Bi-specific T1 positive-contrast-enhanced magnetic resonance imaging molecular probe for hepatocellular carcinoma in an orthotopic mouse model

BACKGROUND Hepatocellular carcinoma(HCC)is the second leading cause of cancer-related mortality.HCC-targeted magnetic resonance imaging(MRI)is an effective noninvasive diagnostic method that involves targeting clinically-related HCC biomarkers,such as alpha-fetoprotein(AFP)or glypican-3(GPC3),with iron oxide nanoparticles.However,in vivo studies of HCC-targeted MRI utilize single-target iron oxide nanoprobes as negative(T2)contrast agents,which might weaken their future clinical applications due to tumor heterogeneity and negative MRI contrast.Ultra-small superparamagnetic iron oxide(USPIO)nanoparticles(approximately 5 nm)are potential optimal positive(T1)contrast agents.We previously verified the efficiency of AFP/GPC3-double-antibody-labeled iron oxide MR molecular probe in vitro.AIM To validate the effectiveness of a bi-specific probe in vivo for enhancing T1-weighted positive contrast to diagnose the early-stage HCC.METHODS The single-and double-antibody-conjugated 5-nm USPIO probes,including antiAFP-USPIO(UA),anti-GPC3-USPIO(UG),and anti-AFP-USPIO-anti-GPC3(UAG),were synthesized.T1-and T2-weighted MRI were performed on day 10 after establishment of the orthotopic HCC mouse model.Following intravenous injection of U,UA,UG,and UAG probes,T1-and T2-weighted images were obtained at 12,12,and 32 h post-injection.At the end of scanning,mice were euthanized,and a histologic analysis was performed on tumor samples.RESULTS T1-and T2-weighted MRI showed that absolute tumor-to-background ratios in UAG-treated HCC mice peaked at 24 h post-injection,with the T1-and T2-weighted signals increasing by 46.7%and decreasing by 11.1%,respectively,relative to pre-injection levels.Additionally,T1-weighted contrast in the UAG-treated group at 24 h post-injection was enhanced 1.52-,2.64-,and 4.38-fold compared to those observed for single-targeted anti-GPC3-USPIO,anti-AFP-USPIO,and nontargeted USPIO probes,respectively.Comparison of U-,UA-,UG-,and UAG-treated tumor sections revealed that UAG-treated mice exhibited increased stained regions compared to those observed in UG-or UA-treated mice.CONCLUSION The bi-specific T1-positive contrast-enhanced MRI probe(UAG)for HCC demonstrated increased specificity and sensitivity to diagnose early-stage HCC irrespective of tumor size and/or heterogeneity.

Tracking of Labelled Stem Cells Using Molecular MR Imaging in a Mouse Burn Model <i>in Vivo</i>as an Approach to Regenerative Medicine

Therapies based on stem cell transplants offer significant potential in the field of regenerative medicine. Monitoring the fate of the transplanted stem cells in a timely manner is considered one of the main limitations for long-standing success of stem cell transplants. Imaging methods that visualize and track stem cells in vivo non-invasively in real time are helpful towards the development of successful cell transplantation techniques. Novel molecular imaging methods which are non-invasive particularly such as MRI have been of great recent interest. Hence, mouse models which are of clinical relevance have been studied by injecting contrast agents used for labelling cells such as super-paramagnetic iron-oxide (SPIO) nanoparticles for cellular imaging. The MR techniques which can be used to generate positive contrast images have been of much relevance recently for tracking of the labelled cells. Particularly when the off-resonance region in the vicinity of the labeled cells is selectively excited while suppressing the signals from the non-labeled regions by the method of spectral dephasing. Thus, tracking of magnetically labelled cells employing positive contrast in vivo MR imaging methods in a burn mouse model in a non-invasive way has been the scope of this study. The consequences have direct implications for monitoring labeled stem cells at some stage in wound healing. We suggest that our approach can be used in clinical trials in molecular and regenerative medicine.