Self-assembled albumin nanoparticles for combination therapy in prostate cancer

Abstract

Resistance to regular treatment strategies is a big challenge in the treatment of castration-resistant prostate cancer. Combination of photothermal and photodynamic therapy (PTT/PDT) with chemotherapy offers unique advantages over monotherapy alone. However, free drugs, such as photosensitizers and chemotherapeutic agents, lack tumor-targeted accumulation and can be easily eliminated from the body. Moreover, most of the PTT drugs are hydrophobic and their organic solvents have in vivo toxicity, thereby limiting their potential in clinical translation. Herein, simple multifunctional nanoparticles (NPs) using IR780 (a near-infrared dye) and docetaxel (DTX)-loaded nanoplatform based on human serum albumin (HSA) (HSA@IR780@DTX) was developed for targeted imaging and for PTT/PDT with chemotherapy for the treatment of castration-resistant prostate cancer treatment. In this platform, HSA is a biocompatible nanocarrier that binds to both DTX and IR780. DTX and IR780, as hydrophobic drug, can induce the self-assembly of HSA proteins. Transmission electron microscopic imaging showed that NPs formed by self-assembly are spherical with a smooth surface with a hydrodynamic diameter of 146.5±10.8 nm. The cytotoxicity of HSA@IR780@DTX NPs with or without laser irradiation in prostate cancer cells (22RV1) was determined via CCK-8 assay. The antitumor effect of HSA@IR780@DTX plus laser irradiation was better than either HSA@IR780@DTX without laser exposure or single PTT heating induced by HSA@IR780 NPs under near-infrared laser, suggesting a significant combined effect in comparison to monotherapy. Near-infrared fluorescence imaging showed that HSA@IR780@DTX NPs could preferentially accumulate in tumors. In vivo therapeutic efficacy experiment showed that xenografted prostate tumors on mice treated with HSA@IR780@DTX plus near-infrared laser irradiation were completely inhibited, whereas tumors on mice treated with chemotherapy alone (HSA@DTX and HSA@IR780@DTX without laser) or PTT/PDT alone (HSA@IR780 with laser) showed moderate growth inhibition. Overall, HSA@IR780@DTX NPs showed notable targeting and theranostic potential for the treatment of castration-resistant prostate cancer.

Keywords: albumin nanoparticles; chemotherapy; combination therapy; photothermal and photodynamic therapy; prostate cancer.

Figure 1

Preparation and characterization of HSA–ICG–DTX complex. (A) TEM images of HAS@DTX, HSA@IR780, and HSA@IR780@DTX. (B) Hydrodynamic diameters of HAS@DTX, HSA@IR780, and HSA@IR780@DTX measured by DLS. (C) UV–Vis–NIR spectra of Free IR780, HAS@DTX, HSA@IR780, and HSA@IR780@DTX. (D) Temperature change of PBS, HSA@IR780, and HSA@IR780@DTX in the irradiation of a NIR laser (808 nm) with a power density of 1 W/cm². (E) Singlet oxygen generation of NPs after NIR laser irradiation. (F) Release profiles of HSA@IR780@DTX with or without laser irradiation. Abbreviations: DTX, docetaxel; FL, fluorescence; HSA, human serum albumin; NIR, near-infrared; PBS, phosphate buffer saline; SOSG, singlet oxygen sensor green; ICG, indocyanine green.

Figure 1

Preparation and characterization of HSA–ICG–DTX complex. (A) TEM images of HAS@DTX, HSA@IR780, and HSA@IR780@DTX. (B) Hydrodynamic diameters of HAS@DTX, HSA@IR780, and HSA@IR780@DTX measured by DLS. (C) UV–Vis–NIR spectra of Free IR780, HAS@DTX, HSA@IR780, and HSA@IR780@DTX. (D) Temperature change of PBS, HSA@IR780, and HSA@IR780@DTX in the irradiation of a NIR laser (808 nm) with a power density of 1 W/cm². (E) Singlet oxygen generation of NPs after NIR laser irradiation. (F) Release profiles of HSA@IR780@DTX with or without laser irradiation. Abbreviations: DTX, docetaxel; FL, fluorescence; HSA, human serum albumin; NIR, near-infrared; PBS, phosphate buffer saline; SOSG, singlet oxygen sensor green; ICG, indocyanine green.

Figure 2

Confocal fluorescence images of ROS generation in MCF-7 cells. From top to bottom: HSA@IR780 NPs, HSA@IR780 NPs plus NIR laser (808 nm, 1 W/cm², 2 min), HSA@IR780@DTX NPs and HSA@IR780@DTX NPs plus NIR laser. The final concentration of HSA@IR780 NPs (calculated as IR780) was 5 µg/mL. The green fluorescence color represents oxidatively stressed cells affected with ROS. Fluorescence images were collected at 510~560 nm, under an excitation at 504 nm. The scale bar is 20 µm. Abbreviations: DTX, docetaxel; HSA, human serum albumin; NIR, near-infrared; NPs, nanoparticles.

Figure 3

Cellular uptake of HSA@IR780 NPs and HSA@IR780@DTX NPs. (A) Confocal fluorescence images of 22RV1 cells localization of HSA@IR780 NPs and HSA@IR780@DTX NPs 45 min post-incubation. Blue fluorescence indicates positive staining of Hochest and red fluorescence is the fluorescence of IR780. (B) Flow cytometry analysis of 22RV1 cell line incubated with PBS, HSA@IR780 NPs, and HSA@IR780@DTX NPs, respectively. Abbreviations: DTX, docetaxel; HSA, human serum albumin; NPs, nanoparticles; PBS, phosphate buffer saline.

Figure 4

In vitro cell experiments. Relative viabilities of 22RV1 cells after incubation with different concentrations of IR780 and DTX in HSA@DTX, HSA@IR780 NPs, and HSA@IR780@DTX NPs with or without 808 nm laser irradiation (1 W/cm², 2 min). Abbreviations: DTX, docetaxel; HSA, human serum albumin; NPs, nanoparticles; NIR, near-infrared.

Figure 5

NIR imaging and biodistribution analysis. (A) The fluorescence images of mice with prostate cancer injected with NPs (the white arrows indicated tumor area). (B) Ex vivo fluorescence images of major organs from those mice at 48 h. (C) Semiquantitative biodistribution of NPs in major organs. The data are shown as mean ± SD (n=3). Abbreviations: NIR, near-infrared; NPs, nanoparticles.

Figure 6

Imaging guided combination therapy on a subcutaneous tumor model. (A) Heating curves of tumor-bearing mice with PBS, HSA@IR780 NPs and HSA@IR780@DTX NPs. Data are expressed as mean ± SD (n=3). (B) The tumor growth curves of different group of mice after various treatments indicated (five mice per group). Error bars were based on standard errors of the mean. (C) Body weight of mice in different group after treatment. Abbreviations: DTX, docetaxel; HSA, human serum albumin; NPs, nanoparticles; PBS, phosphate buffer saline.

Figure 7

Therapeutic efficacy and biosafety evaluation of formed nanoparticles in vivo. Notes: (A) Representative images of mice bearing prostate cancer pre-treatment and after treatments, (B) the corresponding H&E-stained tumor sections, (C) H&E staining of major organs after the treatment of nanoparticles. Abbreviations: DTX, docetaxel; HSA, human serum albumin; NIR, near-infrared; PBS, phosphate buffer saline.

Figure 7

Therapeutic efficacy and biosafety evaluation of formed nanoparticles in vivo. Notes: (A) Representative images of mice bearing prostate cancer pre-treatment and after treatments, (B) the corresponding H&E-stained tumor sections, (C) H&E staining of major organs after the treatment of nanoparticles. Abbreviations: DTX, docetaxel; HSA, human serum albumin; NIR, near-infrared; PBS, phosphate buffer saline.

Scheme 1

A schematic illustration to show the formation of HSA@IR780@DTX nanoparticles by self-assembly between HSA, DTX, and IR780. Abbreviations: HSA, human serum albumin; DTX, docetaxel; PTT, photothermal therapy; PDT, photodynamic therapy; NIR, near-infrared.