Abstract
Titanium dioxide nanoparticles (TiO2-NPs) are highly efficient photosensitizers in traditional photodynamic therapy (PDT). The particle size of TiO2-NPs is small, only about 20 nm. However, the demands of ultraviolet light (UV) excitation feature shallow tissue penetration depth and may lead to severe tissue photon damage. Thus, in this research, TiO2-NPs are modified with semiconductor quantum dots (QDs) CdX (X = S, Te, Se) in various methods, such as ultrasonic, hydrothermal, sol-gel, aqueous phase, and hydrolysis precipitation. The transmission electron microscopy (TEM) images show that the size of CdSe-TiO2 is ranging from 6 to 14 nm. The ultraviolet-visible (UV-Vis) spectrum demonstrates that the CdX (X = S, Te, Se) modification can successfully extend the absorption range of TiO2-NPs into a different visible light region. CdSe QDs have the narrowest band gap compared with CdX (X = S, Te, Se) QDs. Visible light-activated CdSe-TiO2 nanocomposite shows the highest PDT inactivation efficiency toward HL60 cells compared with CdX-TiO2. The photogenerated carrier separation efficiency of CdSe-TiO2 nanocomposite is the highest shown in a fluorescence spectrum (FS). Furthermore, when conjugated with folic acid (FA), the prepared FA-CdX-TiO2 (X = S, Se) exhibits excellent cancer-targeting ability during PDT treatment. Optimum PDT efficiency of FA-CdSe-TiO2 indicates that photocatalytic and targeting ability is much higher than pure TiO2 and CdSe-TiO2. Our results provided a detailed investigation on the PDT performance of CdX (X = S, Te, Se) modified TiO2 and may act as a guide for further design of highly targeted performance visible-light response TiO2-NPs.
Highlights
Photodynamic therapy (PDT) is a nontoxic, noninvasive treatment [1]
Titanium dioxide was modified with quantum dots such as CdS, CdTe, and CdSe, and the particle size and spectral response range of novel nanocomposites were explored by a transmission electron microscope (TEM), XRay Diffraction pattern (XRD), and ultraviolet light (UV)-visible absorption spectrum (UV-Vis)
Results of Fourier transform infrared spectroscopy (FT-IR) indicated folic acid (FA) compounds combine with CdX-TiO2 NPs in the form of esterification
Summary
Photodynamic therapy (PDT) is a nontoxic, noninvasive treatment [1]. Photodynamic therapy is based on the local or systemic administration of photosensitizer, which accumulates intensively in pathological tissues [2,3,4]. Due to the high band gap energy (3.2 eV) of TiO2, the visible light response is ineffective and fast recombination of the electron-hole generated on the surface, which limits the PDT efficiency of titanium dioxide in practical application [11, 12]. As reported in our previous work, coupling TiO2 with low band gap energy metal or nonmetal to form a heterostructure is a feasible strategy to extend the visible light response range of TiO2-based nanocomposites and improve the photocatalytic performance [13,14,15,16]. Our studies further explore and reveal the mechanism of high photocatalytic activity, cancer-targeting functionality, and potential therapeutic effect of CdX-TiO2 nanocomposite modified with folic acid on PDT inactivating HL60 cells in vitro (Figure 1). CdX (X = S, Te, Se) modification can improve the PDT inactivation efficiency of TiO2-NPs in visible light irradiation. TiO2 and may act as a guide for further design of high targeting ability TiO2-NPs in visible light response
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