Highly luminescent and anti-photobleaching core-shell structure of mesoporous silica and phosphatidylcholine modified superparamagnetic iron oxide nanoparticles

Abstract

Highly fluorescent magnetic nanoparticles (Eu(TTA)3(P(Oct)3)3@mSiO2@SPION) [europium (III) chloride hexahydrate = Eu; 4,4,4-trifluoro-1-(2-thienyl)-1,3-butanedione = TTA; trioctylphosphine = (P(Oct)3); mesoporous silica = mSiO2; superparamagnetic iron oxide nanoparticle = SPION] were developed as a dual-functional imaging agent. The hierarchical structure was composed of a magnetic core and mesoporous silica shell was constructed using a cationic surfactant template after coating with phosphatidylcholine of oleic acid coated SPION. Afterward, the surface and cavities of mSiO2@SPION were modified with 3-(trimethoxysilyl) propyl methacrylate (TMSPMA) as a silane coupling agent to introduce methacrylate groups. Eu(TTA)3(P(Oct)3)3 molecules are penetrated, located and bonded covalently inside of the cavities/mesopores of mSiO2, it shows extremely stable anti-photobleaching properties. The emission spectra of Eu(TTA)3(P(Oct)3)3@mSiO2@SPION indicated typical hypersensitivity transition5D0→7F2 at 621 nm. The concentration of Eu(TTA)3(P(Oct)3)3@mSiO2@SPION was varied between 10 and 500 µL/mL to evaluate the cytotoxicity with NCI-H460 (H460) cells using MTT (3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide) assay. In addition, the presence of a strong red-emitting Eu(TTA)3(P(Oct)3)3@mSiO2@SPION in the cytoplasm was observed by fluorescence microscopy. Those results that it can be a potential candidate for dual-functional contrast agent and PL nanomaterials for fabricating the diagnostic kits to amplify the low signal.