Dual-modality contrast agents (DMCA), such as radiolabeled magnetic nanoparticles, are promising candidates for a number of diagnostic applications, since they combine the advantages of two different imaging modalities, namely single photon emission computed tomography (SPECT) or positron emission tomography (PET) with magnetic resonance imaging (MRI). The benefit of such a combination relates to the interpretation of the obtained imaging information in a more efficient and accurate way so that underlying diseases are reliably diagnosed at early stages.

The objective of the project focuses on a novel DMCA and refers to synthesis, basic characterization (crystallographic, morphologic etc.), thorough evaluation of the physical properties (radioactivity, magnetization etc.) and eventually both in vitro and in vivo evaluation on donated human blood and animal models. The DMCA consists of magnetic nanoparticles, mainly iron oxides (i.e. magnetite Fe₃O₄ and/or maghemite Fe₂O₃), radiolabeled with gamma-emitting (i.e. Technetium-99m) and/or positron-emitting (i.e. Gallium-68) isotopes. The DMCA is evaluated extensively all the way up to (i) in vitro biocompatibility experiments conducted on donated human blood, (ii) in vivo biodistribution experiments on animal models and (iii) imaging applications in animal models by means of SPECT/MRI and PET/MRI standard modalities.

For the realization of the project, the following experimental techniques are used:
Wet chemistry methods: for the preparation of the DMCA
X-Ray Diffraction (XRD): to crystallographically characterize the starting materials and the DMCA
Superconducting Quantum Interference Device (SQUID): to study the magnetic properties of starting materials and the DMCA.
Atomic Force Microscopy (AFM): to study the morphology of the DMCA and to obtain reliable quantitative information on their geometric characteristics at the nanoscopic level.
Optical Microscopy (OM): to study the morphology of the DMCA and to obtain reliable quantitative information on their geometric characteristics at the microscopic level to check the possible existence of agglomerates.
Standard MRI unit employed in clinical practice.
Experimental small-animal SPECT camera.
Experimental small-animal PET camera.
All ex vivo biodistribution studies on animal models are conducted at the animal experimentation facilities of the Radiochemical Studies laboratory, I.P.R.E.T.E.A, NCSR “Demokritos”, in compliance with European and national legislation. These studies have been further approved by the Ethics Committee of the NCSR “Demokritos” and animal care and procedures followed are in accordance with institutional guidelines and licenses issued by the Department of Agriculture and Veterinary Policies of the Prefecture of Attiki.

Cancer theranostics is a relatively new term that encompasses both diagnosis and treatment. The hindrances of conventional diagnostic and therapeutic agents are plenty, compromising not only the therapeutic process but even the life of the patient. Therefore, the need for more evolved, cancer-specific and effective theranostic tools is imperative. The development of an effective diagnostic but at the same time therapeutic nanosystem would be a major breakthrough in cancer theragnosis.

The aim of this project is to develop a novel theranostic agent with improved properties that will actively target tumor sites. In particular, the proposed radiolabeled functionalized nanocrystal clusters (Co-CNCs) of magnetic nanoparticles (MNPs) will be capable of dual-modality Positron Emission Tomography (PET)/ Magnetic Resonance Imaging (MRI) attributed to the presence of the radioisotope Gallium-68 (⁶⁸Ga) and the MNPs, respectively. Furthermore, the presence of a chemotherapeutic agent is anticipated to induce a strong antineoplasmatic effect while the addition of a pharmacophore enables us to achieve targeted delivery and improved selectivity of the nanostructure. A triple therapeutic effect will be achieved, after targeted delivery of the functionalized MNPs, attributed to the simultaneous presence of the chemotherapeutic agent, the therapeutic radioisotope Lutetium-177 (¹⁷⁷Lu) and the application of magnetic hyperthermia (MH)

Our project is focused on bispecific targeting of prostate cancer cells. We are evaluating a heterodimer which includes PSMA-617 and DOTA-RM2 in its structure and targets both Prostate-Specific Membrane Antigen (PSMA) and Gastrin- Releasing Peptide Receptors (GRPr) (receptors that exist on prostate cancer cells). All three molecules, the heterodimer and both monomers, are radiolabeled with the diagnostic radionuclide Ga-68 and show high labeling levels (>93%). We are performing internalization assays, specific binding and inhibition potency assays (by calculation of IC₅₀). Two different types of cells are used in these in vitro assays, LNCaP (PSMA+, GRPr -) and PC3 (PSMA-, GRPr+). Our future project involves biodistribution studies on healthy experimental animals and pathological tumor models bearing LNCaP and PC3 tumors.

Gold nanoparticles, have been found highly effective in cancer diagnosis and therapy, due to their own physicochemical properties, easy functionalization of their surface with different chemical entities, low toxicity and biocompatibility. On the other hand ^99mTc is used due to the emission of low energy γ-rays (140keV), suitable half-life (6.02 h) and good availability from ⁹⁹Mo/^99mTc generators. The aim of the study, is to radiolabel Gold Nanoparticles (AuNPs) of different sizes with thiol ligands (as an anchor for AuNPs surface) that allow direct labeling with ^99mTc-carbonyls.  Thiols are the most important type of stabilizing molecules for AuNPs of any size because thiols lead to the formation of strong Au-S bonds. After functionalization and radiolabeling of the AuNPs, we perform in vitro stability studies in human serum as well as in cysteine and histidine solutions, in order to evaluate their stability in vivo. Furthermore, cytotoxicity studies to invest the potential toxic effect of the formed complexes, as well as biodistribution studies in tumor-bearing animal models, are carried out.