István Hajdu

99mTc-labelled nanosystem as tumour imaging agent for SPECT and SPECT/CT modalities

We report the synthesis, in vitro and in vivo investigation of folate-targeted, biocompatible, biodegradable self-assembled nanoparticles radiolabelled with (99m)Tc, as potential new SPECT or SPECT/CT imaging agent. Nanoparticles with hydrodynamic size in the range of 75-200 nm were prepared by self-assembly of chitosan and folated poly-γ-glutamic acid, and then radiolabelled with (99m)Tc. The nanoparticles target tumour cells overexpressing folate receptors and internalize specifically into them to realize early tumour diagnosis detected by SPECT and SPECT/CT modalities. Rat hepatocellular carcinoma cells were used as model system. Cell specificity and tumour targeting efficacy of these nanosystems were investigated in vitro, and in vivo using SPECT and fusion nanoSPECT/CT imaging. In vitro results showed that the radiolabeled nanosystem was efficiently internalized by tumour cells. Whole-body biodistribution of the new radiolabelled, folate-targeted nanoparticles revealed higher uptake in the tumorous kidney compared to the non-tumorous contralateral side. Uptake by the lungs and thyroids was negligible, which confirmed the stability of the nanoparticles in vivo. In vivo SPECT and SPECT/CT imaging visually reinforced the uptake results and were in accordance with the biodistribution data: the new nanoparticles as a targeted contrast agent improve tumour targeting and are able to detect folate-receptor-overexpressing tumours in animal models with enhanced contrast.

Folate receptor targeted self-assembled chitosan-based nanoparticles for SPECT/CT imaging: Demonstrating a preclinical proof of concept

A new biocompatible, biodegradable, self-assembled chitosan-based nanoparticulate product was successfully synthesized and radiolabeled with technetium-99m, and studied as a potential new SPECT or SPECT/CT imaging agent for diagnosis of folate receptor overexpressing tumors. In the present study we examined the conditions of a preclinical application of this labeled nanosystem in early diagnosis of spontaneously diseased veterinary patient using a human SPECT/CT device. The results confirmed that the nanoparticles accumulated in tumor cells overexpressing folate receptors, contrast agent revealed higher uptake in the tumor for a long time. Preclinical trials verified that the new nanoparticles are able to detect folate-receptor-overexpressing tumors in spontaneously diseased animal models with enhanced contrast.

Cancer cell targeting and imaging with biopolymer-based nanodevices

We report here the synthesis, in vitro and in vivo investigation of magnetic resonance imaging (MRI) active nanoparticles, which target folate receptor overexpressing tumor cells. Self-assembled nanoparticles with a hydrodynamic size of 50-200 nm were prepared from poly-γ-glutamic acid and chitosan biopolymers with Gd-ions. The nanoparticles are biocompatible, non-toxic and stable for several months in aqueous media. In vitro assays using confocal microscopy, flow cytometry and MR imaging on HeLa human cervix carcinoma tumor cells showed that folic acid targeted nanoparticles were internalized specifically in a folate receptor dependent manner. In vivo study confirmed, that, considerable accumulation of nanosystems was found compared with the control animal represented by the MR images. Relaxometry measurements demonstrated that the nanoparticle-Gd complexes drastically change the signal intensity of the tumor cells. Because of the contrast enhancement, they are attractive candidates as potential contrast agents for a variety of diagnostic applications including early diagnosis of tumors.

Preclinical evaluation of melanocortin-1 receptor (MC1-R) specific 68Ga- and 44Sc-labeled DOTA-NAPamide in melanoma imaging

Purpose Alpha melanocyte stimulating hormone (&agr;‐MSH) enhances melanogenesis in melanoma malignum by binding to melanocortin‐1 receptors (MC1‐R). Earlier studies demonstrated that alpha‐MSH analog NAPamide molecule specifically binds to MC1‐R receptor. Radiolabeled NAPamide is a promising radiotracer for the non‐invasive detection of melanin producing melanoma tumors by Positron Emission Tomography (PET). In this present study the MC1‐R selectivity of the newly developed Sc‐44‐labeled DOTA‐NAPamide was investigated in vitro and in vivo using melanoma tumors. Methods DOTA‐NAPamide was labeled with Ga‐68 and Sc‐44 radionuclides. The MC1‐R specificity of Ga‐68‐ and Sc‐44‐labeled DOTA‐NAPamide was investigated in vitro and in vivo using MC1‐R positive (B16‐F10) and negative (A375) melanoma cell lines. For in vivo imaging studies B16‐F10 and A375 tumor‐bearing mice were injected with 44Sc/68Ga‐DOTA‐NAPamide (in blocking studies with &agr;‐MSH) and whole body PET/MRI scans were acquired. Radiotracer uptake was expressed in terms of standardized uptake values (SUVs). Results 44Sc/68Ga‐labeled DOTA‐NAPamide were produced with high specific activity (approx. 19 GBq/&mgr;mol) and with excellent radiochemical purity (99%<). MC1‐R positive B16‐F10 cells showed significantly (p ≤ 0.01) higher in vitro radiotracer accumulation than that of receptor negative A375 melanoma cells. In animal experiments, also significantly (p ≤ 0.01) higher Ga‐68‐DOTA‐NAPamide (SUVmean: 0.38 ± 0.02), and Sc‐44‐DOTA‐NAPamide (SUVmean: 0.52 ± 0.13) uptake was observed in subcutaneously growing B16‐F10 tumors, than in receptor negative A375 tumors, where the SUVmean values of Ga‐68‐DOTA‐NAPamide and Sc‐44‐DOTA‐NAPamide were 0.04 ± 0.01 and 0.07 ± 0.01, respectively. Tumor‐to‐muscle (T/M SUVmean) ratios were approximately 15‐fold higher in B16‐F10 tumor‐bearing mice, than that of A375 tumors, and this difference was also significant (p ≤ 0.01) using both radiotracers after 60 min incubation time. Conclusion Our newly synthesized 44Sc‐labeled DOTA‐NAPamide probe showed excellent binding properties to melanocortin‐1 receptor (MC1‐R) positive melanoma cell and tumors. Due to its high specificity and sensitivity 44Sc‐DOTA‐NAPamide is a promising radiotracer in molecular imaging of malignant melanoma. Graphical abstract Figure. No Caption available.