Recent advances in surface engineering of superparamagnetic iron oxide nanoparticles for biomedical applications

In the View of Electrons Transfer and Energy Conversion: The Antimicrobial Activity and Cytotoxicity of Metal-Based Nanomaterials and Their Applications

The global pandemic and excessive use of antibiotics have raised concerns about environmental health, and efforts are being made to develop alternative bactericidal agents for disinfection. Metal-based nanomaterials and their derivatives have emerged as promising candidates for antibacterial agents due to their broad-spectrum antibacterial activity, environmental friendliness, and excellent biocompatibility. However, the reported antibacterial mechanisms of these materials are complex and lack a comprehensive understanding from a coherent perspective. To address this issue, a new perspective is proposed in this review to demonstrate the toxic mechanisms and antibacterial activities of metal-based nanomaterials in terms of energy conversion and electron transfer. First, the antimicrobial mechanisms of different metal-based nanomaterials are discussed, and advanced research progresses are summarized. Then, the biological intelligence applications of these materials, such as biomedical implants, stimuli-responsive electronic devices, and biological monitoring, are concluded based on trappable electrical signals from electron transfer. Finally, current improvement strategies, future challenges, and possible resolutions are outlined to provide new insights into understanding the antimicrobial behaviors of metal-based materials and offer valuable inspiration and instructional suggestions for building future intelligent environmental health.

The function of chitosan/agarose biopolymer on Fe2 O3 nanoparticles and evaluation of their effects on MCF-7 breast cancer cell line and expression of BCL2 and BAX genes

In recent decades, magnetic nanoparticles modified with biocompatible polymers have been recognized as a suitable tool for treating breast cancer. The aim of this research was to evaluate the function of chitosan/agarose-functionalized Fe₂ O₃ nanoparticles on the MCF-7 breast cancer cell line and the expression of BCL2 and BAX genes. Free Fe₂ O₃ nanoparticles were prepared by hydrothermal method. FTIR, XRD, SEM, DLS, VSM, and zeta potential analyses determined the size and morphological characteristics of the synthesized nanoparticles. The effect of Fe₂ O₃ free nanoparticles and formulated Fe₂ O₃ nanoparticles on induction of apoptosis was studied by double-dye Annexin V-FITC and PI. Also, the gene expression results using the PCR method displayed that Fe₂ O₃ formulated nanoparticles induced BAX apoptosis by increasing the anti-apoptotic gene expression and decreasing the expression of pro-apoptotic gene BCL2, so the cell progresses to planned cell death. In addition, the results showed that the BAX/BCL2 ratio decreased significantly after treatment of MCF-7 cells with free Fe₂ O₃ nanoparticles, and the BAX/BCL2 ratio for Fe₂ O₃ formulated nanoparticles increased significantly. Also, to evaluate cell migration, the scratch test was performed, which showed a decrease in motility of MCF-7 cancer cells treated with Fe₂ O₃ nanoparticles formulated with chitosan/agarose at concentrations of 10, 50, 100, and 200 μg/ml.

Influence of surfactants on biomolecular conjugation of magnetic nanoparticles

Here, we report the physicochemical interaction among iron oxide nanoparticles (MNPs) and essential biomolecules, namely, serum albumin (BSA, HSA), collagen and deoxyribonucleic acid (DNA) in the presence of various cationic, anionic and non-ionic surfactants. Iron oxide nanoparticles are synthesized by the wet chemical process and are characterized by X-ray powder diffraction analysis (XRD), Fourier transform infrared spectroscopic, UV-Vis spectroscopy, scanning electron microscopy and energy-dispersive X-ray spectroscopy mapping studies . The conjugation of MNPs protein was analyzed using UV-Vis spectroscopy, fluorescence spectroscopy, circular dichroism technique and gel electrophoresis. The spectroscopic investigation illustrates the surfactant-dependent binding between MNPs and protein. Gel electrophoresis in the absence and presence of MNPs-surfactant systems has been used to study the impact on DNA structure. It was found that Tween 80 imparts better stability as well as biocompatibility to the synthesized MNPs. The findings offer extensive information on the influence of various surfactant coatings on MNP surfaces and their influence on vital biomolecules, making it useful for designing MNPs for biological applications.Communicated by Ramaswamy H. Sarma.

Antioxidant Activity of Bioactive Peptide Fractions from Germinated Soybeans Conjugated to Fe3O4 Nanoparticles by the Ugi Multicomponent Reaction

The conjugation of biomolecules to magnetic nanoparticles has emerged as promising approach in biomedicine as the treatment of several diseases, such as cancer. In this study, conjugation of bioactive peptide fractions from germinated soybeans to magnetite nanoparticles was achieved. Different fractions of germinated soybean peptides (>10 kDa and 5-10 kDa) were for the first time conjugated to previously coated magnetite nanoparticles (with 3-aminopropyltriethoxysilane (APTES) and sodium citrate) by the Ugi four-component reaction. The crystallinity of the nanoparticles was corroborated by X-ray diffraction, while the particle size was determined by scanning transmission electron microscopy. The analyses were carried out using infrared and ultraviolet-visible spectroscopy, dynamic light scattering, and thermogravimetry, which confirmed the coating and functionalization of the magnetite nanoparticles and conjugation of different peptide fractions on their surfaces. The antioxidant activity of the conjugates was determined by the reducing power and hydroxyl radical scavenging activity. The nanoparticles synthesized represent promising materials, as they have found applications in bionanotechnology for enhanced treatment of diseases, such as cancer, due to a higher antioxidant capacity than that of fractions without conjugation. The highest antioxidant capacity was observed for a >10 kDa peptide fraction conjugated to the magnetite nanoparticles coated with APTES.

Synthesis and characterization of magnetite nanoparticles by co-precipitation method coated with biocompatible compounds and evaluation of in-vitro cytotoxicity

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Modified magnetite nanoparticles had low cytotoxicity.

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Nanoparticles had high surface modification and manipulation.

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Magnetite nanoprticles coated with silica and oleic acid was lower toxicity than other coatings.

Recent advances in the use of magnetite nanoparticles for biomedical applications have led to special attention to these nanoparticles. The unique properties of magnetite nanoparticles such as superparamagnetism, low toxicity, and the ability to bond with biological molecules, are suitable for drug delivery, diagnostic methods and therapeutic approaches. The aim of this study was to synthesize magnetite nanoparticles with different biocompatible coatings and investigate their cytotoxicity. Magnetite nanoparticles were synthesized by co-precipitation method and the cytotoxicity of these nanoparticles was investigated with Hepatoma G2 cell using the MTT assay. Treated cells, did not showed any evident cell cycle arrest. The Fourier Transmission Infrared (FTIR) spectroscopy, X- ray powder Diffraction (XRD), Transmission Electron Microscopy (TEM) were evaluated. The results of XRD showed the coated magnetite nanoparticles were 10−12 nm and this size also achieved with TEM images. Synthesized magnetite nanoparticles with SiO₂ and oleic acid coatings had lower cytotoxicity than other coatings.

Protein corona: Dr. Jekyll and Mr. Hyde of nanomedicine

Nanomedicine is an interdisciplinary field of research, comprising science, engineering, and medicine. Many are the clinical applications of nanomedicine, such as molecular imaging, medical diagnostics, targeted therapy, and image-guided surgery. Despite major advances during the past 20 years, many efforts must be done to understand the complex behavior of nanoparticles (NPs) under physiological conditions, the kinetic and thermodynamic principles, involved in the rational design of NP. Once administrated in physiological environment, NPs interact with biomolecules and they are surrounded by protein corona (PC) or biocorona. PC can trigger an immune response, affecting NPs toxicity and targeting capacity. This review aims to provide a detailed description of biocorona and of parameters that are able to control PC formation and composition. Indeed, the review provides an overview about the role of PC in the modulation of both cytotoxicity and immune response as well as in the control of targeting capacity.

Synthesis of a new Ni complex supported on CoFe2O4 and its application as an efficient and green catalyst for the synthesis of bis(pyrazolyl)methane and polyhydroquinoline derivatives

A novel and magnetic nanocatalyst was synthesized for the synthesis of multicomponent compounds.

Silver-coated magnetic nanocomposites induce growth inhibition and protein changes in foodborne bacteria

Cytotoxicity concerns of nanoparticles on animal or human bodies have led to the design of iron oxide core nanocomposites, coated with elemental silver to allow their magnetic removal from bio-mixtures. Although the antimicrobial effect of silver is well-described, the effects of nanoparticles derived from silver on microorganisms remain unfolded. Here, we characterized a customized magnetic silver nanocomposite (Ag-MNP) and evaluated its effects on bacterial growth and protein changes. The Ag-MNP displayed both longitudinal and round shapes under High-Resolution Transmission Electron Microscopy imaging, while the Energy Dispersive X-ray Spectroscopy and X-ray diffraction analysis confirmed the presence of Ag, Fe₃O₄ (Magnetite) and FeO₂ (Goethite). Optical density, bioluminescence imaging, and Colony Forming Unit assessments revealed that the presence of Ag-MNP induced strong dose-dependent bacteria (Escherichia coli O157:H7, Salmonella enterica serovar Typhimurium and S. Anatum) growth inhibition. The TEM imaging showed penetration and infiltration of bacteria by Ag-MNP, leading to membrane degeneration and vacuole formation. The presence of Ag-MNP led to fifteen up-regulated and nine down-regulated proteins (P < 0.05) that are involved in cell membrane synthesis, inhibition of protein synthesis, interference with DNA synthesis, and energy metabolism inhibition. This study provides insights to develop alternative antimicrobials to treat foodborne pathogens with antibiotic resistance avoidance.

Synthesis and characterization of γ-Fe2O3@SiO2–(CH2)3–PDTC–Pd magnetic nanoparticles: a new and highly active catalyst for the Heck/Sonogashira coupling reactions

A novel catalyst is synthesized based on the immobilization of palladium on γ-Fe₂O₃@SiO₂–(CH₂)₃–PDTC nanoparticles and is used as a highly active catalyst for the Heck/Sonogashira coupling reactions.

The Detailed Bactericidal Process of Ferric Oxide Nanoparticles on E. coli

While nanoparticles exert bactericidal effects through the generation of reactive oxygen species (ROS), the processes of the internalization of and the direct physical damage caused by iron oxide nanoparticles are not completely clear. We hypothesize that direct physical or mechanical damage of the cell membrane and cytoplasmic integrity by nanoparticles is another major cause of bacterial death besides ROS. The aim of this study is to investigate the process of the internalization of iron oxide nanoparticles, and to evaluate the effect of direct physical or mechanical damage on bacterial cell growth and death. The results demonstrate that iron oxide nanoparticles not only inhibited E. coli cell growth, but also caused bacterial cell death. Iron oxide nanoparticles produced significantly elevated ROS levels in bacteria. Transmission electronic microscopy demonstrated that iron oxide nanoparticles were internalized into and condensed the cytoplasm. Strikingly, we observed that the internalized nanoparticles caused intracellular vacuole formation, instead of simply adsorbing thereon; and formed clusters on the bacterial surface and tore up the outer cell membrane to release cytoplasm. This is the first time that the exact process of the internalization of iron oxide nanoparticles has been observed. We speculate that the intracellular vacuole formation and direct physical or mechanical damage caused by the iron oxide nanoparticles caused the bactericidal effect, along with the effects of ROS.

Synthesis, Functionalization, and Design of Magnetic Nanoparticles for Theranostic Applications

In order to translate nanotechnology into medical practice, magnetic nanoparticles (MNPs) have been presented as a class of non-invasive nanomaterials for numerous biomedical applications. In particular, MNPs have opened a door for simultaneous diagnosis and brisk treatment of diseases in the form of theranostic agents. This review highlights the recent advances in preparation and utilization of MNPs from the synthesis and functionalization steps to the final design consideration in evading the body immune system for therapeutic and diagnostic applications with addressing the most recent examples of the literature in each section. This study provides a conceptual framework of a wide range of synthetic routes classified mainly as wet chemistry, state-of-the-art microfluidic reactors, and biogenic routes, along with the most popular coating materials to stabilize resultant MNPs. Additionally, key aspects of prolonging the half-life of MNPs via overcoming the sequential biological barriers are covered through unraveling the biophysical interactions at the bio-nano interface and giving a set of criteria to efficiently modulate MNPs' physicochemical properties. Furthermore, concepts of passive and active targeting for successful cell internalization, by respectively exploiting the unique properties of cancers and novel targeting ligands are described in detail. Finally, this study extensively covers the recent developments in magnetic drug targeting and hyperthermia as therapeutic applications of MNPs. In addition, multi-modal imaging via fusion of magnetic resonance imaging, and also innovative magnetic particle imaging with other imaging techniques for early diagnosis of diseases are extensively provided.

Tumor targeting by lentiviral vectors combined with magnetic nanoparticles in mice

Nanomaterials conjugated or complexed with biological moieties such as antibodies, polymers or peptides appear to be suitable not only for drug delivery but also for specific cancer treatment. Here, biocompatible iron oxide magnetic nanoparticles (MNPs) with or without a silica shell coupled with lentiviral vectors (LVs) are proposed as a combined therapeutic approach to specifically target gene expression in a cancer mouse model. Initially, four different MNPs were synthesized and their physical properties were characterized to establish and discriminate their behaviors. MNPs and LVs strictly interacted and transduced cells in vitro as well as in vivo, with no toxicity or inflammatory responses. By injecting LV-MNPs complexes intravenously, green fluorescent protein (GFP) resulted in a sustained long-term expression. Furthermore, by applying a magnetic field on the abdomen of intravenous injected mice, GFP positive cells increased in livers and spleens. In liver, LV-MNPs were able to target both hepatocytes and non-parenchymal cells, while in a mouse model with a grafted tumor, intra-tumor LV-MNPs injection and magnetic plaque application next to the tumor demonstrated the efficient uptake of LV-MNPs complexes with high number of transduced cells and iron accumulation in the tumor site. More important, LV-MNPs with the application of the magnetic plaque spread in all the tumor parenchyma and dissemination through the body was prevented confirming the efficient uptake of LV-MNPs complexes in the tumor. Thus, these LV-MNPs complexes could be used as multifunctional and efficient tools to selectively induce transgene expression in solid tumor for therapeutic purposes.

STATEMENT OF SIGNIFICANCE

Our study describes a novel approach of combining magnetic properties of nanomaterials with gene therapy. Magnetic nanoparticles (MNPs) coated with or without a silica shell coupled with lentiviral vectors (LVs) were used as vehicle to target biological active molecules in a mouse cancer model. After in situ injection, the presence of MNP under the magnetic field improve the vector distribution in the tumor mass and after systemic administration, the application of the magnetic field favor targeting of specific organs for LV transduction and specifically can direct LV in specific cells (or avoiding them). Thus, our findings suggest that LV-MNPs complexes could be used as multifunctional and efficient tools to selectively induce transgene expression in solid tumor for therapeutic purposes.

The role of size polydispersity in magnetic fluid hyperthermia: average vs. local infra/over-heating effects

An efficient and safe hyperthermia cancer treatment requires the accurate control of the heating performance of magnetic nanoparticles, which is directly related to their size. However, in any particle system the existence of some size polydispersity is experimentally unavoidable, which results in a different local heating output and consequently a different hyperthermia performance depending on the size of each particle. With the aim to shed some light on this significant issue, we have used a Monte Carlo technique to study the role of size polydispersity in heat dissipation at both the local (single particle) and global (macroscopic average) levels. We have systematically varied size polydispersity, temperature and interparticle dipolar interaction conditions, and evaluated local heating as a function of these parameters. Our results provide a simple guide on how to choose, for a given polydispersity degree, the more adequate average particle size so that the local variation in the released heat is kept within some limits that correspond to safety boundaries for the average-system hyperthermia performance. All together we believe that our results may help in the design of more effective magnetic hyperthermia applications.

Versatile theranostics agents designed by coating ferrite nanoparticles with biocompatible polymers

Three biocompatible polymers, polyethylene glycol (PEG), dextran and chitosan, have been used in this work to control the colloidal stability of magnetic nanoparticles (14 ± 5 nm in diameter) and to vary the aggregation state in order to study their effect on relaxometric and heating properties. Two different coating strategies have been deeply developed; one based on the formation of an amide bond between citric acid coated nanoparticles (NPs) and amine groups present on the polymer surface and the other based on the NP encapsulation. Relaxometric properties revealed that proton relaxation rates strongly depend on the coating layer hydrophilicity and the aggregation state of the particles due to the presence of magnetic interactions. Thus, while PEG coating reduces particle aggregation by increasing inter-particle spacing leading to reduction of both T1 and T2 relaxation, dextran and chitosan lead to an increase mainly in T2 values due to the aggregation of particles in bigger clusters where they are in close contact. Dextran and chitosan coated NPs have also shown a remarkable heating effect during the application of an alternating magnetic field. They have proved to be potential candidates as theranostic agents for cancer diagnosis and treatment. Finally, cytotoxicity of PEG conjugated NPs, which seem to be ideal for intravenous administration because of their small hydrodynamic size, was investigated resulting in high cell viability even at 0.2 mg Fe ml(-1) after 24 h of incubation. This suspension can be used as drug/biomolecule carrier for in vivo applications.

Wide bandgap mesoporous hematite nanowire bundles as a sensitive and rapid response ethanol sensor

In this study, α-Fe2O3 nanowires were synthesized using mesoporous SBA-15 silica as the hard templates with the nanocasting method, and then mesoporous α-Fe2O3 nanowire bundles (NWBs) were separated from the well-dispersed α-Fe2O3 nanowires (NWs) by the centrifugation technique. Both samples were characterized by x-ray diffraction, transmission electron microscopy (TEM), nitrogen adsorption/desorption isotherm and UV-vis spectra. All results indicated that the α-Fe2O3 NWBs with mesoporous structure presented a higher BET surface area (95 m(2) g(-1)) and wider bandgap (2.08 eV) than those of α-Fe2O3 NWs (32 m(2) g(-1) and 1.91 eV). The bandgap of α-Fe2O3 NWBs was in accordance with the bulk α-Fe2O3, while the BET surface area was much higher. The results from the gas-sensing measurement revealed that the α-Fe2O3 NWBs based gas sensor exhibited a high sensitivity of 21.7, fast response-recovery of 7.5 s and 1 s, and good selectivity to ethanol at 340 °C. The sensitivity (21.7) for ethanol of α-Fe2O3 NWBs was much better than that of the α-Fe2O3 NWs (12.2), which should be attributed to the higher BET surface area and wider bandgap of α-Fe2O3 NWBs.

Characterization, Quantification, and Determination of the Toxicity of Iron Oxide Nanoparticles to the Bone Marrow Cells

Iron oxide nanoparticles (IONPs) have been used to develop iron supplements for improving the bioavailability of iron in patients with iron deficiency, which is one of the most serious nutritional deficiencies in the world. Accurate information about the characteristics, concentration, and cytotoxicity of IONPs to the developmental and reproductive cells enables safe use of IONPs in the supplement industry. The objective of this study was to analyze the physicochemical properties and cytotoxicity of IONPs in bone marrow cells. We prepared three different types of iron samples (surface-modified iron oxide nanoparticles (SMNPs), IONPs, and iron citrate) and analyzed their physicochemical properties such as particle size distribution, zeta potential, and morphology. In addition, we examined the cytotoxicity of the IONPs in various kinds of bone marrow cells. We analyzed particle size distribution, zeta potential, iron levels, and subcellular localization of the iron samples in bone marrow cells. Our results showed that the iron samples were not cytotoxic to the bone marrow cells and did not affect the expression of cell surface markers and lipopolysaccharide (LPS)-induced the secretion of cytokines by murine bone marrow-derived dendritic cells (BMDCs). Our results may be used to investigate the interactions between nanoparticles and cells and tissues and the developmental toxicity of nanoparticles.

Synthesis and design of biologically inspired biocompatible iron oxide nanoparticles for biomedical applications

During the last couple of decades considerable research efforts have been directed towards the synthesis and coating of iron oxide nanoparticles (IONPs) for biomedical applications. To address the current limitations, recent studies have focused on the design of new generation nanoparticle systems whose internalization and targeting capabilities have been improved through surface modifications. This review covers the most recent challenges and advances in the development of IONPs with enhanced quality, and biocompatibility for various applications in biotechnology and medicine.

Surface modification and local orientations of surface molecules in nanotherapeutics

Nanotechnology has emerged as a powerful tool for various therapeutic applications, solving many difficulties in both diagnosis and treatment. However, many obstacles in complex biological systems have impeded the successful application of therapeutic nanoparticles, and fine-tuning nanoparticle properties have become extremely important in developing highly effective nanomedicines. To this end, particles have been engineered in various ways, with a special emphasis on surface modifications. The nanoparticle surface contacts the biological environment, and is a crucial determinant of the response. Thus, surface coating, surface charge, conjugated molecules, shape, and topography have enormous impacts on the total behavior of nanoparticles, including their biodistribution, stability, target localization, cellular interaction, uptake, drug release, and toxicity. Hence, engineering of the particle surface would provide wider dimensions of control for the specific and precise functions in the development of smart nanomedicines. Moreover, local orientation of nanoparticles in vivo and orientations of surface molecules are critical for their efficacy. Herein, we analyze surface functionalities, focusing on their mechanisms and respective advantages, and summarize results of surface engineering and renovating applications of nanoparticles.

One-step template-free synthesis of hollow core–shell α-Fe2O3 microspheres with improved lithium storage and gas-sensing properties

The hollow core–shell α-Fe₂O₃ microspheres with improved lithium storage and gas-sensing properties have been fabricated by the template-free hydrothermal route.

Linker-free conjugation and specific cell targeting of antibody functionalized iron-oxide nanoparticles

Specific targeting is a key step to realize the full potential of iron oxide nanoparticles in biomedical applications, especially tumor-associated diagnosis and therapy. Here, we developed anti-GD2 antibody conjugated iron oxide nanoparticles for highly efficient neuroblastoma cell targeting. The antibody conjugation was achieved through an easy, linker-free method based on catechol reactions. The targeting efficiency and specificity of the antibody-conjugated nanoparticles to GD2-positive neuroblastoma cells were confirmed by flow cytometry, fluorescence microscopy, Prussian blue staining and transmission electron microscopy. These detailed studies indicated that the receptor-recognition capability of the antibody was fully retained after conjugation and the conjugated nanoparticles quickly attached to GD2-positive cells within four hours. Interestingly, longer treatment (12 h) led the cell membrane-bound nanoparticles to be internalized into cytosol, either by directly penetrating the cell membrane or escaping from the endosomes. Last but importantly, the uniquely designed functional surfaces of the nanoparticles allow easy conjugation of other bioactive molecules.

Engineered magnetic nanoparticles for biomedical applications

In the past decades, magnetic nanoparticles (MNPs) have been used in wide range of diverse applications, ranging from separation to sensing. Here, synthesis and applications of functionalized MNPs in the biomedical field are discussed, in particular in drug delivery, imaging, and cancer therapy, highlighting also recent progresses in the development of multifunctional and stimuli-responsive MNPs. The role of their size, composition, and surface functionalization is analyzed, together with their biocompatibility issues.

Alzheimer's disease: pathophysiology and applications of magnetic nanoparticles as MRI theranostic agents

Alzheimer's disease (AD) is the most common form of dementia. During the recent decade, nanotechnology has been widely considered, as a promising tool, for theranosis (diagnosis and therapy) of AD. Here we first discuss pathophysiology and characteristics of AD with a focus on the amyloid cascade hypothesis. Then magnetic nanoparticles (MNPs) and recent works on their applications in AD, focusing on the superparamagnetic iron oxide nanoparticles (SPIONs), are reviewed. Furthermore, the amyloid-nanoparticle interaction is highlighted, with the scope to be highly considered by the scientists aiming for diagnostics and/or treatment of AD employing nanoparticles. Furthermore, recent findings on the "ignored" parameters (e.g., effect of protein "corona" at the surface of nanoparticles on amyloid-β (Aβ) fibrillation process) are discussed.

Apoferritin modified magnetic particles as doxorubicin carriers for anticancer drug delivery

Magnetic particle mediated transport in combination with nanomaterial based drug carrier has a great potential for targeted cancer therapy. In this study, doxorubicin encapsulation into the apoferritin and its conjugation with magnetic particles was investigated by capillary electrophoresis with laser-induced fluorescence detection (CE-LIF). The quantification of encapsulated doxorubicin was performed by fluorescence spectroscopy and compared to CE-LIF. Moreover, the significant enhancement of the doxorubicin signal was observed by addition of methanol into the sample solution.

Influence of the physiochemical properties of superparamagnetic iron oxide nanoparticles on amyloid β protein fibrillation in solution

Superparamagnetic iron oxide nanoparticles (SPIONs) are recognized as promising nanodiagnostic materials due to their biocompatibility, unique magnetic properties, and their application as multimodal contrast agents. As coated SPIONs have potential use in the diagnosis and treatment of various brain diseases such as Alzheimer's, a comprehensive understanding of their interactions with Aβ and other amyloidogenic proteins is essential prior to their clinical application. Here we demonstrate the effect of thickness and surface charge of the coating layer of SPIONs on the kinetics of fibrillation of Aβ in aqueous solution. A size and surface area dependent "dual" effect on Aβ fibrillation was observed. While lower concentrations of SPIONs inhibited fibrillation, higher concentrations increased the rate of Aβ fibrillation. With respect to coating charge, it is evident that the positively charged SPIONs are capable of promoting fibrillation at significantly lower particle concentrations compared with negatively charged or uncharged SPIONs. This suggests that in addition to the presence of particles, which affect the concentration of monomeric protein in solution (and thereby the nucleation time), there are also effects of binding on the protein conformation.

Synthesis of pseudopolyrotaxanes-coated Superparamagnetic Iron Oxide Nanoparticles as new MRI contrast agent

Superparamagnetic Iron Oxide Nanoparticles (SPIONs) were synthesized and coated with pseudopolyrotaxanes (PPRs) and proposed as a novel hybrid nanostructure for medical imaging and drug delivery. PPRs were prepared by addition of α-cyclodextrin rings to functionalized polyethylene glycol (PEG) chain with hydrophobic triazine end-groups. Non-covalent interactions between SPIONs and PPRs led to the assembly of SPIONs@PRs hybrid nanomaterials. Measurements of the (1)H Nuclear Magnetic Resonance (NMR) relaxation times T(1) and T(2) allowed us to determine the NMR dispersion profiles. Comparison between our SPIONs@PRs hybrid nano-compound and the commercial SPION compound, Endorem, showed a higher transverse relaxivity for SPIONs@PRs. In vitro MRI experiments showed that our SPIONs@PRs produces better negative contrast compared to Endorem and can be considered as a novel MRI contrast agent.

Magnetic targeting of surface-modified superparamagnetic iron oxide nanoparticles yields antibacterial efficacy against biofilms of gentamicin-resistant staphylococci

Biofilms on biomaterial implants are hard to eradicate with antibiotics due to the protection offered by the biofilm mode of growth, especially when caused by antibiotic-resistant strains. Superparamagnetic iron oxide nanoparticles (SPIONs) are widely used in various biomedical applications, such as targeted drug delivery and magnetic resonance imaging. Here, we evaluate the hypothesis that SPIONs can be effective in the treatment of biomaterial-associated infection. SPIONs can be targeted to the infection site using an external magnetic field, causing deep penetration in a biofilm and possibly effectiveness against antibiotic-resistant strains. We report that carboxyl-grafted SPIONs, magnetically concentrated in a biofilm, cause an approximately 8-fold higher percentage of dead staphylococci than does gentamicin for a gentamicin-resistant strain in a developing biofilm. Moreover, magnetically concentrated carboxyl-grafted SPIONs cause bacterial killing in an established biofilm. Thus magnetic targeting of SPIONs constitutes a promising alternative for the treatment of costly and recalcitrant biomaterial-associated infections by antibiotic-resistant strains.

Toxicity of nanomaterials

Nanoscience has matured significantly during the last decade as it has transitioned from bench top science to applied technology. Presently, nanomaterials are used in a wide variety of commercial products such as electronic components, sports equipment, sun creams and biomedical applications. There are few studies of the long-term consequences of nanoparticles on human health, but governmental agencies, including the United States National Institute for Occupational Safety and Health and Japan's Ministry of Health, have recently raised the question of whether seemingly innocuous materials such as carbon-based nanotubes should be treated with the same caution afforded known carcinogens such as asbestos. Since nanomaterials are increasing a part of everyday consumer products, manufacturing processes, and medical products, it is imperative that both workers and end-users be protected from inhalation of potentially toxic NPs. It also suggests that NPs may need to be sequestered into products so that the NPs are not released into the atmosphere during the product's life or during recycling. Further, non-inhalation routes of NP absorption, including dermal and medical injectables, must be studied in order to understand possible toxic effects. Fewer studies to date have addressed whether the body can eventually eliminate nanomaterials to prevent particle build-up in tissues or organs. This critical review discusses the biophysicochemical properties of various nanomaterials with emphasis on currently available toxicology data and methodologies for evaluating nanoparticle toxicity (286 references).