles, CA 90032 a) b) Introduction Colloidal semiconductor nanocrystals (Quantum Dots, QDs) can provide three-dimensional (3 D) architectures and have attracted widespread interest, since their nano-size physical properties are quite different from those of the bulk materials depending upon their size, shape, and packing density. 1 Meanwhile, QDs are very attractive as biology labels, because of their small size, emission tunability, superior photostability and longer photoluminescence decay times. QDs can be used mark moleculer of into living cells. 2 Photodynamic therapy (PDT) is an emerging modality for the treatment of a certain types of c) cancer. 3 Recent papers have reported high quantum yields of singlet oxygen (1 O 2) being generated by combining nanoparticles with photosensitizers. 4, 5 Nanoparticles can be ideal carriers of photosensitizer molecules for PDT. The combination of nanomaterials alone with photosensitizers has emerged as a new interdisciplinary research field. 6 However, to the best of our knowledge, no Scheme 1. Fabrication and 1 O 2 generation of Cd. Te-TSPP nanocomposites studies on the water-soluble QDs-organic dye nanocomposites for generating singlet oxygen are published to date. Water-soluble species are critical for artificial biocompatibility materials which are widely used as drug delivery carriers, live cell imaging and in vivo imaging. 7 a) b) Meso-Tetra (4 -sulfonatophenyl) Porphine Dihudrochloride ( TSPP ) We report herein the first preparation of water-soluble QDs, Cd. Te, fabricated together with an organic dye, Meso-Tetra (4 -sulfonatophenyl) Porphine Dihydrochloride (TSPP), a photosensitizer, Figure 3. a) Relative intensity of 1 O 2 production vs. absorbance of Cd. Te-TSPP nanocomposites, TSPP, and Rose Bengal at 355 nm. b). 1 O 2 luminescence decay of Cd. Te and Cd. Te-TSPP in presence/absence of Sodium Azide at 355 nm in D 2 O. C). Photooxidation of Cd. Te-TSPP nanocomposites at different irradiation times. using electrostatic interactions as a versatile means to bind photosensitizers to water-soluble Cd. Te nanocrystals. Results and discussion In a typical assay, the Uv-vis spectra of QD-TSPP nanocomposites are slightly blue shifted compared with that of free TSPP (Figure 1 a), this could be caused by surface plasma change as TSPP deposited on the surface of the QDs, H-aggregates was achieved. 8 An aqueous solution of TSPP with an absorption of 0. 10 at Cd. Te nanoparticles in D 2 O Cd. Te nanoparticles after 30 min irradiation Figure 1. a) Uv-vis spectra for the fabrication of Cd. Te with TSPP in 0. 1 M p. H 7. 0 PBS. b) Fluorescence spectra of Cd. Te, TSPP and Cd. Te-TSPP nanocomposites, respectively. 355 nm corresponds to a concentration of 4 10 -2 m. M. After TSPP was deposited on the QDs surface, the absorption of nanocomposites at 355 nm was improved significantly to 0. 476 corresponding to s a TSPP concentration 2. 6 10 -2 m. M. Emission intensity of Cd. Te-TSPP nanocomposites decreased when TSPP deposited on the Cd. Te surface. The most likely cause is the quenching of photoexcited QDs through charge transfer to the electron-accepting TSPP, which is bound to QDs (Figure 1 b). Cd. Te-TSPP nanocomposites effectively generate 1 O 2 with a quantum yield of 30± 9% as shown in Figure Cd. Te-TSPP nanocomposites in D 2 O Cd. Te-TSPP nanocomposties after 30 min. irradiation 3 a. No 1 O 2 was observed when the Cd. Te nanocrystal was measured in absence of TSPP (Figure 3 b). References: Photooxidation experiments were carried out to determine the stability of the nanocomposites and possible oxidation of the nanocomposites by 1 O 2 using 1 H (1) (a) Alivisatos, A. P. Science 1996, 271, 933. (b) Michalet, X. ; Pinaud, F. F. ; Bentolila, L. A. ; Tsay, J. M. ; Doose, S. ; Li, J. J. ; Sundaresan, G. ; Wu, A. M. ; Gambhir, S. S. ; Weiss, S. Science, 2005, 307, 538. (2) (a) Medintz, I. L. ; Clapp, A. R. ; Mattoussi, H. ; Goldman, E. R. ; Fisher, B. ; Mauro, J. M. Nat. Mater. 2003, 2, 630. (b) Bakalova, R. ; Ohba, H. ; Zhelev, Z. ; NMR. Methionione was added into prepared samples of Cd. Te and Cd. Te-TSPP, respectively. At high concentration no decomposition or oxidation was detected by 1 H NMR (3) spectroscopy, which further confirms that no singlet oxygen is produced by Cd. Te nanocrystals. (4) Future research (5) (6) (7) • To investigate the relationship of QD size and quantum yield. (8) • To investigate the relationship of space between QD and organic dye on quantum yield. Figure 2. High resolution TEM image of Cd. Te nanocrystals(10 -3 m. M), left, and Cd. Te-TSPP nanocomposites ( 10 -3 m. M Cd. Te with 10 -3 m. M TSPP), right. Scale bar 5 nm. Nagase, T. ; Jose, R. ; Ishikawa, M. ; Baba, Y. Nano Lett. 2001, 4, 1567. (a) Yokoyama, M. ; Satoh, A. ; Sakurai, A. ; Okano, T. ; Matsumura, Y. ; Kakizoe, T. ; Kataoka, K. J. Control. Release 1998, 55, 219. (b) Leroux, J-C. ; Allémann, E. ; Jaeghere, F. D. ; Doelker, E. ; Gurny, R. J. of Control. Release, 1996, 39, 339. (a) Imahori, H. ; Arimura, M. ; Hanada, T. ; Nishimura, Y. ; Yamazaki, I. ; Sakata, Y. ; Fukuzumi, S. ; J. Am. Chem. Soc. 2001, 123, 335. (b) Roy, I. ; Ohulchanskyy, T. Y. ; Pudavar, H. E. ; Bergey, E. J. ; Oseroff, A. R. ; Morgan, J. ; Dougherty, T. J. ; Prasad, P. N. J. Am. Chem. Soc. 2003, 125, 7860. Hone, D. C. ; Walker, P. I. ; Evans-Growing, R. ; Fitz. Gerald, S. ; Beeby, A. ; Chambrier, I. ; Cook, M. J. ; Russell, D. A. Langmuir, 2002, 18, 2985. Wang, S. Z. ; Gao, R. M. ; Zhou, F. M. ; Selke, M. J. Mater. Chem. 2004, 14, 487. (a) Pinaud, F. ; King, D. ; Moore, H. P. ; Weiss, S. J. Am. Chem. Soc. 2004, 126, 6115. (b) Medintz, I. L. ; Uyeda, H. T. ; Goldman, E. R. ; Mattoussi, H. Nat. Mater. 2005, 4, 435. (c) Pathak, S. ; Choi, S. K. ; Arnheim, N. ; Thompson, M. E. J. Am. Chem. Soc. 2001, 121, 4103. Luo, Y. H. ; Huang, J. G. ; Ichinose, I. J. Am. Chem. Soc. 2005, 127, 8296. Acknowledgment: The authors thank the NSF PREM and NIH MBRS programs for financial support, and Carol M. Garland of Cal. Tech for TEM measurements.
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