Two-Photon Induced Photoluminescence and Singlet Oxygen Generation from Aggregated Gold Nanoparticles

Abstract

Metal nanoparticles have potential applications as bioimaging and photosensitizing agents. Aggregation effects are generally believed to be adverse to their biomedical applications. Here we have studied the aggregation effects on two-photon induced photoluminescence and singlet oxygen generation of Au nanospheres and Au nanorods of two different aspect ratios. Aggregated Au nanospheres and short Au nanorods were found to display enhanced two-photon induced photoluminescence and singlet oxygen generation capabilities compared to the unaggregated ones. The two-photon photoluminescence of Au nanospheres and short Au nanorods were enhanced by up to 15.0- and 2.0-fold upon aggregation, and the corresponding two-photon induced singlet oxygen generation capabilities were enhanced by 8.3 and 1.8-fold, respectively. The two-photon induced photoluminescence and singlet oxygen generation of the aggregated long Au nanorods were found to be lower than the unaggregated ones. These results support that the change in their two-photon induced photoluminescence and singlet oxygen generation originate from aggregation modulated two-photon excitation efficiency. This finding is expected to foster more biomedical applications of metal nanoparticles as Au nanoparticles normally exist in an aggregated form in the biological environments. Considering their excellent biocompatibility, high inertness, ready conjugation, and easy preparation, Au nanoparticles are expected to find more applications in two-photon imaging and two-photon photodynamic therapy.

Role of 5-aminolevulinic acid-conjugated gold nanoparticles for photodynamic therapy of cancer

“…The results indicate that with different light irradiation, cells treated with 5-ALA-GNPs all produce more singlet oxygen than those treated with 5-ALA alone, and the cells incubated with GNPs alone nearly produce no singlet oxygen compared with the control (nontreated cells). Vankayala et al and Jiang et al showed that GNP itself can effectively generate singlet oxygen induced by light, 44,45 but in these papers, GNPs were usually induced by a UV light with a large irradiation power (around 100 W) and the generation of singlet oxygen was mainly the result of two-photon excitation instead of the mW level irradiation power with 502 and 635 nm wavelengths in our study. Green LED irradiation gives a greater improvement efficiency, whereas the SOG is about 2.74 times higher for conjugates than those of the PpIX alone.…”

Peptide-Conjugated Gold Nanoprobe: Intrinsic Nanozyme-Linked Immunsorbant Assay of Integrin Expression Level on Cell Membrane

“…Comparatively, aggregated Au nanoparticles display enhanced two-photon photoluminescence (TPPL) due to plasmon coupling which is potential for bioimaging application. 38 In this case, TPPL microscopy was employed to provide evidence that Peptide-AuNPs can selectively recognize integrin on HEL cells' cytomembrane.…”

“…The result is in accordance with the previous study that aggregated Au nanospheres behaves rather broad TPPL spectrum ranged from 570 nm to 700 nm. 38,39 The nonlinear optical property of coupled Peptide-AuNPs allows us to deduce inhomogeneous spatial distribution of the integrin. In striking contrast, vacant cells do not emit noticeable photoluminescence 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 9 ( Figure 5b) when TPPL image was collected at the same setting as above (Figure 5b).…”

Novel Mn3[Co(CN)6]2@SiO2@Ag Core–Shell Nanocube: Enhanced Two‐Photon Fluorescence and Magnetic Resonance Dual‐Modal Imaging‐Guided Photothermal and Chemo‐therapy

“…Thus, the enhancement could be resulted from increased extinction at the excitation wavelength when excited at 730 nm. [ 50 ] …”