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  • Colloids and Surfaces B Biointerfaces br in deionized water


     Colloids and Surfaces B: Biointerfaces 173 (2019) 335–345
    in deionized water for 3 h and 12 h, the change in the volumetric flask was observed. As shown in the inset of Fig. 2b, the solution shows no significant change in 3 h and 12 h, and the mean hydrodynamic size of the samples in each solution are 22.4 ± 1.2 and 23.1 ± 1.1 nm re-spectively determined by the dynamic light scattering, indicating that the nanoparticles had good stability in water.
    The instability of the Au2O3 is well known by people [52,53]. The light irradiation can also induce the decomposition of it. Firstly, to investigate the light induced oxygen generation property of the Au2O3, the UV–vis AZD7687 spectra of the samples were conducted. As shown in Fig. 2c, Fe3O4 and [email protected] have no absorption peak in the visible spectral range of test. While the UV–vis absorption peak appears at 560 nm for FeSiAuO, which is mainly due to the surface plasmon resonance absorption of surface-modified Au2O3. Moreover, the light induced oxygen generation ability of the sample can be confirmed by the dissolved oxygen test of the FeSiAuO solution (400 μg/mL), which was received preliminary 30 min purging of N2 for eliminating original dissolved oxygen. As shown in the Fig. 2d, upon the 560 nm light, the concentration of the dissolved oxygen can be remarkably improved from 0.23 ± 0.15 ppm to 6.23 ± 0.15 ppm, which can be attributed to the decomposition of the Au2O3. When removing the light source, the concentration of dissolved oxygen was decreased to a lower level of 4.4 ± 0.15 ppm and further improved to 6.22 ± 0.15 ppm again when taking back the light irradiation. For chemotherapy, DOX can react with intracellular oxygen to generate reactive oxygen species (ROS). when 560 nm light was introduced, Au2O3 will decompose into Au and O2. Then DOX can react with sufficient oxygen to produce re-active oxygen species (ROS) in hypoxic environment, which will en-hance generation efficiency.
    O2 releasing effect of the sample under light irradiation be further confirmed by the XPS surface analysis technology, and the elemental composition of the FeSiAuO can be also determined according to the binding energy of the photoelectron. Since Fe3O4 nanoparticles are coated inside as cores, it is very difficult to detect the energy spectrum peaks of the Fe element. As shown in the Fig. 3, it is clear that the four strong-energy peaks of Si2p, O1s, Au4f and C1s are detected and these signals are derived from the outer cladding-covered SiO2 layer and the modified Au2O3 nanoparticle, which fully proves successful synthesis of composite materials. And the O1s spectrum could be divided into two peaks at 532.5 eV, 529.8 eV from SiO2 and Au2O3, respectively. The Au4f spectrum could be divided into three peaks of Au4f5/2 (87.7 eV), Au4f7/2(86 eV), Au4f7/2(84 eV) from Au2O3 and Au. Most of all, com-pared to the Fig. 3a1 and a2, the peak areas of O and Au for Au2O3 in Fig. 3b1 and b2 are significantly decreased, which can be attributed to the decomposition of Au2O3 under light irradiation. The comparison of Fig. 3a and b also indicate that Au2O3 can decompose into Au and re-leases oxygen up light irradiation. Based on above results, we can infer that the as-prepared nano-carrier possess the ability of
    Magnetic test results of Fe3O4, [email protected] and FeSiAuO samples is given in Fig. 4a, which display the magnetization curves coincide with each other and no hysteresis occurs. Both remanence and coercivity are zero, indicating that the as-prepared samples have super-paramagnetism. According to the sample quality of the test, the sa-turation magnetization of Fe3O4 (test mass is 20.2 mg), [email protected] (test mass is 16.9 mg), FeSiAuO (test mass is 12.1 mg) were calculated as 50.3 emu/g, 9.4 emu/g and 20.6 emu/g, respectively. Magnetic sa-turation of [email protected], FeSiAuO are lower than that of Fe3O4 because Fe3O4 is coated by SiO2 and modified by Au2O3, which further illus-trates the successful preparation of FeSiAuO. 20.6 emu/g of the sa-turation magnetization for FeSiAuO indicates that as-synthesized FeS-iAuO composite nanoparticles still have good magnetic saturation intensity. In addition, the photograph of inset in Fig. 4a shows that the material can be adsorbed by the magnet. Removing the magnetic, the remanence of the material is zero, whose good magnetic responsiveness and redispersibility make it exhibit huge potential in the fields of tar-geting drug release. For drug loading of FeSiAuO sample, high surface