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Congratulations Dr. Shifaa M. A. Siribbal!

Shifaa Siribbal successfully defended her PhD thesis on 11th of July 2016.

Shifaa Siribbal wrote her thesis about the synthesis of Gd2O3 nanoparticles and their use in biomedical applications. The whole research group Mathur congratulates her to the successful defense.



Utilization of nanomaterials is befitting wide areas of research as diverse as chemistry, physics, engineering, materials science, and molecular biology due to their potential in numerous fields of applications, for instance, optics, bioimaging, therapy and drug delivery, and the possibility of combining different functionalities in a single nanosystem. Combination of imaging and therapy capabilities in a single construction is a desired trait for modern nanoprobes useful in nanomedicine. Tailor-made nanomaterials obtained by exploiting the surface chemistry facilitate the conjugation with the drug molecules of interest. Integration of the targeting molecule on the particle surface may enable directed delivery to the malign cells.

In the first step of this research work, single source gadolinium precursors based on new ligands were synthesized to obtain Gd2O3 NPs for bioimaging application. Six new Gd-trifluoro-ß-heteroarylalkenolates and Gd-trifluoro-ß-enaminones compound were prepared from different Gd3+ sources. The crystal structure determination of four complexes elucidated their potential as precursor to Gd2O3 nanoparticles. Gd-trifluoro-ß-heteroarylalkenolates compounds were used as single-source precursor to produce Gd2O3 NPs in a microwave thermal decomposition reaction. The resultant Gd2ONPs were fully characterized for size, morphology, and crystallinity, and  their properties as contrast agents indicated them to be potential candidates for magnetic resonance imaging (MRI).

In the second part of research work, Ag/Gd2Oand Au/Gd2OJanus-type NPs were synthesized for prospective optical and MR imaging. For this purpose, Gd2ONPs were synthesized using homogeneous precipitation method and then functionalized via deposition of Ag and Au NPs on their surface. Successful design of Janus-type NPs was confirmed by microscopic imaging analysis. The XPS analysis was applied to explore the interfacial interaction between the Gd2Oand plasmonic particles of Ag and Au.

In the third part of this work, the synthesis of an efficient bio-conjugated multilayered nanoprobe (Gd2O3@SiO2@Fe3O4) for targeted breast tumor imaging applications was carried out. Nanoprobes were fabricated through different synthetic steps. With a view to reduce the heavy metal toxicity, the surface of Gd2O3@SiO2@Fe3O4 nanoprobe was modified with amine groups using two different ligand molecules (dopamine and APTMS), which provided stabilized and biocompatible NPs. Exterior surface of the as-prepared nanoprobe was further functionalized through click chemistry to covalently immobilize 17α-Ethynylestradiol as a targeting molecule for cancer therapy. Furthermore, the presence of amine moieties on the nanoprobe surface facilitated the conjugation of DOTA-containing 177Lu and 68Ga radioactive nuclides for radiolabeling study. The labeling yield was found to be depend on the nature of ligand molecule.

The fourth part of this thesis deals with hollow Gd2ONPs as nanocarrier for two different model drugs, Congo red (CR) as a drug and Sparfloxacin (SP) as an active antibiotic. The hollow Gd2ONPs were prepared using carbon nanospheres as a hard template. The obtained NPs were efficiently employed for drug delivery of CR molecules, which can be applied for Alzheimer diagnosis and therapy in the future. The release of CR was investigated by UV-vis spectroscopy and cellular internalization of the CR-loaded NPs is examined using Hela cells. In the next step, these NPs were utilized for antimicrobial activity studies by encapsulation of SP. The SP release study and the effect of SP-loaded NPs on gram (+) and gram (-) bacteria showed their potential in inhibition of bacteria growth.