Multifunctional amino functionalized graphene quantum dots wrapped upconversion nanoparticles for photodynamic therapy and X-ray CT imaging

[Display omitted] •GQDs modified NaGdF4:Yb/Er (af-GQDs/UCNPs) theranostic potency was investigated.•The nanosystem displayed good dispersibility in water and excellent upconversion efficiency.•The af-GQDs/UCNPs were established as potential contrast agents for X-ray CT imaging.•The nanocomposites induced remarkable ROS generation under laser excitation.•The bi-functional nanosystem offers simultaneous imaging-guided PDT of cancer. Herein, we designed and developed a multifunctional nanocomposites by complexing NaGdF4:Yb/Er nanoparticles (UCNPs) with amino functionalized graphene quantum dots (af-GQDs). In the as-prepared nanocomposite (af-GQD/UCNPs), properties of UCNPs and af-GQDs were incorporated into a single nanoplatform to endow therapeutic and diagnostic functions. The UCNPs were employed as an imaging probe and a contrast agent for CT imaging, and the af-GQDs served as a therapeutic agent and photosensitizer (PS) by generating singlet oxygen for photodynamic therapy (PDT). Furthermore, the nanocomposites were investigated by electron microscopy, FTIR spectroscopy, zeta potential measurement, UV–vis spectroscopy, upconversion luminescence measurement, and cytotoxicity assessment. The in vitro experiments displayed excellent X-ray attenuation ability and PDT effects of af-GQD/UCNPs. Hence, the proposed multifunctional nanocomposites, which possesses upconversion luminescence, photodynamic, and X-ray attenuation properties, might be a viable option for application in bio-imaging and photodynamic therapy.