Phase and Size Controllable Synthesis of NaYbF4 Nanocrystals in Oleic Acid/ Ionic Liquid Two-Phase System for Targeted Fluorescent Imaging of Gastric Cancer

Upconversion nanocrystals with small size and strong fluorescent signals own great potential in applications such as biomolecule-labeling, in vivo tracking and molecular imaging.Herein we reported that NaYbF 4 : 25%Gd, 2%Tm upconversion nanocrystals with small size and strong fluorescent signals were controllably synthesized by oleic acid (OA)/ ionic liquid (IL) two-phase system for targeted fluorescent imaging of gastric cancer in vivo.The optimal synthesis condition of NaYbF 4 : 25%Gd, 2%Tm upconversion nanocrystals by OA/IL two-phase system was established, adding more metal ion such as Na + ion could facilitate the size control and crystal-phase transition, more importantly, markedly enhancing fluorescent intensity of beta-phase nanocrystals compared with traditional methods.Alpha-phase NaYbF 4 , 2%Tm upconversion nanocrystals with less than 10nm in diameter and beta-phase NaYbF 4 : 25%Gd, 2%Tm upconversion nanocrystals with 30 nm or so in diameter and strong fluorescent signals were obtained, these synthesized nanocrystals exhibited very low cytotoxicity.Folic acid-conjugated silica-modified beta-phase NaYbF 4 : 25%Gd, 2%Tm upconversion nanocrystals were prepared, could actively target gastric cancer tissues implanted into nude mice in vivo, and realized targeted fluorescent imaging.Folic acid-conjugated silica-modified NaYbF 4 : 25%Gd, 2%Tm upconversion nanocrystals show great potential in applications such as targeted near infared radiation fluorescent imaging, magnetic resonance imaging and targeted therapy of gastric cancer in the near future.