A Near Infrared Light Triggered Hydrogenated Black TiO₂ for Cancer Photothermal Therapy

Abstract

White TiO2 nanoparticles (NPs) have been widely used for cancer photodynamic therapy based on their ultraviolet light-triggered properties. To date, biomedical applications using white TiO2 NPs have been limited, since ultraviolet light is a well-known mutagen and shallow penetration. This work is the first report about hydrogenated black TiO2 (H-TiO2 ) NPs with near infrared absorption explored as photothermal agent for cancer photothermal therapy to circumvent the obstacle of ultraviolet light excitation. Here, it is shown that photothermal effect of H-TiO2 NPs can be attributed to their dramatically enhanced nonradiative recombination. After polyethylene glycol (PEG) coating, H-TiO2 -PEG NPs exhibit high photothermal conversion efficiency of 40.8%, and stable size distribution in serum solution. The toxicity and cancer therapy effect of H-TiO2 -PEG NPs are relative systemically evaluated in vitro and in vivo. The findings herein demonstrate that infrared-irradiated H-TiO2 -PEG NPs exhibit low toxicity, high efficiency as a photothermal agent for cancer therapy, and are promising for further biomedical applications.

Black Titanium Dioxide Nanomaterials in Photocatalysis

“…Oxygen vacancies are undetectable in most white TiO 2 nanomaterials, while oxygen vacancy is considered to be one of the feature defects in most black TiO 2 nanomaterials. Electron paramagnetic resonance (EPR) or electron spin resonance (ESR) spectroscope [37][38][39][40]52], Raman spectroscope [9,16,32,[53][54][55], and X-ray diffractometer [23,32,55] [30,33,37,41,52,55,57,59,60].…”

“…It is likely that surface oxygen vacancies are responsible for the enhanced photocatalytic activity [39,70,75], while bulk oxygen vacancies act as trap states and charge carrier recombination centers [76]. Studies also showed that surface Ti 3+ defects could enhance hole trapping and thus facilitate the separation of photo-excited electrons and holes [57], while bulk Ti 3+ sites acted as charge annihilation centers, leading to enhanced nonradiative recombination and shorter lifetime of electrons and holes [57,60]. In addition, Ti 3+ ions with oxygen vacancies can improve the electrical conductivity of TiO 2 [73,77], which may enhance the charge transport and charge-transfer reaction [73].…”

“…Black TiO 2 Nanomaterials by Hydrogen Plasma. Hydrogen plasma technology has attracted increasing interest owing to its effectiveness in engineering surface-disordered TiO 2 nanomaterials with a typical crystalline/amorphous core/shell structure [33,39,57,60]. Ti 3+ species and oxygen vacancies were reported to be the primary defects in some cases [57,58], while Ti-H groups and oxygen vacancies were believed to be the dominant defects in other cases [33,39].…”

Modifying oxide nanomaterials’ properties by hydrogenation

“…[80,81] Hydrogenated TiO 2 nanoparticles have recently been demonstrated with promising medical application due to their extended absorption in the infrared region. [82,83] They can efficiently convert the near-infrared light energy into thermal energy and produce localized heat island. [82] After they are injected near the cancer cells and irradiated with near-infrared light, the locally produced heat can effectively kill the cancer cells without affecting the adjacent healthy cells.…”

“…[82,83] They can efficiently convert the near-infrared light energy into thermal energy and produce localized heat island. [82] After they are injected near the cancer cells and irradiated with near-infrared light, the locally produced heat can effectively kill the cancer cells without affecting the adjacent healthy cells. [82] This process is named as photothermal therapy.…”