Magnetic Relaxation Properties Research Articles

Suppressing effect of shortening vapor cell stem on polarization-induced magnetic gradient relaxation of Xe in NMR co-magnetometers

The Rb polarization-induced magnetic field gradient is one of the crucial sources of Xe spin relaxation in NMR co-magnetometers. The additional volume of the atomic vapor cell stem can enhance the effective magnetic field gradient through the diffusion effect of the optically polarized-Rb atoms, which affects the spin relaxation properties of Xe and degrades the long-term stability of NMR co-magnetometers. Based on the discrete steps random walk diffusion model, the magnetic gradient relaxation properties of Xe diffusing in an asymmetric cell composed of a cubic part and a cylindrical tube (stem) are characterized. Simulation results indicate that a shorter stem can effectively prolong the nuclear spin relaxation time under a constant magnetic field gradient. To verify this conclusion, a cell stem truncating actuator is developed using a high-power CO2 laser to shorten the cell stem, and the magnetic field gradient coil is used to perform the gradient compensation to examine the impact of various stem lengths on the spin relaxation rate. Experiments indicate that under the influence of atomic diffusive motions, shortening the stem length can effectively suppress the polarization-induced magnetic gradient and increase the 129Xe transverse relaxation time from 4.5 s to 21 s. The study posts practical applications for vapor cells with a stem, which is expected to enhance the performance of atomic spin co-magnetometers.

Slow magnetic relaxation and proton conduction in a highly hydrogen-bonded dinuclear holmium(III) complex

Multifunctional magnetic-electrical materials are highly interesting, such as proton-conductive lanthanide single-ion magnets (SIMs). Herein, we reported the synthesis, crystal structure, magnetic and electrical properties of a bifunctional binuclear holmium(III) complex, [Ho2(H2dobdc)(H2O)14]·(H2dobdc)2·8H2O (Ho2, H4dobdc = 2,5-dioxodo-1,4-benzenedicarboxylate), which was constructed by a hydroxy‑functionalizd dicarboxybenzene and holmium(III) ions. Interestingly, single-crystal X-ray diffraction analysis reveals a highly hydrogen-bonded supramolecular structure and highly oxygenated site were formed within the complex. Magnetic measurements indicate the complex exhibits filed-induced slow magnetic relaxation property. Additionally, the impedance spectroscopy measurements show the complex also exhibits humidity- and temperature-dependent proton conduction behaviour via the Grotthus mechanism. These results support a proton-conductive holmium(III) single-ion magnet of Ho2. This work not only provides the first bifunctional HoIII complexes showing slow magnetic relaxation and proton-conducting behaviour but also a supramolecular way for advanced magnetic-electrical systems linking slow magnetic relaxation with unique proton conducting behaviour exploiting a possible cooperative behaviour.

Magnetic resonance relaxometry in assessment of morphological properties of brain gliomas: state of the art

Magnetic resonance (MR) relaxometry, or measurement of tissue magnetic relaxation properties, is a technology intended to quantitatively depict the physical basis of structural MR imaging. This review is devoted to perspective directions of studies and application of MR relaxometry in brain glioma preoperative and pretherapeutic diagnosis. The current data advocate for emerging capabilities of relaxometry in glioma grading (despite possible overlap between different grades) and differentiating between gliomas and tumors of other origin. Some studies showed features of relaxometric values within the perifocal infiltrative edema zone possibly related to glioma infiltrative growth. We separately reviewed the works aimed at searching for the most aggressive and malignant foci in glioma tissue and extremely useful for tumor biopsy or removal. No less important are capabilities of relaxometry in radiogenomics, first of all, in IDH status prediction. The relaxometric method possesses perspective in multiparametric brain glioma diagnostics.

Two mononuclear chromophore coumarin-based Dy(III) complexes with magnetic relaxation and luminescent properties

Lanthanide luminescent single-molecule magnets (SMMs) serve as a kind of multifunctional molecular materials that have attracted extensive attention. Herein, a novel chromophore coumarin ligand 7-(diethylamino)-(2‑hydroxy-3-methoxybenzylidene)-2-oxo-2-chromene-3-carbohydrazide (Hvalcoumarin) is designed to construct the luminescent Dy(III) complexes. Two Dy complexes 1 ([Dy(valcoumarin)(DMF)2Cl2]·(CHCl3)) and 2 [Dy(valcoumarin)(DMF)2(NO3)2] were synthesized based on the luminescent chromophore coumarin ligand (Hvalcoumarin). X-ray crystallography reveals that the Dy(III) center in complex 1 adopts a hepta-coordinated arrangement by a distorted pentagonal bipyramidal geometry. In contrast, complex 2 exhibits a nine-coordinate arrangement by a spherical capped square antiprism geometry. Magnetic investigations reveal that 1 and 2 exhibit a slow magnetic relaxation phenomenon. Furthermore, the luminescent spectra of 1 and 2 display the characteristic emission profiles associated with Dy(III) spectra. Moreover, theoretical calculations also demonstrated the relaxation dynamics of 1 and 2. The results furnish a potent avenue for the acquisition of multifunctional molecular materials with magnetic and luminescent properties.

Magnetic resonance imaging and velocimetry of ethane

This study investigates the experimental conditions required for magnetic resonance imaging (MRI) of thermally polarized hydrocarbon gas, focusing on ethane. The nuclear magnetic resonance (NMR) spectra and relaxation properties of ethane were analysed at different pressures in the range from 1.5 to 6 bar at 7 T using 1H NMR spectroscopy. The spin-lattice relaxation time (T1) and spin-spin relaxation time (T2) were measured, and their dependence on the pressure was determined, showing that both relaxation times increase with pressure. Using the estimated relaxation times, we adjusted parameters for imaging of static ethane using rapid acquisition with relaxation enhancement (RARE) and fast low-angle shot (FLASH). The signal-to-noise ratio (SNR) of ethane images was evaluated and compared to the calculation for the given range of pressures. Then, we imaged flowing gas using a 2D velocity-encoded pulse sequence, which is usually used for liquid flow studies. The MRI-measured flow rates are compared to those pre-set with a pump, showing good agreement in the slow flow range. Overall, the results provide insights into the feasibility of 1H MRI for imaging and flow measurements of thermally polarized ethane.

Bifunctional Lanthanide-Based Coordination Polymers: Conversion of CO2 and Highly Selective Luminescence Sensing for Acetylacetone.

A series of bifunctional Ln(III)-based coordination polymers (CPs) {Ln(L)(DMA)2(NO3)}n [Ln(III) = Eu (1), Gd (2), and Dy (3); organic ligand H2L = 2,2'-(1,3,5,7-tetrahydroxyoctahydro-4,8-ethanopyrrolo[3,4-f]isoindole-2,6(1H,3H)-diyl)diacetic acid)] have been successfully synthesized. CPs 1-3 are isostructural and constructed from the dimeric Ln2 unit in which two adjacent LnIII ions are bridged by two μ3-carboxyl oxygens, and the Ln2 dimeric unit is connected by two NO3- ions, four DMA molecules, and four completely protonated L2- ligands forming a 2D layer structure. The magnetic research reveals that CP 2 shows a significant cryogenic magnetocaloric effect (-ΔSm = 22.9 J kg-1 K-1; T = 2.0 K and ΔH = 7.0 T), whereas CP 3 exhibits slow magnetic relaxation property under Hdc = 0 Oe field. Additionally, the luminescence explorations revealed that CP 1 can act as a recyclable luminescent probe for pollutant acetylacetone among various small organic solvent molecules, and the corresponding detection limit is 10-7 mol/L. More importantly, CP 1 also exhibits good catalytic performance in the cycloaddition reaction of CO2 and epoxides or cyanamides under mild conditions. As far as we know, CP 1 represents the first bifunctional lanthanide homogeneous catalyst that can efficiently catalyze the reaction of cyanamides/epoxides with CO2 simultaneously.

Structural and Nuclear Magnetic Resonance Relaxation Properties of Shale Condensate within Organic Nanopores via Molecular Dynamics Simulations

Structural and Nuclear Magnetic Resonance Relaxation Properties of Shale Condensate within Organic Nanopores via Molecular Dynamics Simulations

Syntheses of new di-nuclear and tetra-nuclear lanthanide 9-anthracenecarboxylates: Magnetocaloric effect, slow magnetic relaxation and luminescent properties

Lanthanide complex-based materials with magnetic and luminescent properties have received a great deal of attention, owing to their importantly potential applications in diverse fields. In this work, the 9-anthracenecarboxylic acid (9-Haca) as bridging ligand was applied in combination with optically active π-conjugated 2,4,6-tri(2-pyridyl)-1,3,5-triazine (tptz) to construct a series of new di-nuclear and tetra-nuclear lanthanide 9-anthracenecarboxylates [La2(9-aca)6(tptz)2(μ-H2O)]·0.25H2O (1), [Ln2(9-aca)6(tptz)2(H2O)2]·0.5AQ·CH3COOH2H2O [Ln = Sm (2a), Eu (2b), Gd (2c), Tb (2d), Dy (2e), Tm (2f); AQ = 9,10-anthracenedione] and [Ln4(9-aca)10(tptz)2(CH3COO)2]·H2O [Ln = Eu (3a), Gd (3b), Dy (3c)]. 1 displays a di-nuclear centrosymmetric moiety [La2(9-aca)6(tptz)2(μ-H2O)] built up from two complex [La(9-aca)2(tptz)] groups bridged by one H2O molecule and two syn-syn-μ2-η1:η1-9-aca‒ bridging ligands, while 2a‒2f are isostructural and comprise another di-nuclear centrosymmetric moieties [Ln2(9-aca)6(tptz)2(H2O)2] based on two complex [Ln(9-aca)2(tptz)(H2O)] groups connected by two syn-syn-μ2-η1:η1-9-aca– bridging ligands. 3a‒3c are isostructural and show tetra-nuclear centrosymmetric moieties [Ln4(9-aca)10(tptz)2(CH3COO)2] containing three types of coordination modes of 9-aca– ligands. The present compounds offer the only examples of lanthanide 9-anthracenecarboxylates decorated by optically active tptz. Magnetic investigations of 2a, 2c‒2f, and 3b‒3c indicate that 3c is typical of slow relaxation of the magnetization, while 2c and 3b show significant magnetocaloric effect (MCE) with the value of –ΔSm of 5.26 J/(kg·K) at 4 K and 15.65 J/(kg·K) at 2 K (ΔH = 7 T), respectively. The luminescent properties were also studied and reveal that the characteristic luminescent properties of the π-conjugated aromatic ligands are introduced into magnetic lanthanide 9-anthracenecarboxylates, simultaneously exhibiting slow magnetic relaxation (or MCE) and luminescent properties.

Design of Heterometallic {LnIII–MV} (Ln = Dy, Er; M = W, Mo) Molecular Nanomagnets: Protonation Induced Structural Diversification

The construction of lanthanide-based molecular magnets by a self-assembly strategy of multidentate building blocks and functional ligands is continuing to be a hot research topic. Among them, embedding 4d/5d-based building blocks into 4f molecular nanomagnets is promising as it can bring about more fascinating structures and stronger interactions between 4d/5d and 4f ions. In this work, we report the self-assembly reaction of trivalent lanthanide ions (DyIII, ErIII), multidentate ligand 1,3-di(2-pyridinyl)-1,3-propanedione (HL), and octacyanometallate building blocks [MV(CN)8]3– (M = W, Mo). Three different types of cyano-bridged complexes: (i) one-dimensional (1-D) chains {[Dy2[W(CN)8](L)3(H2O)3(CH3OH)]·6CH3OH·4H2O}n (1DyW) and {[Dy2[Mo(CN)8](L)3(H2O)4]·15H2O}n (2DyMo); (ii) tetranuclear clusters {[Dy[Mo(CN)8](HL)2(H2O)2]}2·14H2O (3DyMo) and {[Er[Mo(CN)8](HL)2(H2O)2]}2·14H2O (6ErMo); (iii) a trinuclear cluster {[Er2[W(CN)8](L)3(H2O)4]}·4CH3OH·4H2O (4ErW); and one bimetallic cation–anionic pair {[Er(HL)2(H2O)4]·[Mo(CN)8]}·7H2O (5ErMo) were obtained. Single-crystal X-ray diffraction analyses show that 1DyW and 2DyMo crystallize in the monoclinic space group and form neutral cyano-bridged chains; 3DyMo and 6ErMo are isostructural complexes that form a rare example of square-type d–f complexes; 4ErW is a discrete trinuclear complex, and 5ErMo consists of a {Er(HL)2(H2O)4}3+ cation and a [Mo(CN)8]3– anionic moiety. Interestingly, one of the two pyridyl groups in β-diketone ligands is protonated during the formation of 3DyMo, 5ErMo, and 6ErMo, which is uncommon in related complexes. Magnetic analyses reveal that 1DyW, 2DyMo, 5ErMo, and 6ErMo show field-induced single-molecule magnet (SMM) behaviors, and 3DyMo is a typical SMM with an energy barrier of 119.6 K under zero dc field. Ab initio calculations were performed on these series of {LnIII–MV} heteronuclear complexes in order to provide more insights into the magnetic exchange interactions between 4d and 4f centers and their influences on the magnetic relaxation properties.

Nucleic acid amplification strategies for volume-amplified magnetic nanoparticle detection assay.

Magnetic nanoparticles (MNPs) can be quantified based on their magnetic relaxation properties by volumetric magnetic biosensing strategies, for example, alternating current susceptometry. Volume-amplified magnetic nanoparticle detection assays (VAMNDAs) employ analyte-initiated nucleic acid amplification (NAA) reactions to increase the hydrodynamic size of MNP labels for magnetic sensing, achieving attomolar to picomolar detection limits. VAMNDAs offer rapid and user-friendly analysis of nucleic acid targets but present inherence defects determined by the chosen amplification reactions and sensing principles. In this mini-review, we summarize more than 30 VAMNDA publications and classify their detection models for NAA-induced MNP size increases, highlighting the performances of different linear, cascade, and exponential NAA strategies. For some NAA strategies that have not yet been reported in VAMNDA, we predicted their performances based on the reaction kinetics and feasible detection models. Finally, challenges and perspectives are given, which may hopefully inspire and guide future VAMNDA studies.

Fabrication of a series of isostructural water-stable lanthanide metal-organic frameworks: Tunable luminescence, sensing for antibiotics and magnetic properties

A series of new 1D isomorphic lanthanide metal-organic frameworks (Ln-MOFs), {[Ln(L)(H2O)5]·2H2O}n (1-Ln, Ln ​= ​Eu, Tb, Dy and EuxTb1-x), were synthesized via a rigid bifunctional N,O-containing 2-(1H-tetrazol-5-yl)terephthalic acid (H2L) and Ln(III) ions as raw materials. It is worth noting that different ratios of Eu(III) and Tb(III) can be combined into the same Ln-MOFs to generate a series of new differently doped 1-EuxTb1-x MOFs. Under the same excitation wavelength, the double emission peaks of Eu(III) and Tb(III) are produced, and the emission color gradually changes between yellow-green, yellow, orange, and red. The sensing studies have shown that 1-Tb is an excellent reusable luminescence probe, suitable for simultaneous detection of dimetridazole (DMZ), metronidazole (MDZ) and tetracyclinehydrate (TET) in the aqueous solutions. Furthermore, magnetic measurements show that 1-Dy has slow magnetic relaxation properties.

Slow Magnetic Relaxation and Luminescent Properties of Mononuclear Lanthanide-Substituted Keggin-Type Polyoxotungstates with Compartmental Organic Ligands.

The reaction of mid to late lanthanide ions with the N,N′-dimethyl-N,N′-bis(2-hydroxy-3-formyl-5-bromobenzyl)ethylene-diamine organic ligand and monolacunary Keggin type [α-SiW11O39]8– anion affords a series of isostructural compounds, namely, K5[LnIII(α-SiW11O39)(C20H22Br2N2O4)]·14H2O (1-Ln, Ln = Sm to Lu). The molecular structure of these sandwich-type complexes is formed by the LnIII ion in a biaugmented trigonal prismatic geometry, which occupies the external O4 site of the organic ligand and the vacant site of the lacunary polyoxometalate (POM) unit. The empty N2O2 coordination site of the organic ligand allows its unprecedented folding, which displays a relative perpendicular arrangement of aromatic groups. Weak Br···Br and π–π interactions established between adjacent molecular units govern the crystal packing, which results in the formation of assemblies containing six hybrid species assembled in a chairlike conformation. 1-Gd and 1-Yb display slow relaxation of the magnetization after the application of an external magnetic field with maxima in the out-of-phase magnetic susceptibility plots below ∼5–6 K, which is ascribed to the presence of various relaxation mechanisms. Moreover, photoluminescent emission is sensitized for 1-Sm and 1-Eu in the visible region and 1-Er and 1-Yb in the NIR. In contrast, the quenching of metal-centered luminescence in the 1-Tb derivative has been attributed to the out-of-pocket coordination mode of the lanthanide center within the POM fragment. It is demonstrated that the 1-Yb dual magneto-luminescent material represents the first lanthanide-containing POM reported to date with simultaneous slow magnetic relaxation and NIR emission. Solution stability of the hybrid molecular species in water is also confirmed by ESI-mass spectrometry experiments carried out for 1-Tb and 1-Tm.

Schiff base tetranuclear Zn2Ln2 single-molecule magnets bridged by hydroxamic acid in association with near-infrared luminescence.

A series of Zn-Ln heteronuclear SMMs constructed by using a hexadentate compartment Schiff base Zn-precursor and lanthanoid ions were structurally and magnetically characterized, in which the two [Zn-Ln] moieties are bridged by a series of hydroxamic acids, resulting in double-decker tetranuclear complexes with the molecular formulae [ZnL1Ln(C2H5O)(qua)]2(CF3SO3)2·2C2H5OH ((1) Ln = Dy; (7) Ln = Yb), [ZnL1Ln(CH3O)(bnz)]2(CF3SO3)2·2CH3OH ((2) Ln = Dy), [ZnL1Ln(CH3O)(aca)]2(CF3SO3)2·2CH3OH ((3) Ln = Dy; (8) Ln = Yb), [ZnL2Dy(CH3O)(bnz)]2(CF3SO3)2·2CH3OH (4), [ZnL2Dy(CH3O)(aca)]2(CF3SO3)2·2CH3OH (5), and [ZnL3Dy(CH3O)(bnz)]2(CF3SO3)2·2CH3OH (6) (HL1 = N,N'-bis(2-hydroxy-3-methoxybenzylidene)-1,2-phenylenediamine, HL2 = N,N'-bis(2-hydroxy-3-methoxybenzylidene)-propane-1,2-diamine, HL3 = N,N'-bis(3-methoxysalicylidene)-1,3-propanediamine, qua = 2-quinolinecarboxylic acid, bnz = benzhydroxamic acid and aca = acetohydroxamic acid). Strikingly, the slow magnetic relaxation can be tuned by modifying the steric hindrance and/or electronic effect on the backbone of the Shiff base and the terminal substituents of hydroxamic acid, as well the magneto-structural correlations are studied. Furthermore, Yb congeners 7 and 8 were synthesized to explore dual-functional materials with both magnetic and fluorescence properties, and they displayed both slow magnetic relaxation and near-infrared (NIR) properties; the low temperature NIR spectroscopic data were correlated with the corresponding slow magnetic relaxation mechanism involving thermally activated ground states to the excited state.

Cobalt metal-organic coordination polymer constructed from 2,3′-oxybisbenzoic acid and 1,3-di(pyridin-4-yl)propane: Crystal structure, slow magnetic relaxation and catalytic properties

A new metal-organic coordination polymer, [Co(2,3′-oba)(dpp)]n (1) constructed from 2,3′-oxybisbenzoic acid (2,3′-H2oba) and 1,3-di(pyridin-4-yl)propane (dpp) was synthesized by hydrothermal method. The complex 1 is a 2D network structure connected by Co-2,3′-oba-Co-dpp helical chains. The temperature-dependent magnetic susceptibility and alternating current (ac) magnetic susceptibility measurements of the complex 1 were discussed. The complex 1 was shown to be a single-molecule magnet with slow magnetic relaxation behavior having an energy barrier Ueff of 15 ​K and τ0 =1.56 ​× ​10−6 ​s. As a catalyst, complex 1 exhibited excellent catalytic properties on the activation of peroxymonsulfate (PMS) for the dyes degradation. Specifically, an almost complete degradation of Rhb in aqueous solution was achieved by complex 1/PMS system with an efficiency of 99% within 15 ​min. The feasible active components were explored by quenching experiments, and the results showed that sulfate radicals generated in the degradation system was the main active constituent in the degradation process. The complex 1 has a highly stable skeleton structure which enabled its recycling in the dye degradation system. The obtained results provide an effective method for high degradation efficiencies of dyes in water.

Thermal relaxation in a disordered one-dimensional array of interacting magnetic nanoparticles

We consider a system of single-domain magnetic nanoparticles placed along a linear chain and address the effect of the distance between them on the magnetic and thermal relaxation properties of the system. The nanoparticles interact with each other through the dipolar interaction and we introduce disorder into the system by allowing random sizes of the nanoparticles and random directions of their uniaxial anisotropy axes. In particular, the radius of the spherical nanoparticles are drawn from a log-normal distribution. The dynamical behavior of the magnetic moments of the system is studied through numerical simulations of the stochastic Landau-Lifshitz-Gilbert equation, taking into account explicit temperature dependence of the saturation magnetization and uniaxial anisotropy energy density to describe the magnetic properties of perovskite manganite oxide nanoparticles. Hysteresis, zero-field-cooled and field-cooled curves are measured, from which we can find the coercive field and the blocking temperature as a function of the magnitude of the dipolar coupling, controlled by the distance between the particles. We show that both the coercive field and blocking temperature decrease as a function of the separation between the nanoparticles. The magnetic relaxation is measured as a function of both temperature and time, from which we estimate the effective energy barrier distribution of the system. We show that the peak of the energy barrier distribution moves to lower energies as the separation between neighboring particles increases, or equivalently, as the dipolar interaction is reduced.

Octahedral Hexachloro Environment of Dy3+ with Slow Magnetic Relaxation and Luminescent Properties

AbstractThe compound [BiCNIm]3[DyCl6] was synthesized from a nitrile‐functionalized imidazolium ionic liquid [BiCNIm][Cl] and DyCl3 ⋅ 6H2O in acetonitrile using solvothermal conditions. Structural characterization reveals that the Dy3+ ions are in a quasi‐regular octahedral environment, formed by six chloride anions. The magnetic study indicates that this mononuclear compound exhibits a Single Ion Magnet behaviour. This behaviour is compared to that of other mononuclear compounds containing Dy3+ ions in various octahedral environment.

A two-dimensional dysprosium complex exhibits magnetic slow relaxation properties

One coordination polymer {[Dy(BTTA)1.5(H2O)4.5]n (Dy-1) was successfully obtained via solvo-thermal reaction of Dy(NO3)3⋅6H2O and 2,5-bis-(1H-1,2,4-triazol-1-yl)terephthalic acid (H2BTTA). Single-crystal X-ray diffraction analysis shows that the complex exhibits two-dimensional lay-by-lay structure with one-dimensional channels along b direction, while DyIII ion exhibited as distorted spherical capped square antiprism (C4v) finished by nine oxygen atoms from three BTTA ligands and five water molecules. Magnetic studies show that both of the Orbach and Raman processes contribute to the magnetic relaxation behavior of Dy-1 under low temperature.

(Invited) Magnetic Relaxation Nanoparticle Biosensor for Dosimetric, Longitudinal Biochemical Monitoring In Vivo

Introduction: Harnessing the diversity of sensing platforms for applications in complex environments has been an ongoing challenge in biosensing. Most techniques exhibit limitations ranging from biocompatibility, sensitivity, and signal transduction through opaque media, to longevity under non-laboratory conditions. Through multidisciplinary advances in nanoscience and medical devices, we have developed an implant for the measurement of biomarkers using a magnetic particle assay platform1,2. Exposure to target induces a switch from a dispersed to an assembled state with a corresponding change in magnetic relaxation properties allowing for robust contrast. Current applications focus on diagnostics in chronic cardiac disease and spikes in biomarker presence frequently missed by serial sampling. We address design parameters for sensing functionality, tunability, and degradation to lay the groundwork for multi-month implantation in vivo. Materials and Methods: Particle core materials provided magnetic contrast while biological functionality was tuned by surface ligands for affinity toward multivalent targets (Figure 1a). Polyclonal antibodies were conjugated to superparamagnetic iron oxide nanoparticles (20-50 nm) by maleimide-thiol chemistry. Proton Magnetic Relaxation measurements were acquired on a custom-made, single-sided, inhomogeneous field relaxometer (0.43 Tesla, 25°C, NMR MOUSE) fitted with a programmable robotic scanning stage3. A Carr-Purcell-Meiboom-Gill pulse sequence was used: TE = 0.035 ms, 5454 echoes, 15 scans, TR = 6 s. Relaxation times were determined by single exponential fit to echo peak intensities with a custom MATLAB script. Delrin diffusion devices were filled with particle colloidal suspension and sealed with 30 nm pore polycarbonate semi-permeable membranes via double-sided, pressure-sensitive adhesive (Figure 1b). Devices were exposed to target while sensor response was read every 90-120 minutes for up to 48 hrs. Degradation was measured by quantitating loss of ligand from the surface (ELISA) and changes in sensor performance after elevated temperature storage (37°C) for up to 12 weeks. Results and Discussion: Ligand valency was tuned over an order of magnitude (4-40 Antibodies/Particle) by varying bioconjugation strategies and reagents. Conjugation stability under standard storage conditions indicated a lifetime >5 months by isolating free from bound protein by centrifugation. A maximum 1% of conjugated ligand was released, minimally decreasing valency and sensor functionality. Assay performance showed prozone agglutination behavior with quantitative exposure ranging from 50-2000 ng/mL of target and contrast in <2 hrs. Device dosimeter performance was validated for a cardiac Myoglobin model. Saturation was tuned from 4 to 12 μg/mL*hrs corresponding with 8 to >24 hrs of continuous biomarker elevation at 0-500 ng/mL. 4 hr equilibration and irreversible dosimeter signal stability post-exposure for >12 hrs was also observed (Figure 1c). Biochemical and aggregation performance degradation parameters were evaluated. Over 6.5 weeks of elevated temperature storage, 1.8% of the conjugated antibody was unbound. Sensor longitudinal performance on exposure to target over 12 weeks of incubation showed a monotonically decreasing response magnitude and rate (Figure 1d). Exponential fit to sensor response decay curve predicts a 29 week “switch” (on/off) sensor lifetime for an infarction model (500 ng/mL Myo). These results indicate our sensor can be derivatized for a cardiac biomarker with usable sensitivity and saturation dosimeter response corresponding to elevations expected in a Myocardial Infarction (MI). Device performance can be tuned by matching sensor characteristics with the physiological range of target sensitivity and saturation desired. By tuning bioconjugation strategies we enhanced the performance of the biosensor by an order of magnitude over prior studies. Sensor lifetime and nanostructure degradation studies have shown the limiting performance factor is not the loss of ligand from the surface of the particles but rather the loss of binding activity as seen in elevated temperature experiments. Conclusions: This implant has the potential to broaden diagnostics in personalized medicine by addressing the hurdles of longevity and robust sensor signal stability in complex environments. In situ diagnostics offer continuous sentineling of critical biomarkers, providing a deeper understanding of local biology in dynamic, heterogeneous systems. This monitoring provides valuable timescale data to clinicians with insight into their patients’ lab results for early intervention and data collection throughout treatment. This implant has the capacity to bridge the gap between lab and clinical grade sensors, significantly improving interventional medicine by leveraging the robust and tunable nature of magnetic relaxation particle assays.

Molecular phenotyping of oxidative stress in diabetes mellitus with point-of-care NMR system

Diabetes mellitus is one of the fastest-growing health burdens globally. Oxidative stress, which has been implicated in the pathogenesis of diabetes complication (e.g., cardiovascular event), remains poorly understood. We report a new approach to rapidly manipulate and evaluate the redox states of blood using a point-of-care NMR system. Various redox states of the hemoglobin were mapped out using the newly proposed (pseudo) two-dimensional map known as T1–T2 magnetic state diagram. We exploit the fact that oxidative stress changes the subtle molecular motion of water proton in the blood, and thus inducing a measurable shift in magnetic resonance relaxation properties. We demonstrated the clinical utilities of this technique to rapidly stratify diabetes subjects based on their oxidative status in conjunction to the traditional glycemic level to improve the patient stratification and thus the overall outcome of clinical diabetes care and management.

Magnetic Properties and Electronic Structure of the S = 2 Complex [MnIII{(OPPh2)2N}3] Showing Field-Induced Slow Magnetization Relaxation

The high-spin S = 2 Mn(III) complex [Mn{(OPPh2)2N}3] (1Mn) exhibits field-induced slow relaxation of magnetization (Inorg. Chem. 2013, 52, 12869). Magnetic susceptibility and dual-mode X-band electron paramagnetic resonance (EPR) studies revealed a negative value of the zero-field-splitting (zfs) parameter D. In order to explore the magnetic and electronic properties of 1Mn in detail, a combination of experimental and computational studies is presented herein. Alternating-current magnetometry on magnetically diluted samples (1Mn/1Ga) of 1Mn in the diamagnetic gallium analogue, [Ga{(OPPh2)2N}3], indicates that the slow relaxation behavior of 1Mn is due to the intrinsic properties of the individual molecules of 1Mn. Investigation of the single-crystal magnetization of both 1Mn and 1Mn/1Ga by a micro-SQUID device reveals hysteresis loops below 1 K. Closed hysteresis loops at a zero direct-current magnetic field are observed and attributed to fast quantum tunneling of magnetization. High-frequency and -field EPR (HFEPR) spectroscopic studies reveal that, apart from the second-order zfs terms (D and E), fourth-order terms (B4m) are required in order to appropriately describe the magnetic properties of 1Mn. These studies provide accurate spin-Hamiltonian (sH) parameters of 1Mn, i.e., zfs parameters |D| = 3.917(5) cm-1, |E| = 0.018(4) cm-1, B04 = B42 = 0, and B44 = (3.6 ± 1.7) × 10-3 cm-1 and g = [1.994(5), 1.996(4), 1.985(4)], and confirm the negative sign of D. Parallel-mode X-band EPR studies on 1Mn/1Ga and CH2Cl2 solutions of 1Mn probe the electronic-nuclear hyperfine interactions in the solid state and solution. The electronic structure of 1Mn is investigated by quantum-chemical calculations by employing recently developed computational protocols that are grounded on ab initio wave function theory. From computational analysis, the contributions of spin-spin and spin-orbit coupling to the magnitude of D are obtained. The calculations provide also computed values of the fourth-order zfs terms B4m, as well as those of the g and hyperfine interaction tensor components. In all cases, a very good agreement between the computed and experimentally determined sH parameters is observed. The magnetization relaxation properties of 1Mn are rationalized on the basis of the composition of the ground-state wave functions in the absence or presence of an external magnetic field.