Targeted and effective photodynamic therapy for cancer using functionalized nanomaterials

Abstract

Photodynamic therapy (PDT) is an emerging, non-invasive therapeutic strategy that involves photosensitizer (PS) drugs and external light for the treatment of diseases. Despite the great progress in PS-mediated PDT, their clinical applications are still hampered by poor water solubility and tissue/cell specificity of conventional PS drugs. Therefore, great efforts have been made towards the development of nanomaterials that can tackle fundamental challenges in conventional PS drug-mediated PDT for cancer treatment. This review highlights recent advances in the development of nano-platforms, in which various functionalized organic and inorganic nanomaterials are integrated with PS drugs, for significantly enhanced efficacy and tumor-selectivity of PDT.

Keywords: Cancer therapy; Inorganic nanomaterials; Nanoparticles; Near-infrared light; Organic nanomaterials; Photodynamic therapy; Photosensitizer; Targeted therapy.

Graphical abstract

Figure 1

Schematic illustration of ICG/Ce6-loaded liposomes as NIR light-activatable PDT agents. Phototoxicity of Ce6 was effectively inactivated by ICG upon irradiation at 660 nm. However, upon irradiation at 808 nm, degradation of ICG makes Ce6 recover its capacity to generate singlet oxygen for PDT. Reproduced with permission from Ref. 28. Copyright 2015, Royal Society of Chemistry.

Figure 2

Schematic illustration of Ce6-loaded HANPs for combined fluorescent imaging and targeted photodynamic therapy. Reproduced with permission from Ref. 35. Copyright 2012, Elsevier Ltd.

Figure 3

Schematic illustration showing the mechanism of FA-GO-PEG/C₆₀ hybrid for synergistic combined PTT and PDT. Reproduced with permission from Ref. 49. Copyright 2015, Royal Society of Chemistry.

Figure 4

Schematic illustration of combined PDT and gene silencing for effective destruction of deep tissue buried tumors using SOD1-silencing siRNA/lipid-coated Au NEs. Reproduced with permission from Ref. 65. Copyright 2015, Elsevier Ltd.

Figure 5

Schematic illustration of trimodality fluorescence/thermal/photoacoustic imaging-guided synergistic photothermal/photodynamic cancer therapy using photosensitizer (Ce6)-encapsulated plasmonic gold vesicles (GVs). Reproduced with permission from Ref. 67. Copyright 2013, American Chemical Society.

Figure 6

Synthetic scheme of (A) PpIX-doped ORMOSIL nanoparticles for two-photon fluorescence imaging and PDT and (B) PEG-coated, IR-820-doped ORMOSIL nanoparticles for in vivo NIR fluorescence imaging. Reproduced with permission from Ref. 70. Copyright 2012, Elsevier Ltd.

Figure 7

Schematic illustration of QD–RLuc8 conjugates for BRET-mediated PDT. The bioluminescent QD–RLuc8 conjugates emit 655 nm photons after coelenterazine addition, which can activate PS-loaded micelles for PDT. Reproduced with permission from Ref. 86. Copyright 2012, Elsevier Ltd.