Development of silica coated europium doped gadolinium based contrast agents for dual modal imaging of cancer cells

Abstract

There is an alarming increase in the mortality rate due to the cancer all over the world. Cancer diagnosis at the early stage is the key to reduce the mortality rate and for the proper treatment. Magnetic resonance imaging (MRI) is a three dimensional technique to view the soft tissues with high spatial resolution. But the limitation of this technique is its poor sensitivity. To improve the sensitivity, the MRI can be combined with highly sensitive optical imaging. By combining the two imaging modalities, dual modal imaging is achieved. Europium (Eu3+) ions with its superior luminescent properties can be doped into the gadolinium oxide nanoparticles which intrinsically possess favourable magnetic properties for dual modal imaging. Europium doped gadolinium oxide (Eu:Gd2O3) nanoparticles were synthesized by three different techniques such as co-precipitation method, polyol method and microwave-assisted combustion synthesis. In the Chapter 2, the Eu:Gd2O3 nanorods were prepared by using co-precipitation method and then it was coated with silica to increase the biocompatibility. Initially, Eu:Gd(OH)3 nanorods were formed and after the calcination process Eu:Gd2O3 nanorods were produced. In the XRD spectrum, it was noted that the peak position and the intensity matches the standard crystallographic data. Eu:Gd2O3 nanorods posses cubic crystal system with the unit cell parameters a = b = c = 10.82 Å, and#945; = and#946; = and#947; = 90 °, and cell volume = 1266.74 Å3 . The crystallinity of the nanorods decreases after coating with silica. TEM images proves that the prepared Eu:Gd2O3 nanoparticles exhibits rodlike morphology with a length of around 600 nm and a diameter of 40 nm. Silica layer with the thickness of 15 nm was coated over the nanorods. The silica coating was also confirmed by the FTIR studies. Emission peak at 611 nm was observed due to the presence of Eu3+ ions in both the uncoated and silica-coated Eu:Gd2O3 nanorods. The emission intensity of the silica-coated nanorods was found to increase, due to the total internal reflection phenomenon that exists at the silica interface. The color co-ordinates of the uncoated and silica-coated nanorods were found to be (0.63, 0.37) and (0.65, 0.35) respectively. The lifetime of the uncoated and silica-coated nanorods were determined to be 1.16 ms and 0.90 ms respectively. Invitro cytotoxicity of the silica-coated nanorods shows a slight decrease in the cell viability till the concentration of 200 and#956;g/mL. The paramagnetic nature of the uncoated and silica-coated nanorods was confirmed by VSM. Invitro magnetic resonance images of the silica-coated nanorods shows bright contrast images when the concentration is increased. The relaxivity value was calculated to be 3.581 mM-1 s -1 newline