Characteristics of magnetic labeling on liver tumors with anti-alpha-fetoprotein-mediated Fe3O4 magnetic nanoparticles

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 anti-AFP-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 non-targeted 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.

ENO1-targeted superparamagnetic iron oxide nanoparticles for detecting pancreatic cancer by magnetic resonance imaging

The aim of this study was to investigate in vitro magnetic resonance imaging (MRI) of PDAC using ENO1‐targeted superparamagnetic iron oxide nanoparticles and xenograft models. Expression level and location of ENO1 protein in pancreatic cancer cell lines of CFPAC‐1 and MiaPaCa‐2 were detected by Western blotting, flow cytometry and confocal microscopy. Dex‐g‐PCL/SPIO nanoparticles targeting ENO1 were constructed with ENO1 antibody and characterized by MRI. In addition, ENO1‐Dex‐g‐PCL/SPIO nanoparticles were tested to assess their efficacy on the detection of PDAC using in vitro and in vivo MRI. The results showed that ENO1 was expressed in both human PDAC cell lines of CFPAC‐1 and MiaPaCa‐2, demonstrating that the localization of cytoplasm and membrane was dominant. It was confirmed that ENO1 antibody was connected to the SPIO surface in ENO1‐Dex‐g‐PCL/SPIO nanoparticles. The nanoparticles had satisfactory superparamagnetism and significantly enhance the detection of PDAC by in vivo and in vitro MRI. In conclusion, ENO1 can serve as a membrane protein expressed on human PDAC cell lines. ENO1‐targeted SPIO nanoparticles using ENO1 antibody can increase the efficiency of detection of PDAC by in vitro and in vivo MRI.

Development and in vitro study of a bi-specific magnetic resonance imaging molecular probe for hepatocellular carcinoma

BACKGROUND

Hepatocellular carcinoma (HCC) ranks second in terms of cancer mortality worldwide. Molecular magnetic resonance imaging (MRI) targeting HCC biomarkers such as alpha-fetoprotein (AFP) or glypican-3 (GPC3) offers new strategies to enhance specificity and help early diagnosis of HCC. However, the existing iron oxide nanoparticle-based MR molecular probes singly target AFP or GPC3, which may hinder their efficiency to detect heterogeneous micro malignant HCC tumors < 1 cm (MHCC). We hypothesized that the strategy of double antibody-conjugated iron oxide nanoparticles which simultaneously target AFP and GPC3 antigens may potentially be used to overcome the tumor heterogeneity and enhance the detection rate for MRI-based MHCC diagnosis.

AIM

To synthesize an AFP/GPC3 double antibody-labeled iron oxide MRI molecular probe and to assess its impact on MRI specificity and sensitivity at the cellular level.

METHODS

A double antigen-targeted MRI probe for MHCC anti-AFP–USPIO–anti-GPC3 (UAG) was developed by simultaneously conjugating AFP andGPC3 antibodies to a 5 nm ultra-small superparamagnetic iron oxide nanoparticle (USPIO). At the same time, the singly labeled probes of anti-AFP–USPIO (UA) and anti-GPC3–USPIO (UG) and non-targeted USPIO (U) were also prepared for comparison. The physical characterization including morphology (transmission electron microscopy), hydrodynamic size, and zeta potential (dynamic light scattering) was conducted for each of the probes. The antigen targeting and MRI ability for these four kinds of USPIO probes were studied in the GPC3-expressing murine hepatoma cell line Hepa1-6/GPC3. First, AFP and GPC3 antigen expression in Hepa1-6/GPC3 cells was confirmed by flow cytometry and immunocytochemistry. Then, the cellular uptake of USPIO probes was investigated by Prussian blue staining assay and in vitro MRI (T2-weighted and T2-map) with a 3.0 Tesla clinical MR scanner.

RESULTS

Our data showed that the double antibody-conjugated probe UAG had the best specificity in targeting Hepa1-6/GPC3 cells expressing AFP and GPC3 antigens compared with single antibody-conjugated and unconjugated USPIO probes. The iron Prussian blue staining and quantitative T2-map MRI analysis showed that, compared with UA, UG, and U, the uptake of double antigen-targeted UAG probe demonstrated a 23.3% (vs UA), 15.4% (vs UG), and 57.3% (vs U) increased Prussian stained cell percentage and a 14.93% (vs UA), 9.38% (vs UG), and 15.3% (vs U) reduction of T2 relaxation time, respectively. Such bi-specific probe might have the potential to overcome tumor heterogeneity. Meanwhile, the coupling of two antibodies did not influence the magnetic performance of USPIO, and the relatively small hydrodynamic size (59.60 ± 1.87 nm) of double antibody-conjugated USPIO probe makes it a viable candidate for use in MHCC MRI in vivo, as they are slowly phagocytosed by macrophages.

CONCLUSION

The bi-specific probe presents enhanced targeting efficiency and MRI sensitivity to HCC cells than singly- or non-targeted USPIO, paving the way for in vivo translation to further evaluate its clinical potential.

Detecting GPC3-Expressing Hepatocellular Carcinoma with L5 Peptide-Guided Pretargeting Approach: In Vitro and In Vivo MR Imaging Experiments

Objective

To investigate the potential of L5 peptide-guided pretargeting approach to identify GPC3-expressing hepatocellular carcinoma (HCC) using ultrasmall superparamagnetic iron oxide (USPIO) as the MR probe.

Methods

Immunofluorescence with carboxyfluorescein- (FAM-) labeled L5 peptide was performed in HepG2 cells. Polyethylene glycol-modified USPIO (PEG-USPIO) and its conjugation with streptavidin (SA-PEG-USPIO) were synthesized, and their hydrodynamic diameters, zeta potential, T₂ relaxivity, and cytotoxicity were measured. In vitro and in vivo two-step pretargeting MR imaging was performed on HepG2 cells and tumor-bearing mice after the administration of biotinylated L5 peptide (first step), followed by SA-PEG-USPIO (second step). Prussian blue staining was performed to assess iron deposition in tumors.

Results

The high specificity of L5 peptide for GPC3 was demonstrated. Generation of SA-PEG-USPIO nanoparticles with good biocompatibility (an average hydrodynamic diameter of 35.97 nm and a zeta potential of -7.91 mV), superparamagnetism (R ₂ = 0.1039 × 10³ mM^-1s^-1), and low toxicity was achieved. The pretargeting group showed more enhancement than the nonpretargeting group both in vitro (60% vs 20%, P < 0.05) and in vivo (32% vs 6%, P < 0.001). Substantial iron deposition was only observed in HepG2 cells and tumors in the pretargeting group.

Conclusion

L5 peptide-guided, two-step pretargeting approach with USPIO as the MR imaging probe is a lucrative strategy to specifically identify GPC3-expressing HCC.

Characterizations of Anti-Alpha-Fetoprotein-Conjugated Magnetic Nanoparticles Associated with Alpha-Fetoprotein for Biomedical Applications

In this work, we report characterizations of biofunctionalized magnetic nanoparticles (BMNPs) associated with alpha-fetoprotein (AFP) for biomedical applications. The example BMNP in this study is anti-alpha-fetoprotein (anti-AFP) conjugated onto dextran-coated Fe₃O₄ labeled as Fe₃O₄-anti-AFP, and the target is AFP. We characterize magnetic properties, such as increments of magnetization ΔM_H and effective relaxation time Δτ_eff in the reaction process. It is found that both ΔM_H and Δτ_eff are enhanced when the concentration of AFP, Ф_AFP, increases. The enhancements are due to magnetic interactions among BMNPs in magnetic clusters, which contribute extra M_H after the association with M_H and in turn enhance τ_eff. The screening of patients carrying hepatocellular carcinoma (HCC) is verified via ΔM_H/M_H. The proposed method can be applied to detect a wide variety of analytes. The scaling characteristics of ΔM_H/M_H show the potential to develop a vibrating sample magnetometer system with low field strength for clinic applications.

Lung Cancer-Targeting Peptides with Multi-subtype Indication for Combinational Drug Delivery and Molecular Imaging

Lung cancer is the leading cause of cancer-related death worldwide. Most targeted drugs approved for lung cancer treatment are tyrosine kinase inhibitors (TKIs) directed against EGFR or ALK, and are used mainly for adenocarcinoma. At present, there is no effective or tailored targeting agent for large cell carcinoma (LCC) or small cell lung cancer (SCLC). Therefore, we aimed to identify targeting peptides with diagnostic and therapeutic utility that possess broad subtype specificity for SCLC and non-small cell lung cancer (NSCLC). We performed phage display biopanning of H460 LCC cells to select broad-spectrum lung cancer-binding peptides, since LCC has recently been categorized as an undifferentiated tumor type within other histological subcategories of lung cancer. Three targeting phages (HPC1, HPC2, and HPC4) and their respective displayed peptides (HSP1, HSP2, and HSP4) were able to bind to both SCLC and NSCLC cell lines, as well as clinical specimens, but not to normal pneumonic tissues. In vivo optical imaging of phage homing and magnetic resonance imaging (MRI) of peptide-SPIONs revealed that HSP1 was the most favorable probe for multimodal molecular imaging. Using HSP1-SPION, the T2-weighted MR signal of H460 xenografts was decreased up to 42%. In contrast to the tight binding of HSP1 to cancer cell surfaces, HSP4 was preferentially endocytosed and intracellular drug delivery was thereby effected, significantly improving the therapeutic index of liposomal drug in vivo. Liposomal doxorubicin (LD) conjugated to HSP1, HSP2, or HSP4 had significantly greater therapeutic efficacy than non-targeting liposomal drugs in NSCLC (H460 and H1993) animal models. Combined therapy with an HSP4-conjugated stable formulation of liposomal vinorelbine (sLV) further improved median overall survival (131 vs. 84 days; P = 0.0248), even in aggressive A549 orthotopic models. Overall, these peptides have the potential to guide a wide variety of tailored theranostic agents for targeting therapeutics, non-invasive imaging, or clinical detection of SCLC and NSCLC.

Ultrasound-Induced Magnetic Imaging of Tumors Targeted by Biofunctional Magnetic Nanoparticles

Biofunctional magnetic nanoparticles (MNPs) have been widely applied in biomedical engineering. MNPs are used as a contrast medium in magnetic imaging. Current methods of magnetic imaging, such as magnetic particle imaging and magnetic relaxometry, use small amounts of MNPs at target points far from the surface of the patient's body; these methods always consume considerable power to produce magnetic fields of high uniformity or gradient excitations. Some drawbacks, such as a limited imaging region, imaging system shielding, and complex algorithms based on assumptions of MNP properties or environmental factors, also limit the application of MNP methods in clinics. Therefore, this work proposes an interdisciplinary methodology of ultrasound-induced magnetic imaging that lacks these drawbacks. In the proposed imaging method, magnet sets were designed with uniform magnetic fields to magnetize MNPs. Besides, magnetized MNPs are subjected to ultrasound vibrations; the motion of the MNPs induces weak induction voltages at the imaging pickup coils. The highly sensitive scanning superconducting quantum interference device biosusceptometry with three sets of ultrasound focus chips was developed to construct magnetic tomography at three depths. A phantom test showed favorable consistency between the visual photos and the magnetic images of alpha-fetoprotein antibody (anti-AFP) MNP distribution on gauzes. In animal tests, rats with liver tumors were imaged at the pre-injection and post-injection of anti-AFP MNPs. The consistent results of magnetic images and ultrasound images implied that the proposed method has high clinical potential.

A Tumor-specific MicroRNA Recognition System Facilitates the Accurate Targeting to Tumor Cells by Magnetic Nanoparticles

Targeted therapy for cancer is a research area of great interest, and magnetic nanoparticles (MNPs) show great potential as targeted carriers for therapeutics. One important class of cancer biomarkers is microRNAs (miRNAs), which play a significant role in tumor initiation and progression. In this study, a cascade recognition system containing multiple plasmids, including a Tet activator, a lacI repressor gene driven by the TetOn promoter, and a reporter gene repressed by the lacI repressor and influenced by multiple endogenous miRNAs, was used to recognize cells that display miRNA signals that are characteristic of cancer. For this purpose, three types of signal miRNAs with high proliferation and metastasis abilities were chosen (miR-21, miR-145, and miR-9). The response of this system to the human breast cancer MCF-7 cell line was 3.2-fold higher than that to the human breast epithelial HBL100 cell line and almost 7.5-fold higher than that to human embryonic kidney HEK293T cells. In combination with polyethyleneimine-modified MNPs, this recognition system targeted the tumor location in situ in an animal model, and an ~42% repression of tumor growth was achieved. Our study provides a new combination of magnetic nanocarrier and gene therapy based on miRNAs that are active in vivo, which has potential for use in future cancer therapies.

Assaying Carcinoembryonic Antigens by Normalized Saturation Magnetization

Biofunctionalized magnetic nanoparticles (BMNs) that provide unique advantages have been extensively used to develop immunoassay methods. However, these developed magnetic methods have been used only for specific immunoassays and not in studies of magnetic characteristics of materials. In this study, a common vibration sample magnetometer (VSM) was used for the measurement of the hysteresis loop for different carcinoembryonic antigens (CEA) concentrations (Φ CEA) based on the synthesized BMNs with anti-CEA coating. Additionally, magnetic parameters such as magnetization (M), remanent magnetization (M R), saturation magnetization (M S), and normalized parameters (ΔM R/M R and ΔM S/M S) were studied. Here, ΔM R and ΔM s were defined as the difference between any Φ CEA and zero Φ CEA. The parameters M, ΔM R, and ΔM S increased with Φ CEA, and ΔM S showed the largest increase. Magnetic clusters produced by the conjugation of the BMNs to CEAs showed a ΔM S greater than that of BMNs. Furthermore, the relationship between ΔM S/M S and Φ CEA could be described by a characteristic logistic function, which was appropriate for assaying the amount of CEAs. This analytic ΔM S/M S and the BMNs used in general magnetic immunoassays can be used for upgrading the functions of the VSM and for studying the magnetic characteristics of materials.

Dual-imaging model of SQUID biosusceptometry for locating tumors targeted using magnetic nanoparticles

BACKGROUND

For intraoperative imaging in operating theaters or preoperative imaging in clinics, compact and economic integration rather than large and expensive equipment is required to coregister structural and functional imaging. However, current technologies, such as those integrating optical and gamma cameras or infrared and fluorescence imaging, involve certain drawbacks, including the radioactive biorisks of nuclear medicine indicators and the inconvenience of conducting measurements in dark environments.

METHODS

To specifically and magnetically label liver tumors, an anti-alpha-fetoprotein (AFP) reagent was synthesized from biosafe iron oxide magnetic nanoparticles (MNPs) coated with anti-AFP antibody and solved in a phosphate buffered saline solution. In addition, a novel dual-imaging model system integrating an optical camera and magnetic scanning superconducting-quantum-interference device (SQUID) biosusceptometry (SSB) was proposed. The simultaneous coregistration of low-field magnetic images of MNP distributions and optical images of anatomical regions enabled the tumor distribution to be determined easily and in real time. To simulate targeted MNPs within animals, fewer reagents than the injected dose were contained in a microtube as a sample for the phantom test. The phantom test was conducted to examine the system characteristics and the analysis method of dual images. Furthermore, the animal tests were classified into two types, with liver tumors implanted either on the backs or livers of rats. The tumors on the backs were to visually confirm the imaging results of the phantom test, and the tumors on the livers were to simulate real cases in hepatocellular carcinoma people.

RESULTS

A phantom test was conducted using the proposed analysis method; favorable contour agreement was shown between the MNP distribution in optical and magnetic images. Consequently, the positioning and discrimination of liver tumors implanted on the backs and livers of rats were verified by conducting in vivo and ex vivo tests. The results of tissue staining verified the feasibility of using this method to determine the distribution of liver tumors.

CONCLUSION

The results of this study indicate the clinical potential of using anti-AFP-mediated MNPs and the dual-imaging model SSB for discriminating and locating tumors.