Harvesting Chlorella species using magnetic iron oxide nanoparticles

Microalgae are very useful organisms as it provides many beneficial products for human use. For large scale cultivation and further applications, its harvesting procedure needs to be enhanced to make the production process of the end product highly affordable. Magnetic nanoparticles have great potential to harvest microalgae as it can easily attract and attach to the algal cell surface forming a layer, which can be harvested quickly under the influence of a magnetic field. Our work on Chlorella pyrenoidosa and Chlorella minutissima shows, 500 mg of the synthesized bare iron oxide nanoparticles, harvests 90% of Chlorella pyrenoidosa (1 g L^?1), in 60 s at pH 3 and 600 mg iron oxide nanoparticles, harvests 85% of Chlorella minutissima (1 g L^?1) in 60 s at pH 5, which can decrease the amount of time and energy consumed in the overall production costs.     

Cleavable ester-linked magnetic nanoparticles for labeling of solvent-exposed primary amine groups of peptides/proteins

To study the solvent-exposed lysine residues of peptides/proteins, we previously reported disulfide-linked N-hydroxysuccinimide ester-modified silica-coated iron oxide magnetic nanoparticles (NHS–SS–SiO₂@Fe₃O₄ MNPs). The presence of a disulfide bond in the linker limits the use of disulfide reducing agent during protein digestion and allows unwanted disulfide formation between the MNPs and protein. In the current work, the disulfide bond was replaced with a cleavable ester group to synthesize NHS ester-modified SiO₂@Fe₃O₄ MNPs. Use of the cleavable ester group provides an improved method for protein labeling and allows the use of disulfide reducing agents during protein digestion.     

D-mannose-modified iron oxide nanoparticles for stem cell labeling

New surface-modified iron oxide nanoparticles were developed by precipitation of Fe(II) and Fe(III) salts with ammonium hydroxide according to two methods. In the first method, precipitation was done in the presence of D-mannose solution (in situ coating); the second method involved oxidation of precipitated magnetite with sodium hypochlorite followed by addition of D-mannose solution (postsynthesis coating). Selected nanoparticles were characterized by transmission electron microscopy (TEM), atomic force microscopy (AFM), elemental analysis, dynamic light scattering, infrared (IR), X-ray powder analysis, and ultrasonic spectrometry. While the first preparation method produced very fine nanoparticles ca. 2 nm in diameter, the second one yielded ca. 6 nm particles. Addition of D-mannose after synthesis did not affect the iron oxide particle size. UV-vis spectroscopy suggested that D-mannose suppresses the nonspecific sorption of serum proteins from DMEM culture medium on magnetic nanoparticles. Rat bone marrow stromal cells (rMSCs) were labeled with uncoated and d-mannose-modified iron oxide nanoparticles and with Endorem (Guerbet, France; control). Optical and transmission electron microscopy confirmed the presence of D-mannose-modified iron oxide nanoparticles inside the cells. D-mannose-modified nanoparticles crossed the cell membranes and were internalized well by the cells. Relaxivity measurements of labeled cells in gelatin revealed very high relaxivities only for postsynthesis D-mannose-coated iron oxide nanoparticles.     

Magnetically recyclable, antimicrobial, and catalytically enhanced polymer-assisted “green” nanosystem-immobilized Aspergillus niger amyloglucosidase

The present work reports the integration of polymer matrix-supported nanomaterial and enzyme biotechnology for development of industrially feasible biocatalysts. Aqueous leaf extract of Mesua ferrea L. was used to prepare silver nanoparticles distributed within a narrow size range (1–12 nm). In situ oxidative technique was used to obtain poly(ethylene glycol)-supported iron oxide nanoparticles (3–5 nm). Sonication-mediated mixing of above nanoparticles generated the immobilization system comprising of polymer-supported silver–iron oxide nanoparticles (20–30 nm). A commercially important enzyme, Aspergillus niger amyloglucosidase was coupled onto the immobilization system through sonication. The immobilization enzyme registered a multi-fold increment in the specific activity (807 U/mg) over the free counterpart (69 U/mg). Considerable initial activity of the immobilized enzyme was retained even after storing the system at room temperature as well as post-repeated magnetic recycling. Evaluation of the commendable starch saccharification rate, washing performance synergy with a panel of commercial detergents, and antibacterial potency strongly forwards the immobilized enzyme as a multi-functional industrially feasible system.     

Formulation of novel lipid-coated magnetic nanoparticles as the probe for in vivo imaging

Background  

Application of superparamagnetic iron oxide nanoparticles (SPIOs) as the contrast agent has improved the quality of magnetic resonance (MR) imaging. Low efficiency of loading the commercially available iron oxide nanoparticles into cells and the cytotoxicity of previously formulated complexes limit their usage as the image probe. Here, we formulated new cationic lipid nanoparticles containing SPIOs feasible for in vivo imaging.     

Functionalization and peptide-based delivery of magnetic nanoparticles as an intracellular MRI contrast agent

We report the development of functionalized superparamagnetic iron oxide nanoparticles with a PEG-modified, phospholipid micelle coating, and their delivery into living cells. The size of the coated particles, as determined by dynamic light scattering and electron microscopy, was found to be between 12 and 14 nm. The PEG-phospholipid coating resulted in high water solubility and stability, and the functional groups of modified PEG allowed for bioconjugation of various moieties, including a fluorescent dye and the Tat peptide. Efficient delivery of the functionalized nanoparticles into living cells was confirmed by fluorescence microscopy, relaxation time measurements, and magnetic resonance imaging (MRI). This demonstrates the feasibility of using functionalized magnetic nanoparticles with uniform (~10 nm) sizes as an MRI contrast agent for intracellular molecular imaging in deep tissue. These micelle-coated iron oxide nanoparticles offer a versatile platform for conjugation of a variety of moieties, and their small size confers advantages for intracellular molecular imaging with minimal perturbation.Abbreviations CPP cell penetrating peptide - CPMG Carr–Purcell–Meiboom–Gill spin-echo method - CTAB cetyltrimethylammonium bromide - DLS dynamic light scattering - DMEM Dulbeccos modified Eagles medium - DSPE 1,2-distearoyl-sn-glycero-3-phosphoethanolamine - FCS fetal calf serum - FGM-2 fibroblast growth medium 2 - HDF human dermal fibroblast - HS horse serum - MDBK Madin–Darby bovine kidney - MIONs superparamagnetic iron oxide nanoparticles - mMIONs micelle-coated MIONs - MRI magnetic resonance imaging - PBS phosphate-buffered saline - PEG poly(ethylene glycol) - SPDP N-succinimidyl 3-(2-pyridyldithio)propionate - TCEP tris(2-carboxyethyl)phosphine hydrochloride - TEM transmission electron microscopy     

Poly(L-lysine)-modified iron oxide nanoparticles for stem cell labeling

New surface-modified iron oxide nanoparticles were developed by precipitation of Fe(II) and Fe(III) salts with ammonium hydroxide and oxidation of the resulting magnetite with sodium hypochlorite, followed by the addition of poly( L-lysine) (PLL) solution. PLL of several molecular weights ranging from 146 ( L-lysine) to 579 000 was tested as a coating to boost the intracellular uptake of the nanoparticles. The nanoparticles were characterized by TEM, dynamic light scattering, FTIR, and ultrasonic spectrometry. TEM revealed that the particles were ca. 6 nm in diameter, while FTIR showed that their surfaces were well-coated with PLL. The interaction of PLL-modified iron oxide nanoparticles with DMEM culture medium was verified by UV-vis spectroscopy. Rat bone marrow stromal cells (rMSCs) and human mesenchymal stem cells (hMSC) were labeled with PLL-modified iron oxide nanoparticles or with Endorem (control). Optical microscopy and TEM confirmed the presence of PLL-modified iron oxide nanoparticles inside the cells. Cellular uptake was very high (more than 92%) for PLL-modified nanoparticles that were coated with PLL (molecular weight 388 00) at a concentration of 0.02 mg PLL per milliliter of colloid. The cellular uptake of PLL-modified iron oxide was facilitated by its interaction with the negatively charged cell surface and subsequent endosomolytic uptake. The relaxivity of rMSCs labeled with PLL-modified iron oxide and the amount of iron in the cells were determined. PLL-modified iron oxide-labeled rMSCs were imaged in vitro and in vivo after intracerebral grafting into the contralateral hemisphere of the adult rat brain. The implanted cells were visible on magnetic resonance (MR) images as a hypointense area at the injection site and in the lesion. In comparison with Endorem, nanoparticles modified with PLL of an optimum molecular weight demonstrated a higher efficiency of intracellular uptake by MSC cells.     

Erythrocyte CuZn superoxide dismutase activity is decreased in iron-deficiency anemia

Iron and copper and essential microminerals that are intimately related. The present study was performed to determine the effect of iron-deficiency anemia (IDA) and treatment with iron on laboratory indicators of copper status. Hemoglobin, mean corpuscular volume erythrocyte Zn protoporphyrin, serum ferritin, serum copper, serum ceruloplasmin, and erythrocyte CuZn-superoxide dismutase (SOD) activity were studied in 12 adult women with IDA before and after iron treatment for 60–90 d (100 mg/d Fe, as ferric polymaltose) and in 27 women with normal iron status. Prior to treatment with iron, serum copper and ceruloplasmin were not different between the groups and treatment with iron did not affect these measures. IDA women, before and after treatment with iron, presented a 2.9- and 2-fold decrease in erythrocyte CuZn-SOD activity compared to women with normal iron status (p <0.001). Treatment with iron increased erythrocyte CuZn-SOD activity of the IDA group; however, this change was not statistically significant. in conclusion, CuZn-SOD activity is decreased in IDA. Measurement of this enzyme activity is not useful for evaluating copper nutrition in iron-deficient subjects.     

Surface modification of iron oxide nanoparticles with polyarginine as a highly positively charged magnetic nano-adsorbent for fast and effective recovery of acid proteins

Polyarginine has been successfully bound onto iron oxide nanoparticles via carbodiimide activation as a highly positively charged magnetic nano-adsorbent for protein separation. They were nearly superparamagnetic with a mean diameter of 10.3 ± 2.36 nm, and the binding process did not change the spinel structure of iron oxide. From the analyses of FTIR spectra and zeta potential, the binding of polyarginine on the surface of iron oxide was confirmed and the resultant polyarginine-coated magnetic nanoparticles (PA-MNPs) were positively charged even up to pH 11. By thermogravimetric analysis, the typical product contained about 7.1 wt% of polyarginine. From the adsorption of the proteins with different pI values, the resultant PA-MNPs were found to be quite efficient for the fast and effective adsorption of acid proteins. For the typical acid protein, bovine serum albumin (BSA), the adsorption equilibrium was achieved within few minutes and obeyed the Langmuir isotherm equation. At pH 7 and 25 °C, the maximum adsorption capacity and equilibrium constant were 67.6 mg/g and 0.0623 L/mg, respectively. Moreover, by SDS–polyacrylamide gel electrophoresis, the capability of PA-MNPs for the separation of BSA-lysozyme mixture and egg white was further confirmed. Accordingly, the PA-MNPs were useful for the fast and effective magnetic recovery of acid proteins.     

Gum Arabic coated magnetic nanoparticles with affinity ligands specific for antibodies

A novel magnetic support based on gum Arabic (GA) coated iron oxide magnetic nanoparticles (MNP) has been endowed with affinity properties towards immunoglobulin G (IgG) molecules. The success of the in situ triazine ligand synthesis was confirmed by fluorescence assays. Two synthetic ligands previously developed for binding to IgG, named as ligand 22/8 (artificial Protein A) and ligand 8/7 (artificial Protein L) were immobilized on to MNPs coated with GA (MNP_GA). The dimension of the particles core was not affected by the surface functionalization with GA and triazine ligands. The hydrodynamic diameters of the magnetic supports indicate that the coupling of GA leads to the formation of larger agglomerates of particles with about 1 µm, but the introduction of the triazine ligands leads to a decrease on MNPs size. The non‐functionalized MNP_GA bound 28 mg IgG/g, two times less than bare MNP (60 mg IgG/g). MNP_GA modified with ligand 22/8 bound 133 mg IgG/g support, twice higher than the value obtained for ligand 8/7 magnetic adsorbents (65 mg/g). Supports modified with ligand 22/8 were selected to study the adsorption and the elution of IgG. The adsorption of human IgG on this support followed a Langmuir behavior with a Q_máx of 344 mg IgG/g support and K_a of 1.5 × 10⁵ M. The studies on different elution conditions indicated that although the 0.05 M citrate buffer (pH 3) presented good recovery yields (elution 64% of bound protein), there was occurrence of iron leaching at this acidic pH. Therefore, a potential alternative would be to elute bound protein with a 0.05 M glycine‐NaOH (pH 11) buffer. Copyright © 2010 John Wiley & Sons, Ltd.     

Facile and rapid magnetic relaxation switch immunosensor for endocrine-disrupting chemicals

In order to develop facile, fast and sensitive detection methods for endocrine-disrupting chemicals (EDCs), we described a sensitive biosensing system involving magnetic relaxation switch, based on the assembly of cross-linked superparamagnetic iron oxide (CLIO) nanoparticles induced by the antigen-antibody biorecognition. The design of smart CLIO-based superparamagnetic iron oxide nanoparticles and antigen-OVA was described for the detection of bisphenol A [2,2-bis (4-hydroxyphenol) propane (BPA)]. The addition of BPA to the rapid magnetic relaxation switch immunosensor led to transverse relaxation time (T2) shortening compared to a blank control as shown by NMR relaxometry measurements. This process was also applied to the rapid and facile determination of concentrations of BPA in drinking water (tap water). Good linearity for all calibration curves was obtained, and the limit of detection (LOD) for BPA was 0.4 ng/mL in tap water.     

Ultrasmall mixed ferrite colloids as multidimensional magnetic resonance imaging, cell labeling, and cell sorting agents

One area that has been overlooked in the evolution of magnetic nanoparticle technology is the possibility of introducing informational atoms into the iron oxide core of the coated colloid. Introduction of suitable atoms into the iron oxide core offers an opportunity to produce a quantifiable probe, thereby adding one or more dimensions to the magnetic colloid's informational status. Lanthanide-doped iron oxide nanoparticles have been synthesized to introduce informational atoms through the formation of colloidal mixed ferrites. These colloids are designated ultrasmall mixed ferrite iron oxides (USMIOs). USMIOs containing 5 mol % europium exhibit superparamagnetic behavior with an induced magnetization of 56 emu/g Fe at 1.5 T, a powder X-ray diffraction pattern congruent with magnetite, and R1 and R2 relaxivity values of 15.4 (mM s) (-1) and 33.9 (mM s) (-1), respectively, in aqueous solution at 37 degrees C and 0.47 T. USMIO can be detected by five physical methods, combining the magnetic resonance imaging (MRI) qualities of iron with the sensitive and quantitative detection of lanthanide metals by neutron activation analysis (NA), time-resolved fluorescence (TRF), X-ray fluorescence, along with detection by electron microscopy (EM). In addition to quantitative detection using neutron activation analysis, the presence of lanthanides in the iron oxide matrix confers attractive optical properties for long-term multilabeling studies with europium and terbium. These USMIOs offer high photostability, a narrow emission band, and a broad absorption band combining the high sensitivity of time-resolved fluorescence with the high spatial resolution of MRI. USMIO nanoparticles are prepared through modifications of traditional magnetite-based iron oxide colloid synthetic methods. A 5 mol % substitution of ferric iron with trivalent europium yielded a colloid with nearly identical magnetic, physical, and chemical characteristics to its magnetite colloid parent.     

In-Vivo Imaging of Cell Migration Using Contrast Enhanced MRI and SVM Based Post-Processing

The migration of cells within a living organism can be observed with magnetic resonance imaging (MRI) in combination with iron oxide nanoparticles as an intracellular contrast agent. This method, however, suffers from low sensitivity and specificty. Here, we developed a quantitative non-invasive in-vivo cell localization method using contrast enhanced multiparametric MRI and support vector machines (SVM) based post-processing. Imaging phantoms consisting of agarose with compartments containing different concentrations of cancer cells labeled with iron oxide nanoparticles were used to train and evaluate the SVM for cell localization. From the magnitude and phase data acquired with a series of T2*-weighted gradient-echo scans at different echo-times, we extracted features that are characteristic for the presence of superparamagnetic nanoparticles, in particular hyper- and hypointensities, relaxation rates, short-range phase perturbations, and perturbation dynamics. High detection quality was achieved by SVM analysis of the multiparametric feature-space. The in-vivo applicability was validated in animal studies. The SVM detected the presence of iron oxide nanoparticles in the imaging phantoms with high specificity and sensitivity with a detection limit of 30 labeled cells per mm³, corresponding to 19 μM of iron oxide. As proof-of-concept, we applied the method to follow the migration of labeled cancer cells injected in rats. The combination of iron oxide labeled cells, multiparametric MRI and a SVM based post processing provides high spatial resolution, specificity, and sensitivity, and is therefore suitable for non-invasive in-vivo cell detection and cell migration studies over prolonged time periods.     

Improvement of MRI probes to allow efficient detection of gene expression

Recently, it has been demonstrated that magnetic resonance imaging (MRI) utilizing monocrystalline iron oxide nanoparticles (MIONs) targeted to an engineered transferrin receptor enables imaging of gene expression. However, the relatively high doses of iron oxides used indicated the need for improved MR imaging probes to monitor changes in gene expression in vivo. Using alternative conjugation chemistries to link targeting ligands and iron oxide nanoparticles, we present the development and characterization as well as improved receptor binding and MRI detection of a novel imaging probe. Iron oxide nanoparticles with a cross-linked dextran coat were conjugated to transferrin (Tf) through the linker molecule N-succinimidyl 3-(2-pyridyldithio)propionate (SPDP) to yield Tf-S-S-CLIO. The characteristics of this conjugate were evaluated in comparison to Tf-MION and Tf-CLIO generated by oxidative activation of the dextran-coat with subsequent reduction of Schiff's base. SPDP conjugation allowed approximately a 4-fold increase in the number of Tf molecules attached per iron oxide nanoparticle and resulted in a more than 10-fold improvement of binding and uptake by cells. This translated into an imaging probe that was 16 times better for imaging gene expression in a cellular MRI assay. This novel probe for MRI may substantially increase the sensitivity for the detection of endogenous or genetically induced transferrin receptor expression in small numbers of cells and may significantly reduce the imaging dose from over 100 mg/kg to doses of iron oxides that are currently used in clinical imaging.     

Targeted Herceptin–dextran iron oxide nanoparticles for noninvasive imaging of HER2/neu receptors using MRI

A novel magnetic resonance imaging (MRI) contrast agent containing Herceptin is reported. The surfaces of superparamagnetic iron oxide nanoparticles were modified with dextran and conjugated with Herceptin (Herceptin–nanoparticles) to improve their dispersion, magnetization, and targeting of the specific receptors on cells. From analytical results, we found that Herceptin–nanoparticles were well dispersed in solutions of various pH range, and had no hysteresis, high saturation magnetization (80 emu/g), and low cytotoxicity to a variety of cells. Notably, the magnetic resonance enhancements for the different breast cancer cell lines (BT-474, SKBR-3, MDA-MB-231, and MCF-7) are proportional to the HER2/neu expression level in vitro. When Herceptin–nanoparticles were administered to mice bearing breast tumor allograft by intravenous injection, the tumor site was detected in T ₂-weighted magnetic resonance images as a 45% enhancement drop, indicating a high level of accumulation of the contrast agent within the tumor sites. Therefore, targeting of cancer cells was observed by in vitro and in vivo MRI studies using Herceptin–nanoparticles contrast agent. In addition, Herceptin–nanoparticles enhancing the magnetic resonance signal intensity were sufficient to detect the cell lines with a low level of HER2/neu expression. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

A Simple One Pot Purification of Bacterial Amylase From Fermented Broth Based on Affinity Toward Starch-Functionalized Magnetic Nanoparticle

Surface-functionalized adsorbant particles in combination with magnetic separation techniques have received considerable attention in recent years. Selective manipulation on such magnetic nanoparticles permits separation with high affinity in the presence of other suspended solids. Amylase is used extensively in food and allied industries. Purification of amylase from bacterial sources is a matter of concern because most of the industrial need for amylase is met by microbial sources. Here we report a simple, cost-effective, one-pot purification technique for bacterial amylase directly from fermented broth of Bacillus megaterium utilizing starch-coated superparamagnetic iron oxide nanoparticles (SPION). SPION was prepared by co-precipitation method and then functionalized by starch coating. The synthesized nanoparticles were characterized by transmission electron microscopy (TEM), a superconducting quantum interference device (SQUID, zeta potential, and ultraviolet–visible (UV-vis) and Fourier-transform infrared (FTIR) spectroscopy. The starch-coated nanoparticles efficiently purified amylase from bacterial fermented broth with 93.22% recovery and 12.57-fold purification. Sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE) revealed that the molecular mass of the purified amylase was 67 kD, and native gel showed the retention of amylase activity even after purification. Optimum pH and temperature of the purified amylase were 7 and 50°C, respectively, and it was stable over a range of 20°C to 50°C. Hence, an improved one-pot bacterial amylase purification method was developed using starch-coated SPION.     

Glycol chitosan/heparin immobilized iron oxide nanoparticles with a tumor-targeting characteristic for magnetic resonance imaging

We described the preparation of the glycol chitosan/heparin immobilized iron oxide nanoparticles (composite NPs) as a magnetic resonance imaging agent with a tumor-targeting characteristic. The iron oxide nanoseeds used clinically as a magnetic resonance imaging agent were immobilized into the glycol chitosan/heparin network to form the composite NPs. To induce the ionic interaction between the iron oxide nanoseeds and glycol chitosan, gold was deposited on the surface of iron oxide nanoseeds. After the immobilization of gold-deposited iron oxide NPs into the glycol chitosan network, the NPs were stabilized with heparin based on the ionic interaction between cationic glycol chitosan and anionic heparin. FE-SEM (field emission-scanning electron microscopy) and a particle size analyzer were used to observe the formation of the stabilized composite NPs, and a Jobin-Yvon Ultima-C inductively coupled plasma-atomic emission spectrometer (ICP-AES) was used to measure the contents (%) of formed iron oxide nanoseeds as a function of reaction temperature and formed gold deposited on the iron oxide nanoparticles. We also evaluated the time-dependent excretion profile, in vivo biodistribution, circulation time, and tumor-targeting ability of the composite NPs using a noninvasive NIR fluorescence imaging technology. To observe the MRI contrast characteristic, the composite NPs were injected into the tail veins of tumor-bearing mice to demonstrate their selective tumoral distribution. The MR images were collected with conventional T(2)-weighted spin echo acquisition parameters.     

Efficient labeling of mesenchymal stem cells using cell permeable magnetic nanoparticles

For the purpose of successfully monitoring labeled cells, optimum labeling efficiency without any side effect is a prerequisite. Magnetic cellular imaging is a new and growing field that allows the visualization of implanted cells in vivo. Herein, superparamagnetic iron oxide (SPIO) nanoparticles were conjugated with a non-toxic protein transduction domain (PTD), identified by the authors and termed low molecular weight protamine (LMWP), to generate efficient and non-toxic cell labeling tools. The cells labeled with LMWP-SPIO presented the highest iron content compared to those labeled with naked SPIO and the complex of SPIO with poly-l-lysine, which is currently used as a transfection agent. In addition to the iron content assay, Prussian staining and confocal observation demonstrated the highest intracellular LMWP-SPIO presence, and the labeling procedure did not alter the cell differentiation capacity of mesenchymal stem cells. Taken together, cell permeable magnetic nanoparticles conjugated with LMWP can be suggested as labeling tools for efficient magnetic imaging of transplanted cells.     

Iron Oxide Nanoparticle-Micelles (ION-Micelles) for Sensitive (Molecular) Magnetic Particle Imaging and Magnetic Resonance Imaging

Background

Iron oxide nanoparticles (IONs) are a promising nanoplatform for contrast-enhanced MRI. Recently, magnetic particle imaging (MPI) was introduced as a new imaging modality, which is able to directly visualize magnetic particles and could serve as a more sensitive and quantitative alternative to MRI. However, MPI requires magnetic particles with specific magnetic properties for optimal use. Current commercially available iron oxide formulations perform suboptimal in MPI, which is triggering research into optimized synthesis strategies. Most synthesis procedures aim at size control of iron oxide nanoparticles rather than control over the magnetic properties. In this study, we report on the synthesis, characterization and application of a novel ION platform for sensitive MPI and MRI.

Methods and Results

IONs were synthesized using a thermal-decomposition method and subsequently phase-transferred by encapsulation into lipidic micelles (ION-Micelles). Next, the material and magnetic properties of the ION-Micelles were analyzed. Most notably, vibrating sample magnetometry measurements showed that the effective magnetic core size of the IONs is 16 nm. In addition, magnetic particle spectrometry (MPS) measurements were performed. MPS is essentially zero-dimensional MPI and therefore allows to probe the potential of iron oxide formulations for MPI. ION-Micelles induced up to 200 times higher signal in MPS measurements than commercially available iron oxide formulations (Endorem, Resovist and Sinerem) and thus likely allow for significantly more sensitive MPI. In addition, the potential of the ION-Micelle platform for molecular MPI and MRI was showcased by MPS and MRI measurements of fibrin-binding peptide functionalized ION-Micelles (FibPep-ION-Micelles) bound to blood clots.

Conclusions

The presented data underlines the potential of the ION-Micelle nanoplatform for sensitive (molecular) MPI and warrants further investigation of the FibPep-ION-Micelle platform for in vivo, non-invasive imaging of fibrin in preclinical disease models of thrombus-related pathologies and atherosclerosis.     

Reversible immobilization of invertase on Cu-chelated polyvinylimidazole-grafted iron oxide nanoparticles

Polyvinylimidazole (PVI)-grafted iron oxide nanoparticles (PVIgMNP) were prepared by grafting of telomere of PVI on the iron oxide nanoparticles. Different metal ions (Cu²⁺, Zn²⁺, Cr²⁺, Ni²⁺) ions were chelated on polyvinylimidazole-grafted iron oxide nanoparticles, and then the metal-chelated magnetic particles were used in the adsorption of invertase. The maximum invertase immobilization capacity of the PVIgMNP–Cu²⁺ beads was observed to be 142.856 mg/g (invertase/PVIgMNP) at pH 5.0. The values of the maximum reaction rate (V _max) and Michaelis–Menten constant (Km) were determined for the free and immobilized enzymes. The enzyme adsorption–desorption studies, pH effect on the adsorption efficiency, affinity of different metal ions, the kinetic parameters and storage stability of free and immobilized enzymes were evaluated.