Resonance Detection Research Articles

A Novel Microwave Humidity Sensor Based on Resonant Cavity Perturbation Method

This article proposes a novel humidity sensor using a microwave resonant cavity as the sensing device. This sensor comprises a high-quality factor resonant cavity and frequency detection circuits. The working frequency of the resonator is 9.6 GHz, it has the characteristics that the resonance frequency can be adjusted, and it is designed with embedded air guide holes to allow moist air to enter the interior of the resonant cavity. According to the perturbation theory, when humid air is distributed in the resonator’s sensing area, the resonator’s resonant frequency changes according to different relative humidity (RH) levels. Then, the frequency detection circuit is used to detect the resonance frequency change, and the RH level related to the shift in the resonance frequency can be obtained. In order to get more accurate measurement results, a temperature and atmospheric pressure compensation algorithm is introduced to correct the measurement results. Experiments show that the proposed humidity sensor effectively detects humidity in an RH environment of 20%-95%. It has the characteristics of fast detection speed and high stability, which avoids the need to use the conventional detection method of the vector network analyzer.

Sulfur and nitrogen co-doped magnetic biochar coupled with hydroxylamine for high-efficiency of persulfate activation and mechanism study

Biochar has recently become a central issue in advanced oxidation processes (AOPs) based on peroxydisulfate (PDS) activation. However, the PDS activation by biochar must be improved. In this study, S, N co-doped magnetic biochar (IBC) was prepared by a simple impregnation-pyrolysis method using Eichhornia crassipes stems with inherent sulfur and nitrogen as the raw materials for biochar. The reductant hydroxylamine (HA) was employed to further enhance PDS activation by the IBC for organic pollutant degradation. Incorporating HA in PDS activation over IBC significantly improved its compatibility with complex water, catalytic degradation, stability performance, and mineralization rate of organic pollutants. The outstanding performance of the HA/PDS/IBC system for organic degradation was due to the increased free radicals SO4·-, O2·-, and non-radical 1O2 generated, as well as the electrons transferred between IBC, PDS, and organic pollutants, which were verified by electron paramagnetic resonance (EPR) detection and electrochemical characterizations. Furthermore, HA-enhanced Fe(III)/Fe(II) cycling, surface functional groups, and S and N doping contributed to the generation of reactive oxygen species (ROS). Moreover, the toxicity assessment indicated that the toxicity of the degradation intermediates decreased. Therefore, this research proposes a new insight into the enhanced degradation of pollutants by increasing PDS activation using biochar-based catalytic materials.

15N NMR study of azo-hydrazo tautomerism: Past and present

15N NMR data (1J(15N, 1H) coupling constants and 15N chemical shifts) seem to be the most suitable ones to characterize azo-hydrazo tautomerism quantitatively. The reason is that nitrogen atoms of –NN−/−NH-N = fragments are directly involved in azo-hydrazo equilibrium.First data was measured and published in 1970 and 15N selectively enriched compounds had to be prepared since electro magnets were used in NMR spectrometers at that time providing very low resonance frequencies (from 60 to 100 MHz for protons) and have had, consequently, very low sensitivity. Moreover, a choice of 15N enriched 15N anilines was very limited and these compounds were relatively very expensive.At present, the situation is completely different. There has been a huge increase of NMR spectrometer frequencies used for measurement of NMR spectra and even routinely used NMR spectrometers having 400–600 MHz proton frequencies are sufficiently sensitive to provide 1J(15N, 1H) coupling constants and 15N chemical shifts at the natural abundance level of15N. Inverse detection of resonances is now routinely used. The lower magnetogyric ratio of appropriate nucleus the higher signal enhancement is achieved: this is the very case of the 15N isotope. Theoretical enhancement factor obtained for inverse detection of 15N compared with direct one is ca 300! Application of cryoprobes where electronics is chilled either by liquid nitrogen or even liquid helium reducing electric noise allows to reduce time of accumulation from 8 to 16 times!Some representative examples are presented both from past to present demonstrating the fact that thorough analyses of NMR spectra allow determining the proper constitutions of compounds studies and excluding the wrong ones.

Ferrimagnet based spin Hall detector of subterahertz frequency signals

A concept of a subterahertz (sub-THz) frequency range signals detector based on a ferrimagnet/normal metal (FiM/NM) heterostructure is proposed. An external linearly polarized electromagnetic (EM) wave excites precession in the FiM and spin pumping at the FiM/NM interface. The excited spin current in the NM converts into a direct current via the inverse spin Hall effect. We show that non-zero uncompensation between magnetic spins in FiM gives a non-zero output rectified voltage for both “easy axis” and “easy plane” uniaxial anisotropies. The increase in the uncompensation parameter removes degeneracy from two normal resonance modes and changes the sensitivity to the EM wave. Namely, the sensitivity of the higher mode increases, and the lower mode decreases with increasing the uncompensation parameter. We believe that our results can be helpful for the practical development of sub-THz frequency tunable resonance detector based on the FiM.

Insights into enhanced removal of fluoranthene by sulfidated nanoscale zero-valent iron: In aqueous solution and soil slurry

In this study, 90.9% fluoranthene (FLT) was degraded in sodium percarbonate (2Na2CO3·3H2O2, SPC) oxidation system by Fe(II) combined with sulfidated nano zero valent iron (S-nZVI) activation within 60 min in aqueous solution. Scavenging experiments and electron paramagnetic resonance detection suggested that HO•, O2−•, and 1O2 contributed to the removal of FLT in SPC/Fe(II)/S-nZVI system. Based on the FLT degradation intermediates that were analyzed by GC-MS in SPC/Fe(II)/S-nZVI process, three potential FLT degradation pathways were speculated. The removal efficiency of FLT was inhibited with the presence of humic acid (HA) unless the concentration of HA was controlled at 1.0 mg L−1, and the presence of 1.0 mg L−1 HA favored the generation of HO•. The excellent removal performance of FLT (88.6%) could be achieved in actual groundwater by increasing the chemical dosages and adjusting the initial solution pH to acid environment. In soil slurry tests, the optimal reaction time and soil/water ratio were obtained as 24 h and 2/10, respectively, and the desired FLT degradation performances were obtained at pH 3 and 5 with the soil/water ratio of 2/10. This work effectively demonstrates the application potential of SPC/Fe(II)/S-nZVI system for the remediation of PAHs contamination in actual industrial sites.

A novel approach for measuring membrane permeability for organic compounds via surface plasmon resonance detection

Well-known methods for measuring permeability of membranes include static or flow diffusion chambers. When studying the effects of organic compounds on plants, the use of such model systems allows to investigate xenobiotic behavior at the cuticular barrier level and obtain an understanding of the initial penetration processes of these substances into plant leaves. However, the use of diffusion chambers has disadvantages, including being time-consuming, requiring sampling, or a sufficiently large membrane area, which cannot be obtained from all types of plants. Therefore, we propose a new method based on surface plasmon resonance imaging (SPRi) to enable rapid membrane permeability evaluation. This study presents the methodology for measuring permeability of isolated cuticles for organic compounds via surface plasmon resonance detection, where the selected model analyte was the widely used pesticide metazachlor. Experiments were performed on the cuticles of Ficus elastica, Citrus pyriformis, and an artificial PES membrane, which is used in passive samplers for the detection of xenobiotics in water and soils. The average permeability for metazachlor was 5.23 × 10−14 m2 s−1 for C. pyriformis, 1.34 × 10−13 m2 s−1 for F. elastica, and 7.74 × 10−12 m2 s−1 for the PES membrane. We confirmed that the combination of a flow-through diffusion cell and real-time optical detection of transposed molecules represents a promising method for determining the permeability of membranes to xenobiotics occurring in the environment. This is necessary for determining a pesticide dosage in agriculture, selecting suitable membranes for passive samplers in analytics, testing membranes for water treatment, or studying material use of impregnated membranes.

First Detection of the Pekeris Internal Global Atmospheric Resonance: Evidence from the 2022 Tonga Eruption and from Global Reanalysis Data

Abstract We used observations and model simulation to examine the atmospheric pulses that dominate the far field in the hours after the January 2022 Tonga eruption. We analyzed radiance observations taken from the Himawari-8 geostationary satellite and showed that both a Lamb wave front with the expected horizontal phase speed ∼315 m s−1 and a distinct front with phase speed ∼245 m s−1 can be detected. The slower phase speed is consistent with that expected for the global internal resonant mode that had been proposed by Pekeris in 1937 and in other idealized theoretical studies over the past century, but which had never been detected in the atmosphere. A simulation of the eruption aftermath was performed with a high-resolution atmospheric general circulation model. A hot anomaly over the volcano location was introduced instantaneously to the model fields and the model was integrated for another 12 h. This produced a simulated wave pulse that, in the far field, agreed reasonably well with barograph observations of the Lamb wave. The model results also showed the presence of the slower pulse and that this disturbance had a vertical structure with a 180° phase shift in the stratosphere, in agreement with the theoretical prediction for the internal resonant mode. An implication is that the continuously ringing Lamb wave global normal modes that have been seen in analyses of long observational records ought to have lower-frequency internal Pekeris mode counterparts, a prediction that we confirm though analysis of 67 years of hourly global reanalysis data. Significance Statement Our demonstration that both a surface-trapped Lamb wave and a slower horizontal phase speed internal Pekeris wave can be realized as normal modes of the global atmosphere resolves a very long-standing and fundamental issue in dynamical meteorology. Our result also has broader implications. The 2022 Tonga eruption produced a surprisingly large ocean tsunami even in a remote ocean basin, and it is possible that the slower atmospheric Pekeris mode can play a role in exciting the remarkable ocean response. Also the spectral peaks seen in atmospheric variability corresponding to the Pekeris normal mode provide features for comparison with global model simulations of the atmosphere, along with the Lamb modes detected in earlier studies.

Miniaturized anti-interference cantilever-enhanced fiber-optic photoacoustic methane sensor

To realize all-optical passive detection of CH 4 in narrow spaces and harsh environments, a compact cantilever-enhanced fiber-optic photoacoustic sensor (CEFPS) resistant to electromagnetic and ambient noise interference is proposed. Through theoretical analysis and finite element simulation, a miniaturized photoacoustic cell (PAC) with diffusion holes has been designed and fabricated. The diffusion holes are used for the circulation of the gas to be measured and attenuate the external noise coupled into the PAC. The concentration information of CH 4 is obtained by demodulating the vibration amplitude of the built-in cantilever generated by the photoacoustic pressure. The design of the built-in cantilever structure avoids the possibility of mechanical damage and reduces the interference of external noise in the detection of photoacoustic signals. The experimental results and the Allan-Werle deviation analysis of the CH 4 signal show that the minimum detection limit (MDL) is 0.32 ppm with an integration time of 60 s. The normalized noise equivalent absorption (NNEA) coefficient is calculated as 2.44 × 10 −8 cm −1 W/Hz 1/2 . The developed CEFPS achieves performance comparable to conventional resonant photoacoustic spectroscopy CH 4 detectors, although the volume is two orders of magnitude lower. • A miniaturized all-optical anti-interference cantilever-enhanced photoacoustic methane sensor is presented. • The cantilever acoustic-sensitive element and miniaturized photoacoustic cell (PAC) adopt a built-in design. • The direct effect of environmental noise interference, wind disturbance and mechanical damage on the cantilever is avoided. • The sensitivity of the sensor reaches the traditional resonant photoacoustic spectroscopy trace gas detection technology. • At the same time, the volume of the built-in miniaturized non-resonant PAC is reduced by about two orders of magnitude.

Research on extraction method of tunnel magnetic resonance detection signal based on collaborative filtering

Magnetic resonance detection of tunnel as a non-invasive, direct and quantitative geophysical method for detecting groundwater has attracted much attention in the research of tunnel water hazard early warning. In view of the complex environment where the magnetic resonance detection signal is only nanovolt and the tunnel space, the peak noise and environmental noise are much greater than those of ground magnetic resonance detection. In this paper, we propose a peak noise suppression method based on collaborative filtering to suppress the peak noise of tunnel magnetic resonance rotation detection. In this method, the co-filtering parameters are calculated by using the data without peak noise, and then the peak noise suppression of rotation detection is realized. Through simulation, this method can effectively suppress the peak noise in the tunnel rotation detection magnetic resonance signal and improve the signal quality without changing the relaxation and attenuation characteristics of the tunnel magnetic resonance detection signal. The noise reduction effect of peak noise suppression method based on collaborative filtering is compared and analyzed when the amplitude and quantity of peak noise are different. The influence of this method on the peak noise suppression effect under different Gaussian noise levels is discussed. It is concluded that collaborative filtering can suppress the peak and part of Gaussian noise well without losing the effective magnetic resonance signal.

Contributions for enhanced tracking of (onshore) wind turbines modal parameters

The structural performance of wind turbines is highly dependent on their dynamic behaviour, meaning the monitoring of their structural health should take their dynamic response into account, which can be pursued through the continuous application of Operational Modal Analysis (OMA) to time-series recorded on the structure and subsequent tracking of modal properties. However, it is impractical to manually analyse long periods of data, being therefore essential to automatize OMA.Furthermore, it is necessary to link the results obtained in each dataset. This is usually based on the comparison between estimated modal properties and a trusted set of references. However, the identification of said set of references is normally performed manually, taking time, and producing a result that may be biased. Additionally, in the case of wind turbines, due to the diversity of their operating condition, several sets of references have to be defined, making this process even more cumbersome and subjective.In this sense, this work takes advantage from a continuous monitoring program of an onshore wind turbine, to propose and validate a procedure for the automatic determination of a set of reference modal properties and their subsequent use in modal tracking, which is then validated with results from 18 months of continuously recorded data. Additionally, a complementary very expedite procedure for a preliminary evaluation of the wind turbine dominant frequencies, and detection of eventual problematic resonances, is presented and evaluated using alternative sensors (accelerations, strains and rotations) and data from 3 different turbine models.

Early Pathological and Magnetic Resonance Detection of Cerebral Injury Using a Rat Model of Neonatal Hypoxic Ischemic Encephalopathy

Perinatal hypoxic-ischemic encephalopathy (HIE) is an acute disease that may afflict newborns, resulting in variable long- and short-term neurodevelopmental outcomes. Early diagnosis is critical to identifying infants who may benefit from intervention; however, early diagnosis relies heavily on clinical criteria. No molecular or radiological tests have shown promise in detecting early cerebral injury. Studies have shown that magnetic resonance imaging (MRI) can show changes in both blood flow/ischemia and metabolic disruption. However, they have all been used to evaluate the secondary phase of the disease (>12 h) after the onset of the injury. Early diagnosis is critical to rapidly starting therapeutic hypothermia in eligible infants, which is currently recommended to be initiated within 6 h of birth. The rat model of hypoxic-ischemic injury was developed in 1981 and has been validated and used extensively to study changes in brain perfusion, cerebral injury markers, and morphology. However, it has primarily been used as a "late model", evaluating injury several days after the initial ischemic insult. The model has been known to have poor sensitivity in evaluating reliable and reproducible early cerebral changes. The objective of this study was to develop a reliable model to study early gross morphological and radiological markers of HIE using pathological staining and cerebral magnetic resonance imaging/magnetic resonance spectroscopy.

Interactions of cellulose- and lignin-derived radicals during pyrolysis: An in-situ Electron Paramagnetic Resonance (EPR) study

Lignocellulosic biomass can be converted to biochar, bio-oil and gas through reactions of non-volatile stabilised free radicals (SFRs) and volatile radicals during thermal conversion. In the process, the interactions between radicals from different biomass components play an essential role. Figuring out the interactions of radicals during pyrolysis holds the key to revealing the interaction mechanism of biomass components. In this study, the evolution of SFRs during the co-pyrolysis of cellulose and lignin was explored using in-situ electron paramagnetic resonance (EPR) detection. The interactions of cellulose- and lignin-derived radicals were analysed based on the variation of SFRs, thermogravimetric behavior and Raman spectrum measurement. The results indicate that the interactions of radicals influence char yield, char structure and the SFRs evolution during pyrolysis. The interaction of volatile radicals and SFRs increases the char yield and promotes the condensation of aromatic structure in biochar. At temperatures above 400 °C, the interaction between cellulose- and lignin-derived SFRs leads to the coupling of radicals, which forms an unstable structure in the hot nascent biochar. In the subsequent cooling process, the weak bonds from interactions may break due to the structure shrinkage, which promotes radical reactions and further changes the char structure.

Visible-light-responsive Z-scheme α-Fe2O3/SWCNT/NH2-MIL-125 heterojunction for boosted photodegradation of ofloxacin

In this study, Fe2O3/SWCNT/NH2-MIL-125 (Fe2O3/CNT/MIL) heterostructure was described for ofloxacin (OFX) antibiotics degradation under visible light irradiation (λ > 420 nm). Firstly, α-Fe2O3-derived from MIL-88(Fe) was fabricated via carbonization under an air atmosphere and combined with single-walled CNTs (SWCNTs) to improve electrical conductivity. Subsequently, microcrystals NH2-MIL-125 were successfully decorated on α-Fe2O3/SWCNT surface under solvothermal methods to obtain a new type of the Z-scheme Fe2O3/CNT/MIL heterojunction. The photodegradation rate of OFX in the presence of Fe2O3/CNT/MIL nanocomposite reached 99.3 % in 65 min with a rate constant of 0.065 min−1. This decent photocatalytic activity is principally attributed that the introduction of the α-Fe2O3 and NH2-MIL-125 can notably boost the separation of photogenerated electron-hole pairs. Furthermore, loading SWCNTs boosted the electrical conductivity of α-Fe2O3 and NH2-MIL-125 to improve photodegradation activity. Also, trapping experiments revealed that •OH and •O2− were the main active species, which can also be verified by the detection of electron paramagnetic resonance (EPR). Our findings provide novel ideas for the development of visible-light-responsive materials for improvement in the advanced oxidation process (AOP).

In situ laser-ultrasonic monitoring of elastic parameters during natural aging in an Al-Zn-Mg-Cu alloy (AA7075) sheet

Solution heat treatment increases the formability of 7xxx series aluminum alloys by dissolution of nanoscale hardening phases. However, subsequent natural aging at room temperature partly reverses this process within a few hours, posing a logistical challenge to industrial operations as formability decreases and springback increases. Hence, non-destructive monitoring of mechanical properties may help facilitate forming of parts from 7xxx series alloys, but no suitable non-destructive direct measurement technique has been established so far. Here we demonstrate an in situ laser ultrasonic method based on the generation and detection of plate resonances to continuously monitor small changes (<1%) of Young’s modulus, shear modulus, and Poisson’s ratio during natural aging of an age-hardenable aluminum alloy (AA7075) sheet. Additionally, we followed plastic mechanical properties by tensile testing and we intermittently measured electrical conductivity and performed differential scanning calorimetry to assess precipitation during natural aging. We find qualitative correlation between Guinier-Preston zone formation and an increase in elastic moduli and material strength.

A dual-axis high-order harmonic and single-axis phase-insensitive demodulation atomic magnetometer for in situ NMR detection of Xe

Based on the parametric oscillation process, we demonstrate the dual-axis phase-sensitive demodulation (PSD) and single-axis phase-insensitive demodulation (PISD) for the atomic magnetometer in an in situ nuclear magnetic resonance (NMR) detection system, which can separate the precession signals of NMR from the oscillating magnetic fields. The two orthogonal magnetic fields can be detected simultaneously and independently by selecting the optimal demodulation phases with the traditional PSD method. The response signals of the parametric modulation magnetometer demodulated with high order harmonic signals are evaluated, which is a new exploration. The first order harmonic demodulation can present the best sensitivity about 250 fT/Hz1/2. The high order harmonic demodulation technology supplies a twofold 3 dB bandwidth. With the PISD method, a single-axis demodulation technique is proposed. The transverse nuclear spin precession magnetic fields can be extracted effectively with the demodulation R signal outputs by setting a specific longitudinal modulation magnetic field amplitude, which is a new demodulation strategy compared with the traditional demodulation method for the NMR system.

Modified Transceiver Antenna for NQR Detection of Explosive Objects in Demining Conditions

This paper presents the conceptual stages of the simulation and development of a modified transceiver antenna for a high-power pulsed nuclear quadrupole resonance (NQR) detector of explosives containing the 14N isotope. At a frequency of 4.645 MHz, better characteristics are obtained using a nine-turn coil shaped as half of a Fermat spiral with an outer radius of 75 mm. Using a COMSOL Multiphysics numerical parametric simulation and a materials browser, it was possible to calculate a physical system with parameters as close to reality as possible. According to the results of the experimental studies of the radio frequency (RF) energy, the proposed antenna features an increase in the working area compared to a similar antenna, the topology of the conductive coil of which has the form of an Archimedean spiral. The resulting diagrams of the distribution of the magnetic induction also indicate that the topology of the electromagnetic (EM) field does not depend on the orientation of the sample under study relative to the axis of the radial symmetry observed in square–rectangular planar antennas.

Controllable synthesis of FeMn bimetallic ferrocene-based metal-organic frameworks to boost the catalytic efficiency for removal of organic pollutants.

A series of FeMn bimetallic ferrocene-based metal-organic frameworks (FeMn-Fc-MOFs) with various molar ratios of Fe and Mn (1:9, 2:8, 4:6, 6:4) were successfully synthesized using a simple hydrothermal synthesis method and employed as an efficient activator on persulfate (PS) activation for water decontamination. Characterizations demonstrated that Fe and Mn were smoothly introduced into ferrocene-based MOFs and various molar ratios of Fe:Mn had some influence on crystallinity and surface structure of FeMn-Fc-MOFs. Within 120min, Fe4Mn6-Fc-MOFs demonstrated the best catalytic activity among the different molar ratios, and acid orange 7(AO7) degradation rate was up to 92.0%. In addition, electrochemical experiments revealed that Fe4Mn6-Fc-MOFs possessed superior electron transfer capability than other FeMn-Fc-MOFs, leading to better catalytic performance. Moreover, quenching tests and electron paramagnetic resonance (EPR) detection indicated that hydroxyl radicals and sulfate radicals were both responsible for AO7 decomposition. Notably, the redox cycle of Fe(II)/Fe(III) and Mn(II)/Mn(IV) was discovered in the Fe4Mn6-Fc-MOFs/PS system, which was considered as the limiting process for the cleavage of the O-O bond in PS to generate active radicals. Ultimately, the Fe4Mn6-Fc-MOFs exhibits an excellent universality and good cycling stability for 5 continuous runs. This paper broadens the application of ferrocene-based MOFs on heterogeneous PS activation in environmental catalysis.

Low-boiling Point Perfluorocarbon Nanodroplets as Dual-Phase Dual-Modality MR/US Contrast Agent.

Detection of bare gas microbubbles by magnetic resonance (MR) at low concentrations typically used in clinical contrast-ultrasound studies was recently demonstrated using hyperCEST. Despite the enhanced sensitivity achieved with hyperCEST, in vivo translation is challenging as on-resonance saturation of the gas-phase core of microbubbles consequently results in saturation of the gas-phase hyperpolarized 129 Xe within the lungs. Alternatively, microbubbles can be condensed into the liquid phase to form perfluorocarbon nanodroplets, where 129 Xe resonates at a chemical shift that is separated from the gas-phase signal in the lungs. For ultrasound applications, nanodroplets can be acoustically reverted back into their microbubble form to act as a phase-change contrast agent. Here, we show that low-boiling point perfluorocarbons, both in their liquid and gas form, generate phase-dependent hyperCEST contrast. Magnetic resonance detection of ultrasound-mediated phase transition demonstrates that these perfluorocarbons could be used as a dual-phase dual-modality MR/US contrast agent.

DNA walking system integrated with enzymatic cleavage reaction for sensitive surface plasmon resonance detection of miRNA

Abnormal expression levels of miRNA are associated with various tumor diseases, for example, glioma tumors are characterized by the up-regulation of miRNA-182. Surface plasmon resonance (SPR) assay for miRNA-182 from glioma patients was performed via DNA walking amplification strategy. The duplex between aminated swing arm DNA (swDNA) and block DNA (blDNA), and aminated track DNA (trDNA) with a biotin tag were tethered on the poly(ethylene glycol) (PEG)-modified chips. Upon formation of miRNA/blDNA duplex, the SPR signal decreased with the walking process of swDNA, as the biotinylated fragment of trDNA (biotin-TTGGAGT) was detached from the sensor surface caused by the nicking endonuclease Nb.BbvCI. Such a repeated hybridization and cleavage cycle occurred continuously and the detachment of more biotinylated fragments of trDNA from the chips led to the attachment of fewer streptavidin (SA) molecules and then smaller SPR signals. MiRNA-182 with concentrations ranging from 5.0 fM to 1.0 pM could be readily determined and a detection limit of 0.62 fM was achieved. The proposed method was highly selective and possessed remarkable capability for evaluating the expression levels of miRNA-182 in serum samples from healthy donors and glioma patients. The sensing protocol holds great promise for early diagnosis of cancer patients.

Glu-Urea-Lys Scaffold Functionalized Superparamagnetic Iron Oxide Nanoparticles Targeting PSMA for In Vivo Molecular MRI of Prostate Cancer.

The prostate specific membrane antigen (PSMA), extensively overexpressed on prostate cancer (PCa) cell surface, has been validated as a diagnostic biomarker for PCa. However, insufficient attention has been paid to the development of PSMA-specific probes loaded with small chemical molecules for the in vivo molecular imaging of PCa. In this study, we innovatively labelled superparamagnetic iron oxide nanoparticles with a PSMA-targeting Glu-Urea-Lys scaffold. An optimized synthetic route was developed to offer a physiochemically stable probe. The probe demonstrated high binding affinity (0.38 ± 0.08 μg(Fe)/mL) and binding specificity to PSMA expressed on prostate cancer cell surface in vitro. In a xenograft PCa mouse model, significant negative contrast of the implanted prostate cancer xenograft could be specifically observed by MRI 6 h after tail vein injection of the tracer (Fe, 20 mg/kg), exhibiting its potential to exclusively enhance magnetic resonance detection of PCa.