Efficacy of sequential use of superparamagnetic iron oxide and gadolinium in liver MR imaging

Functionalized Magnetite Nanoparticles: Characterization, Bioeffects, and Role of Reactive Oxygen Species in Unicellular and Enzymatic Systems

The current study evaluates the role of reactive oxygen species (ROS) in bioeffects of magnetite nanoparticles (MNPs), such as bare (Fe3O4), humic acids (Fe3O4-HA), and 3-aminopropyltriethoxysilane (Fe3O4-APTES) modified MNPs. Mössbauer spectroscopy was used to identify the local surrounding for Fe atom/ions and the depth of modification for MNPs. It was found that the Fe3O4-HA MNPs contain the smallest, whereas the Fe3O4-APTES MNPs contain the largest amount of Fe2+ ions. Bioluminescent cellular and enzymatic assays were applied to monitor the toxicity and anti-(pro-)oxidant activity of MNPs. The contents of ROS were determined by a chemiluminescence luminol assay evaluating the correlations with toxicity/anti-(pro-)oxidant coefficients. Toxic effects of modified MNPs were found at higher concentrations (>10−2 g/L); they were related to ROS storage in bacterial suspensions. MNPs stimulated ROS production by the bacteria in a wide concentration range (10−15−1 g/L). Under the conditions of model oxidative stress and higher concentrations of MNPs (>10−4 g/L), the bacterial bioassay revealed prooxidant activity of all three MNP types, with corresponding decay of ROS content. Bioluminescence enzymatic assay did not show any sensitivity to MNPs, with negligible change in ROS content. The results clearly indicate that cell-membrane processes are responsible for the bioeffects and bacterial ROS generation, confirming the ferroptosis phenomenon based on iron-initiated cell-membrane lipid peroxidation.

Conjugation strategies on functionalized iron oxide nanoparticles as a malaria vaccine delivery system

Vaccination has been used effectively to protect from infectious diseases and non-infectious diseases such as cancer and allergies. Different forms of particulate arrangements, including nanoparticles, virus-like particles (VLPs), and virosomes, have been built recently depending on the type of pathogen to be targeted. The ability to conjugate the recombinant Plasmodium yoelii, 19-kDa C-terminal fragment of merozoite surface protein 1 (PyMSP119) on the surface of superparamagnetic magnetite nanoparticles (SPIONs) was explored as a new technique of enhancing vaccination against malaria. Different conjugation strategies were performed to correlate the effects of nanoparticle chemistry surfaces to bind later with the malaria protein. (SPIONs) were prepared by chemical coprecipitation method and coated with 3-aminopropyltriethoxysilane (APTS) alone (as a surface coater), or with both APTS and polyethylene glycol (PEG) (as a shield to protect the malaria protein from proteolytic enzymes) by using a modified silanisation method. X-ray powder diffraction (XRD, Philips Model) patterns indicated that the SPIONs were of high purity with an inverse spinal structure. Fourier Transform Infrared Spectroscopy (FTIR) was collected using PerkinElmer Spectrum 100 Series; spectra of uncoated and coated magnetite nanoparticles confirmed that the silane layer had been coated on the surface Fe3O4. The SPIONs were superparamagnetic as investigated by Vibrating Sample Magnetometry (VSM, Princeton Applied Research, model ISS) and relatively stable in aqueous phase at room temperature and could also be quickly recovered from suspension using an external magnet. Introduce the carboxyl groups onto the SPIONs surfaces, resulting in a relatively high protein binding capacity onto the nanoparticle surfaces. The bare particles had a mean size of around 20 nm with a relatively narrow size distribution. 82% of African Green Monkey fibroblast (COS-7) were alive in nanoparticle suspension using the MTT assay method. The quantity of protein explicitly bound to particles was determined using Sodium Dodecyl Sulfate (SDS) - Polyacrylamide Gel Electrophoresis (PAGE). SDS–PAGE. When the conjugation blend was prepared in EDC, there was approximately 100% binding between PyMSP119 and the Fe3O4-COOH particles because no protein band was apparent at the expected molecular weight for PyMSP119 (45 kDa). The current study investigates the theory that the gradual, persistent release of the malaria antigen may stimulate and maintain an elevated level of immune response for an extended period in vivo, which will be the scope of future work.

Synthesis of poly(acrylic acid) coated magnetic nanospheres via a multiple polymerization route

Magnetic nanospheres are versatile candidates for both fundamental and practical applications. Before they are applied in more complicated fields, their surface must be modified by several functionalities. However, the surface modification can be affected by the magnetic nanoparticles (MNP) embedded in the polymer matrix. Herein, the synthesis of poly(acrylic acid) coated magnetic nanospheres via a multiple polymerization route is described. During the synthesis process, seed emulsion polymerization was applied to redistribute the MNP in the polymer matrix, and the relationship between the structure of magnetic nanospheres and the thickness of the grafted poly(acrylic acid) layer was investigated. The development of size, morphology and magnetic properties of the nanospheres were characterized by transmission electron microscopy, dynamic light scattering, thermogravimetric analysis, X-ray diffraction and vibrating sample magnetometry. This work would pave the way to design and preparation of new structure of functional magnetic nanospheres with precise surface modification.

Overendocytosis of superparamagnetic iron oxide particles increases apoptosis and triggers autophagic cell death in human osteosarcoma cell under a spinning magnetic field

The toxicity of superparamagnetic iron oxide nanoparticles (SPIONs) is still a vital topic of debate and the mechanisms remain unclear. In the present study, overdose SPIONs could induce osteosarcoma cell death and the effects were exaggerated when combined with spinning magnetic field (SMF). In the combination group, mitochondrial transmembrane potential decrease more obviously and reactive oxygen species (ROS) was found to generate much higher in line with that of the apoptosis ratio. Meantime, amount of autophagy was induced. Inhibiting the autophagy generation by 3-methyladenine (3-MA) increase cell viability but decrease the caspase 3/7 and caspase 8 activities in combination groups, and inhibiting apoptosis took the same effect. In the end, the SPIONs effects on xenograft mice was examed by intratumoral injection. The result showed that the combination group could greatly decrease the tumor volume and prolong the lifespan of mice. In sum, the result indicated that overdose SPIONs induced ROS generation, and excessive ROS induced by combination of SPIONs and SMF contribute to autophagy formation, which play a apoptosis-promoting role that formed as a platform to recruits initiate the caspase activities.

Polymer encapsulation of inorganic nanoparticles for biomedical applications

Hybrid inorganic colloidal particles have attracted a great attention in the last years, and they have been largely used in various applications and more particularly in biomedical nanotechnology. Recently, they are used as carriers for biomolecules, and exploited for use in microsystems, microfluidics and in lab-on-a chip based bionanotechnology. Various kinds of hybrid particles can be listed starting from classical inorganic nanoparticles such as silica, gold, silver, iron oxide and those exhibiting intrinsic properties such as semiconducting nanoparticles (e.g. quantum dots). As a general tendency, to be conveniently used in biomedical applications, the encapsulation of the inorganic nanoparticles in a polymer matrix is incontestably needed. Consequently, various chemistry-based encapsulation processes have been developed and showed promising results as compared to the encapsulation using preformed polymers.

Reactive magnetic poly(divinylbenzene-co-glycidyl methacrylate) colloidal particles for specific antigen detection using microcontact printing technique

Epoxy-functionalized magnetic poly(divinylbenzene-co-glycidyl methacrylate) colloidal particles (mPDGs) were prepared by co-polymerization of 1,4-divinylbenzene and glycidyl methacrylate monomers. The reaction was conducted by batch emulsion polymerization in the presence of an oil in water magnetic emulsion as a seed. The chemical composition, morphology, iron oxide content, magnetic properties, particle size and colloidal stability of the prepared magnetic polymer particles were characterized using Fourier transform infrared spectroscopy, transmission electron microscopy, thermal gravimetric analysis, vibrating sample magnetometry, dynamic light scattering, and zeta potential determination, respectively. The prepared mPDGs were immobilized on a self-assembled monolayer of 3-aminopropyltriethoxysilane (APTES)/octadecyltrichlorosilane (OTS), which were patterned on glass using microcontact printing technique, forming mPDGs-APTES/OTS reactive surface. This construction (mPDGs-APTES/OTS) was used as a solid support for immunoassay. The immobilized magnetic particles were bioconjugated with monoclonal anti-human IL-10 antibody to provide specific and selective recognition sites for the recombinant human IL-10 protein (antigen). Fluorescence microscopic examination was carried out to follow this immunoassay using fluorescently labeled anti-human IL-10 antibody. The results obtained proved the successful use of mPDGs-APTES/OTS microcontact printed surfaces in an immunoassay, which can be exploited and integrated into microsystems in order to elaborate medical devices (e.g. biosensors) which could provide rapid analysis at high sensitivity with low volumes of analyte.

Individual inorganic nanoparticles: preparation, functionalization and in vitro biomedical diagnostic applications

Inorganic nanoparticles have become the focus of modern materials science due to their potential technological importance, particularly in bionanotechnology, which stems from their unique physical properties including size-dependent optical, magnetic, electronic, and catalytic properties. The present article provides an overview on the currently used individual inorganic nanoparticles for in vitro biomedical domains. These inorganic nanoparticles include iron oxides, gold, silver, silica, quantum dots (QDs) and second harmonic generation (SHG) particles. For each of these interesting nanoparticles, the main issues starting from preparation up to bio-related applications are presented.

Boron as a platform for new drug design

INTRODUCTION

Boron lies on the borderline between metals and non-metals in the periodic table. As such, it possesses peculiarities which render it suitable for a variety of applications in chemistry, technology and medicine. However, boron's peculiarities have been exploited only partially so far.

AREAS COVERED

In this review, the authors highlight selected areas of research which have witnessed new uses of boron compounds in recent times. The examples reported illustrate how difficulties in the synthesis and physicochemical characterization of boronated molecules, encountered in past years, can be overcome with positive effects in different fields.

EXPERT OPINION

Many potentialities of boron-based systems reside in the peculiar properties of both boron atoms (the ability to replace carbon atoms, electron deficiency) and of boronated compounds (hydrophobicity, lipophilicity, versatile stereochemistry). Taken in conjunction, these properties can provide innovative drugs. The authors highlight the need to further investigate the assembly of boronated compounds, in terms of drug design, since the mechanisms required to obtain supramolecular structures may be unconventional compared with the more standard molecules used. Furthermore, the authors propose that computational methods are a valuable tool for assessing the role of multicenter, quasi-aromatic bonds and its peculiar geometries.

Fine tuning of the relaxometry of γ-Fe2O3@SiO2 nanoparticles by tweaking the silica coating thickness

We report the fine-tuning of the relaxometry of gamma-Fe2O3@SiO2 core-shell nanoparticles by adjusting the thickness of the coated silica layer. It is clear that the coating thickness of Fe2O3@SiO2 nanoparticles has a significant impact on the r(1) (at low B0 fields), r(2), and r(2)* relaxivities of their aqueous suspensions. These studies clearly indicate that the silica layer is heterogeneous and has regions that are porous to water and others-that are not. It is also shown, that the viability and the mitochondrial dehydrogenase expression of the microglial cells do not appear to be sensitive to the vesicular load with these core-shell nanoparticles. The adequate silica-shell thickness can therefore be tuned to allow for both a sufficiently high response as contrast agent, and-adequate grafting of targeted biomolecules.

Imaging of liver cancer

Improvements in imaging technology allow exploitation of the dual blood supply of the liver to aid in the identification and characterisation of both malignant and benign liver lesions. Imaging techniques available include contrast enhanced ultrasound, computed tomography and magnetic resonance imaging. This review discusses the application of several imaging techniques in the diagnosis and staging of both hepatocellular carcinoma and cholangiocarcinoma and outlines certain characteristics of benign liver lesions. The advantages of each imaging technique are highlighted, while underscoring the potential pitfalls and limitations of each imaging modality.

Magnetic nanoparticles for improving cell invasion in tissue engineering

It has been widely recognized that cells are seeded onto only the superficial layer of three-dimensional (3D) scaffolds in tissue engineering technology. This leads to tissue necrosis that occurs in the central part of 3D scaffolds. To solve this issue, an effective cell seeding technique into the central part of 3D scaffolds is required. Chitosan has characteristics of biocompatibility, biodegradability, and low-toxicity. In this study, we developed novel magnetic nanoparticles (MNs) coated with chitosan for enhancing cellular invasion using magnetic force. Cell-invasion efficiency was enhanced by introducing our novel MNs into cells and by the presence of magnetic force. This invasion efficacy depends on the degree of magnetic force. Matrix metalloproteinases and adhesion molecules that were upregulated in response to the attached nanoparticles and exposure to a magnetic force may also play a crucial role in improving cell-invasive ability in this system. This current system can efficiently enhance cell seeding into the depth of the scaffold, increase subsequent cell-cell interactions and shorten the period of cell proliferation. This system is thought to be useful in the development of cell-based strategies for the repair or replacement of tissue and other novel therapies.

Combined SPIO-gadolinium magnetic resonance imaging in cirrhotic patients: negative predictive value and role in screening for hepatocellular carcinoma

BACKGROUND

The objective of our study was to assess the negative predictive value (NPV) of double-contrast MRI (DC-MRI) with SPIO and gadolinium, and to determine the role of DC-MRI in screening for hepatocellular carcinoma (HCC) in cirrhotic patients.

METHODS

We retrospectively included 160 DC-MRI scans done as second-line investigations in 119 patients with cirrhosis over a 25-month period. Two radiologists independently classified the MRI scans as strongly suggesting HCC (HCC Group), showing benign nodules (benign nodules Group), showing no nodules (no-nodules Group) or indeterminate; they assigned a diagnostic confidence score (DCS) using a 0-10 scale. The reference standard was histology or results of follow-up investigations. Mean follow-up was 16.9 months (12-28 months).

RESULTS

The radiologists disagreed for two scans (kappa = 0.98). Of 112 scans [benign nodules Group (n = 32) and no-nodules Group (n = 80)], 11 were excluded (3 patients lost to follow-up and 8 who died with no known cancer) while a HCC was detected during follow-up in 8 patients, yielding a NPV of 92% (93/101) (95% confidence interval, 85%-97%). The DCS was in the 4-6 range (indicating uncertainty) for only 6 (3.75%) scans.

CONCLUSIONS

DC-MRI is reliable and reproducible. Its high NPV suggests a role as a second-line investigation after ultrasonography, for HCC screening.

Technology Insight: advances in liver imaging

The role of diagnostic imaging in the assessment of liver disease continues to gain in importance. The classic techniques used for liver imaging are ultrasonography, CT and MRI. In the past decade, there have been significant advances in all three techniques. In this article, we discuss the advances in ultrasonography, CT and MRI that have improved assessment of focal and diffuse liver disease, including the development of hardware, software, processing algorithms and procedural innovations.

MR contrast agents for liver imaging: what, when, how

The major classes of contrast agents currently used for magnetic resonance (MR) imaging of the liver include extracellular agents (eg, low-molecular-weight gadolinium chelates), reticuloendothelial agents (eg, ferumoxides), hepatobiliary agents (eg, mangafodipir), blood pool agents, and combined agents. Mechanisms of action, dosage, elimination, toxic effects, indications for use, and MR imaging technical considerations vary according to class. Gadolinium chelates are the most widely used. Ferumoxides are a useful adjunct for detection of hepatocellular carcinoma, particularly when used in combination with gadolinium to achieve improved lesion-to-liver contrast over that achievable with gadolinium alone. Mangafodipir is a prototype hepatobiliary agent that is taken up by lesions with functioning hepatocytes. It may be used for MR cholangiography as well as liver imaging. Although mangafodipir is no longer commercially available in the United States, it is currently marketed and used in Europe. Blood pool agents have not yet been approved for human use in the United States. However, a new combined MR contrast agent, gadobenate dimeglumine, recently was approved, and other agents are in various stages of development.

Preoperative assessment of focal liver lesions: multidetector computed tomography challenges magnetic resonance imaging

PURPOSE

To investigate prospectively multidetector computed tomography (CT) (MDCT) and magnetic resonance (MR) imaging (MRI) in the preoperative assessment of focal liver lesions.

MATERIAL AND METHODS

Multiphasic MDCT and conventional gadolinium-enhanced MRI were performed on 31 consecutive patients prior to hepatic surgery. All images were blindly analyzed as consensus reading. Lesion counts and their relation to vascular structures and possible extrahepatic disease were determined. The data from the MDCT and MRI were compared with the results obtained by intraoperative ultrasound (IOUS) and palpation. Histopathologic verification was available.

RESULTS

At surgery, IOUS and palpation revealed 45 solid liver lesions. From these, preoperative MDCT detected 43 (96%) and MRI 35 (78%) deposits. MDCT performed statistically better than MRI in lesion detection (P=0.008). Assessment of lesion vascular proximity was correctly determined by MDCT in 98% of patients and by MRI in 87%. Statistical difference was found (P=0.002). IOUS and palpation changed the preoperative surgical plan as a result of extrahepatic disease in 8/31 (26%) cases. In MDCT as well in MRI extrahepatic involvement was suspected in two cases.

CONCLUSION

MDCT was superior to MRI and nearly equal to IOUS in liver lesion detection and in the determination of lesion vascular proximity. However, both techniques fail to reliably detect extrahepatic disease.

Cell response to dextran-derivatised iron oxide nanoparticles post internalisation

Magnetic nanoparticles have been used for many years as magnetic resonance imaging contrast agents. Despite the fact that there are currently several dextran-coated iron oxide nanoparticles are in preclinical and clinical use, there is very little information available concerning the influence such particles have on cells in culture. The prerequisite for particles employed as contrast agents is capture and subsequent uptake by cells. This study involved the use of magnetic nanoparticles synthesised and derivatised with dextran, compared to similar underivatised plain particles. The influence in vitro was assessed using human dermal fibroblasts and various techniques to observe cell-particles interaction, including light and fluorescence microscopy, scanning and transmission electron microscopy. The results indicate that although both the uncoated and the dextran-derivatised particles are uptaken into the cell, the derivatised particles induce alterations in cell behaviour and morphology distinct from the plain particles, suggesting that cell response is dependent on the particles coating.

Magnetic resonance imaging of hepatocellular carcinoma

Hepatocellular carcinoma (HCC), the most common primary hepatic malignancy, usually develops in patients with cirrhosis, growing sequentially from low-grade dysplastic nodules to frank malignant HCC. Its recognition is critical because curative treatment and prognosis require early diagnosis. Survival in patients with HCC relates directly to the number, size, and extent of lesions at diagnosis. Imaging of HCC is complicated because the tumor has a varied imaging appearance and frequently coexists with other cirrhotic nodules. Magnetic resonance imaging (MRI), the best available diagnostic technique, offers good contrast resolution and diagnostic sensitivity ranging from 33% to 77%. The main difficulty is not in diagnosing large tumors, but rather small tumors (<2 cm), because of considerable overlap on imaging between benign (regenerative), borderline (dysplastic), and malignant nodules. Increasing degrees of histological malignancy are associated with increasing arterialization and loss of portal blood supply; therefore, recognition of HCC requires dynamic imaging with gadolinium-enhanced T1-weighted sequence. Typically, HCC is a focal lesion with high signal intensity on T2-weighted images, variable signal intensity on T1-weighted images, intense arterial phase enhancement after gadolinium injection, and isointensity or hypointensity at the portal venous phase. The sensitivity of MRI for detecting small lesions is low, and improvement is still needed. Newer contrast agents, higher field strength (3 Tesla) imaging, and perfusion and diffusion MRI techniques possibly will provide greater sensitivity and specificity for detecting small HCCs in the future.

Liver tumour MRI: what do we need for lesion characterization?

BACKGROUND

Hepatic lesions constitute a daily challenge to radiology in clinical settings, and non-invasive methods are valuable in the characterization of these liver tumours. We undertook our investigation to assess the lesion characterization potential of MRI by evaluating several unenhanced MR sequences and the dynamic gadolinium (Gd)-enhanced technique.

METHODS

A total of 116 focal liver lesions in 116 patients were included in our retrospective study, and histological verification was available for 107 lesions. Nine haemangiomas had a follow-up of 2 years. The 1.5-T MR system was used. T1- and T2-weighted sequences and dynamic Gd-enhanced studies were evaluated by two individual readers as separate sequences and also collectively. Lesions were classified into benign or malignant, and a specific diagnosis was proposed. The McNemar test was used in statistical analysis, and interobserver variation was measured using kappa statistics.

RESULTS

Lesion classification into benign and malignant tumours (by evaluating all images in concert) was assessed in 83% and 89% of cases by readers 1 and 2, respectively. From single sequences, best lesion classification was achieved with Gd-enhanced T1 by both readers. The difference in classification was statistically significant when all sequences were evaluated in comparison with any single sequence alone (P = 0.02). Specific diagnosis was correctly determined using all sequences together in 60% and 71% of cases by readers 1 and 2, respectively. For individual sequences, correct diagnosis was most frequently proposed with a Gd-enhanced T1-weighted sequence by both readers (59% and 65% for readers 1 and 2, respectively).

CONCLUSION

Multisequential MRI using Gd-enhanced imaging performs extremely well in liver lesion classification, and with moderate ability to determine a specific diagnosis.