This study reports a single near‑infrared light‑triggered nanoplatform denoted UCNPs@SiO2‑MB@PDA. The construct uses upconversion nanoparticles (UCNPs) as the core, a silica (SiO2) shell loaded with the photosensitizer methylene blue (MB) prepared via an inverse microemulsion method, and a final surface modification with a polydopamine (PDA) layer. The design integrates both photodynamic and photothermal components in one nanosystem to enable multimodal antitumor therapy.
Under 980 nm near‑infrared (NIR) excitation, the UCNP core emits red light. That emission is harnessed in two ways. First, the red emission activates MB via luminescence resonance energy transfer, resulting in generation of singlet oxygen and enabling photodynamic therapy (PDT). Second, the PDA shell absorbs multiple emission bands from the UCNPs and converts the absorbed light into heat, producing photothermal therapy (PTT). Combining these two mechanisms in a single particle is intended to produce synergistic tumor cell killing, particularly useful for treating deeper tumors where direct visible light penetration is limited.
The authors assembled the platform by placing UCNPs at the core, forming a silica shell by an inverse microemulsion technique that encapsulates and loads MB, and then coating the particle surface with PDA. The silica layer acts both as a loading reservoir for the photosensitizer and as a structural shell, while the PDA layer serves as a broadband light absorber and photothermal transducer.
The PDA outer layer absorbs multiband emission from the UCNPs and transforms optical energy into heat. The reported photothermal conversion efficiency for the PDA‑containing nanoplatform under the described conditions is 35.6%. This quantitative efficiency supports the platform’s capacity to produce significant localized heating for PTT in addition to PDT activity from MB activation.
In vitro experiments demonstrated that the material exhibits good biocompatibility and can be effectively internalized by tumor cells. The authors evaluated cellular uptake and viability in HeLa cells, indicating that the nanoplatform is taken up by cells and is tolerated in the absence of NIR activation, consistent with an acceptable biocompatibility profile for in vitro use.
When HeLa cells were exposed to the nanoplatform and subjected to near‑infrared irradiation, the combined PDT/PTT treatment produced markedly greater cytotoxicity than either modality alone. At a particle concentration of 200 μg/mL under NIR light, the HeLa cell survival rate decreased to 18.9%, demonstrating strong antitumor activity attributable to the synergistic effects of singlet oxygen generation and photothermal heating.
Live/dead cell staining assays corroborated the enhanced cell kill observed with combined treatment. The staining results confirmed that the UCNPs@SiO2‑MB@PDA platform produced substantial tumor cell death under NIR irradiation, supporting the interpretation that simultaneous activation of PDT and PTT yields superior antitumor performance compared with monotherapy in this in vitro model.
The UCNPs@SiO2‑MB@PDA nanoplatform couples near‑infrared activation, photodynamic therapy, and photothermal therapy in a single construct. Key reported features include red emission from UCNPs activating MB to generate singlet oxygen, PDA‑mediated photothermal conversion with an efficiency of 35.6%, effective cellular internalization, acceptable in vitro biocompatibility, and potent HeLa cell killing with survival reduced to 18.9% at 200 μg/mL under NIR irradiation. The authors propose this approach as a promising strategy for precise and effective treatment of deep tumors, given the NIR excitation and dual therapeutic mechanisms.
Note: All details above are taken from the source abstract and article metadata. Additional experimental details, in vivo results, long‑term toxicity, and clinical translation considerations were not reported in the provided source text.