Perfluorocarbons-Based 19F Magnetic Resonance Imaging in Biomedicine.

Fluorine-19 (19F) magnetic resonance (MR) molecular imaging is a promising noninvasive and quantitative molecular imaging approach with intensive research due to the high sensitivity and low endogenous background signal of the 19F atom in vivo. Perfluorocarbons (PFCs) have been used as blood substitutes since 1970s. More recently, a variety of PFC nanoparticles have been designed for the detection and imaging of physiological and pathological changes. These molecular imaging probes have been developed to label cells, target specific epitopes in tumors, monitor the prognosis and therapy efficacy and quantitate characterization of tumors and changes in tumor microenvironment noninvasively, therefore, significantly improving the prognosis and therapy efficacy. Herein, we discuss the recent development and applications of 19F MR techniques with PFC nanoparticles in biomedicine, with particular emphasis on ligand-targeted and quantitative 19F MR imaging approaches for tumor detection, oxygenation measurement, smart stimulus response and therapy efficacy monitoring, et al.

19F MRI in orthotopic cancer model via intratracheal administration of ανß3-targeted perfluorocarbon nanoparticles.

AIM: To demonstrate the feasibility of intratracheal administration in orthotopic lung cancer model with 19F MRI. MATERIALS & METHODS: αvß3-integrin targeting ability of the perfluorocarbon (PFC) nanoparticles was tested. Orthotopic lung cancer model was established in rabbits under computed tomography guidance. αvß3-targeted PFC nanoparticles were administrated intratracheally or intravenously, and 19F MRI was performed before and up to 24 h after administration. RESULTS: The targeted PFC nanoparticles could bind with αvß3-integrin. PFC concentrations in the tumors of intratracheal group after administration were significantly higher than intravenous group. CONCLUSION: Intratracheal administration of PFC nanoparticles was shown to be feasible and efficacious. 19F MRI with αvß3-targeted PFC nanoparticles provided quantitative assessment of nanoparticles distribution and tumor angiogenesis.

Imaging c-Met expression using 18F-labeled binding peptide in human cancer xenografts.

OBJECTIVES: c-Met is a receptor tyrosine kinase shown inappropriate expression and actively involved in progression and metastasis in most types of human cancer. Development of c-Met-targeted imaging and therapeutic agents would be extremely useful. Previous studies reported that c-Met-binding peptide (Met-pep1, YLFSVHWPPLKA) specifically targets c-Met receptor. Here, we evaluated 18F-labeled Met-pep1 for PET imaging of c-Met positive tumor in human head and neck squamous cell carcinoma (HNSCC) xenografted mice. METHODS: c-Met-binding peptide, Met-pep1, was synthesized and labeled with 4-nitrophenyl [18F]-2-fluoropropionate ([18F]-NPFP) ([18F]FP-Met-pep1). The cell uptake, internalization and efflux of [18F]FP-Met-pep1 were assessed in UM-SCC-22B cells. In vivo pharmacokinetics, blocking and biodistribution of the radiotracers were investigated in tumor-bearing nude mice by microPET imaging. RESULTS: The radiolabeling yield for [18F]FP-Met-pep1 was over 55% with 97% purity. [18F]FP-Met-pep1 showed high tumor uptake in UM-SCC-22B tumor-bearing mice with clear visualization. The specificity of the imaging tracer was confirmed by significantly decreased tumor uptake after co-administration of unlabeled Met-pep1 peptides. Prominent uptake and rapid excretion of [18F]FP-Met-pep1 was also observed in the kidney, suggesting this tracer is mainly excreted through the renal-urinary routes. Ex vivo biodistribution showed similar results that were consistent with microPET imaging data. CONCLUSIONS: These results suggest that 18F-labeled c-Met peptide may potentially be used for imaging c-Met positive HNSCC cancer in vivo and for c-Met-targeted cancer therapy.

Folate receptor-targeted 19 F MR molecular imaging and proliferation evaluation of lung cancer.

BACKGROUND: Folate receptors (FRs) hold great potential as important diagnostic and prognostic biological marker for cancer. PURPOSE: To assess the targeted capability of the FR-targeted perfluorocarbon (PFC) nanoparticles and to assess in vivo the relationship between FR expression and tumor proliferation with fluorine-19 (19 F) MR molecular imaging. STUDY TYPE: Prospective animal cancer model. ANIMAL MODEL: H460 (n = 14) and A549 (n = 14) nude mice subcutaneous tumor models. FIELD STRENGTH: 9.4T, 1 H and 19 F RARE sequences. ASSESSMENT: Intracellular uptake of the PFC nanoparticles was tested in H460 and A549 cell lines. 19 F MRI of H460 and A549 subcutaneous tumors was performed following intravenous injection of PFC nanoparticles. The concentration of PFC in tumors were compared. 3'-Deoxy-3'-18 F-fluorothymidine (18 F-FLT) positron emission tomography / computed tomography (PET/CT) imaging, Ki-67, and proliferating cell nuclear antigen (PCNA) staining were performed to confirm tumor proliferation. STATISTICAL TESTS: One-way or two-way analysis of variance. P < 0.05 was considered a significant difference. RESULTS: The diameter of the FR-targeted nanoparticles was 108.8 ± 0.56 nm, and the zeta potential was -58.4 ± 10.8 mV. H460 cells incubated with FR-targeted nanoparticles showed ∼59.87 ± 3.91% nanoparticles-labeled, which is significantly higher than the other groups (P < 0.001). The PFC concentration in H460 tumors after injection with FR-targeted nanoparticles was 4.64 ± 1.21, 8.04 ± 1.38, and 9.16 ± 2.56 mmol/L at 8 hours, 24 hours, and 48 hours, respectively (P < 0.05 compared to others). The ratio of 18 F-FLT uptake for H460 and A549 tumors was 3.32 ± 0.17 and 1.48 ± 0.09 (P < 0.05), and there was more Ki-67 and PCNA in H460 tumor than A549. DATA CONCLUSION: 19 F MRI with FR-targeted PFC nanoparticles can be used in differentiating of FR-positive and FR-negative tumors, and further, in evaluation of the two cancer models proliferation. LEVEL OF EVIDENCE: 1 Technical Efficacy: Stage 2 J. Magn. Reson. Imaging 2018;48:1617-1625.