Cover Picture: Nanomaterials for Fluorescence and Multimodal Bioimaging (Chem. Rec. 3/2023)

Bioconjugated nanomaterials replace molecular probes in bioanalysis and bioimaging in vitro and in vivo. Nanoparticles of silica, metals, semiconductors, polymers, and supramolecular systems, conjugated with contrast agents and drugs for image-guided (MRI, fluorescence, PET, Raman, SPECT, photodynamic, photothermal, and photoacoustic) therapy infiltrate into preclinical and clinical settings. Small bioactive molecules like peptides, proteins, or DNA conjugated to the surfaces of drugs or probes help us to interface them with cells and tissues. Nevertheless, the toxicity and pharmacokinetics of nanodrugs, nanoprobes, and their components become the clinical barriers, underscoring the significance of developing biocompatible next-generation drugs and contrast agents. This account provides state-of-the-art advancements in the preparation and biological applications of bioconjugated nanomaterials and their molecular, cell, and in vivo applications. It focuses on the preparation, bioimaging, and bioanalytical applications of monomodal and multimodal nanoprobes composed of quantum dots, quantum clusters, iron oxide nanoparticles, and a few rare earth metal ion complexes.     

Redox Properties and in Vivo Magnetic Resonance Imaging of Cyclodextrin-Polynitroxides Contrast Agents

This paper reports the synthesis, characterization and in vivo application of water-soluble supramolecular contrast agents (Mw: 5–5.6 kDa) for MRI obtained from β-cyclodextrin functionalized with different kinds of nitroxide radicals, both with piperidine structure ( CD2 and CD3 ) and with pyrrolidine structure ( CD4 and CD5 ). As to the stability of the radicals in presence of ascorbic acid, CD4 and CD5 have low second order kinetic constants (≤0.05 M⁻¹ s⁻¹) compared to CD2 (3.5 M⁻¹ s⁻¹) and CD3 (0.73 M⁻¹ s⁻¹). Relaxivity (r₁) measurements on compounds CD3 - CD5 were carried out at different magnetic field strength (0.7, 3, 7 and 9.4 T). At 0.7 T, r₁ values comprised between 1.5 mM⁻¹ s⁻¹ and 1.9 mM⁻¹ s⁻¹ were found while a significant reduction was observed at higher fields (r₁≈0.6-0.9 mM⁻¹ s⁻¹ at 9.4 T). Tests in vitro on HEK293 human embryonic kidney cells, L929 mouse fibroblasts and U87 glioblastoma cells indicated that all compounds were non-cytotoxic at concentrations below 1 μmol mL⁻¹. MRI in vivo was carried out at 9.4 T on glioma-bearing rats using the compounds CD3 - CD5 . The experiments showed a good lowering of T₁ relaxation in tumor with a retention of the contrast for at least 60 mins confirming improved stability also in vivo conditions.     

MRI相关定量参数在肩峰下撞击综合征诊断中的价值及与肩关节功能、治疗效果的关系

为分析MRI相关定量参数对肩峰下撞击综合征(SIS)的诊断价值,本研究将56例SIS患者设为SIS组,同期56例健康体检者设为对照组,对比了两组对象的一般资料、肩关节功能评分(Constant评分)及MRI相关定量参数水平,探讨了 MRI定量参数与Constant评分、SIS发病相关影响因素、治疗效果的关系及对SIS的...     

LF-NMR和MRI对干制虾仁复水过程水分状态及品质变化的研究

采用低场核磁(LF-NMR)及其成像技术(MRI)研究干制虾仁在25℃复水过程中的水分含量、分布及状态变化,并通过线性回归分析不同复水时间干制虾仁的LF-NMR参数与质构特性及复水率的相关性。实验结果表明,干制虾仁复水过程中存在结合水、不可移动水和自由水3个组分峰,随着复水时间的增加,结合水无明显变化,而自由水、不易流动水含量增加,且自由度增加,流动性增大。LF-NMR参数(T_(22)、T_(23)、A_(22)、A_(23)和A_(Total))和硬度、咀嚼性、弹性、凝聚性以及复水率有极显著的相关性(R~2≥0.613),为干制虾仁复水过程中品质的快速无损预测提供了一种新方法。     

顺磁性聚酯金属配合物的合成及其驰豫性能的研究

本文通过二乙三胺五乙酸（ＤＴＰＡ）或乙二胺四乙酸（ＥＤＴＡ）的双酸酐与二元醇或二元酚进行聚合反应，制备了两个系列共１５种新的聚酯型大分子配体及其顺磁性金属配合物，用核磁、红外光谱以及元素分析表征了配体和配合物的结构。初步试验结果表明，与相应的小分子金属配合物相比，聚酯金属配合物具有较高的弛豫性能。     

Assessment of pulmonary air trapping and obstruction in expiration: an experimental MRI study

PURPOSE: The aim of this experimental study was to evaluate the potential of a simple expiration technique by means of magnetic resonance imaging (MRI) in an animal model to detect pulmonary air-trapping areas after artificial bronchial obstruction. MATERIAL AND METHODS: Sixteen pigs were evaluated by means of a modified T1-weighted FLASH with fat saturation in respiratory arrest (TR=4.6 ms, TE=1.8 ms, alpha=10 degrees, S.D.=3-5 mm). A measurement of the signal intensity (SI) in the peripheral lung tissue was made in both inspiration and expiration before and after inhalation of 2 ml of 0.5% acetylcholine to simulate a bronchial obstruction. A final measurement of the lung SI was also made after bronchospasmolytic induction through salbutamol (beta2-mimetic bronchodilator). RESULTS: In expiration, a mean SI increase in peripheral lung tissue of about 183% was seen in comparison to inspiration (mean SI increase of 11-32). After inhalation of 0.5% acetylcholine, the expirational signal increase in peripheral lung tissue was only 114% of the original SI. The expirational signal homogeneity decreased after inhalation of acetylcholine. After inhalation of salbutamol, the lung tissue signal elevation in expiration was 193%. CONCLUSION: We interpret the low expiratory signal elevation after acetylcholine inhalation as a result of an air-trapped bronchial constriction in certain areas. The simple expiratory technique in an animal model showed that it is suitable to demonstrate obstructive air trapping using MRI.     

Improved l1-SPIRiT using 3D walsh transform-based sparsity basis

l1-SPIRiT is a fast magnetic resonance imaging (MRI) method which combines parallel imaging (PI) with compressed sensing (CS) by performing a joint l1-norm and l2-norm optimization procedure. The original l1-SPIRiT method uses two-dimensional (2D) Wavelet transform to exploit the intra-coil data redundancies and a joint sparsity model to exploit the inter-coil data redundancies. In this work, we propose to stack all the coil images into a three-dimensional (3D) matrix, and then a novel 3D Walsh transform-based sparsity basis is applied to simultaneously reduce the intra-coil and inter-coil data redundancies. Both the 2D Wavelet transform-based and the proposed 3D Walsh transform-based sparsity bases were investigated in the l1-SPIRiT method. The experimental results show that the proposed 3D Walsh transform-based l1-SPIRiT method outperformed the original l1-SPIRiT in terms of image quality and computational efficiency.     

Evaluation of aortic stenosis severity using 4D flow jet shear layer detection for the measurement of valve effective orifice area

Aims

The objective of this study was to evaluate the potential of 4D flow MRI to assess valve effective orifice area (EOA) in patients with aortic stenosis as determined by the jet shear layer detection (JSLD) method.

Methods and Results

An in-vitro stenosis phantom was used for validation and in-vivo imaging was performed in 10 healthy controls and 40 patients with aortic stenosis. EOA was calculated by the JSLD method using standard 2D phase contrast MRI (PC-MRI) and 4D flow MRI measurements (EOA_JSLD-2D and EOA_JSLD-4D, respectively). As a reference standard, the continuity equation was used to calculate EOA (EOA_CE) with the 2D PC-MRI velocity field and compared to the EOA_JSLD measurements. The in-vitro results exhibited excellent agreement between flow theory (EOA = 0.78 cm²) and experimental measurement (EOA_JSLD-4D = 0.78 ± 0.01 cm²) for peak velocities ranging from 0.9 to 3.7 m/s. In-vivo results showed good correlation and agreement between EOA_JSLD-2D and EOA_CE (r = 0.91, p < 0.001; bias: − 0.01 ± 0.38 cm²; agreement limits: 0.75 to − 0.77 cm²), and between EOA_JSLD-4D and EOA_CE (r = 0.95, p < 0.001; bias: − 0.09 ± 0.26 cm²; limits: 0.43 to − 0.62 cm²).

Conclusion

This study demonstrates the feasibility of measuring EOA_JSLD using 4D flow MRI. The technique allows for optimization of the EOA measurement position by visualizing the 3D vena contracta, and avoids potential sources of EOA_CE measurement variability.     

Correction strategy for diffusion-weighted images corrupted with motion: application to the DTI evaluation of infants' white matter

Objective

Diffusion imaging techniques such as DTI and HARDI are difficult to implement in infants because of their sensitivity to subject motion. A short acquisition time is generally preferred, at the expense of spatial resolution and signal-to-noise ratio. Before estimating the local diffusion model, most pre-processing techniques only register diffusion-weighted volumes, without correcting for intra-slice artifacts due to motion or technical problems. Here, we propose a fully automated strategy, which takes advantage of a high orientation number and is based on spherical-harmonics decomposition of the diffusion signal.

Material and methods

The correction strategy is based on two successive steps: 1) automated detection and resampling of corrupted slices; 2) correction for eddy current distortions and realignment of misregistered volumes. It was tested on DTI data from adults and non-sedated healthy infants.

Results

The methodology was validated through simulated motions applied to an uncorrupted dataset and through comparisons with an unmoved reference. Second, we showed that the correction applied to an infant group enabled to improve DTI maps and to increase the reliability of DTI quantification in the immature cortico-spinal tract.

Conclusion

This automated strategy performed reliably on DTI datasets and can be applied to spherical single- and multiple-shell diffusion imaging.