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Metabolism is a fundamental process that underlies human health and diseases. Nuclear magnetic resonance (NMR) techniques offer a powerful approach to identify metabolic processes and track the flux of metabolites at the molecular level in living systems. An in vitro study through in-cell NMR tracks metabolites in real time and investigates protein structures and dynamics in a state close to their most natural environment. This technique characterizes metabolites and proteins involved in metabolic pathways in prokaryotic and eukaryotic cells. In vivo magnetic resonance spectroscopy (MRS) enables whole-organism metabolic monitoring by visualizing the spatial distribution of metabolites and targeted proteins. One limitation of these NMR techniques is the sensitivity, for which a possible improved approach is through isotopic enrichment or hyperpolarization methods, including dynamic nuclear polarization (DNP) and parahydrogen-induced polarization (PHIP). DNP involves the transfer of high polarization from electronic spins of radicals to surrounding nuclear spins for signal enhancements, allowing the detection of low-abundance metabolites and real-time monitoring of metabolic activities. PHIP enables the transfer of nuclear spin polarization from parahydrogen to other nuclei for signal enhancements, particularly in proton NMR, and has been applied in studies of enzymatic reactions and cell signaling. This review provides an overview of in-cell NMR, in vivo MRS, and hyperpolarization techniques, highlighting their applications in metabolic studies and discussing challenges and future perspectives., (© 2024. The Author(s).)

In NMR-based untargeted metabolomic studies, 1 H NMR spectra are usually divided into equal bins/buckets to diminish the effects of peak shift caused by sample status or instrument instability, and to reduce the number of variables used as input for the multivariate statistical analysis. It was noticed that the peaks near bin boundaries may cause significant changes in integral values of adjacent bins, and the weaker peak may be obscured if it is allocated in the same bin with intense peaks. Several efforts have been taken to improve the performance of binning. Here we propose an alternative method, named P-Bin, based on the combination of the classic peak-picking and binning procedures. The location of each peak defined by peak-picking is used as the center of the individual bin. P-Bin is expected to keep all spectral information associated with the peaks and significantly reduce the data size as the spectral regions without peaks are not considered. In addition, both peak-picking and binning are routine procedures, making P-Bin easy to be implemented. To verify the performance, two sets of experimental data from human plasma and Ganoderma lucidum (G. lucidum) extracts were processed using the conventional binning method and the proposed method, before the principal component analysis (PCA) and the orthogonal projection to latent structures discriminant analysis (OPLS-DA). The results indicate that the proposed method has improved both the clustering performance of PCA score plots and the interpretability of OPLS-DA loading plots, and P-Bin could be an improved version of data preparation for metabonomic study., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2023 Elsevier Inc. All rights reserved.)

In-cell NMR spectroscopy is an effective tool for observing proteins at atomic resolution in their native cellular environment. However, its utility is limited by its low sensitivity and the extensive line broadening caused by nonspecific interactions in the cells, which is even more pronounced in human cells due to the difficulty of overexpressing or delivering high concentrations of isotopically labeled proteins. Here, we present a high-sensitivity tag (wPSP-6F) containing two trifluoromethyl groups that can efficiently label globular proteins with molecular weights in the 6-40 kDa range under mild conditions. This tag allowed us to detect globular proteins in human cells at concentrations as low as 1.0 μM, which would not have been achievable with 15 N or 3-fluorotyrosine labeling. Moreover, we detected conformational changes and interactions of proteins in the cellular environment. The new sensitive 19 F NMR tag may significantly expand the scope of protein NMR in human cells., (© 2023 Wiley-VCH GmbH.)

A novel approach, concentration-ordered NMR spectroscopy (CORDY), is being proposed based on the principle that the ratio of the NMR peak area to its associated number of spins is proportional to the concentration of the assigned compound. Besides, prior information of chemical shift distribution and line shape characteristics of different chemical groups is utilized to shrink the solution space. CORDY generates a pseudo-two-dimensional NMR spectrum with chemical shifts in one axis and concentrations in the other, resulting in both separation and quantitation of components in complex samples. The method was validated by application to three samples-a model mixture containing six amino acids, sugar-free Red Bull, and human urine. It was demonstrated that CORDY could successfully separate the components with up to 2 orders of magnitude in the concentration dimension for the samples used in the current study. In addition, a combination of CORDY and DOSY (CORDY-DOSY) has been found to be more efficient in resolving the molecules with similar concentrations or self-diffusion coefficients.

Purpose: CEST has become a preeminent technology for the rapid detection and grading of tumors, securing its widespread use in both laboratory and clinical research. However, many existing CEST MRI agents exhibit a sensitivity limitation due to small chemical shifts between their exchangeable protons and water. We propose a new group of CEST MRI agents, free-base porphyrins and chlorin, with large exchangeable proton chemical shifts from water for enhanced detection., Methods: To test these newly identified CEST agents, we acquired a series of Z-spectra at multiple pH values and saturation field strengths to determine their CEST properties. The data were analyzed using the quantifying exchange using saturation power method to quantify exchange rates. After identifying several promising candidates, a porphyrin solution was injected into tumor-bearing mice, and MR images were acquired to assess detection feasibility in vivo., Results: Based on the Z-spectra, the inner nitrogen protons in free-base porphyrins and chlorin resonate from -8 to -13.5 ppm from water, far shifted from the majority of endogenous metabolites (0-4 ppm) and Nuclear Overhauser enhancements (-1 to -3.5 ppm) and far removed from the salicylates, imidazoles, and anthranillates (5-12 ppm). The exchange rates are sufficiently slow to intermediate (500-9000 s -1 ) to allow robust detection and were sensitive to substituents on the porphyrin ring., Conclusion: These results highlight the capabilities of free-base porphyrins and chlorin as highly upfield CEST MRI agents and provide a new scaffold that can be integrated into a variety of diagnostic or theranostic agents for biomedical applications., (© 2019 International Society for Magnetic Resonance in Medicine.)

Nano contrast agents (Nano CA) are nanomaterials used to increase contrast in the medical magnetic resonance imaging (MRI). However, the related relaxation mechanism of the Nano CA is not clear yet and little significant breakthrough in relaxivity enhancement has been achieved. Herein, a new hydrophilic Gd-DOTA complex functionalized with different chain length of PEG was synthesized and incorporated into graphene quantum dots (GQD) to obtain paramagnetic graphene quantum dots (PGQD). We performed a variable-temperature and variable-field intensity NMR study in aqueous solution on the water exchange and rotational dynamics of three different chain lengths of PGQD. The optimal GQD with paramagnetic chain length shows a great improvement in performance on 1 H NMR relaxometric studies. In vitro results demonstrated that the relaxivity of the designed PGQD could be controlled by regulating the PEG length, and its relaxivity was ∼16 times higher than that of current commercial MRI contrast agents (e.g., Gd-DTPA), on a "per Gd" basis. The relaxivity of the Nano CA can be rationally tuned to obtain unmatched potentials in MR imaging, exemplified by preparation of the paramagnetic GQD with the enhanced T 1 relaxivity. The fabricated PGQDs with suitable PEG length got the best relaxivity at 1.5 T. After intravenous injection, its feeding process by solid tumor could even be monitored by clinically used 1.5 T MRI scanners. This research will also provide an excellent platform for the design and synthesis of highly effective MR contrast agents.

Background: The rational design of theranostic nanoprobe to present responsive effect of therapeutic potency and enhanced diagnostic imaging in tumor milieu plays a vital role for efficient personalized cancer therapy and other biomedical applications. We aimed to afford a potential strategy to pose both T 1 - and T 2 -weighted MRI functions, and thereby realizing imaging guided drug delivery and targeted therapy., Results: Theranostic nanocomposites Mn-porphyrin&Fe 3 O 4 @SiO 2 @PAA-cRGD were fabricated and characterized, and the nanocomposites were effectively used in T 1 - and T 2 -weighted MRI and pH-responsive drug release. Fluorescent imaging also showed that the nanocomposites specifically accumulated in lung cancer cells by a receptor-mediated process, and were nontoxic to normal cells. The r 2 /r 1 ratio was 20.6 in neutral pH 7.4, which decreased to 7.7 in acidic pH 5.0, suggesting the NCs could act as an ideal T 1 /T 2 dual-mode contrast agent at acidic environments of tumor. For in vivo MRI, T 1 and T 2 relaxation was significantly accelerated to 55 and 37%, respectively, in the tumor after i.v. injection of nanocomposites., Conclusion: The synthesized nanocomposites exhibited highly sensitive MRI contrast function no matter in solution, cells or in vivo by synergistically enhancing positive and negative magnetic resonance imaging signals. The nanocomposites showed great potential for integrating imaging diagnosis and drug controlled release into one composition and providing real-time imaging with greatly enhanced diagnostic accuracy during targeted therapy.

Biothiols such as cysteine (Cys), homocysteine (Hcy), and glutathione (GSH) play an important role in regulating the vital functions of living organisms. Knowledge of their biodistribution in real-time could help diagnose a variety of conditions. However, existing methods of biothiol detection are invasive and require assays. Herein we report a molecular biosensor for biothiol detection using the nuclear spin resonance of (129)Xe. The (129)Xe biosensor consists of a cryptophane cage encapsulating a xenon atom and an acrylate group. The latter serves as a reactive site to covalently bond biothiols through a thiol-addition reaction. The biosensor enables discrimination of Cys from Hcy and GSH through the chemical shift and average reaction rate. This biosensor can be detected at a concentration of 10 μM in a single scan and it has been applied to detect biothiols in bovine serum solution. Our results indicate that this biosensor is a promising tool for the real-time imaging of biothiol distributions.

Liposomes are effective drug delivery systems that can be functionalized with imaging contrast agents, providing both diagnosis and monitoring of disease treatment. Here we describe the design of a theranostic liposomal drug delivery system whose biodistribution can be real time imaged by contrast enhanced MRI and can achieve tandem chemotherapy drug delivery. Because T1 relaxation of MRI depends upon the chemical structure of contrast agent as well as its interaction with neighbor environment, we rationally designed a functional liposome for in vivo T1 enhanced MRI. The liposome shows a 36-fold higher T1 relaxation rate over the commercial MRI contrast agent Omniscan® and a long circulation time up to 300min in vivo. Moreover, the multifunctional liposome carries both hydrophobic and hydrophilic chemotherapeutic drugs, can synergistically enhance therapeutic effects of multiple drugs and selectively deliver them to lung tumors, leading to lower doses, toxicity and sustained release. The nanoparticles, which exhibit favorable biodistributions to tumors, offer new possibilities for the simultaneous delivery of more than one drug and the evaluation of therapeutic response in vivo by T1 enhanced MRI., Statement of Significance: Cancer cells invoke different mechanisms to resist cancer therapies, particularly when delivering a single agent in a given therapy. The combination of two (or more) thermotherapy agents provides a promising way to circumvent such situations of drug resistance, due to a favorable synergistic effect that "tricks" the drug resistance mechanism. However, challenges to the simultaneous delivery of two drugs prevail, especially with regards to the simultaneous delivery of hydrophobic and hydrophobic drugs. Furthermore, non-invasive in vivo imaging of drug distribution enables the real-time monitoring and prediction of therapeutic responses to treatment. In this study, we rationally designed a theranostic liposomal drug delivery system whose biodistribution can be imaged via T1-weighted MRI in real-time and can achieve tandem chemotherapy drug delivery. This original study will be of considerable use to the wider drug delivery community., (Copyright © 2016 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.)

Mercury pollution, in the form of mercury ions (Hg(2+)), is a major health and environmental hazard. Commonly used sensors are invasive and limited to point measurements. Fluorescence-based sensors do not provide depth resolution needed to image spatial distributions. Herein we report a novel sensor capable of yielding spatial distributions by MRI using hyperpolarized (129)Xe. A molecular clamp probe was developed consisting of dipyrrolylquinoxaline (DPQ) derivatives and twocryptophane-A cages. The DPQ derivatives act as cation receptors whereas cryptophane-A acts as a suitable host molecule for xenon. When the DPQ moiety interacts with mercury ions, the molecular clamp closes on the ion. Due to overlap of the electron clouds of the two cryptophane-A cages, the shielding effect on the encapsulated Xe becomes important. This leads to an upfield change of the chemical shift of the encapsulated Xe. This sensor exhibits good selectivity and sensitivity toward the mercury ion. This mercury-activated hyperpolarized (129)Xe-based chemosensor is a new concept method for monitoring Hg(2+) ion distributions by MRI., (© 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)

Real-time diagnosis and monitoring of disease development, and therapeutic responses to treatment, are possible by theranostic magnetic resonance imaging (MRI). Here we report the synthesis of a multifunctional liposome, which contains Gd-DOTA (an MRI probe), paclitaxel and c(RGDyk) (a targeted peptide). This nanoparticle overcame the insolubility of paclitaxel, reduced the side effects of FDA-approved formulation of PTX-Cre (Taxol®) and improved drug delivery efficiency to the tumor. c(RGDyk) modification greatly enhanced the cytotoxicity of the drug in tumor cells A549. The T1 relaxivity in tumor cells treated with the targeted liposome formulation was increased 16-fold when compared with the non-targeted group. In vivo, the tumors in mice were visualized using T1-weighted imaging after administration of the liposome. Also the tumor growth could be inhibited well after the treatment. Fluorescence images in vitro and ex vivo also showed the targeting effect of this liposome in tumor cells, indicating that this nanovehicle could limit the off-target side effects of anticancer drugs and contrast agents. These findings lay the foundation for further tumor inhibition study and application of this delivery vehicle in cancer therapy settings.

A novel thermo-sensitive micelle contrast agent and its enhancement of MRI contrast with temperature are reported. The morphology changes sharply near 37 °C, resulting in a significant amplification of the CEST signal. This enables detection of small changes in body temperature.

To realize sensing and labeling biomarkers is quite challenging in terms of designing multimodal imaging probes. In this study, we developed a novel β‐galactosidase (β‐gal) activated bimodal imaging probe that combines near‐infrared (NIR) fluorescence and magnetic resonance imaging (MRI) to enable real‐time visualization of activity in living organisms. Upon β‐gal activation, Gal‐Cy‐Gd‐1 exhibits a remarkable 42‐fold increase in NIR fluorescence intensity at 717 nm, allowing covalent labeling of adjacent target enzymes or proteins and avoiding molecular escape to promote probe accumulation at the tumor site. This fluorescence reaction enhances the longitudinal relaxivity by approximately 1.9 times, facilitating high‐resolution MRI. The unique features of Gal‐Cy‐Gd‐1 enable real‐time and precise visualization of β‐gal activity in live tumor cells and mice. The probe's utilization aids in identifying in situ ovarian tumors, offering valuable assistance in the precise removal of tumor tissue during surgical procedures in mice. The fusion of NIR fluorescence and MRI activation through self‐immobilizing target enzymes or proteins provides a robust approach for visualizing β‐gal activity. Moreover, this approach sets the groundwork for developing other activatable bimodal probes, allowing real‐time in vivo imaging of enzyme activity and localization. [ABSTRACT FROM AUTHOR]

A new magnetic resonance imaging (MRI) molecular sensor for hydrogen sulfide detection and imaging using the nuclear spin resonance of hyperpolarized 129Xe is developed. The designed MRI sensor employs cryptophane for NMR sensing, together with an azide group serving as a reaction site. It demonstrates a 'proof-of-concept' that a fluorescent H2S probe can be linked to a xenon-binding cryptophane and thereby converted into an MRI probe, which could provide a very generalizable template. [ABSTRACT FROM AUTHOR]

Keywords: 19F MRI; Biosensors; Fluorescence Imaging; Hypoxia; Nitroreductase EN 19F MRI Biosensors Fluorescence Imaging Hypoxia Nitroreductase 1 1 1 12/07/22 20221212 NES 221212 B Eine bimodale Bildgebungssonde b FCy7-NO SB 2 sb wurde eingesetzt, um die bei Lungenkrebs überexprimierte Nitroreduktase in vivo abzubilden, wie Xin Zhou et al. in ihrem Forschungsartikel berichten (e202213495). 19F MRI, Biosensors, Fluorescence Imaging, Hypoxia, Nitroreductase Die Integration zweier komplementärer Bildgebungstechnologien in FCy7-NO SB 2 sb ermöglicht einen empfindlichen Nachweis von Nitroreduktase in einem breiten Konzentrationsbereich ohne Gewebetiefenbegrenzung. [Extracted from the article]

Mercury pollution, in the form of mercury ions (Hg2+), is a major health and environmental hazard. Commonly used sensors are invasive and limited to point measurements. Fluorescence-based sensors do not provide depth resolution needed to image spatial distributions. Herein we report a novel sensor capable of yielding spatial distributions by MRI using hyperpolarized 129Xe. A molecular clamp probe was developed consisting of dipyrrolylquinoxaline (DPQ) derivatives and twocryptophane-A cages. The DPQ derivatives act as cation receptors whereas cryptophane-A acts as a suitable host molecule for xenon. When the DPQ moiety interacts with mercury ions, the molecular clamp closes on the ion. Due to overlap of the electron clouds of the two cryptophane-A cages, the shielding effect on the encapsulated Xe becomes important. This leads to an upfield change of the chemical shift of the encapsulated Xe. This sensor exhibits good selectivity and sensitivity toward the mercury ion. This mercury-activated hyperpolarized 129Xe-based chemosensor is a new concept method for monitoring Hg2+ ion distributions by MRI. [ABSTRACT FROM AUTHOR]

Melanoma is a malignant tumor of melanocytes. Although extensive investigations have been done to study metabolic changes in primary melanoma in vivo and in vitro, little effort has been devoted to metabolic profiling of metastatic tumors in organs other than lymph nodes. In this work, NMR-based metabolomics combined with multivariate data analysis is used to study metastatic B16-F10 melanoma in C57BL/6J mouse spleen. Principal component analysis, an unsupervised multivariate data analysis method, is used to detect possible outliers, while orthogonal projection to latent structure (OPLS), a supervised multivariate data analysis method, is employed to find important metabolites responsible for discriminating the control and the melanoma groups. Two different strategies, i.e. spectral binning and spectral deconvolution, are used to reduce the original spectral data before statistical analysis. Spectral deconvolution is found to be superior for identifying a set of discriminatory metabolites between the control and the melanoma groups, especially when the sample size is small. OPLS results show that the melanoma group can be well separated from its control group. It is found that taurine, glutamate, aspartate, O-phosphoethanolamine, niacinamide, ATP, lipids and glycerol derivatives are decreased statistically and significantly while alanine, malate, xanthine, histamine, dCTP, GTP, thymidine, 2′-deoxyguanosine are statistically and significantly elevated. These significantly changed metabolites are associated with multiple biological pathways and may be potential biomarkers for metastatic melanoma in spleen. [ABSTRACT FROM AUTHOR]

Hyperpolarization is one of the methods for NMR signal enhancement. NMR sensitivity can be further enhanced by combining hyperpolarization with chemical exchange saturation transfer (CEST), which termed “Hyper‐CEST”. A H2S sensor is reported that contains a cryptophane group for NMR sensing and a naphthalimide group for fluorescence sensing, together with an azide group as the reaction site. Upon reacting with H2S, the fluorescence and 129Xe NMR signal changes, which may provide a universal template for converting a fluorescence sensor into an 129Xe Hyper‐CEST MRI sensor. More information can be found in the Communication by X. Zhou, M. Liu, et al. on page 7648. [ABSTRACT FROM AUTHOR]

The longitudinal magnetization of hyperpolarized media, such as hyperpolarized 129 Xe, 3 He, etc., is nonrenewable. When the MRI data acquisition begins at the k -domain center, a constant flip angle (CFA) results in an image of high signal-to-noise ratio (SNR) but sacrifices the accuracy of spatial information. On the other hand, a variable flip angle (VFA) strategy results in high accuracy but suffers from a low SNR. In this paper, we propose a novel scheme to optimize both the SNR and accuracy, called constant-variable flip angles (CVFA). The proposed scheme suggests that hyperpolarized magnetic resonance signals are firstly acquired through a train of n ∗ CFA excitation pulses, followed by a train of N – n ∗ VFA excitation pulses. We simulate and optimize the flip angle used in the CFA section, the number of CFA excitation pulses, the number of VFA excitation pulses, and the initial and final variable flip angles adopted in the VFA section. Phantom and in vivo experiments demonstrate the good performance of the CVFA designs and their ability to maintain both high SNR and spatial resolution. [ABSTRACT FROM AUTHOR]