Lanthanide-DTPA grafted silica nanoparticles as bimodal-imaging contrast agents.
The design and synthesis of a combined MRI-optical probe for bio-imaging are reported. The materials studied join the properties of lanthanide (Ln(3+)) complexes and nanoparticles (NPs), offering an excellent solution for bimodal imaging. The hybrid SiO(2)@APS/DTPA:Gd:Ln (Ln = Eu(3+) or Tb(3+)) (APS: 3-aminopropyltriethoxysilane, DTPA: diethylenetriamine pentaacetic acid) system increases the payload of the active magnetic centre (Gd(3+)) and introduces a Ln(3+) long-life excited state (Eu(3+): 0.35 ± 0.02 ms, Tb(3+): 1.87 ± 0.02 ms), with resistance to photobleaching and sharp emission bands. The Eu(3+) ions reside in a single low-symmetry site. Although the photoluminescence emission is not influenced by the simultaneous presence of Gd(3+) and Eu(3+), a moderate r(1) increase and a larger enhancement of r(2) are observed, particularly at high fields, due to susceptibility effects on r(2). The presence of Tb(3+) instead of Eu(3+) further raises r(1) but decreases r(2). These values are constant over a wide (5-13) pH range, indicating the paramagnetic NPs stability and absence of leaching. The uptake of NPs by living cells is fast and results in an intensity increase in the T(1)-weighted MRI images. The optical properties of the NPs in cellular pellets are also studied, confirming their potential as bimodal imaging agents.
Department of Chemistry, CICECO, University of Aveiro, 3810-193 Aveiro, Portugal. slpinho@ua.pt
Sonia L C
SL
Pinho
Henrique
H
Faneca
Carlos F G C
CF
Geraldes
Marie-Hélène
MH
Delville
Luís D
LD
Carlos
João
J
Rocha
D000818:Animals; D002460:Cell Line; D003287:Contrast Media / Q000737:chemistry*; D028581:Lanthanoid Series Elements / Q000737:chemistry*; D049449:Luminescence; D008279:Magnetic Resonance Imaging; D051379:Mice; D004369:Pentetic Acid / Q000737:chemistry*; D012822:Silicon Dioxide / Q000737:chemistry*
D003287:Contrast Media; D028581:Lanthanoid Series Elements; D012822:Silicon Dioxide; D004369:Pentetic Acid