Iron Oxide Nanoparticles Research Articles

Silica-coated superparamagnetic iron oxide nanoparticles interacting with superoxide dismutase in the mouse primary hepatocytes

Given the great potential of superparamagnetic iron oxide nanoparticles (SPIONs) in the application of biomedical and water treatment fields, it is of vital significance to evaluate their toxicity and explore the underlying mechanism. Silica-coated SPIONs (SPIONs@SiO2) might generate oxidative stress and cytotoxicity by interfering antioxidant enzyme. This study investigated the response of superoxide dismutase (SOD) under SPIONs@SiO2-induced oxidative stress using a strategy integrating cellular and molecular methods. Results showed that intracellular SOD activity exhibited hormetic effects in response to SPIONs@SiO2-induced structural changes of SOD molecule and oxidative stress, which subsequently generated lipid oxidation and cell viability loss in the mouse primary hepatocytes. The structural changes and increasing activity of SOD molecule were resulted from the direct interaction with SPIONs@SiO2. Then, multi-spectroscopy, zeta potential measurements and isothermal titration calorimetry were used to study the interaction of SPIONs@SiO2 with SOD and the underlying mechanism. SOD interacts with SPIONs@SiO2 through electrostatic and hydrophobic forces, enhancing the hydrophobicity around Tyr 108. The enthalpy and entropy change of the interaction are 1.03 × 105 J.mol−1 and 474.6 J.mol−1.K−1, respectively, indicating the dominant driving forces are hydrophobic forces. The interaction led to the loosen of peptide chains and the reduction of aggregation state. And the α-helix content of SOD decreased to 13 % in the presence of SPIONs@SiO2.

Efficient synthesis of novel phenanthroline-dimedone derivatives using Pd@HQBI-SPION as a versatile palladium-immobilized catalyst

This paper presents the synthesis and application of a novel catalyst for carbon–carbon bond formations, comprising palladium immobilized on 2-(5-hydroxyquinolin-8-yl)-1H-benzo[d]imidazole-5-carboxylic acid modified superparamagnetic iron oxide nanoparticles (Pd@HQBI-SPION). The synthesis involved the attachment of HQBI ligands to SPION using APTES, followed by the immobilization of palladium. Characterization techniques, including FTIR, TEM, and magnetic measurements, confirmed the successful synthesis and structural integrity of Pd@HQBI-SPION. The catalytic activity of Pd@HQBI-SPION was evaluated in various carbon–carbon bond formation reactions, demonstrating high efficiency and reusability. 8 different derivatives bearing several electron withdrawing and electron donating functionalities were used as starting materials and the products were obtained in high isolated yields (75–97%). The catalyst exhibited excellent performance in one-pot synthesis of phenanthroline-dimedone polycyclic derivatives via C-alkylation followed by intramolecular O-alkylation of phenanthroline with dimedone. The products are obtained in high to excellent yields is described. This protocol presents a highly selective synthetic method for the construction of polycyclic aromatic compounds containing nitrogen and oxygen atoms.

Construction of iron oxide nanoparticles modified with Angelica sinensis polysaccharide for the treatment of iron deficiency anemia

Construction of iron oxide nanoparticles modified with Angelica sinensis polysaccharide for the treatment of iron deficiency anemia

A Multifunctional Exosome with Dual Homeostasis Disruption Augments cGAS-STING-Mediated Tumor Immunotherapy by Boosting Ferroptosis.

Ferroptosis has shown great potential in activating antitumor immunity. However, the cunning tumor cells can evade ferroptosis by increasing the efflux of iron and promoting the production of the reductant glutathione to mitigate oxidative stress. Herein, a multifunctional exosome loaded with manganese-doped iron oxide nanoparticles (MnIO), GW4869, and l-buthionine sulfoximine (BSO) is developed to disrupt the iron metabolism homeostasis and redox homeostasis to enhance tumor immunotherapy. The efficient transport of MnIO by exosomes and the inhibition of iron exocytosis by GW4869 led to a high retention of up to 29.57% ID/g for iron in the tumors. Such a high retention of iron, in combination with the BSO-induced disruption of the redox homeostasis, effectively promotes the ferroptosis of tumor cells. Consequently, the multifunctional exosomes that noticeably enhance ferroptosis by dual homeostasis disruption provoke the cGAS-STING-based antitumor immune response and effectively suppress tumor growth and lung metastasis in orthotopic breast cancer.

Magnetic targeting enhances the neuroprotective function of human mesenchymal stem cell-derived iron oxide exosomes by delivering miR-1228-5p

BackgroundTreating mitochondrial dysfunction is a promising approach for the treatment of post-stroke cognitive impairment (PSCI). HuMSC-derived exosomes (H-Ex) have shown powerful therapeutic effects in improving mitochondrial function, but the specific effects are unclear and its brain tissue targeting needs to be further optimized.ResultsIn this study, we found that H-Ex can improve mitochondrial dysfunction of neurons and significantly enhance the cognitive behavior performance of MCAO mice in OGD/R-induced SHSY5Y cells and MCAO mouse models. Based on this, we have developed an exosome delivery system loaded with superparamagnetic iron oxide nanoparticles (Spion-Ex) that can effectively penetrate the blood-brain barrier (BBB). The research results showed that under magnetic attraction, Spion-Ex can more effectively target the brain tissue and significantly improve mitochondrial function of neurons after stroke. Meanwhile, we further confirmed that miR-1228-5p is a key factor for H-Ex to improve mitochondrial function and cognitive behavior both in vivo and in vitro. The specific mechanism is that the increase of miR-1228-5p mediated by H-Ex can inhibit the expression of TRAF6 and activate the TRAF6-NADPH oxidase 1 (NOX1) pathway, thereby exerting protective effects against oxidative damage. More importantly, we found that under magnetic attraction, Spion-Ex exhibited excellent cognitive improvement effects by delivering miR-1228-5p.ConclusionsOur research found that H-Ex has a good therapeutic effect on PSCI by increasing the expression of miR-1228-5p in PSCI, while H-Ex loaded with Spion-Ex exhibited more excellent effects on improving mitochondrial function and cognitive impairment under magnetic attraction, which can be used as a novel strategy for the treatment of PSCI.

The synergistic effects on the magnetic CoNi and Fe3O4 nanoparticles co-embedded porous carbon toward enhanced microwave absorbing performance

Abstract Lightweight and environmentally friendly three-dimensional biomass-derived porous carbon (3D BPC) holds great potential as a highly effective material for microwave absorption (MA) applications. However, the high complex permittivity and lack of magnetic loss in a single 3D BPC lead to impedance mismatching and a limited absorption bandwidth. Developing 3D BPC–based absorbers with multiple loss mechanisms and excellent impedance matching remains a notable yet challenging task. In this study, inspired by a synergistic composition and microstructure design, 3D BPC co-embedded with magnetic cobalt–nickel (CoNi) and iron(III) oxide (Fe3O4) nanoparticles (3D BPC@CoNi@Fe3O4) was developed. 3D BPC@CoNi@Fe3O4 exhibited consistently low complex permittivity, primarily due to the suppression of conductive loss, whereas the introduction of magnetic phases (CoNi and Fe3O4) enhanced the magnetic loss. Optimised impedance matching, achieved through the synergistic regulation of the electromagnetic parameters, emerged as the key mechanism for improving the MA properties. The as-synthesised 3D BPC@CoNi@Fe3O4 composite, with only 20 wt.% loading demonstrated a wide effective absorption bandwidth (reflection loss [RL] < −10 dB) of 6.08 GHz and an impressive minimum RL value of −40.08 dB. These findings offer valuable insights into the development of high-performance 3D BPC–based microwave absorbers through composition and microstructure optimisation.

Structure and Magnetic Properties of Iron Oxide Nanoparticles Subjected to Mechanical Treatment

Iron oxide nanoparticles have been fabricated using the electric wire explosion (EWE) technique. The structure and magnetic properties of the nanoparticles have been analyzed before and after mechanical grinding in a ball mill for different time periods, focusing on potential bioapplications. The phase composition of the nanoparticles (70% Fe3O4, 30% Fe2O3) has remained unchanged despite the mechanical effects. The average nanoparticle size has not been affected either. The observation of the Verwey transition in the studied nanoparticles, along with the structural data, provides a better understanding of the physical properties of EWE ensembles of nanoparticles in different states. The analysis of the structure and magnetic properties reveals the development of a material with a high level of internal stress. This finding may be of interest for bioapplications due to its potential impact on the material performance.

Ce-Doped Iron Oxide Anticorrosive Coatings: Effect of c(Ce4+):c(Fe3+) Ratio on Structure, Morphology, and Coating Anticorrosion Performance

Utilizing hydrothermal methods, Ce-doped iron oxide nanoparticles were synthesized from precursor solutions under different c(Ce4:c(Fe3+) precursor solutions. The effects of the c(Ce4+):c(Fe3+) ratio in the precursor solutions on the nanoparticle morphology and nanoparticle structure of the Ce-doped iron oxide were investigated using X-Ray diffraction, transmission electron microscopy, and scanning electron microscopy. Fourier transform infrared spectroscopy (FTIR) was used to examine the bond energy strength of the Ce-doped iron oxide nanoparticles. The electrochemical properties of the Ce-doped iron oxide nanoparticles were tested using an electrochemical workstation and a saltwater immersion resistance test. The corrosion resistance of Ce-doped iron oxide coatings at different c(Ce4+):c(Fe3+) ratios was systematically analyzed, uncovering corrosion resistance mechanisms and self-healing capabilities. The results show that as the c(Ce4+):c(Fe3+) ratio decreases, the lattice constants of the samples increase along with the average grain size. Both smaller and larger c(Ce4+):c(Fe3+) ratios are detrimental to lattice distortion in α-Fe2O3. The reduced number of valence electrons provided by cerium ions in Ce-doped iron oxide hinders the generation of holes and exerts a minor influence on the crystal band structure, leading to weaker electrochemical stability. The Ce-doped iron oxide coating prepared at a c(Ce4+):c(Fe3+) ratio of 1:60 readily generates a higher number of reactive hydroxyl radicals during corrosion, thus exhibiting enhanced self-healing capabilities and corrosion resistance.

Evaluating the Photocatalytic Activity of Green Synthesized Iron Oxide Nanoparticles

Water pollution from dyes is a major environmental challenge, demanding advanced materials for efficient degradation. In this study, we synthesized iron oxide nanoparticles (IONPs) using an aqueous extract of Senegalia catechu leaves and evaluated their photocatalytic activity in methylene blue (MB) dye degradation under sunlight irradiation. The IONPs were characterized by UV-visible spectroscopy (UV–vis), Fourier Transform Infrared Spectroscopy (FT-IR), X-ray Diffraction (XRD), Scanning Electron Microscopy (SEM), and Energy Dispersive X-ray Spectroscopy (EDS). XRD pattern showed a highly crystalline structure with an average crystallite size of 34.7 nm, while SEM images revealed predominantly spherical particles with uneven surface texture. Photocatalytic efficiency exceeded 80% MB dye degradation after 120 min of sunlight exposure. Optimization of catalyst dose, pH, dye concentration, and other parameters is essential for maximizing degradation efficiency. The IONPs demonstrated reusability over four degradation cycles, retaining effective photocatalytic performance. This study underscores the potential of green-synthesized IONPs as eco-friendly photocatalysts for wastewater treatment and environmental remediation.

Magnetic particle imaging enables non-radioactive quantitative sentinel lymph node identification: feasibility proof in murine models

Abstract Background Sentinel lymph node biopsy (SLNB) is an important cancer diagnostic-staging procedure. Conventional SLNB procedures with 99mTc radiotracers and scintigraphy are constrained by tracer half-life and in some cases insufficient image resolution. Here we explore an alternative magnetic (non-radioactive) image guided SLNB procedure. Purpose To demonstrate that magnetic particle imaging (MPI) lymphography can sensitively, specifically, and quantitatively identify and map SLNs in murine models in multiple regional lymphatic basins. Materials and Methods Iron oxide nanoparticles were administered intradermally to healthy C57BL/6 mice (male, 12-week-old, n = 5). The nanoparticles (0.675 mg Fe/kg) were injected into the tongue, forepaw, base of tail, or hind footpad, then detected by 3D MPI at multiple timepoints between 1 hour and 4-6 days. In this mouse model, the SLN is represented by the first lymph node draining from the injection site. SLNs were extracted to verify the MPI signal ex vivo and processed using Perl’s Prussian iron staining. Paired t-test was conducted to compare MPI signal from SLNs in vivo vs. ex vivo and considered significant if p < .05. Results MPI lymphography identified SLNs in multiple lymphatic pathways, including the cervical SLN draining the tongue, axillary SLN draining the forepaw, inguinal SLN draining the tail, and popliteal SLN draining the footpad. MPI signal in LNs was present after 1 hour and stable for the duration of the study (4-6 days). Perl’s Prussian iron staining was identified in the subcapsular space of excised SLNs. Conclusion Our data supports the use of MPI lymphography to specifically detect SLN(s) using a magnetic tracer for a minimum of 4-6 days, thereby providing information required to plan the SLN approach in cancer surgery. As clinical-scale MPI is developed, translation will benefit from a history of using iron-oxide nanoparticles in human imaging and recent regulatory-approvals for use in SLNB.

Enhancing Proton Radiosensitivity of Chondrosarcoma Using Nanoparticle-Based Drug Delivery Approaches: A Comparative Study of High- and Low-Energy Protons

To overcome chondrosarcoma’s (CHS) high chemo- and radioresistance, we used polyethylene glycol-encapsulated iron oxide nanoparticles (IONPs) for the controlled delivery of the chemotherapeutic doxorubicin (IONPDOX) to amplify the cytotoxicity of proton radiation therapy. Human 2D CHS SW1353 cells were treated with protons (linear energy transfer (LET): 1.6 and 12.6 keV/µm) with and without IONPDOX. Cell survival was assayed using a clonogenic test, and genotoxicity was tested through the formation of micronuclei (MN) and γH2AX foci, respectively. Morphology together with spectral fingerprints of nuclei were measured using enhanced dark-field microscopy (EDFM) assembled with a hyperspectral imaging (HI) module and an axial scanning fluorescence module, as well as scanning electron microscopy (SEM) coupled with energy-dispersive X-Ray spectroscopy (EDX). Cell survival was also determined in 3D SW3153 spheroids following treatment with low-LET protons with/without the IONPDOX compound. IONPDOX increased radiosensitivity following proton irradiation at both LETs in correlation with DNA damage expressed as MN or γH2AX. The IONPDOX–low-LET proton combination caused a more lethal effect compared to IONPDOX–high-LET protons. CHS cell biological alterations were reflected by the modifications in the hyperspectral images and spectral profiles, emphasizing new possible spectroscopic markers of cancer therapy effects. Our findings show that the proposed treatment combination has the potential to improve the management of CHS.

Engineering Protein-Nanoparticle Hybrids as Targeted Contrast Agents.

Iron oxide nanoparticles (IONPs) have shown great promise in biomedical applications, particularly as MRI contrast agents due to their magnetic properties and biocompatibility. Although several IONPs have been approved by regulatory agencies as MRI contrast agents, their primary application as negative contrast agents limits their usage. Additionally, there is an emerging need for the development of molecular contrast agents that can specifically target biomarkers, enabling more accurate and sensitive diagnostics. To address these challenges, we exploited the engineerability of proteins to stabilize IONPs with tailored magnetic properties, creating protein-stabilized iron oxide nanoparticles (Prot-IONPs) and leveraged the chemical diversity of proteins to functionalize Prot-IONPs with targeting moieties. As a proof-of-concept, we used alendronate (Ald) to target atherosclerotic plaques in the aorta. Simple protein functionalization allowed targeting while maintaining the stability and relaxation properties of the Prot-IONPs. Prot-IONPs-Ald successfully enabled positive contrast imaging of atherosclerotic plaques in vivo in an atherosclerotic mouse model (ApoE-/- mice on a high-fat diet). This study demonstrates the potential of engineering protein-nanoparticle hybrids as versatile platforms for developing targeted in vivo MRI contrast agents.

Straightforward Synthesis Methodology for Obtaining Excellent ORR Electrocatalysts From Biomass Residues Through a One Pot‐High Temperature Treatment Approach

AbstractMaterials prepared from biomass residues are potential candidates to substitute the Pt‐based commercial electrocatalysts in oxygen reduction reaction (ORR). Although some investigations have reported activity and durability comparable to Pt/C using biomass‐derived catalysts based on Fe─N─C sites, it remains a challenge to decrease the environmental impact of the production of these materials. A straightforward procedure is developed to obtain excellentORR electrocatalysts from biomass residues which requires a single high‐temperature treatment. The final washing step is avoided by optimizing the initial amount of Fe precursor (FeC2O4). Besides the formation of iron oxide nanoparticles, a highly dispersed Fe phase is detected by High Angle Annular Dark Field Scanning Transmission Electron Microscopy and Energy Dispersive X‐Ray Spectroscopy (HAADF‐STEM‐XEDS) analysis as well as graphitic carbon structures. The best performance for almond shell‐based electrocatalysts is achieved for the sample containing 4.6 wt. % of Fe. The procedure developed is also applied to oceanic posidonia and eucalyptus residues, also showing excellent ORR behavior. The best sample is studied in a primary Zn‐air battery (ZAB) obtaining a maximum power density of 59 mW cm−2 and 755 mAh gZn−1 capacity.

Ternary polymeric beads of chitosan-based polyaniline doped iron oxide used for removal of cadmium and lead ions from water: Kinetic, isotherm and mechanism studies

ABSTRACT In this study, the binary polymeric magnetic beads were synthesized successfully by one-pot polymerization of polyaniline (PA) doped magnetic iron oxide nanoparticles (MNPs) followed by chitosan (CTS) cross-linkage. The newly fabricated ternary magnetic beads (CTS@MPA) were applied to enhance the removal of Pb(II) and Cd(II) ions from the aqueous media. The prepared nanocomposite was characterized using Fourier-transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDX), and vibrating sample magnetometry (VSM). Adsorption experiments were carried out under optimum conditions. To evaluate the experimental data, the isotherm and kinetic models were conducted. The behavior of adsorption was assessed, and the coefficient of determination values demonstrated that the adsorption process best fitted the Freundlich model due to high values of R2 (0.957 & 0.981). The maximum adsorption capacity was obtained at 150.82 mg.g−1 and 169.21 mg.g−1 for Pb(II) and Cd(II) ions, respectively. Kinetic studies showed that adsorption follows a pseudo-second-order model (R2 = 0.952 & 0.985). Weber-Morris claims that intraparticle diffusion plays a significant role in the adsorption kinetics. Finally, the thermodynamic study is demonstrated, and the adsorption is endothermic, and the mechanism follows a physisorption pattern.

Nanoparticle Clustering in Supraparticles to Control Magnetic Long‐Range Interactions

AbstractTo tailor superparamagnetic iron oxide nanoparticles (SPIONs) to the specific needs of diverse application fields, it is essential to understand not only their intrinsic properties but also their interactions with each other. Theoretical models predicting/explaining the magnetization behavior of macroscopic samples containing millions of SPIONs are intricate due to the complexity of the underlying relaxation mechanisms in alternating fields. This study introduces supraparticles (SPs) as model architectures to empirically investigate magnetic interactions within and between large SPION clusters (>100 nanoparticles (NPs)). For this purpose, NP dispersions containing SPIONs and silica (SiO2)NPs as non‐magnetic building blocks are spray‐dried to form binary SPs. Selective salt‐induced agglomeration of the two building block types before spray‐drying is utilized to tailor SP architectures, including control over SPION cluster size, shape, and proximity. Magnetic particle spectroscopy (MPS), operating under ambient conditions, reveals altered magnetization behavior for different cluster structures. Not only the nearest SPION neighbors, but the whole cluster structure up to several micrometers is decisive for the magnetization behavior. This highlights the importance of long‐range magnetic interactions. This work presents a versatile approach for designing model architectures to advance empirical interaction studies between SPIONs in macroscopic samples.

Magnetic resonance imaging tracing of superparamagnetic iron oxide nanoparticle-labeled mesenchymal stromal cells for repairing spinal cord injury.

Mesenchymal stromal cell transplantation Is an effective and promising approach for treating various systemic and diffuse diseases. However, the biological characteristics of transplanted mesenchymal stromal cells in humans remain unclear, including cell viability, distribution, migration, and fate. Conventional cell tracing methods cannot be used in the clinic. The use of superparamagnetic iron oxide nanoparticles as contrast agents allows for the observation of transplanted cells using magnetic resonance imaging. In 2016, the National Medical Products Administration of China approved a new superparamagnetic iron oxide nanoparticle, Ruicun, for use as a contrast agent in clinical trials.In the present study, an acute hemi-transection spinal cord injury model was established in beagle dogs. The injury was then treated by transplantation of Ruicun-labeled mesenchymal stromal cells. The results indicated that Ruicun-labeled mesenchymal stromal cells repaired damaged spinal cord fibers and partially restored neurological function in animals with acute spinal cord injury. T2*-weighted imaging revealed low signal areas on both sides of the injured spinal cord. The results of quantitative susceptibility mapping with ultrashort echo time sequences indicated that Ruicun-labeled mesenchymal stromal cells persisted stably within the injured spinal cord for over 4 weeks. These findings suggest that magnetic resonance imaging has the potential to effectively track the migration of Ruicun-labeled mesenchymal stromal cells and assess their ability to repair spinal cord injury.

Elucidating the Dynamics of Biodegradation and Biosynthesis of Magnetic Nanoparticles in Human Stem Cells.

Iron oxide nanoparticles, due to their magnetic properties, are versatile tools for biomedical applications serving both diagnostic and therapeutic roles. Their performance is intricately intertwined with their fate in the demanding biological environment. Once inside cells, these nanoparticles can be degraded, implying a loss of magnetic efficacy, but also transformed into neo-synthesized magnetic nanoparticles, potentially restoring functionality. This study aims to delineate biological features governing these processes. Magnetic nanoparticles are internalized in human mesenchymal stem cells (hMSCs), and their biotransformations are investigated from nano- to micro-scale using electron microscopy (STEM-HAADF, HRTEM, SAED), a benchtop magnetic sensor, and fine structural characterizations (synchrotron XRD, VSM). Results evidence a delicate equilibrium between the biodegradation and biosynthesis of magnetic nanoparticles, with biotransformation kinetics depending on cell density at magnetic labeling and on spatial cell configuration (monolayers vs spheroids). The biotransformed nanoparticles, composed of magnetite or maghemite, are localized within endosomal/lysosomal compartments and associated with the recruitment of ferritin proteins.

Eco-Friendly Synthesis of Iron Oxide Nanoparticles from Bambusa vulgaris Extract for Enhancing Seed Germination and Physiological Parameters in Oryza sativa

Eco-Friendly Synthesis of Iron Oxide Nanoparticles from Bambusa vulgaris Extract for Enhancing Seed Germination and Physiological Parameters in Oryza sativa

Investigation of iron oxide nanoparticle formation in a spray-flame synthesis process using laser-induced incandescence

In this work, iron-oxide nanoparticle formation in the spray-flame synthesis (SFS) process of the standardized SpraySyn 2.0 burner was investigated in situ using laser-induced incandescence (LII). For the evaluation of these measurements, prior LII-experiments within iron-oxide aerosols (Fe3O4 and α-Fe2O3) with known primary particle size distribution and morphological properties were performed to determine the thermal accommodation coefficient (TAC) α, which led to approx. α = 0.08. The applicability of the TAC results within the flame was validated using spectrally and temporally resolved measurements in the flame at 65 mm HAB employing a spectrograph. Data for a bimodal particle size distribution, obtained from Transmission Electron Microscopy (TEM), were used in the LII-evaluation. The validated TAC was then used to evaluate the primary particle size evolution from in situ Time-Resolved (TiRe) LII-measurements using PMTs along the centre axis of the burner, ranging from 10 mm to 50 mm HAB. These measurements reveal a relatively constant effective particle diameter along HAB with dp,eff ≈ 300 nm. To further investigate particle formation in SFS, 2-dimensional time-resolved LII-measurements in the SFS flame were performed, showing a clear particle formation region up to approx. 30 mm HAB, from where on a constant particle mass is observed.

Superparamagnetic iron oxide nanoparticles functionalized with on-demand redox-responsive contractible coordination polymer brush as molecular actuator driven by π-dimerization

Nanomachines require molecular actuators to be coupled to a condensed phase. In this work, a redox responsive 1D contractible coordination polymer (ZnL) used as non-interlocked actuator is grafted onto superparamagnetic iron oxide nanoparticles (SPIONs) in a brush-like configuration. Oxidized rod-like ZnL oligomers have ability to reversibly self-fold upon reduction via π-dimerization of their bis-viologen units. Unlike in usual responsive brushes, ZnL chains behave individually, generating spatially controlled mechanical motion at nanoparticle surface associated to significant variations of particle diameters. ZnL oligomers were “grafted to” SPIONs in a single step. Reduction of colloidal dispersions was perform by visible light illumination with the help of a photoreductant. π-dimerization was assessed by UV–vis–NIR and reversible contraction of ZnL brush was characterized by DLS. Effects of ZnL chains length and grafting density on mechanism and performance of contractibility were studied. ZnL brush can alternately be contracted and extended with excellent reversibility. Combined UV–vis–NIR, DLS and TGA analyses demonstrate that π-dimerization is only intramolecular and that chains behave as independent actuators. Maximal contraction of 22 nm is obtained for largest particles (DH = 86 nm). Full to partial contraction of the brush depends on grafting density with a threshold at ≈ 47 chains per particle.