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

Iron-based compounds coordinated with phospho-polymers as biocompatible probes for dual 31P/1H magnetic resonance imaging and spectroscopy

In this work, we present the synthesis and evaluation of magnetic resonance (MR) properties of novel phosphorus/iron-containing probes for dual 31P and 1H MR imaging and spectroscopy (MRI and MRS). The presented probes are composed of biocompatible semitelechelic and multivalent phospho-polymers based on poly(2-methacryloyloxyethyl phosphorylcholine) (pMPC) coordinated with small paramagnetic Fe3+ ions or superparamagnetic maghemite (γ-Fe2O3) nanoparticles via deferoxamine group linked to the end or along the polymer chains. All probes provided very short 1H T1 and T2 relaxation times even at low iron concentrations. The presence of iron had a significant impact on the shortening of 31P relaxation, with the effect being more pronounced for probes based on γ-Fe2O3 and multivalent polymer. While the water-soluble probe having one Fe3+ ion per polymer chain was satisfactorily visualized by both 31P-MRS and 31P-MRI, the probe with multiple Fe3+ ions could only be detected by 31P-MRS, and the probes consisting of γ-Fe2O3 nanoparticles could not be imaged by either technique due to their ultra-short 31P relaxations. In this proof-of-principle study performed on phantoms at a clinically relevant magnetic fields, we demonstrated how the different forms and concentrations of iron affect both the 1H MR signal of the surrounding water molecules and the 31P MR signal of the phospho-polymer probe. Thus, this double contrast can be exploited to simultaneously visualize body anatomy and monitor probe biodistribution.

Hydrophilic Copolymers with Hydroxamic Acid Groups as a Protective Biocompatible Coating of Maghemite Nanoparticles: Synthesis, Physico-Chemical Characterization and MRI Biodistribution Study

Superparamagnetic iron oxide nanoparticles (SPION) with a "non-fouling" surface represent a versatile group of biocompatible nanomaterials valuable for medical diagnostics, including oncology. In our study we present a synthesis of novel maghemite (γ-Fe₂O₃) nanoparticles with positive and negative overall surface charge and their coating by copolymer P(HPMA-co-HAO) prepared by RAFT (reversible addition-fragmentation chain-transfer) copolymerization of N-(2-hydroxypropyl)methacrylamide (HPMA) with N-[2-(hydroxyamino)-2-oxo-ethyl]-2-methyl-prop-2-enamide (HAO). Coating was realized via hydroxamic acid groups of the HAO comonomer units with a strong affinity to maghemite. Dynamic light scattering (DLS) demonstrated high colloidal stability of the coated particles in a wide pH range, high ionic strength, and the presence of phosphate buffer (PBS) and serum albumin (BSE). Transmission electron microscopy (TEM) images show a narrow size distribution and spheroid shape. Alternative coatings were prepared by copolymerization of HPMA with methyl 2-(2-methylprop-2-enoylamino)acetate (MMA) and further post-polymerization modification with hydroxamic acid groups, carboxylic acid and primary-amino functionalities. Nevertheless, their colloidal stability was worse in comparison with P(HPMA-co-HAO). Additionally, P(HPMA-co-HAO)-coated nanoparticles were subjected to a bio-distribution study in mice. They were cleared from the blood stream by the liver relatively slowly, and their half-life in the liver depended on their charge; nevertheless, both cationic and anionic particles revealed a much shorter metabolic clearance rate than that of commercially available ferucarbotran.

Iron-Based Oxygen Scavengers on Mesoporous Silica Nanospheres

Iron-based materials are among the most commonly used oxygen scavengers. Here, we investigated the mesoporous silica nanosphere (MSN)-supported iron-based scavengers, such as FeO_x nanoparticles and different atomic layer deposition (ALD) coatings (FeO_x and Fe). We found that the scavenger performance is a result of a complex interplay between available Brunauer-Emmett-Teller surface area and the scavenger composition, with the combination of infiltrated nanoparticles and Fe-ALD coating resulting in the best performance. When the glucose-based treatment of MSN is used to further enhance oxygen scavenging capacity, Fe-ALD coating yields the best performance, with a high oxygen adsorption capacity of 126.8 mL/g. ALD deposition of Fe represents a versatile method to introduce Fe-based oxygen scavengers onto different supports, and it can facilitate the integration of scavengers with different types of packaging, as the deposition can be performed at a low temperature of 150 °C.

Development of Positively Charged Poly-L-Lysine Magnetic Nanoparticles as Potential MRI Contrast Agent

A colloidal solution of magnetic nanoparticles (MNPs) modified with biocompatible positively charged poly-L-lysine (PLL) with an oleate (OL) layer employed as an initial coating was produced as a potential MRI contrast agent. The effect of various PLL/MNPs' mass ratios on the samples' hydrodynamic diameter, zeta potential, and isoelectric point (IEP) was studied by the dynamic light-scattering method. The optimal mass ratio for MNPs' surface coating was 0.5 (sample PLL_0.5-OL-MNPs). The average hydrodynamic particle size in the sample of PLL_0.5-OL-MNPs was 124.4 ± 1.4 nm, and in the PLL-unmodified nanoparticles, it was 60.9 ± 0.2 nm, indicating that the OL-MNPs' surface became covered by PLL. Next, the typical characteristics of the superparamagnetic behavior were observed in all samples. In addition, the decrease in saturation magnetizations from 66.9 Am²/kg for MNPs to 35.9 and 31.6 Am²/kg for sample OL-MNPs and PLL_0.5-OL-MNPs also confirmed successful PLL adsorption. Moreover, we show that both OL-MNPs and PLL_0.5-OL-MNPs exhibit excellent MRI relaxivity properties and a very high r₂⁽*⁾/r₁ ratio, which is very desirable in biomedical applications with required MRI contrast enhancement. The PLL coating itself appears to be the crucial factor in enhancing the relaxivity of MNPs in MRI relaxometry.

A Neurospheroid-Based Microrobot for Targeted Neural Connections in a Hippocampal Slice

Functional restoration by the re-establishment of cellular or neural connections remains a major challenge in targeted cell therapy and regenerative medicine. Recent advances in magnetically powered microrobots have shown potential for use in controlled and targeted cell therapy. In this study, a magnetic neurospheroid (Mag-Neurobot) that can form both structural and functional connections with an organotypic hippocampal slice (OHS) is assessed using an ex vivo model as a bridge toward in vivo application. The Mag-Neurobot consists of hippocampal neurons and superparamagnetic nanoparticles (SPIONs); it is precisely and skillfully manipulated by an external magnetic field. Furthermore, the results of patch-clamp recordings of hippocampal neurons indicate that neither the neuronal excitabilities nor the synaptic functions of SPION-loaded cells are significantly affected. Analysis of neural activity propagation using high-density multi-electrode arrays shows that the delivered Mag-Neurobot is functionally connected with the OHS. The applications of this study include functional verification for targeted cell delivery through the characterization of novel synaptic connections and the functionalities of transported and transplanted cells. The success of the Mag-Neurobot opens up new avenues of research and application; it offers a test platform for functional neural connections and neural regenerative processes through cell transplantation.

Tumor necrosis factor-alpha antibody labeled-polyethylene glycol-coated nanoparticles: A mesenchymal stem cells-based drug delivery system in the rat model of cisplatin-induced nephrotoxicity

Background and Aim: A delivery system consisting of bone marrow mesenchymal stem cells (MSCs) loaded with polyethylene glycol (PEG) coated superparamagnetic iron oxide nanoparticles (SPIONs) was constructed to treat a rat model of cisplatin (Cis)-induced nephrotoxicity with 1/10 of the common dose of anti-tumor necrosis factor-alpha (TNF-α) antibodies (infliximab). Materials and Methods: Morphology, size, crystallinity, molecular structure, and magnetic properties of uncoated and PEG-coated SPIONs were analyzed. A delivery system consisting of MSCs containing infliximab-labeled PEG-coated SPIONs (Infliximab-PEG-SPIONs-MSCs) was generated and optimized before treatment. Fifty female Wistar rats were divided into five equal groups: Group 1: Untreated control; Group 2 (Cis): Rats were administered Cis through intraperitoneal (i.p.) injection (8 mg/kg) once a week for 4 weeks; Group 3 (Infliximab): Rats were injected once with infliximab (5 mg/kg), i.p. 3 days before Cis administration; Group 4 (Cis + MSCs): Rats were injected with Cis followed by an injection of 2 × 106 MSCs into the tail vein twice at a 1-week interval; and Group 5 (Cis + Infliximab (500 μg/kg)-PEG-SPIONs-MSCs): Rats were injected with the delivery system into the tail vein twice at a 1-week interval. Besides histological examination of the kidney, the Doppler ultrasound scanner was used to scan the kidney with the Gray-color-spectral mode. Results: In vivo, intra-renal iron uptake indicates the traffic of the delivery system from venous blood to renal tissues. Cis-induced nephrotoxicity resulted in a significant increase in TNF-α and malondialdehyde (MDA) (p < 0.05), bilirubin, creatinine, and uric acid (p < 0.01) levels compared with the untreated control group. The different treatments used in this study resulted in the amelioration of some renal parameters. However, TNF-α levels significantly decreased in Cis + Infliximab and Cis + MSCs (p < 0.05) groups. The serum levels of MDA significantly decreased in Cis + Infliximab (p < 0.05), Cis + MSCs (p < 0.05), and Cis + Infliximab-PEG-SPIONs-MSCs (p < 0.01). Furthermore, the serum activities of antioxidant enzymes were significantly elevated in the Cis + MSCs and Cis + Infliximab-PEG-SPIONs-MSCs groups (p < 0.05) compared to the Cis-induced nephrotoxicity rat model. Conclusion: With the support of the constructed MSCs-SPIONs infliximab delivery system, it will be possible to track and monitor cell homing after therapeutic application. This infliximab-loading system may help overcome some challenges regarding drug delivery to the target organ, optimize therapeutics' efficacy, and reduce the dose. The outcomes of the current study provide a better understanding of the potential of combining MSCs and antibodies-linked nanoparticles for the treatment of nephrotoxicity. However, further investigation is recommended using different types of other drugs. For new approaches development, we should evaluate whether existing toxicity analysis and risk evaluation strategies are reliable and enough for the variety and complexity of nanoparticles.

Long-Chain Poly-d-Lysines Interact with the Plasma Membrane and Induce Protective Autophagy and Intense Cell Necrosis

Polylysines have been frequently used in drug delivery and antimicrobial and cell adhesion studies. Because of steric hindrance, chirality plays a major role in the functional difference between poly-l-lysine (PLL) and poly-d-lysine (PDL), especially when they interact with the plasma membranes of mammalian cells. Therefore, it is speculated that the interaction between chiral polylysines and the plasma membrane may cause different cellular behaviors. Here, we carefully investigated the interaction pattern of PLL and PDL with plasma membranes. We found that PDL could be anchored onto the plasma membrane and interact with the membrane lipids, leading to the rapid morphological change and death of A549 cells (a human lung cancer cell line) and HPAEpiCs (a human pulmonary alveolar epithelial cell line). In contrast, PLL exhibited good cytocompatibility and was not anchored onto the plasma membranes of these cells. Unlike PLL, PDL could trigger protective autophagy to prevent cells in a certain degree, and the PDL-caused cell death occurred via intense necrosis (featured by increased intracellular Ca²⁺ content and plasma membrane disruption). In addition, it was found that the short-chain PDL with a repeat unit number of 9 (termed DL9) could locate in lysosomes and induce autophagy at high concentrations, but it could not elicit drastic cell death, which proved that the repeat unit number of polylysine could affect its cellular action. This research confirms that the interaction between chiral polylysines and the plasma membrane can induce autophagy and intense necrosis, which provides guidance for the future studies of chiral molecules/drugs.

A Magnetically Powered Stem Cell-Based Microrobot for Minimally Invasive Stem Cell Delivery via the Intranasal Pathway in a Mouse Brain

Targeted stem cell delivery with microrobots has emerged as a potential alternative therapeutic strategy in regenerative medicine, and intranasal administration is an effective approach for minimally invasive delivery of therapeutic agents into the brain. In this study, a magnetically powered stem cell-based microrobot ("Cellbot") is used for minimally invasive targeted stem cell delivery to the brain through the intranasal passage. The Cellbot is developed by internalizing superparamagnetic iron oxide nanoparticles (SPIONs) into human nasal turbinate stem cells. The SPIONs have no influence on hNTSC characteristics, including morphology, cell viability, and neuronal differentiation. The Cellbots are capable of proliferation and differentiation into neurons, neural precursor cells, and neurogliocytes. The Cellbots in the microfluidic channel can be reliably manipulated by an external magnetic field for orientation and position control. Using an ex vivo model based on brain organoids, it is determined that the Cellbots can be transplanted into brain tissue. Using a murine model, it is demonstrated that the Cellbots can be intranasally administered and magnetically guided to the target tissue in vivo. This approach has the potential to effectively treat central nervous system disorders in a minimally invasive manner.

Photoacoustic Properties of Polypyrrole Nanoparticles

Photoacoustic imaging, an emerging modality, provides supplemental information to ultrasound imaging. We investigated the properties of polypyrrole nanoparticles, which considerably enhance contrast in photoacoustic images, in relation to the synthesis procedure and to their size. We prepared polypyrrole nanoparticles by water-based redox precipitation polymerization in the presence of ammonium persulphate (ratio nPy:nOxi 1:0.5, 1:1, 1:2, 1:3, 1:5) or iron(III) chloride (nPy:nOxi 1:2.3) acting as an oxidant. To stabilize growing nanoparticles, non-ionic polyvinylpyrrolidone was used. The nanoparticles were characterized and tested as a photoacoustic contrast agent in vitro on an imaging platform combining ultrasound and photoacoustic imaging. High photoacoustic signals were obtained with lower ratios of the oxidant (nPy:nAPS ≥ 1:2), which corresponded to higher number of conjugated bonds in the polymer. The increasing portion of oxidized structures probably shifted the absorption spectra towards shorter wavelengths. A strong photoacoustic signal dependence on the nanoparticle size was revealed; the signal linearly increased with particle surface. Coated nanoparticles were also tested in vivo on a mouse model. To conclude, polypyrrole nanoparticles represent a promising contrast agent for photoacoustic imaging. Variations in the preparation result in varying photoacoustic properties related to their structure and allow to optimize the nanoparticles for in vivo imaging.

In Vitro Evaluation of Hyperthermia Magnetic Technique Indicating the Best Strategy for Internalization of Magnetic Nanoparticles Applied in Glioblastoma Tumor Cells

This in vitro study aims to evaluate the magnetic hyperthermia (MHT) technique and the best strategy for internalization of magnetic nanoparticles coated with aminosilane (SPIONAmine) in glioblastoma tumor cells. SPIONAmine of 50 and 100 nm were used for specific absorption rate (SAR) analysis, performing the MHT with intensities of 50, 150, and 300 Gauss and frequencies varying between 305 and 557 kHz. The internalization strategy was performed using 100, 200, and 300 µgFe/mL of SPIONAmine, with or without Poly-L-Lysine (PLL) and filter, and with or without static or dynamic magnet field. The cell viability was evaluated after determination of MHT best condition of SPIONAmine internalization. The maximum SAR values of SPIONAmine (50 nm) and SPIONAmine (100 nm) identified were 184.41 W/g and 337.83 W/g, respectively, using a frequency of 557 kHz and intensity of 300 Gauss (≈23.93 kA/m). The best internalization strategy was 100 µgFe/mL of SPIONAmine (100 nm) using PLL with filter and dynamic magnet field, submitted to MHT for 40 min at 44 °C. This condition displayed 70.0% decreased in cell viability by flow cytometry and 68.1% by BLI. We can conclude that our study is promising as an antitumor treatment, based on intra- and extracellular MHT effects. The optimization of the nanoparticles internalization process associated with their magnetic characteristics potentiates the extracellular acute and late intracellular effect of MHT achieving greater efficiency in the therapeutic process.

Nanoparticles for Stem Cell Tracking and the Potential Treatment of Cardiovascular Diseases

Stem cell-based therapies have been shown potential in regenerative medicine. In these cells, mesenchymal stem cells (MSCs) have the ability of self-renewal and being differentiated into different types of cells, such as cardiovascular cells. Moreover, MSCs have low immunogenicity and immunomodulatory properties, and can protect the myocardium, which are ideal qualities for cardiovascular repair. Transplanting mesenchymal stem cells has demonstrated improved outcomes for treating cardiovascular diseases in preclinical trials. However, there still are some challenges, such as their low rate of migration to the ischemic myocardium, low tissue retention, and low survival rate after the transplantation. To solve these problems, an ideal method should be developed to precisely and quantitatively monitor the viability of the transplanted cells in vivo for providing the guidance of clinical translation. Cell imaging is an ideal method, but requires a suitable contrast agent to label and track the cells. This article reviews the uses of nanoparticles as contrast agents for tracking MSCs and the challenges of clinical use of MSCs in the potential treatment of cardiovascular diseases.

In vitro cellular activity of maghemite/cerium oxide magnetic nanoparticles with antioxidant properties

Magnetic γ-Fe₂O₃/CeO₂ nanoparticles were obtained by precipitation of Ce(NO₃)₃ with ammonia in the presence of γ-Fe₂O₃ seeds. The formation of CeO₂ nanoparticles on the seeds was confirmed by transmission electron microscopy linked with selected area electron diffraction, energy-dispersive X-ray spectroscopy, electron energy loss spectroscopy, and dynamic light scattering. The γ-Fe₂O₃/CeO₂ particle surface was functionalized with PEG-neridronate to improve the colloidal stability in PBS and biocompatibility. Chemical and in vitro biological assays proved that the nanoparticles, due to the presence of cerium oxide, effectively scavenged radicals, thus decreasing oxidative stress in the model cell line. PEG functionalization of the nanoparticles diminished their in vitro aggregation and facilitated lysosomal cargo degradation in cancer cells during autophagy, which resulted in concentration-dependent cytotoxicity of the nanoparticles. Finally, the iron oxide core allowed easy magnetic separation of the particles from liquid media and may enable monitoring of nanoparticle biodistribution in organisms using magnetic resonance imaging.

Tb-Doped core-shell-shell nanophosphors for enhanced X-ray induced luminescence and sensitization of radiodynamic therapy

The development of radiation responsive materials, such as nanoscintillators, enables a variety of exciting new theranostic applications. In particular, the ability of nanophosphors to serve as molecular imaging agents in novel modalities, such as X-ray luminescence computed tomography (XLCT), has gained significant interest recently. Here, we present a radioluminescent nanoplatform consisting of Tb-doped nanophosphors with an unique core/shell/shell (CSS) architecture for improved optical emission under X-ray excitation. Owing to the spatial confinement and separation of luminescent activators, these CSS nanophosphors exhibited bright optical luminescence upon irradiation. In addition to standard physiochemical characterization, these CSS nanophosphors were evaluated for their ability to serve as energy mediators in X-ray stimulated photodynamic therapy, also known as radiodynamic therapy (RDT), through attachment of a photosensitizer, rose bengal (RB). Furthermore, cRGD peptide was used as a model targeting agent against U87 MG glioblastoma cells. In vitro RDT efficacy studies suggested the RGD-CSS-RB in combination with X-ray irradiation could induce enhanced DNA damage and increased cell killing, while the nanoparticles alone are well tolerated. These studies support the utility of CSS nanophosphors and warrants their further development for theranostic applications.

Influence of Dextran Molecular Weight on the Physical Properties of Magnetic Nanoparticles for Hyperthermia and MRI Applications

Dextran-coated magnetic nanoparticles are promising biocompatible agents in various biomedical applications, including hyperthermia and magnetic resonance imaging (MRI). However, the influence of dextran molecular weight on the physical properties of dextran-coated magnetic nanoparticles has not been described sufficiently. We synthesise magnetite nanoparticles with a dextran coating using a co-precipitation method and study their physical properties as a function of dextran molecular weight. Several different methods are used to determine the size distribution of the particles, including microscopy, dynamic light scattering, differential centrifugal sedimentation and magnetic measurements. The size of the dextran-coated particles increases with increasing dextran molecular weight. We find that the molecular weight of dextran has a significant effect on the particle size, efficiency, magnetic properties and specific absorption rate. Magnetic hyperthermia measurements show that heating is faster for dextran-coated particles with higher molecular weight. The different molecular weights of the coating also significantly affected its MRI relaxation properties, especially the transversal relaxivity r₂. Linear regression analysis reveals a statistically significant dependence of r₂ on the differential centrifugal sedimentation diameter. This allows the targeted preparation of dextran-coated magnetic nanoparticles with the desired MRI properties. These results will aid the development of functionalised magnetic nanoparticles for hyperthermia and MRI applications.

Covalent Organic Framework Embedded with Magnetic Nanoparticles for MRI and Chemo-Thermotherapy

Nanoscale imine-linked covalent organic frameworks (nCOFs) were first loaded with the anticancer drug Doxorubicin (Dox), coated with magnetic iron oxide nanoparticles (γ-Fe₂O₃ NPs), and stabilized with a shell of poly(l-lysine) cationic polymer (PLL) for simultaneous synergistic thermo-chemotherapy treatment and MRI imaging. The pH responsivity of the resulting nanoagents (γ-SD/PLL) allowed the release of the drug selectively within the acidic microenvironment of late endosomes and lysosomes of cancer cells (pH 5.4) and not in physiological conditions (pH 7.4). γ-SD/PLL could efficiently generate high heat (48 °C) upon exposure to an alternating magnetic field due to the nCOF porous structure that facilitates the heat conduction, making γ-SD/PLL excellent heat mediators in an aqueous solution. The drug-loaded magnetic nCOF composites were cytotoxic due to the synergistic toxicity of Dox and the effects of hyperthermia in vitro on glioblastoma U251-MG cells and in vivo on zebrafish embryos, but they were not significantly toxic to noncancerous cells (HEK293). To the best of our knowledge, this is the first report of multimodal MRI probe and chemo-thermotherapeutic magnetic nCOF composites.

7-T MRI tracking of mesenchymal stromal cells after lung injection in a rat model

Background

Mesenchymal stromal cells (MSCs) are able to migrate and engraft at sites of inflammation, injuries, and tumours, but little is known about their fate after local injection. The purpose of this study is to perform MSC tracking, combining in vivo 7-T magnetic resonance imaging (MRI) and histological assessment, following lung injection in a rat model.

Methods

Five lungs were injected with ferumoxide-labelled MSCs and five with perfluorocarbon-labelled MSCs and underwent 7-T MRI. MRI acquisitions were recorded immediately (T₀), at 24 h (T₂₄) and/or 48 h (T₄₈) after injection. For each rat, labelled cells were assessed in the main organs by MRI. Target organs were harvested under sterile conditions from rats sacrificed 0, 24, or 48 h after injection and fixed for histological analysis via confocal and structured illumination microscopy.

Results

Ferumoxide-labelled MSCs were not detectable in the lungs, whereas they were not visible in the distant sites. Perfluorocarbon-labelled MSCs were seen in 5/5 injected lungs at T₀, in 1/2 at T₂₄, and in 1/3 at T₄₈. The fluorine signal in the liver was seen in 3/5 at T₀, in 1/2 at T24, and in 2/3 at T₄₈. Post-mortem histology confirmed the presence of MSCs in the injected lung.

Conclusions

Ferumoxide-labelled cells were not seen at distant sites; a linear decay of injected perfluorocarbon-labelled MSCs was observed at T₀, T₂₄, and T₄₈ in the lung. In more than half of the experiments, perfluorocarbon-labelled MSCs scattering to the liver was observed, with a similar decay over time as observed in the lung.

Heme-binding ability of bovine milk proteins

Bovine milk proteins bind calcium and some bind other metal ions or heme. The examination of heme-binding proteins in colostrum and milk using hemin-agarose beads (HA) showed α-casein, κ-casein and lactoferrin (Lf) to be heme-binding proteins. α-Casein and Lf are iron- and heme-binding proteins, and α- and κ-casein bind to HA, as does Lf. κ-Casein and Lf have higher affinity to zinc ion than does α-casein, and κ-casein and Lf interact with α-casein-immobilized beads (CasB). The addition of α-casein to κ-casein bound to CasB decreased the amount of bound κ-casein compared with in the absence of α-casein, and κ-casein likely increases α-casein self-association. α-Casein binds Lf bound to neither iron nor heme, as shown by experiments with the apo-form. Beads with immobilized poly-L-lysine bind heme but Lf inhibits this binding. These results indicate that α-casein, κ-casein and Lf are both heme- and zinc-binding proteins, and that α-casein interacts with κ-casein and Lf through protein-protein interactions. Additionally, Lf shows higher affinity to hemin than does poly-L-lysine.

Quasi-amorphous and Hierarchical Fe2O3 Supraparticles: Active T1-Weighted Magnetic Resonance Imaging in Vivo and Renal Clearance

The exploration of magnetic resonance imaging (MRI) agents possessing excellent performances and high biosafety is of great importance for both fundamental science research and biomedical applications. In this study, we present that monodisperse Fe₂O₃ supraparticles (SPs) can act as T₁-weighted MRI agents, which not only possess a distinct off-on MRI switch in the tumor microenvironment but also are readily excreted from living bodies due to its quasi-amorphous structure and hierarchical topology design. First, the Fe₂O₃ SPs have a surface-to-volume ratio obviously smaller than that of their building blocks by means of self-assembly processes, which, on the one hand, causes a rather low r₁ relaxivity (0.19 mM^-1 s^-1) and, on the other hand, can effectively prevent their aggregation after intravenous injection. Second, the Fe₂O₃ SPs have a dramatic disassembly/degradation-induced active T₁-weighted signal readout (more than 6 times the r₁ value enhancement and about 20 times the r₂/r₁ ratio decrease) in the tumor microenvironment, resulting in a high signal-to-noise ratio for imaging performances. Therefore, they possess excellent in vivo imaging capacity, even with a tumor size as small as 5 mm³. Third, the disassembled/decomposed behaviors of the Fe₂O₃ SPs facilitate their timely clearance/excretion from living bodies. In particular, they exhibit distinct renal clearance behavior without any kidney damage with the right dosage. Fourth, the favorable biodegradability of the as-prepared Fe₂O₃ SPs can further relieve the concerns about the unclear biological effects, particularly on nanomaterials, in general.

Prospect of Different Types of Magnetic Nanoparticles in Stem Cell Therapy

Magnetic targeting (MT) has been an emerging technology which is used to improve the delivery and retention of transplanted therapeutic cells in target site over the past 20 years. Meanwhile, stem cells have also been a research hotspot in cell therapy in recent years. Several researchers have combined the MT technology with Stem cell therapy in order to improve the efficacy. However, Different types of Magnetic Nano particles (MNPs) have presented different effects, and how to choose a proper MNPs became a question. This article aims to introduce the preparation method and application field of different types of magnetic Nanoparticles, discuss the pros and cons of different types of MNPs in stem cell therapy and make a prospect of MT technology in Stem cell therapy.

Engineered iron oxide nanoparticles to improve regenerative effects of mesenchymal stem cells

Abstract

Mesenchymal stem cells (MSCs) based therapies are a major field of regenerative medicine. However, the success of MSC therapy relies on the efficiency of its delivery and retention, differentiation, and secreting paracrine factors at the target sites. Recent studies show that superparamagnetic iron oxide nanoparticles (SPIONs) modulate the regenerative effects of MSCs. After interacting with the cell membrane of MSCs, SPIONs can enter the cells via the endocytic pathway. The physicochemical properties of nanoparticles, including size, surface charge (zeta-potential), and surface ligand, influence their interactions with MSC, such as cellular uptake, cytotoxicity, homing factors, and regenerative related factors (VEGF, TGF-β1). Therefore, in-depth knowledge of the physicochemical properties of SPIONs might be a promising lead in regenerative and anti-inflammation research using SPIONs mediated MSCs. In this review, recent research on SPIONs with MSCs and the various designs of SPIONs are examined and summarized.

Graphic abstract

A graphical abstract describes important parameters in the design of superparamagnetic iron oxide nanoparticles, affecting mesenchymal stem cells. These physicochemical properties are closely related to the mesenchymal stem cells to achieve improved cellular responses such as homing factors and cell uptake.

p53 inhibits the proliferation of male germline stem cells from dairy goat cultured on poly-L-lysine

Male germline stem cells (mGSCs) can transmit genetic materials to the next generation and dedifferentiate into pluripotent stem cells. However, in livestock, mGSC lines are difficult to establish, because of the factors that affect their isolation and culture. The extracellular matrix serves as a substrate for attachment and affects the fate of these stem cells. Poly-L-lysine (PL), an extracellular matrix of choice, inhibits and/or kills cancer cells, and promotes the attachment of stem cells in culture. However, how it affects the characteristics and potentials of these stem cells in culture needs to be elucidated. Here, we isolated, enriched and cultured dairy goat mGSCs on five types of extracellular matrices. To explore the best extracellular matrix to use for culturing them, the characteristics and proliferation ability of the cells were determined. Results showed that the cells shared several characteristics with previously reported mGSCs, including the poor effect of PL on their proliferative and colony-forming abilities. Further examination showed upregulation of p53 expression in these cells, which could be inhibiting their proliferation. When a p53 inhibitor was included in the culture medium, it was confirmed to be responsible for the inhibition of proliferation in mGSCs. Optimal concentration of the inhibitor in the culture of these cells was 5 µM. Furthermore, addition of the p53 inhibitor increased the expression of the markers of self-renewal and cell cycle in goat mGSCs. In summary, suppressing p53 is beneficial for the proliferation of dairy goat mGSCs, cultured on PL.

QSAR modeling of the toxicity classification of superparamagnetic iron oxide nanoparticles (SPIONs) in stem-cell monitoring applications: an integrated study from data curation to model development

The use of in silico approaches for the prediction of biomedical properties of nano-biomaterials (NBMs) can play a significant role in guiding and reducing wetlab experiments. Computational methods, such as data mining and machine learning techniques, can increase the efficiency and reduce the time and cost required for hazard and risk assesment and for designing new safer NBMs. A major obstacle in developing accurate and well-validated in silico models such as Nano Quantitative Structure-Activity Relationships (Nano-QSARs) is that although the volume of data published in the literature is increasing, the data are fragmented in many different publications and are not sufficiently curated for modelling purposes. Moreover, NBMs exhibit high complexity and heterogeneity in their structures, making data collection and curation and QSAR model development more challenging compared to traditional small molecules. The aim of this study was to construct and fully validate a Nano-QSAR model for the prediction of toxicological properties of superparamagnetic iron oxide nanoparticles (SPIONs), focusing on their application as Magnetic Resonance Imaging (MRI) contrast agents for non-invasive stem cell labelling and tracking. To achieve this goal, we first performed an extensive search through the literature for collecting and curating relevant data and we developed a dataset containing both physicochemical and toxicological properties of SPIONs. The data were analysed next, using Automated machine learning (Auto-ML) approaches for optimising the development and validation of nanotoxicity classification QSAR models of SPIONs. Further analysis of relative attribute importances revealed that physicochemical properties such as the size and the magnetic core are the dominant attributes correlated to the toxicity of SPIONs. Our results suggest that as more systematic information from NBM experimental tests becomes available, computational tools could play an important role in supporting the safety-by-design (SbD) concept in regenerative medicine and disease therapeutics.

Efficient Labeling Of Mesenchymal Stem Cells For High Sensitivity Long-Term MRI Monitoring In Live Mice Brains

BACKGROUND

Regenerative medicine field is still lagging due to the lack of adequate knowledge regarding the homing of therapeutic cells towards disease sites, tracking of cells during treatment, and monitoring the biodistribution and fate of cells. Such necessities require labeling of cells with imaging agents that do not alter their biological characteristics, and development of suitable non-invasive imaging modalities.

PURPOSE

We aimed to develop, characterize, and standardize a facile labeling strategy for engineered mesenchymal stem cells without altering their viability, secretion of FGF21 protein (neuroprotective), and differentiation capabilities for non-invasive longitudinal MRI monitoring in live mice brains with high sensitivity.

METHODS

We compared the labeling efficiency of different commercial iron oxide nanoparticles towards our stem cells and determined the optimum labeling conditions using prussian blue staining, confocal microscopy, transmission electron microscopy, and flow cytometry. To investigate any change in biological characteristics of labeled cells, we tested their viability by WST-1 assay, expression of FGF21 by Western blot, and adipogenic and osteogenic differentiation capabilities. MRI contrast-enhancing properties of labeled cells were investigated in vitro using cell-agarose phantoms and in mice brains transplanted with the therapeutic stem cells.

RESULTS

We determined the nanoparticles that showed best labeling efficiency and least extracellular aggregation. We further optimized their labeling conditions (nanoparticles concentration and media supplementation) to achieve high cellular uptake and minimal extracellular aggregation of nanoparticles. Cell viability, expression of FGF21 protein, and differentiation capabilities were not impeded by nanoparticles labeling. Low number of labeled cells produced strong MRI signal decay in phantoms and in live mice brains which were visible for 4 weeks post transplantation.

CONCLUSION

We established a standardized magnetic nanoparticle labeling platform for stem cells that were monitored longitudinally with high sensitivity in mice brains using MRI for regenerative medicine applications.

Protease Responsive Essential Amino-Acid Based Nanocarriers for Near-Infrared Imaging

Delivery of the theranostic agents with effective concentration to the desired sites inside the body is a major challenge in disease management. Nanotechnology has gained attention for the delivery of theranostic agents to the targeted location. The use of essential amino-acid based homopolymers for the synthesis of biocompatible and biodegradable nanoparticles (NPs) could serve as a nanocarrier for delivery applications. In this study, poly-l-lysine (PLL) and salts were used to fabricate the NPs for the delivery of exogenous contrast agents. Here, indocyanine green (ICG) was encapsulated within these NPs, and a simple two-step green chemistry-based self-assembly process was used for the fabrication. The morphological and biochemical characterizations confirm the formation of ICG encapsulating spherical PLL NPs with an average diameter of ~225 nm. Further, a detailed study has been carried out to understand the role of constituents in the assembly mechanism of PLL NPs. Our results show a controlled release of the ICG from PLL NPs in the presence of the proteolytic enzyme. In-vitro cellular studies suggest that the PLL NPs were readily taken up by the cells showing their superior delivery efficiency of ICG in comparison to the free-form of the ICG.

Radiolabeled PET/MRI Nanoparticles for Tumor Imaging

The development of integrated positron emission tomography (PET)/magnetic resonance imaging (MRI) scanners opened a new scenario for cancer diagnosis, treatment, and follow-up. Multimodal imaging combines functional and morphological information from different modalities, which, singularly, cannot provide a comprehensive pathophysiological overview. Molecular imaging exploits multimodal imaging in order to obtain information at a biological and cellular level; in this way, it is possible to track biological pathways and discover many typical tumoral features. In this context, nanoparticle-based contrast agents (CAs) can improve probe biocompatibility and biodistribution, prolonging blood half-life to achieve specific target accumulation and non-toxicity. In addition, CAs can be simultaneously delivered with drugs or, in general, therapeutic agents gathering a dual diagnostic and therapeutic effect in order to perform cancer diagnosis and treatment simultaneous. The way for personalized medicine is not so far. Herein, we report principles, characteristics, applications, and concerns of nanoparticle (NP)-based PET/MRI CAs.

Poly[N-(2-hydroxypropyl)methacrylamide]-Modified Magnetic γ-F2 O3 Nanoparticles Conjugated with Doxorubicin for Glioblastoma Treatment

With the aim to develop a new anticancer agent, we prepared poly[N-(2-hydroxypropyl)methacrylamide-co-methyl 2-methacrylamidoacetate] [P(HP-MMAA)], which was reacted with hydrazine to poly[N-(2-hydroxypropyl)methacrylamide-co-N-(2-hydrazinyl-2-oxoethyl)methacrylamide] [P(HP-MAH)] to conjugate doxorubicin (Dox) via hydrazone bond. The resulting P(HP-MAH)-Dox conjugate was used as a coating of magnetic γ-Fe₂ O₃ nanoparticles obtained by the coprecipitation method. In vitro toxicity of various concentrations of Dox, P(HP-MAH)-Dox, and γ-Fe₂ O₃ @P(HP-MAH)-Dox nanoparticles was determined on somatic healthy cells (human bone marrow stromal cells hMSC), human glioblastoma line (GaMG), and primary human glioblastoma (GBM) cells isolated from GBM patients both at a short and prolonged exposition time (up to 7 days). Due to hydrolysis of the hydrazone bond in acid milieu of tumor cells and Dox release, the γ-Fe₂ O₃ @P(HP-MAH)-Dox nanoparticles significantly decreased the GaMG and GBM cell growth compared to free Dox and P(HP-MAH)-Dox in low concentration (10 nM), whereas in hMSCs it remained without effect. γ-F₂ O₃ @PHP nanoparticles alone did not affect the viability of any of the tested cells.

Surface-Engineered Super-Paramagnetic Iron Oxide Nanoparticles For Chromium Removal

Background

Super-paramagnetic iron oxide nanoparticles (SPIONs) are widely used metal nanoparticles for various applications for its magnetic property and biocompatibility. In recent years, pollution of our environment especially with heavy metals in waterbodies has become a major threat and has left us very minimal sources of freshwater to drink. SPIONs or surface modified SPIONs can be used to remove these heavy metals

Methods

SPIONs were synthesized by co-precipitation method and further coated with a biopolymer, chitosan. Chromium solution was treated with the synthesized SPIONs to study the efficiency of chromium removal by surface adsorption. Later, the adsorption was analysed by direct and indirect analysis methods using UV-VIS spectrophotometry and isotherm studies.

Results

Stable chitosan-coated SPIONs were synthesized and they adsorbed chromium better than the uncoated SPIONs, where it was adsorbing up to 100 ppm. Adsorption was found to be increasing with decrease in pH.

Conclusion

The surface-modified SPIONs expressed cumulative adsorption action. Even after the adsorption studies, chitosan-coated SPIONs were possessing magnetic property. Thus, the surface-modified SPIONs can become an ideal nanotechnology tool to remove the chromium from groundwater.

Kinetics of Poly-l-lysine Adsorption on Mica and Stability of Formed Monolayers: Theoretical and Experimental Studies

Various physicochemical parameters of poly-l-lysine (PLL) solutions comprising the diffusion coefficient, the electrophoretic mobility, the density, and the intrinsic viscosity were determined for the pH range 3.0-9.2. This allowed us to calculate derivative parameters characterizing the PLL molecule such as: zeta potential, the number of electrokinetic charges, ionization degree, contour length, and cross section area. These data were exploited in theoretical calculations of PLL adsorption kinetics on solid substrates under diffusion transport. A hybrid approach was used comprising a blocking function derived from the random sequential adsorption (RSA) model. In experiments, the PLL adsorption on mica was studied using the streaming potential measurements and interpreted in terms of a general electrokinetic model. This confirmed a side-on adsorption mechanism of the macroion molecules at the examined pH range. Additionally, using this method, the stability of PLL monolayers was determined performing in situ desorption kinetic experiments. In this way, the equilibrium adsorption constant and the energy minimum depth were determined. It was confirmed that the monolayer stability decreases with pH following the decrease in the number of electrokinetic charges per molecule. This confirmed the electrostatic interaction driven adsorption mechanism of PLL. It is also predicted that at pH 5.7-7.4 the monolayers were stable under diffusion-controlled desorption over the time exceeding 100 h. In addition to their significance for basic science, the results obtained in this work can be exploited for developing procedures for preparing stable PLL monolayers of well controlled coverage and electrokinetic properties.

Tracking iron oxide labelled mesenchymal stem cells(MSCs) using magnetic resonance imaging (MRI) in a rat model of hepatic cirrhosis

Homing and tumor attenuation potential of BM-MSCs labelled with superparamagnetic iron-oxide nanoparticles (SPIONs) in a rat model of hepatic cirrhosis was evaluated. Rat BM-MSCs were derived, characterized and labelled with SPIONs (200 nm; 25 mg Fe/ml). Hepatic cirrhosis was induced in Wistar rats (n=30; 10/group) with carbon tetrachloride (CCl4; 0.3 mL/kg body weight) injected twice a week for 12 weeks. Group-I was administered vehicle (castor-oil) alone; Group-II received two doses of unlabelled BM-MSCs (3x106 cells) and Group-III received two doses of SPIONs labelled BM-MSCs (3x106 cells) via tail vein injection (0.5 ml) at weekly intervals. All animals were sacrificed after two weeks for histological, radiological and biochemical analysis. Derived BM-MSCs demonstrated MSCs related CD markers. Histology confirmed induction of hepatic cirrhosis with CCL4. Levels of alanine-aminotransferase, aspartate-aminotransferase,alkaline-phosphatase and gamma glutamyl-transferase returned to normal levels following treatment with BM-MSCs. Uptake and homing of SPIONs labelled BM-MSCs, and reduction in the size of cirrhotic nodules were confirmed using transmission electron microscopy and magnetic resonance imaging respectively. BM-MSCs reduced the pathological effects of CCL4 induced hepatic cirrhosis and labelling BMMSCs with SPIONs were non-toxic and enabled efficient tracking using non-invasive methods.

Manganese-Zinc Ferrites: Safe and Efficient Nanolabels for Cell Imaging and Tracking In Vivo

Manganese-zinc ferrite nanoparticles were synthesized by using a hydrothermal treatment, coated with silica, and then tested as efficient cellular labels for cell tracking, using magnetic resonance imaging (MRI) in vivo. A toxicity study was performed on rat mesenchymal stem cells and C6 glioblastoma cells. Adverse effects on viability and cell proliferation were observed at the highest concentration (0.55 mM) only; cell viability was not compromised at lower concentrations. Nanoparticle internalization was confirmed by transmission electron microscopy. The particles were found in membranous vesicles inside the cytoplasm. Although the metal content (0.42 pg Fe/cell) was lower compared to commercially available iron oxide nanoparticles, labeled cells reached a comparable relaxation rate R ₂, owing to higher nanoparticle relaxivity. Cells from transgenic luciferase-positive rats were used for in vivo experiments. Labeled cells were transplanted into the muscles of non-bioluminescent rats and visualized by MRI. The cells produced a distinct hypointense signal in T₂- or T₂*-weighted MR images in vivo. Cell viability in vivo was verified by bioluminescence.

Epsilon-poly-l-lysine decorated ordered mesoporous silica contributes to the synergistic antifungal effect and enhanced solubility of a lipophilic drug

The emergence of drug-resistant fungal strains remains a severe threat for the public health, which prompts strict restrictions on the uses of antifungal drugs. However, the majority of lipophilic fungistatic agents are poorly water soluble with a low oral adsorption characteristic posing challenges for the precise prescriptions. In this study, a natural antimicrobial cationic peptide of epsilon-poly-l-lysine (EPL) decorated ordered mesoporous silica (SBA-15) was facilely prepared for the efficient loading of antifungal itraconazole (ITZ) drugs. The characterized mesoporous SBA-15/EPL/ITZ composite exhibited remarkable antifungal performance against Aspergillus fumigatus as a model mold, which was attributed to synergistic antifungal activities of ITZ and EPL in the mesopores. Moreover, the in vitro release behaviors of ITZ in the composite nanoexcipients both in simulated gastric fluid and fasted state simulated intestinal fluid were studied. The observed release kinetics of ITZ demonstrated a contributing role of SBA-15/EPL to enhance the solubility of ITZ and thereby may promote its flux across the gastrointestinal epithelium, which is beneficial for the absorption of drugs. Additionally, SBA-15/EPL/ITZ composites showed desirable biocompatibility toward mammalian red blood cells, human cervical cancer cells (Hela) and human embryonic kidney cells (HEK-293T). Furthermore, the pharmacokinetic profiles of obtained nano-formulations were assessed in rats, among which the improved adsorption of SBA-15/EPL/ITZ composites (AUC_{0-24h sum}: 8381.7 nM·h) was identified compared with that of pure ITZ (525.1 nM·h) and the commercial drug of Sporanox (7516.6 nM·h). Collectively, the prepared SBA-15/EPL/ITZ provides an ecofriendly and integrated nanocomposite with enhanced solubility of lipophilic drugs to combat proliferations of infectious fungi.

Scavenging of reactive oxygen species by phenolic compound-modified maghemite nanoparticles

Maghemite (γ-Fe₂O₃) nanoparticles obtained through co-precipitation and oxidation were coated with heparin (Hep) to yield γ-Fe₂O₃@Hep, and subsequently with chitosan that was modified with different phenolic compounds, including gallic acid (CS-G), hydroquinone (CS-H), and phloroglucinol (CS-P), to yield γ-Fe₂O₃@Hep-CS-G, γ-Fe₂O₃@Hep-CS-H, and γ-Fe₂O₃@Hep-CS-P particles, respectively. Surface modification of the particles was analyzed by transmission electron microscopy, dynamic light scattering, attenuated total reflection Fourier transform infrared spectroscopy, and thermogravimetric analysis. Magnetic measurements indicated that the polymer coating does not affect the superparamagnetic character of the iron oxide core. However, magnetic saturation decreased with increasing thickness of the polymer coating. The antioxidant properties of the nanoparticles were analyzed using a 2,2-diphenyl-1-picrylhydrazyl (DPPH) assay. Cellular uptake and intracellular antioxidant activity of the particles were evaluated by an iron assay and flow cytometry, respectively, using L-929 and LN-229 cells. Compared to the control, the phenolic modification significantly reduced intracellular reactive oxygen species (ROS) levels to 35-56%, which was associated with a 6-8-times higher cellular uptake in L-929 cells and a 21-31-times higher cellular uptake in LN-229 cells. In contrast, γ-Fe₂O₃@Hep particles induced a 3.8-times and 14.9-times higher cellular uptake without inducing antioxidant activity. In conclusion, the high cellular uptake and the antioxidant properties associated with the phenolic moieties in the modified particles allow for a potential application in biomedical areas.

Organic Semiconducting Polymer Nanoparticles for Photoacoustic Labeling and Tracking of Stem Cells in the Second Near-Infrared Window

Photoacoustic (PA) imaging and tracking of stem cells plays an important role in the real-time assessment of cell-based therapies. Nevertheless, the limitations of conventional inorganic PA contrast agents and the narrow range of the excitation wavelength in the first near-infrared (NIR-I) window hamper the applications of PA imaging in living subjects. Herein, we report the design and synthesis of a second near-infrared (NIR-II) absorptive organic semiconducting polymer (OSP)-based nanoprobe (OSPN⁺) for PA imaging and tracking of stem cells. Comparison studies in biological tissue show that NIR-II light excited PA imaging of the OSPN⁺ has significantly higher signal-to-noise ratio than NIR-I light excited PA imaging, thereby demonstrating the superiority of the OSPN⁺ for deep tissue imaging. With good biocompatibility, appropriate size, and optimized surface property, the OSPN⁺ shows enhanced cellular uptake for highly efficient PA labeling of stem cells. In vivo investigations reveal significant NIR-II PA contrast enhancement of the transplanted OSPN⁺-labeled human mesenchymal stem cells by 40.6- and 21.7-fold in subcutaneous and brain imaging, respectively, compared with unlabeled cases. Our work demonstrates a class of OSP-based nanomaterials for NIR-II PA stem cell imaging to facilitate a better understanding and evaluation of stem cell-based therapies.

Cytotoxicity of doxorubicin-conjugated poly[N-(2-hydroxypropyl)methacrylamide]-modified γ-Fe2O3 nanoparticles towards human tumor cells

Doxorubicin-conjugated magnetic nanoparticles containing hydrolyzable hydrazone bonds were developed using a non-toxic poly[N-(2-hydroxypropyl)methacrylamide] (PHPMA) coating, which ensured good colloidal stability in aqueous media and limited internalization by the cells, however, enabled adhesion to the cell surface. While the neat PHPMA-coated particles proved to be non-toxic, doxorubicin-conjugated particles exhibited enhanced cytotoxicity in both drug-sensitive and drug-resistant tumor cells compared to free doxorubicin. The newly developed doxorubicin-conjugated PHPMA-coated magnetic particles seem to be a promising magnetically targeted vehicle for anticancer drug delivery.

Poly-l-lysine-coated superparamagnetic nanoparticles: a novel method for the transfection of pro-BDNF into neural stem cells

Poly-l-lysine-coated superparamagnetic iron oxide nanoparticles (SPIONs-PLL) were prepared and used as a novel-carrier for the transfer of brain-derived neurotrophic factor (BDNF) into neural stem cells (NSCs) under the beneficial influence of an external magnetic field. Pro-BDNF, a gene from human brain cDNA libraries, was obtained by polymerase chain reaction and constructed in a mammalian expression vector (PSecTag2/HygroB). The nanoparticles (NPs) were examined using Fourier transform infrared spectroscopy, zeta potential, and Transmission electron microscopy. From the results, the levels of BDNF among the transfected and untransfected cells were 30.326 ± 5.9 and 5.85 ± 3.11 pg/mL, respectively, as detected by an ELISA method. Moreover, the enhanced green fluorescent protein vector was used to evaluate the gene expression efficiency for SPIONs-PLL as a non-viral carrier in NSCs. This was performed under the influence of a magnetic field and the transfection reagents (such as Lipofectamine 2000), which served as a positive control. The histological analysis revealed that the concentration of intracellular NPs was significantly higher than intercellular NPs. These results suggest that SPIONs-PLL can serve as a novel alternative for the transfection of BDNF-NSCs and could be used in gene therapy.

Magnetically Controlled Liposome Aggregates for On-Demand Release of Reactive Payloads

A colloidal system able to act as a miniature reactor for on-demand release of reactive payloads has been demonstrated. The system is based on submicrometer aggregates consisting of anionic liposomes that act as storage reservoirs for the reactants, superparamagnetic iron oxide nanoparticles (SPIONs) that enable magnetic positioning in space and controlled release of reactants from the liposomes by radiofrequency stimulation, and an oppositely charged polyelectrolyte (poly-l-lysine) that keeps the constituent elements within the aggregates at a defined ratio. The kinetics of liposome-PLL-SPION heteroaggregation was systematically mapped and a suitable composition of the liposome bilayer was found such that the system exhibits stability at ambient conditions and radiofrequency triggered release at physiological temperature. The functionality of the system was demonstrated using a reaction between resazurin and ascorbic acid. The ability to release the reactants on-demand at defined time points was demonstrated. The system opens up opportunities for the controlled local delivery of unstable of highly bioactive molecules produced in situ and on demand from stable precursors.

Shape-, size- and structure-controlled synthesis and biocompatibility of iron oxide nanoparticles for magnetic theranostics

In the past decade, iron oxide nanoparticles (IONPs) have attracted more and more attention for their excellent physicochemical properties and promising biomedical applications. In this review, we summarize and highlight recent progress in the design, synthesis, biocompatibility evaluation and magnetic theranostic applications of IONPs, with a special focus on cancer treatment. Firstly, we provide an overview of the controlling synthesis strategies for fabricating zero-, one- and three-dimensional IONPs with different shapes, sizes and structures. Then, the in vitro and in vivo biocompatibility evaluation and biotranslocation of IONPs are discussed in relation to their chemo-physical properties including particle size, surface properties, shape and structure. Finally, we also highlight significant achievements in magnetic theranostic applications including magnetic resonance imaging (MRI), magnetic hyperthermia and targeted drug delivery. This review provides a background on the controlled synthesis, biocompatibility evaluation and applications of IONPs as cancer theranostic agents and an overview of the most up-to-date developments in this area.

Interaction of poly-l-lysine coating and heparan sulfate proteoglycan on magnetic nanoparticle uptake by tumor cells

Background

Poly-l-lysine (PLL) enhances nanoparticle (NP) uptake, but the molecular mechanism remains unresolved. We asked whether PLL may interact with negatively charged glycoconjugates on the cell surface and facilitate uptake of magnetic NPs (MNPs) by tumor cells.

Methods

PLL-coated MNPs (PLL-MNPs) with positive and negative ζ-potential were prepared and characterized. Confocal and transmission electron microscopy was used to analyze cellular internalization of MNPs. A colorimetric iron assay was used to quantitate cell-associated MNPs (MNP_cell).

Results

Coadministration of PLL and dextran-coated MNPs in culture enhanced cellular internalization of MNPs, with increased vesicle size and numbers/cell. MNP_cell was increased by eight- to 12-fold in response to PLL in a concentration-dependent manner in human glioma and HeLa cells. However, the application of a magnetic field attenuated PLL-induced increase in MNP_cell. PLL-coating increased MNP_cell regardless of ζ-potential of PLL-MNPs, whereas magnetic force did not enhance MNP_cell. In contrast, epigallocatechin gallate and magnetic force synergistically enhanced PLL-MNP uptake. In addition, heparin, but not sialic acid, greatly reduced the enhancement effects of PLL; however, removal of heparan sulfate from heparan sulfate proteoglycans of the cell surface by heparinase III significantly reduced MNP_cell.

Conclusion

Our results suggest that PLL-heparan sulfate proteoglycan interaction may be the first step mediating PLL-MNP internalization by tumor cells. Given these results, PLL may facilitate NP interaction with tumor cells via a molecular mechanism shared by infection machinery of certain viruses.

Magnetic iron oxide nanoparticles as drug carriers: preparation, conjugation and delivery

Magnetic nanoparticles (MNPs), particularly made of iron oxides, have been extensively studied as diagnostic imaging agents and therapeutic delivery vehicles. In this review, special emphasis is set on the 'recent advancements of drug-conjugated MNPs used for therapeutic applications'. The most prevalent preparation methods and chemical functionalization strategies required for translational biomedical nanoformulations are outlined. Particular attention is, then, devoted to the tailored conjugation of drugs to the MNP carrier according to either noncovalent or covalent attachments, with advantages and drawbacks of both pathways conferred. Notable examples are presented to demonstrate the advantages of MNPs in respective drug-delivery applications. Understanding of the preparation, conjugation and delivery processes will definitely bring, in the next decades, a novel magneto-nanovehicle for effective theranostics.