UCNPs@gelatin-ZnPc nanocomposite: synthesis, imaging and anticancer properties

To enhance the total emission intensity, particularly the red emission of Yb,Er co-doped nanoparticles for red light activated photodynamic therapy (PDT), we doped Mn²⁺ ions into the NaGdF₄:Yb,Er core, and subsequently coated the NaGdF₄:Yb active shell to fabricate core-shell structured, up-conversion nanoparticles of NaGdF₄:Yb,Er,Mn@NaGdF₄:Yb (abbreviated as UCNPs). A novel and facile encapsulation method with gelatin has been proposed to transfer oleic acid (OA) stabilized UCNPs into an aqueous solution and simultaneously decorate zinc phthalocyanine (ZnPc) photosensitizer molecules. In the encapsulation process, ZnPc molecules are wrapped in the interlaced net structure of the peptide chain from gelatin, forming the UCNPs@gel-ZnPc nanocomposite. The nanoplatform has high emission intensity and excellent biocompatibility, as was expected. More importantly, the enhanced red emission of UCNPs has significant overlap with the UV absorbance of ZnPc; therefore, it can effectively activate the sensitizer to produce a large amount of singlet oxygen reactive oxygen species (ROS, ¹O₂) to kill cancer cells, which has evidently been verified by the in vitro results. Combined with the inherent up-conversion luminescence (UCL) imaging properties, this UCNPs@gel-ZnPc nanoplatform could have potential application in PDT and imaging fields.