Semimetal nanomaterials of antimony as highly efficient agent for photoacoustic imaging and photothermal therapy

Abstract

In this study we report semimetal nanomaterials of antimony (Sb) as highly efficient agent for photoacoustic imaging (PAI) and photothermal therapy (PTT). The Sb nanorod bundles have been synthesized through a facile route by mixing 1-octadecane (ODE) and oleyl amine (OAm) as the solvent. The aqueous dispersion of PEGylated Sb NPs, due to its broad and strong photoabsorption ranging from ultraviolet (UV) to near-infrared (NIR) wavelengths, is applicable as a photothermal agent driven by 808 nm laser with photothermal conversion efficiency up to 41%, noticeably higher than most of the PTT agents reported before. Our in vitro experiments also showed that cancer cell ablation effect of PEGylated Sb NPs was dependent on laser power. By intratumoral administration of PEGylated Sb NPs, 100% tumor ablation can be realized by using NIR laser irradiation with a lower power of 1 W/cm(2) for 5 min (or 0.5 W/cm(2) for 10 min) and no obvious toxic side effect is identified after photothermal treatment. Moreover, intense PA signal was also observed after intratumoral injection of PEGylated Sb NPs and NIR laser irradiation due to their strong NIR photoabsorption, suggesting PEGylated Sb NPs as a potential NIR PA agent. Based on the findings of this work, further development of using other semimetal nanocrystals as highly efficient NIR agents can be achieved for vivo tumor imaging and PTT.

Keywords: Antimony; Nanorod bundles; Photoacoustic imaging (PAI); Photothermal therapy (PTT); Semimetal.

Figure 1

(a) TEM (left), HRTEM (top right) and SAED (bottom right) images of the as-prepared Sb NPs, (b) XRD and (c) EDS of the as-prepared Sb NPs.

Figure 2

(a) UV–vis-NIR absorption spectra of PEGylated Sb NPs. The inset is a image of PEGylated Sb NPs aqueous solution with concentration of 0.25 mg/mL. (b) Temperature variation of pure water and PEGylated Sb NPs solutions with various concentrations versus laser irradiation time. (c) The photothermal response of PEGylated Sb NPs solution irradiated under an 808 nm laser at 2 W/cm² for 300 s, then the laser was turned off. (d) Linear relationship between time and −lnθ obtained from the cooling time of (c).

Figure 3

(a) Relative viabilities of 4T1 tumor cells and hepatic L02 cells after incubation with PEGylated Sb NPs at various concentrationsfor 24 h. (b) Fluorescence images of Calceine AM/PI stained 4T1 cancer cells without and with PEGylated Sb NPs (100 μg/mL) incubation after irradiated under the 808 nm laser at0.5, 1 and 2 W/cm². (c) Relative viabilities of 4T1 cancer cells with and without PEGylated Sb NPs caused photothermal destruction at various laser power densities. The standard deviations of five parallel samples were used to determine the error bars.

Figure 4

(a) IR thermal images of 4T1 tumor mice with and without PEGylated Sb NPs injection before and after the 808 nm laser irridiation at 1 W/cm² for 5 min. (b) The temperature variation on tumors of mice with and without PEGylated Sb NPs injection after the 808 nm laser irradiation at 1 W/cm². (c) PA imaging of mice bearing 4T1 tumors without and with 40 μg PEGylated Sb NPs injection under the irradiation of NIR laser with different wavelengths. (d) PA signal intensity ratio of 10 min after 40 μg PEGylated Sb NPs injection vs before injection at different wavelengths of 808, 730 and 680 nm.

Figure 5

(a) The 4T1 tumor growth curves of mice after various treatments. The tumor volumes were normalized to their initial tumor sizes. Laser wavelength = 808 nm; irradiation time = 5 min (1 W/cm²) or 10 min (0.5 W/cm²). Standard deviations of 5–7 mice per group were used to determine error bars. (b) Survival curves of 4T1 tumor mice after various treatments. (c) Representative photographs of 4T1 tumor-bearing mice after various treatments. (d) H&E stained tumor slices collected from different groups of mice immediately after 808 nm laser irradiation.