ZnFe2O4, a semiconductor catalyst with high photocatalytic activity, is ultrasensitive to ultraviolet (UV) light and tumor H2O2 for producing reactive oxygen species (ROS).

To solve the issue of limited penetration depth and overheating of the excited 980 nm near-infrared (NIR) light, and unstable and insufficient loading amount of photosensitizers (PSs) in photodynamic therapy (PDT), we have constructed a well-defined core–shell structured NaGdF4:Yb/Tm@NaGdF4:Yb@NaNdF4:Yb@NaGdF4@mSiO2@TiO2 (UCNPs@mSiO2@TiO2) nanocomposite by coating a layer of TiO2 PSs/photocatalyst on an effective 808 nm-to-UV/visible upconversion luminescent (UCL) core to achieve simultaneous multiple bioimaging and efficient PDT. The design of quenching-shield layer can eliminate the back energy transfer from activator Tm3+ to sensitized Nd3+, thus significantly improving the UCL emission. The high surface area of mesoporous silica-coated UCNPs facilitates the stable and high loading amount of anatase TiO2. In vivo results indicate that 808 nm NIR light-mediated PDT using UCNPs@mSiO2@TiO2 as photosensitizers shows much higher antitumor efficacy than those with 980 nm and UV irradiations due to the higher tissue penetration depth. Meanwhile, the platform itself as an imaging nanoprobe endows the sample with multiple imaging (UCL/CT/MRI) properties. Our work makes great progress toward the integrity of diagnosis and PDT induced by a single 808 nm NIR light.

Here a multifunctional nanoplatform (upconversion nanoparticles (UCNPs)-platinum(IV) (Pt(IV))-ZnFe O , denoted as UCPZ) is designed for collaborative cancer treatment, including photodynamic therapy (PDT), chemotherapy, and Fenton reaction. In the system, the UCNPs triggered by near-infrared light can convert low energy photons to high energy ones, which act as the UV-vis source to simultaneously mediate the PDT effect and Fenton's reaction of ZnFe O nanoparticles. Meanwhile, the Pt(IV) prodrugs can be reduced to high virulent Pt(II) by glutathione in the cancer cells, which can bond to DNA and inhibit the copy of DNA. The synergistic therapeutic effect is verified in vitro and in vivo results. The cleavage of Pt(IV) from UCNPs during the reduction process can shift the larger UCPZ nanoparticles (NPs) to the smaller ones, which promotes the enhanced permeability and retention (EPR) and deep tumor penetration. In addition, due to the inherent upconversion luminescence (UCL) and the doped Yb and Fe in UCPZ, this system can serve as a multimodality bioimaging contrast agent, covering UCL, X-ray computed tomography, magnetic resonance imaging, and photoacoustic. A smart all-in-one imaging-guided diagnosis and treatment system is realized, which should have a potential value in the treatment of tumor.

A hollow structured biophotocatalyst comprising an UCNP core and mesoporous cerium oxide shell was constructed to realize oxygen self-efficient photodynamic therapy upon 980 nm laser irradiation under multiple imaging guidance.