Photodynamic therapy (PDT) is a promising treatment modality for cancer management. So far, most PDT studies have focused on delivery of photo­sensitizers to tumors. O₂, another essential component of PDT, is not artificially delivered but taken from the biological milieu. However, cancer cells demand a large amount of O₂ to sustain their growth and that often leads to low O₂ levels in tumors. The PDT process may further potentiate the oxygen deficiency, and in turn, adversely affect the PDT efficiency. In the present study, a new technology called red blood cell (RBC)-facilitated PDT, or RBC-PDT, is introduced that can potentially solve the issue. As the name tells, RBC-PDT harnesses erythrocytes, an O₂ transporter, as a carrier for photosensitizers. Because photosensitizers are adjacent to a carry-on O₂ source, RBC-PDT can efficiently produce ¹O₂ even under low oxygen conditions. The treatment also benefits from the long circulation of RBCs, which ensures a high intraluminal concentration of photosensitizers during PDT and hence maximizes damage to tumor blood vessels. When tested in U87MG subcutaneous tumor models, RBC-PDT shows impressive tumor suppression (76.7%) that is attributable to the codelivery of O₂ and photosensitizers. Overall, RBC-PDT is expected to find wide applications in modern oncology.

Gd-encapsulated carbonaceous dots (Gd@C-dots) hold great potential in clinical applications as a novel type of T₁ contrast agent for magnetic resonance imaging (MRI). However, current synthetic methods require multiple purification steps due to poor size control, making them unsuitable for high throughput. Herein, a novel, mesoporous silica nanoparticle (MSN)-templated method for the size-controlled synthesis of Gd@C-dots is reported. Briefly, MSNs nanoreactors of different pore sizes are loaded with Gd precursors. Upon calcination, carbon layers are grown around the Gd cations. The spatial restraint of the silica cavity facilitates size control of the produced Gd@C-dots. Specifically, using 3, 7, and 11 nm MSNs as templates allows the synthesis of 3.0, 7.4, and 9.6 nm Gd@C-dots, respectively. A significant size impact on the magnetic and optical properties of the nanoparticles is shown, with the smallest Gd@C-dots showing the highest r₁ relaxivity (10 mM⁻¹ s⁻¹) and fluorescence quantum yield (30.2%). The 3.0-nm Gd@C-dots were then conjugated with a tumor-targeting ligand, c(RGDyK), and injected into U87MG xenograft tumor models. Good tumor targeting was observed in T₁-weighted MRI images; whereby the unbound nanoparticles were efficiently excreted through renal clearance, avoiding long-term toxicity to the host.