Surface Of Iron Oxide Nanoparticles Research Articles

Antibody-Decorated Nanoplatform to Reprogram Macrophage and Block Immune Checkpoint LSECtin for Effective Cancer Immunotherapy.

Repolarizing tumor-associated macrophages (TAMs) into tumor-inhibiting M1 macrophages has been considered a promising strategy for enhanced cancer immunotherapy. However, several immunosuppressive ligands (e.g., LSECtin) can still be highly expressed on M1 macrophages, inducing unsatisfactory therapeutic outcomes. We herein developed an antibody-decorated nanoplatform composed of PEGylated iron oxide nanoparticles (IONPs) and LSECtin antibody conjugated onto the surface of IONPs via the hydrazone bond for enhanced cancer immunotherapy. After intravenous administration, the tumor microenvironment (TME) pH could trigger the hydrazone bond breakage and induce the disassociation of the nanoplatform into free LSECtin antibodies and IONPs. Consequently, the IONPs could repolarize TAMs into M1 macrophages to remodel immunosuppressive TME and provide an additional anticancer effect via secreting tumoricidal factors (e.g., interlukin-12). Meanwhile, the LSECtin antibody could further block the activity of LSECtin expressed on M1 macrophages and relieve its immunosuppressive effect on CD8+ T cells, ultimately leading to significant inhibition of tumor growth.

Detection of tetanus toxoid with iron magnetic nanobioprobe

Diagnosis of diseases with low facilities, speed, accuracy and sensitivity is an important matter in treatment. Bioprobes based on iron oxide nanoparticles are a good candidate for early detection of deadly and infectious diseases such as tetanus due to their high reactivity, biocompatibility, low production cost and sample separation under a magnetic field. In this study, silane groups were coated on surface of iron oxide nanoparticles using tetraethoxysilane (TEOS) hydrolysis. Also, NH2 groups were generated on the surface of silanized nanoparticles using 3-aminopropyl triethoxy silane (APTES). Antibody was immobilized on the surface of silanized nanoparticles using TCT trichlorothriazine as activator. Silanization and stabilized antibody were investigated by using of FT-IR, EDX, VSM, SRB technique. UV/vis spectroscopy, fluorescence, agglutination test and ELISA were used for biosensor performance and specificity. The results of FT-IR spectroscopy showed that Si–O–Si and Si-O-Fe bonds and TCT chlorine and amine groups of tetanus anti-toxoid antibodies were formed on the surface of iron oxide nanoparticles. The presence of Si, N and C elements in EDX analysis confirms the silanization of iron oxide nanoparticles. VSM results showed that the amount of magnetic nanoparticles after conjugation is sufficient for biological applications. Antibody stabilization on nanoparticles increased the adsorption intensity in the uv/vis spectrometer. The fluorescence intensity of nano bioprobe increased in the presence of 10 ng ml−1. Nanobio probes were observed as agglomerates in the presence of tetanus toxoid antigen. The presence of tetanus antigen caused the formation of antigen-nanobioprobe antigen complex. Identification of this complex by HRP-bound antibody confirmed the specificity of nanobioprobe. Tetanus magnetic nanobioprobe with a diagnostic limit of 10 ng ml−1 of tetanus antigen in a short time can be a good tool in LOC devices and microfluidic chips.

Comparison of different iron oxides for degradation of tetracycline anti-bacterial drug

Abstract Nanomaterials have a wide range of applications including novel biomedical studies are devoted to improving the functionality and effectively of traditional and unmodified systems, both drug carriers and common scaffolds for tissue engineering or advanced hydrogels for wound healing purposes. In this regard, metal oxide nanoparticles show great potential as versatile tools in biomedical science. In particular, iron oxide nanoparticles with different shape and sizes hold outstanding physiochemical characteristics, such as high specific area and structure that make them unique nanomaterials to be used in diverse aspects of medicine and biological systems. The challenges associated with the uncontrolled presence of antibiotics such as tetracycline in the environment have necessitated their removal through different techniques. Tetracycline is hard to degrade in living organisms and can even be converted to more toxic substances. In this article different type of iron oxides were subjected to photo degradation of antibacterial drug Tetracycline under UV light illumination and direct sunlight and the results were promising to degrade the drug within 20 min. The SEM, TEM, EDAX and XRD for the catalyst were characterized to confirm the presence of iron oxide, the size and shape of the particle. The kinetics of photo degradation of tetracycline followed the pseudo-first-order mechanism, proceeding through hydroxyl radicals generated under illumination. Moreover, the photo generated hydrogen peroxide could lead to heterogeneous photocatalytic processes on the surface of iron oxide nanoparticles; additionally generating hydroxyl and hydroperoxyl radicals enables photo degradation of tetracycline.

Vinorelbine-loaded multifunctional magnetic nanoparticles as anticancer drug delivery systems: synthesis, characterization, and in vitro release study.

In this study, a multifunctional therapeutic agent combining chemotherapy and photothermal therapy on a single platform has been developed in the form of vinorelbine-loaded polydopamine-coated iron oxide nanoparticles. Vinorelbine (VNB) is loaded on the surface of iron oxide nanoparticles produced by a solvothermal technique after coating with polydopamine (PDA) with varying weight ratios as a result of dopamine polymerisation and covalent bonding of thiol-polyethylene glycol (SH-PEG). The VNB/PDA/Fe3O4 nanoparticles have a saturation magnetisation value of 60.40 emu/g in vibrating sample magnetometry, which proves their magnetisation. Vinorelbine, which is used as an effective cancer therapy agent, is included in the nanocomposite structure, and in vitro drug release studies under different pH conditions (pH 5.5 and 7.4) and photothermal activity at 808 nm NIR laser irradiation are investigated. The comprehensive integration of precise multifunctional nanoparticles design, magnetic response, and controlled drug release with photothermal effect brings a different perspective to advanced cancer treatment research.

Piper chaba Stem Extract Facilitated the Synthesis of Iron Oxide Nanoparticles as an Adsorbent to Remove Congo Red Dye.

In this study, a straightforward, eco-friendly, and facile method for synthesizing iron oxide nanoparticles (IONPs) utilizing Piper chaba steam extract as a reducing and stabilizing agent has been demonstrated. The formation of stable IONPs coated with organic moieties was confirmed from UV-vis, FTIR, and EDX spectroscopy and DLS analysis. The produced IONPs are sufficiently crystalline to be superparamagnetic having a saturation magnetization value of 58 emu/g, and their spherical form and size of 9 nm were verified by XRD, VSM, SEM, and TEM investigations. In addition, the synthesized IONPs exhibited notable effectiveness in the removal of Congo Red (CR) dye with a maximum adsorption capacity of 88 mg/g. The adsorption kinetics followed pseudo-second-order kinetics, meaning the adsorption of CR on IONPs is mostly controlled by chemisorption. The adsorption isotherms of CR on the surface of IONPs follow the Langmuir isotherm model, indicating the monolayer adsorption on the homogeneous surface of IONPs through adsorbate-adsorbent interaction. The IONPs have revealed good potential for their reusability, with the adsorption efficiency remaining at about 85% after five adsorption-desorption cycles. The large-scale, safe, and cost-effective manufacturing of IONPs is made possible by this environmentally friendly process.

Design, Synthesis, and Evaluation of Novel Magnetic Nanoparticles Combined with Thiophene Derivatives for the Removal of Cr(VI) from an Aqueous Solution.

Most heavy metals are harmful to human health and the environment, even at extremely low concentrations. In natural waters, they are usually found only in trace amounts. Researchers are paying great attention to nanotechnology and nanomaterials as viable solutions to the problem of water pollution. This research focuses on the synthesis of organic thiophene derivatives that can be used as grafted ligands on the surface of silica-coated iron oxide nanoparticles to remove Cr(VI) chromium ions from water. The Vilsmeier-Haack reaction allows the formation of aldehyde groups in thiophene derivatives, and the resulting products were characterized by the FT-IR, NMR, and GC-MS. Schiff base is used as a binder between organic compounds and nanoparticles by the reaction of aldehyde groups in thiophene derivatives and amine groups on the surface of coated iron oxide nanoparticles. Schiff base functionalized Fe3O4 composites (MNPs@SiO2-SB-THCA) and (MNPs@SiO2-SB-THCTA) were successfully synthesized by homogeneous and heterogeneous methods and characterized by a combination of FT-IR, transmission electron microscopy, X-ray photoelectron spectroscopy, and thermogravimetric analysis. The adsorption studies, kinetic modeling, adsorption isotherms, and thermodynamics of the two materials, MNPs@SiO2-SB-THCA and MNPs@SiO2-SB-THCTA, were investigated for the removal of Cr(VI) from water at room temperature and at 50 mg/L. The high adsorption capacity at pH 6 for MNPs@SiO2-SB-THCTA was 15.53 mg/g, and for MNPs@SiO2-SB-THCA, it was 14.31 mg/g.

Functional magnetic nanoparticles for protein delivery applications: understanding protein-nanoparticle interactions.

Iron oxide nanoparticles (IONPs) surface functionalised with thermo-responsive polymers can encapsulate therapeutic proteins and release them upon heating with an alternating magnetic field above the lower critical solution temperature (LCST). In order to make this delivery system clinically-relevant, we prepared IONPs coated with poly-N-isopropylmethacrylamide (PNIPMAM), a polymer with LCST above human body temperature. The optimal polymer chain length and nanoparticle size to achieve LCST of ca. 45 °C were 19 kDa PNIPMAM and 16 nm IONPs. The PNIPMAM-coated IONPs could encapsulate a range of proteins which were released upon heating above LCST in the presence of a competitor protein or serum. A small amount of encapsulated protein leakage was observed below LCST. The efficiency of protein encapsulation and release was correlated with molecular weight and glycosylation state of the proteins. Magnetic heating resulted in a faster protein release as compared to conventional heating without significant temperature increase of the bulk solution.

Antioxidant Iron Oxide Nanoparticles: Their Biocompatibility and Bioactive Properties

A lot of nanomaterials have been applied to various nano-biotechnological fields, such as contrast agents, drug or gene delivery systems, cosmetics, and so on. Despite the expanding usage of nanomaterials, concerns persist regarding their potential toxicity. To address this issue, many scientists have tried to develop biocompatible nanomaterials containing phytochemicals as a promising solution. In this study, we synthesized biocompatible nanomaterials by using gallic acid (GA), which is a phytochemical, and coating it onto the surface of iron oxide nanoparticles (IONPs). Importantly, the GA-modified iron oxide nanoparticles (GA-IONPs) were successfully prepared through environmentally friendly methods, avoiding the use of harmful reagents and extreme conditions. The presence of GA on the surface of IONPs improved their stability and bioactive properties. In addition, cell viability assays proved that GA-IONPs possessed excellent biocompatibility in human dermal papilla cells (HDPCs). Additionally, GA-IONPs showed antioxidant activity, which reduced intracellular reactive oxygen species (ROS) levels in an oxidative stress model induced by hydrogen peroxide (H2O2). To investigate the impact of GA-IONPs on exosome secretions from oxidative stress-induced cells, we analyzed the number and characteristics of exosomes in the culture media of HDPCs after H2O2 stimulation or GA-IONP treatment. Our analysis revealed that both the number and proportions of tetraspanins (CD9, CD81, and CD63) in exosomes were similar in the control group and the GA-IONP-treated groups. In contrast, exosome secretion was increased, and the proportion of tetraspanin was changed in the H2O2-treated group compared to the control group. It demonstrated that treatment with GA-IONPs effectively attenuated exosome secretion induced by H2O2-induced oxidative stress. Therefore, this GA-IONP exhibited outstanding promise for applications in the field of nanobiotechnology.

Fe2+ /Fe3+ Sites Control Dicarboxylic Acid Adsorption on Iron Oxide Nanoparticle Surfaces for Photocatalytic Application Studied by Operando ATR-FTIR Spectroscopy

Fe2+ /Fe3+ Sites Control Dicarboxylic Acid Adsorption on Iron Oxide Nanoparticle Surfaces for Photocatalytic Application Studied by Operando ATR-FTIR Spectroscopy

Surface Modifications of Superparamagnetic Iron Oxide Nanoparticles with Polyvinyl Alcohol and Activated Charcoal as Methylene Blue Adsorbents

As novel methylene blue adsorbents, polyvinyl alcohol and activated charcoal were used to modify the surface of superparamagnetic iron oxide nanoparticles. The adsorption capacity after 69 h was 26.50 ± 0.99–40.21 ± 1.30 mg/g, depending on the temperature (333.15, 310.15, and 298.15 K) and the initial concentration of methylene blue, which was between 0.017 and 0.020 mg/mL. Based on thermodynamics parameters, the adsorption process can be considered to be spontaneous endothermic physisorption. Kinetics studies show that the pseudo-second-order model was the best-fitted model. Adsorption isotherm studies show that the best-fitted models were the Langmuir, Langmuir, and Temkin and Pyzhev isotherm models when adsorbing MB at 333.15, 310.15, and 298.15 K, respectively.

Fluorescent Microscopy of Hot Spots Induced by Laser Heating of Iron Oxide Nanoparticles

Determination of the iron oxide nanoparticles (IONPs) local temperature during laser heating is important in the aspect of laser phototherapy. We have carried out theoretical modeling of IONPs local electromagnetic (EM) field enhancement and heating under the laser action near individual IONPs and ensembles of IONPs with different sizes, shapes and chemical phases. For experimental determination of IONPs temperature, we used fluorescence thermometry with rhodamine B (RhB) based on its lifetime. Depending on the IONPs shape and their location in space, a significant change in the spatial distribution of the EM field near the IONPs surface is observed. The local heating of IONPs in an ensemble reaches sufficiently high values; the relative change is about 35 °C for Fe2O3 NPs. Nevertheless, all the studied IONPs water colloids showed heating by no more than 10 °C. The heating temperature of the ensemble depends on the thermal conductivity of the medium, on which the heat dissipation depends. During laser scanning of a cell culture incubated with different types of IONPs, the temperature increase, estimated from the shortening of the RhB fluorescence lifetime, reaches more than 100 °C. Such “hot spots” within lysosomes, where IONPs predominantly reside, lead to severe cellular stress and can be used for cell therapy.

Phase Composition of Iron Oxide Nanoparticles Studied Using Hard X-ray Absorption Spectroscopy

At the surface of iron oxide nanoparticles, an oxidized or disordered layer is often found. Due to the large surface-to-volume ratio of nanomaterials, such a surface layer plays an important role in the overall magnetic properties of the particles. Consequently, it is important to characterize the surface layer if applications of iron oxide nanoparticles, e.g., for magnetic hyperthermia, magnetic particle imaging, or ferrofluidics, are envisaged. In this work, we tuned the phase of the surface layer of 14 nm iron oxide nanoparticles via annealing procedures. The phase composition of the particles is systematically studied using hard X-ray absorption spectroscopy.

Surface Adsorption Mechanism between Lead(II,IV) and Nanomaghemite Studied on Polluted Water Samples Collected from the Peruvian Rivers Mantaro and Cumbaza.

Real water remediation is an important issue that requires the development of novel adsorbents with remarkable adsorption properties, permitting reusability. In this work, the surface and adsorption properties of bare magnetic iron oxide nanoparticles were systematically studied, before and after the application of a maghemite nanoadsorbent in two real Peruvian effluents severely contaminated with Pb(II), Pb(IV), Fe(III), and others. We were able to describe the Fe and Pb adsorption mechanisms that occurred at the particle surface. 57Fe Mössbauer and X-ray photoelectron spectroscopy results together with kinetic adsorption analyses gave evidence for two involved surface mechanisms: (i) surface deprotonation of maghemite nanoparticles (isoelectric point of pH = 2.3), forming Lewis sites bonding Pb complexes; and (ii) the formation of a thin inhomogeneous secondary layer of iron oxyhydroxide and adsorbed Pb compounds, as favored by surface physicochemical conditions. The magnetic nanoadsorbent enhanced the removal efficiency to values of ca. 96% and provided adsorptive properties with reusability due to the conserved morphological, structural, and magnetic properties. This makes it favorable for large-scale industrial applications.

Interactions of Common Biological Buffers with Iron Oxide Nanoparticles.

Iron oxide nanoparticles (IONPs) have been studied extensively for biomedical applications, which require that they be aqueous-stable at physiological pH. The structures of some of these buffers, however, may also allow for binding to surface iron, thus potentially exchanging with functionally relevant ligands, and altering the desired properties of the nanoparticles. We report here on the interactions of five common biologically relevant buffers (MES, MOPS, phosphate, HEPES, and Tris) with iron oxide nanoparticles through spectroscopic studies. The IONPs in this study are capped with 3,4-dihydroxybenzoic acid (3,4-DHBA) to serve as models for IONP functionalized with catechol ligands. Unlike previous studies, which relied exclusively on dynamic light scattering (DLS) and ζ-potential measurements to characterize buffer interactions with IONPs, we use Fourier transform infrared (FTIR) and ultraviolet-visible (UV-visible) spectroscopic techniques to characterize the IONP surface to demonstrate binding of buffers and etching of the IONP surface. Our findings establish that phosphate and Tris bind to the IONP surface, even in the presence of strongly bound catechol ligands. We further observe significant etching of IONPs in Tris buffer, with the release of surface Fe into solution. Minor etching is noted in HEPES, and to a lesser degree, in MOPS, while no etching is observed in MES. Our findings suggest that, while morpholino buffers, such as MES and MOPS, may be more appropriate for use with IONPs, proper buffer selection should always be considered on a case-by-case basis.

Spy chemistry enables stable protein immobilization on iron oxide nanoparticles with enhanced magnetic properties

Iron oxide nanoparticles (IONPs) modified with functional proteins hold great promise in the biomedical field. However, conventional protein modification strategies, such as adsorption and covalent coupling, are either unstable or nonspecific, or may result in the changes of protein structure and ultimately the loss of protein activity. Modification of active proteins on small-sized IONPs with a particle size of less than 30 nm is especially difficult due to their high surface energy. Herein, we developed a universal modification method based on Spy chemistry for rapid and stable protein immobilization on small-sized IONPs, which only requires the presence of active groups on the surface of nanoparticles that can couple with SpyCatcher. In short, the SpyCatcher peptides were first coated on the surface of IONPs by cross-linking with activated groups, and then the SpyTag peptide fused with a model protein (enhanced green fluorescent protein, EGFP) was engineered (SpyTag-EGFP) and directly coupled to SpyCatcher-modified IONPs by self-assembly, which is spontaneous and robust while avoiding the effect of chemical reactions on functional protein activity. The obtained EGFP-functionalized IONPs exhibited enhanced and stable green fluorescence and improved magnetic properties. In addition, the cell internalization efficiency of EGFP-functionalized IONPs was significantly increased as compared to unmodified IONPs, providing an ideal solution for efficient cell labeling and tracking. In conclusion, here we report a rapid and easy strategy for EGFP immobilization on IONPs based on Spy chemistry, which could be further adapted to other functional proteins in the future. SpyCatcher-modified IONPs and SpyTag-X (arbitrary functional fusion proteins) hold great potential to be applied as a versatile platform for protein immobilization on IONPs and enable its multifunctional application in the future.

Cluster formation by the precise joining of iron oxide nanoparticles on low energy nitrogen ion irradiation

In this work, we have studied low-energy (5 keV) nitrogen ion-induced modification of the surface of iron oxide nanoparticles. The iron oxide nanoparticles were spin-coated on a silicon substrate. The thin films of iron oxide nanoparticles were irradiated at two different ion fluences of 1 × 1016 and 3 × 1016 ions cm−2, respectively. At a fluence of 1 × 1016 ions cm−2, the nanoparticles incline to join with each other forming small clusters which can be attributable due to Ostwald ripening because of the ion-induced defects. At higher fluence of 3 × 1016 ions cm−2, large nanoclusters are formed due to coalescence. We have investigated the morphological and structural properties of both the pristine and altered surface in detail to understand the cluster formation. We anticipate that such reformed surfaces can be beneficial to enhance the surface plasmon resonance.

Adsorption and Desorption Study of Reusable Magnetic Iron Oxide Nanoparticles Modified with Justicia adhatoda Leaf Extract for the Removal of Textile Dye and Antibiotic.

The release of tetracycline hydrochloride (TCH) and methylene blue (MB) dye into the aquatic system uncontrollably caused major environmental and health problems; hence, their prevention required serious attention. Adsorption process is now being researched in order to increase adsorption efficiency and reprocess to alleviate environmental issues. The use of magnetic nanoparticle as an adsorbent for wastewater treatment has a lot of prospective. A magnetic iron oxide nanoparticle surface modified by Vasaka (Justicia adhatoda) leaf extract (JA-MIONs) is used to give a fast removal approach for MB dye and TCH antibiotics. Dynamic light scattering, UV–Vis and band gap measurement, powder X-ray diffraction, Fourier-transform infrared spectroscopy, and transmission electron microscopy were operated to analyse the formation and size of these magnetic nanoparticles. The impacts of different factors such as contact time (30–150 min), adsorbate concentration (10–50 mg/L), pH (4–10), and adsorbent dose (2–10 mg) were explored. Adsorption kinetics and isotherms show that it follows the pseudo-first-order kinetic and the Freundlich isotherm, with maximum adsorption capacities of 76.92 mg/g for MB and 200 mg/g for TCH at 298 K. The reusability of the JA-MIONs eventually exhibited a decline in the adsorption percentage of MB and TCH after five and four times respectively. After the desorption-adsorption cycles, this adsorbent continued to exhibit significant adsorption capacity. This investigation furnished the significant reference data for the synthesis of JA-MIONs as a novel and auspicious adsorbent for the industrial clean-up of toxic dyes and heavily used antibiotics from water.

Multifunctional Iron Oxide Nanocarriers Synthesis for Drug Delivery, Diagnostic Imaging, and Biodistribution Study.

The aim of the current study is to design the radiolabeled and drug-loaded nanocarrier with high loading capacity and pH-dependent drug release characteristics that could effectively transport loaded compounds to various organs for efficient diagnostic imaging and chemotherapeutic drug delivery. The aqueous extract of green tea leaves was used to synthesize the small-sized iron oxide nanoparticles (IONPs). The nanoparticles were characterized with UV-visible spectroscopy, Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and energy-dispersive X-ray analysis (EDX). Iron oxide nanoparticles with sizes smaller than 50nm were successfully synthesized, making them suitable for in vivo studies. In drug loading trials, 94% of the drug was loaded onto the active surface of iron oxide nanoparticles from the solution. The in vitro drug release study revealed that an acidic environment (pH 4.5) effectively triggers the release of doxorubicin (DOX) from the nanoparticles as compared to a neutral environment (pH 7.4). The gamma-emitting radionuclide 99mTc was successfully labeled with IONPs for biodistribution and imaging studies. The efficiency of radiolabeling was observed to be ≥ 99%. Furthermore, the in vivo biodistribution study of radiolabeled IONPs in rabbit model showed rapid accumulation in various organs such as heart, liver, and kidneys. This work suggested that green synthesized iron oxide nanoparticles are potential nanocarriers for diagnostic imaging and efficiently distributing DOX to specific organs. The aqueous extract of green tea leaves was used for the facile green synthesis of iron oxide nanoparticles (IONPs). Furthermore, the chemotherapeutic drug doxorubicin (DOX) and gamma-emitting radionuclide 99mTc were loaded on these iron oxide nanoparticles to evaluate the in vivo biodistribution and drug delivery studies in the rabbit models.

Green synthesis of spermine coated iron nanoparticles and its effect on biochemical properties of Rosmarinus officinalis

In this study, aqueous spinach extract was used for the green synthesis of iron nanoparticles. The surface of iron oxide nanoparticles was coated with spermine. The physicochemical properties of nanoparticles were investigated using UV-Vis, TGA, FTIR, VSM, TEM, and DLS. The results showed that the nanoparticles had a spherical structure. The surface charge of the Fe3O4-NPs increased from −3.2 to 18.42 (mV) after Fe3O4 coating by spermine. In order to investigate the effect of nanoparticles on physicochemical properties of rosemary under drought stress conditions, an experiment was carried out in a completely randomized design. The results showed that the amount of antioxidant enzymes and secondary metabolites increased significantly under drought stress. Moreover, the use of spermine-coated iron nanoparticles can be useful in increasing resistance to drought stress in plants by increasing the activity of some antioxidant enzymes and secondary metabolites. The biocompatibility of Nanoparticles in cell suspension was investigated. the ability of Fe3O4-SM NPs to interact with DNA and protect it against DNaseI and ultrasonic waves using agarose gel electrophoresis was studied. The ability of Fe3O4-SM to neutralize the negative charge of DNA and protect it against DNaseΙ and ultrasonic waves was confirmed using an agarose gel electrophoresis assay.

Sensitive T2 MRI Contrast Agents from the Rational Design of Iron Oxide Nanoparticle Surface Coatings

Iron oxide nanoparticles are an FDA-approved and gadolinium-free alternative to conventional magnetic resonance imaging (MRI) contrast agents. While their magnetic cores are responsible for T2 contrast, the nonmagnetic polymers at the particle interfaces can affect the diffusion of bulk water near the particles. We show here how this interaction can alter the relaxation dynamics of water protons and, consequently, the nanoparticle’s contrast performance. Libraries of iron oxide nanocrystals of different core diameters and surface coatings can form biocompatible, non-cytotoxic, and colloidally stable suspensions with excellent MRI properties. Both the grafting density and thickness of polymer coatings influence the amount of time water protons spend around a nanoparticle and thus their contrast agent performance. Characterization of the diameter-dependent contrast performance of these materials revealed that nanoparticles with dense, hydrophilic polymer coatings reached the static dephasing regime, and optimal T2 relaxivity, at smaller dimensions than other systems. We rationalized that such coatings offered a slow compartment for water diffusion near the magnetic particle, resulting in an effective diffusion constant lower than bulk water. By manipulating the surface coating and core diameter together, we could generate a material with one of the largest T2 relaxivities ever reported (510 mM–1 s–1) for an isolated nanocrystal. This conceptual framework can explain the complex structure–performance trends of this class of T2 contrast agents and those already reported in the existing literature. Water diffusion at iron oxide nanocrystals (IONCs) interfaces is an essential consideration in designing sensitive and possibly responsive T2 MRI contrast agents.