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  • br Fig Optimization for the preparation

    2019-10-07


    Fig. 1. Optimization for the preparation of core–shell nanoparticles [email protected] (A) TEM images of the nanoparticles (CTMR-doped silica core coated with pure silica shell) prepared with 1.5 (a), 3 (b), 6 (c) and 9 μmol (d) of APTES-CTMR; (B) effect of the APTES-CTMR amount on the luminescence intensity and the ratio of luminescence intensity to the amount of APTES-CTMR; (C) TEM images of the nanoparticles (pure silica core coated with BHHBCB-Eu3+-doped silica shell) prepared with 1 (e), 2.5 (f), 3.75 (g), and 5 μmol (h) of APTES-BHHBCB-Eu3+; (D) effect of the APTES-BHHBCB-Eu3+ amount on the luminescence intensity and the ratio of luminescence intensity to the amount of APTES-BHHBCB-Eu3+. Scale bar, 100 nm. Luminescence intensity of nanoparticles (6 μg/mL) was measured in 50 mM PBS at pH 7.4.
    Fig. 2. TEM images of the nanoparticles [email protected] (A) and [email protected] (C), and their particle size distribution histograms (B, D) and FT-IR spectra (E). Scale bar, 100 nm.
    Fig. 3. (A) UV–vis N-octanoyl-L-Homoserine lactone spectra of
    [email protected], [email protected]
    [email protected]-Eu-FA. (C) Steady-state emission spectra (λex = 330 nm) of [email protected] BHHBCB-Eu and [email protected]
    monodisperse and spherical morphology (Fig. 2C), with average size of ~54 nm in diameter (Fig. 2D). The increased hydrated particle dia-meter of 295.4 nm of [email protected] implied the presence of FA-PEG2000 moieties on the surface of core–shell nanoparticles (Fig. S1B). The ζ-potentials of the nanoparticles [email protected] and [email protected] in water were determined to be 30.5 mV and 33.4 mV (Fig. S2), which benefits to the monodisperse of nanoparticles in aqueous media.
    FT-IR spectra of [email protected] and [email protected] were recorded to identify the characteristic absorptions of two kinds of nanoparticles. As shown in Fig. 2E, the absorption at ~1077 cm−1 as-signed to the νSi-O vibration and broad absorption at ~3421 cm−1 as-signed to the νN-H or νO-H vibration were observed in the IR spectra of two kinds of nanoparticles. However, after the FA-functionalization, a characteristic absorption at ~1162 cm−1 that can be assigned to the νC-O-C vibration was observed, which suggested the presence of FA-PEG2000 moieties on the surface of [email protected]
    The photophysical properties of [email protected] and [email protected] BHHBCB-Eu-FA, including UV–vis absorption, steady-state lumines-cence and TGL spectra, were then measured in 50 mM PBS at pH 7.4. As shown in Fig. 3A, the absorption spectra of two kinds of nanoparticles exhibited strong visible absorptions centered at 542 nm and UV ab-sorptions centered at 330, which could be attributed to the typical absorptions of CTMR and BHHBCB-Eu3+. It was noticed that FA-PEG2000-COOH displayed a strong absorption at ~260 nm, and which was also observed in the spectrum of [email protected], de-monstrating the successful conjugation of FA-PEG2000-COOH to the surface of [email protected] Fig. 3B and C showed the steady-state excitation and emission spectra of [email protected] and [email protected] BHHBCB-Eu-FA. Excitation spectra of two kinds of nanoparticles dis-played typical CTMR and BHHBCB-Eu3+ excitation peaks centered at 542 and 330 nm, respectively. Under excitation at 542 nm, CTMR emission of [email protected] at 584 nm was clearly observed, while under excitation at 330 nm, two emission peaks at 584 nm and 612 nm attributed to the typical emissions of CTMR and BHHBCB-Eu3+ were noticed. TGL spectra of both [email protected] and [email protected] BHHBCB-Eu-FA showed the same excitation peak at 330 nm, and 
    several sharp emission peaks associated with the 5D0 → 7FJ transitions (J = 0–4) of Eu3+ ions (λem,max = 612 nm, J = 2). The emission life-times of CTMR and BHHBCB-Eu3+ in [email protected] were measured to be 1.87 ns and 410 μs, respectively (Fig. S3). These sig-nificant differences of emission lifetimes in a nanoprobe facilitate the “double-check” imaging of cancer cells at both steady-state lumines-cence and TGL modes.