Multifunctional upconversion–nanoparticles–trismethylpyridylporphyrin–fullerene nanocomposite: a near-infrared light-triggered theranostic platform for imaging-guided photodynamic therapy

Photodynamic therapy (PDT) is an excellent therapeutic modality for various malignant and nonmalignant cancers. This approach utilizes reactive oxygen species generated through the reaction between photosensitizer and oxygen in tissues upon light irradiation to achieve effective treatment. However, limited penetration depth and oxygen-deficient microenvironment hinder the efficiency of PDT. In this work, we design a multifunctional near-infrared (NIR)-triggered theranostic agent based on upconversion–nanoparticles-Polyoxyethylene bis (amine)–trismethylpyridylporphyrin–fullerene nanocomposite (UCNP–PEG–FA/PC70) for imaging (fluorescence/upconversion luminescence/magnetic resonance imaging)-guided photodynamic therapy. In this multimodal nanocompsite, UCNPs are employed as light transducers to convert NIR light into ultraviolet–visible light to activate PC70 to generate singlet oxygen (1O2) even under low-oxygen conditions. Meanwhile, the upconversion emission, magnetic resonance imaging and fluorescence signal coming from UCNPs and PC70 nanocomposite enable UCNP–PEG–FA/PC70 to act as a multimodal imaging diagnostic agent, which facilitates the imaging-guided PDT. Furthermore, folate-mediated active targeting would enhance the accumulation of multifunctional hybrid in tumor. In vitro as well as in vivo results suggest that this smart nanocomposite is promising as an NIR light-triggered and -targeted theranostic platform for imaging-guided PDT of cancer, which may provide a solution to the bottleneck problems of PDT, namely, limited penetration depth and oxygen-deficient microenvironment.