Abstract
Photodynamic therapy (PDT) has been reported as a possible pathway for the treatment of tumors. The exploration for promising PDT systems thus attracts continuous research efforts. This work focused on an ordered core–shell structure encapsulated by mesoporous SiO2 with the upconverting emission property following a surfactant-assisted sol–gel technique. The mesoporous silica shell possessed a high surface area-to-volume ratio and uniform distribution in pore size, favoring photosensitizer (rose bengal) loading. Simultaneously, upconverting nanocrystals were synthesized and used as the core. After modification via hydrophobic silica, the hydrophobic upconverting nanocrystals became hydrophilic ones. Under near-infrared (NIR) light irradiation, the nanomaterials exhibited strong green upconverting luminescence so that rose bengal could be excited to produce singlet oxygen. The photodynamic therapy (PDT) feature was evaluated using a 1O2 fluorescent indicator. It was found that this core–shell structure generates 1O2 efficiently. The novelty of this core–shell structure was the combination of upconverting nanocrystals with a mesoporous SiO2 shell so that photosensitizer rose bengal could be effectively adsorbed in the SiO2 shell and then excited by the upconverting core.
Highlights
The penetration depth of excitation light in a living body is still too short to be applied; some photosensitizer molecules are incompatible with water-based environments; their photostability under excitation light is unsatisfied [4,5,6,7,8]
The application of RE-based upconverting nanomaterials which transform NIR radiation to higher-energy excitation light may offer a new pathway for photodynamic therapy (PDT)
Oleic acid was applied during synthesis to stabilize the formation of β-NaYF4 nanocrystals
Summary
It has been reported that tumor tissues are sensitive to some photosensitive reagents when being exposed to an appropriate irradiation wavelength which makes photodynamic therapy (PDT) a candidate for effective and economical treatment method for body tumors and premalignant conditions [1]. The application of RE-based upconverting nanomaterials which transform NIR radiation to higher-energy excitation light may offer a new pathway for PDT. They present good photostability, low toxicity, and unique emission bands upon NIR excitation [10,11,12,13,14,15].
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