Rational engineering of semiconductor QDs enabling remarkable ¹O₂ production for tumor-targeted photodynamic therapy

Semiconductor quantum dots (QDs) have served as superior optically active nanomaterials for molecular imaging and photodynamic therapy (PDT), but the low singlet oxygen (¹O₂) quantum yield and lack of tumor selectivity have limited their applications for tumor PDT in vivo. Here, we report the rational engineering of QDs into tumor-targeting hybrid nanoparticles through micelle-encapsulating a pre-assembled unique QD-Zn-porphyrin complex, a highly fluorescent organic photosensitizer rhodamine 6G (R6G), and a near-infrared fluorophore NIR775 with folic acid labeled phospholipid polymers. These nanoparticles have large porphyrin payloads and strong light absorption capability, thus contributing to an extremely high ¹O₂ quantum yield (∼0.91) via an efficient dual energy transfer process. In vivo studies show that they can preferably accumulate in tumors through folate receptor-mediated active delivery, permitting non-invasive fluorescence imaging and effective PDT of tumors in living mice. This study highlights the utility of hybrid semiconductor QDs for both tumor imaging and PDT in vivo.