一类基于1,4,7,10-四氮杂环十二烷-1,4,7,10-四乙酸-酰肼结构的新型含钆磁共振对比剂的设计、合成及性能表征（英文）

磁共振成像技术被广泛应用于诊断医学和软组织成像,而磁共振对比剂有助于提高成像对比度.报道了一类共十二种基于钆-1,4,7,10-四氮杂环十二烷-1,4,7,10-四乙酸(DOTA)-酰肼结构的新型磁共振对比剂的设计、合成及性能表征. 0.5 T磁场下测得的弛豫率结果显示,对比剂5d、5h和5l的纵向弛豫率优于临床使用对比剂Gd-DOTA,分别达到4.67、4.85和5.33L·mmol-1·s-1.进一步动物活体体内肝靶向磁共振成像研究显示,对比剂5d具有作为肝靶向磁共振对比剂的应用潜力.     

Gd3+/Yb3+掺杂ZnO量子点作为双模式磁共振/CT成像探针

基于结合磁共振成像(MRI)的高空间分辨率和CT成像的深穿透能力设计思想,在乙醇溶液中水解醋酸锌、醋酸钆和醋酸镱,制备了油酸稳定的Gd3+/Yb3+掺杂ZnO量子点(ZnO∶Gd/Yb),并对其表面进行了氨基修饰。研究了ZnO∶Gd/Yb量子点的弛豫性能、X射线吸收性能、细胞毒性及体外MRI和CT成像。当Zn2+,Gd3+,Yb3+的摩尔比为1.0∶0.12∶0.20时,ZnO∶Gd/Yb量子点展现了最高的弛豫效率6.06 mmol/(L.s)对X-射线的吸收能力也显著高于临床CT造影剂碘比醇。体外MRI和CT成像实验表明,当Gd3+的浓度为1.5 mmol/L时,T1加权MRI信号明显增强,当Yb3+的浓度为5 g/L时,可呈现清晰的CT图像。细胞毒性实验表明,ZnO∶Gd/Yb量子点的浓度低于1.5 mmol/L(Gd3+)时,量子点的毒性相对较低。     

大分子对磁共振造影剂配体改性的研究进展

磁共振成像造影剂是一种信号增强剂,在临床上已有广泛应用。本文介绍了磁共振造影剂配体的种类、结构、改性研究情况和发展趋势,并通过弛豫理论解释合成大分子配体的原因。将含有大分子、靶向性、天然大分子、荧光探针的配体与顺磁性金属Gd（Ⅲ）螯合,制得功能磁共振造影剂,可有效增加弛豫效果和降低生物毒性。     

二乙三胺四乙酸双核钆磁共振成像造影剂的合成及其弛豫性能

合成了以对苯二甲酰基(TP)为连接体的双核Gd-DTTA(DTTA:二乙三胺四乙酸)线型磁共振造影剂Gd2(TP(DTTA)2)。在20 MHz、37℃和pH=7的条件下,此造影剂对水质子的纵向弛豫效率为21.7 L/(mmol·s),比已有的双核Gd-DTTA型磁共振造影剂提高了70%。荧光寿命测试显示,Tb2(TP(DTTA)2)的内配层水分子数q=1.4。结果显示,刚性连接链有利于提高多核造影剂的弛豫效率。     

一种大环类双核非离子型磁共振对比剂的合成及弛豫性能(英文)

磁共振成像技术被广泛应用于诊断医学和软组织成像,而磁共振对比剂有助于提高成像对比度.报道了一种基于钆-DOTA-酰肼结构(DOTA=1,4,7,10-四氮杂环十二烷-1,4,7,10-四乙酸)的新型双核非离子型磁共振对比剂(Gd-DOTAH)2-SBDC的设计、合成及弛豫性能.在0.5 T磁场下,测得其纵向弛豫率为每分子10.6 L·mmol~(-1)·s~(-1)或5.3L·mmol~(-1)·Gd~(-1)·s~(-1),高于目前临床使用的单核大环对比剂钆-DOTA.体外磁共振成像研究显示该磁共振对比剂具有提高诊断灵敏度和准确度的特点.同时,该对比剂分子中含有能与髓鞘特异性结合的二苯乙烯结构,具有成为髓鞘靶向磁共振对比剂的应用潜力.另外,探讨了该对比剂的两条合成路线(A和B),总收率分别为70%和75%.综合考虑适用性,合成路线B更优.     

温度和pH敏感高分子含钆核磁共振成像造影剂的合成及性能

以N-异丙基丙烯酰胺为温度敏感单体,以甲基丙烯酸为p H敏感单体,与三丙烯酸菲洛啉钆进行无皂乳液聚合,一步合成了具有温度和pH敏感的高分子含钆核磁共振成像(MRI)造影剂(TPRPP).动态光散射测试结果表明,TPRPP的粒径随温度或p H值的变化而发生较大的改变.体外MRI测试结果表明,TPRPP的横向弛豫时间(T_1)的加权弛豫率约为11.3 L/(mmol·s),为临床造影剂Magnevist~的2.6倍.体内MRI结果表明,TPRPP在肝和脾中具有明显的正增强效果.研究结果表明,TPRPP是一种优异的多功能MRI造影剂,具有极大的临床研究价值.     

肝靶向性聚天冬酰胺磁共振成像造影剂

用吡哆胺(PM)作为肝靶向基团,先与DTPA双N-羟基琥珀酰亚胺活性酯(SuO-DTPA-OSu)反应生成含一个吡哆胺的DTPA单N-羟基琥珀酰亚胺活性酯(SuO-DTPA-PM),再分别与α,β-聚(2-羟乙基)-L-天冬酰胺和α,β-聚(2-胺乙基)-L-天冬酰胺反应,合成了2类肝靶向性大分子配体,并制备了它们的Gd(Ⅲ)配合物.对所合成的大分子配体以及钆配合物进行了表征.测试了配合物的弛豫率.初步测试大分子载体PHEA和PAEA及其钆配合物的细胞毒性.研究了大分子配体在小白鼠体内分布和大分子钆配合物对大白鼠肝脏造影成像性能.结果表明,与临床广泛应用的小分子磁共振成像造影剂Gd-DTPA相比,以上2类大分子造影剂的弛豫率有明显的提高,并且具有较好的肝靶向性和肝脏成像对比度及清晰度.     

成像核弛豫速率和化学位移与其分子量大小和钆喷酸浓度的相关性

在测试磁共振成像(MRI)用造影剂钆喷酸葡胺(Magnevist)溶液的纵向弛豫速率和化学位移实验中, 观察到溶液中被观测核的弛豫速率加快和化学位移变化与其分子大小和造影剂浓度呈密切的相关性: 对于小分子成像核(水), 弛豫速率和化学位移都与造影剂浓度变化呈很好的线性关系; 而对于大分子成像核(PEG-2000和PEG-6000), 其化学位移和弛豫速率与造影剂浓度变化则呈非线性关系.     

磁共振对比剂标记的聚合物传输siRNA抑制基因表达

二乙烯三胺(DETA)修饰生物可降解的聚乙二醇(PEG)-聚天冬氨酸(PAsp)两嵌段聚合物PEG-PAsp,并通过配体交换将PEG-PAsp(DETA)修饰到磁共振(MR)对比剂SPIO表面,阳离子嵌段PAsp(DETA)可负载核酸分子siRNA,从而获得兼具MR显像和核酸传输功能的生物可降解载体.细胞毒性研究证实该载体聚合物具有较好的生物安全性,可被肿瘤细胞高效吸收,且使转基因细胞株A549-Lue(恒定表达萤火虫荧光素酶)中荧光素酶的活性下调60％.MR成像也证实,SPIO经载体负载后,其横场弛豫率比游离的水溶性SPIO (WSPIO)提高了3倍以上,达到147 Fe (mmol/L)-1s-1,显著提高了磁共振的显像效果.     

肝组织特异性非离子型高分子磁共振造影剂的制备及性能评价

L-酪氨酸甲酯与DTPA双N-羟基琥珀酰亚胺活性酯(SuO-DTPA-OSu)反应,合成了含L-酪氨酸甲酯残基的DTPA单N-羟基琥珀酰亚胺活性酯(SuO-DTPA-Tyr).以EDC/NHS为媒介,通过一步反应将不同量的乳糖酸偶联到α,β-聚[(2-氨乙基)-L-天冬酰胺]上,然后将含有苯环的结构的SuO-DTPA-Tyr与联有D-半乳糖的α,β-聚[(2-氨乙基)-L-天冬酰胺]反应,合成了3种含糖量不同的大分子配体,并制备了其Gd(III)螯合物.结果表明,EDC/NHS方法操作简便,产率高且易于提纯;而SuO-DTPA-Tyr上L-酪氨酸甲酯残基的引入,不仅实现了高分子造影剂的非离子化,同时L-酪氨酸甲酯残基上的苯环结构也可以方便核磁氢谱的指认.大分子配体的细胞毒性随含糖量降低而增加,但均小于同浓度聚(L-赖氨酸)的毒性;大分子螯合物的细胞毒性与商用小分子造影剂的细胞毒性相当,但其弛豫率明显高于小分子造影剂的弛豫率;大分子螯合物在小白鼠肝部有比商用小分子造影剂(钆喷酸葡胺)更好的成像增强效果及更长的停留时间,且在注射后前6h,含D-半乳糖酸残基的大分子螯合物比不含D-半乳糖酸残基的大分子螯合物在小白鼠肝部的代谢速率慢,并呈现出更清晰的造影效果.     

Tetraphenylporphyrin‐based dual‐functional medical agent for magnetic resonance and fluorescence imaging

A bimodal magnetic resonance imaging contrast agent, TPP‐M‐Gd, was developed by modifying tetraphenylporphyrin (TPP) with a small dendritic molecule as a ligand (M) to chelate gadolinium (Gd) ions. The ligand featured four carboxylate groups, which contributed to good water solubility and a strong combination with metal ions. The longitudinal relaxivity (R₁) of the resulting agent was calculated to be 12.45 mM^?1 s^?1, which is much higher than that of DTPA‐Gd (4.49 mM^?1 s^?1). The magnetic resonance imaging experiments showed that the newly synthesized contrast agent could enhance T₁‐weighted magnetic resonance imaging quality both in vitro and in vivo. In addition, TPP‐M‐Gd exhibited good fluorescent property as shown in cell imaging experiments. The cytotoxicity of TPP‐M‐Gd was even better than that of clinically approved DTPA‐Gd, which makes it a promising dual‐functional medical imaging agent to provide more detailed information about biological and disease‐related events.     

Gadolinium-based contrast agents built of DO3A-pyridine scaffold: Precisely tuning carboxylate group for enhanced magnetic resonance imaging

It is greatly desired to develop novel gadolinium-based contrast agents (GBCAs) as improved platforms for magnetic resonance imaging (MRI). Herein, we report the syntheses of a series of nonionic cyclen-based GBCAs by precisely tuning carboxylate group on DO3A-pyridine scaffold. [Gd-DO3A-4cp] is isolated which adopts an octadentate coordination mode with a free carboxylate group at 4-position of pyridine. It shows the r₁ relaxivity of 5.8 (mmol/L)⁻¹ s^-1 (3 T, 25 °C), which is 75% higher than 3.3 (mmol/L)⁻¹ s^-1 of the clinic used [Gd-DOTA]. The possible mechanisms behind the enhanced relaxivity are investigated and proposed by structure-property relationship studies. After validation of low cytotoxicity and considerable kinetic inertness, in-vivo studies are further examined, demonstrating its good MRI performance, biodistribution as well as the way of excretion.     

Synthesis and characterization of an MRI Gd‐based probe designed to target the translocator protein

DPA‐713 is the lead compound of a recently reported pyrazolo[1,5‐a]pyrimidineacetamide series, targeting the translocator protein (TSPO 18 kDa), and as such, this structure, as well as closely related derivatives, have been already successfully used as positron emission tomography radioligands. On the basis of the pharmacological core of this ligands series, a new magnetic resonance imaging probe, coded DPA‐C₆‐(Gd)DOTAMA was designed and successfully synthesized in six steps and 13% overall yield from DPA‐713. The Gd‐DOTA monoamide cage (DOTA = 1,4,7,10‐tetraazacyclododecane‐1,4,7,10‐tetraacetic acid) represents the magnetic resonance imaging reporter, which is spaced from the phenylpyrazolo[1,5‐a]pyrimidineacetamide moiety (DPA‐713 motif) by a six carbon‐atom chain. DPA‐C₆‐(Gd)DOTAMA relaxometric characterization showed the typical behavior of a small‐sized molecule (relaxivity value: 6.02 mM^?1 s^?1 at 20 MHz). The good hydrophilicity of the metal chelate makes DPA‐C₆‐(Gd)DOTAMA soluble in water, affecting thus its biodistribution with respect to the parent lipophilic DPA‐713 molecule. For this reason, it was deemed of interest to load the probe to a large carrier in order to increase its residence lifetime in blood. Whereas DPA‐C₆‐(Gd)DOTAMA binds to serum albumin with a low affinity constant, it can be entrapped into liposomes (both in the membrane and in the inner aqueous cavity). The stability of the supramolecular adduct formed by the Gd‐complex and liposomes was assessed by a competition test with albumin. Copyright © 2013 John Wiley & Sons, Ltd.     

Synthesis, binding affinity, and relaxivity of target-specific MRI contrast agents

Although magnetic resonance imaging (MRI) is one of the most important imaging modalities of the central nervous system (CNS), one of the main drawbacks of MRI is its limited specificity. This can potentially be partially alleviated by target-specific contrast agents. In the present paper we describe a simple high yield synthesis of two such gadolinium-based spiperone targeted MRI contrast agents, 1a and 1b. The R₁ relaxivities of 1a and 1b were evaluated and found to be 5.94 and 8.31 mM⁻¹ s⁻¹, respectively at 9.4T, while their R₂ relaxivities at the same magnetic field were found to be 18.05 and 22.60 mM⁻¹ s⁻¹, respectively. In addition and very importantly compound 1a, which is a gadolinium-based, spiperone-targeted MRI contrast agent, was found to preserve some of the spiperone affinity toward the dopamine D2 receptor. Compounds 1a and 1b thus represent potential agents for in vitro dopamine receptor imaging using MRI in experimental models. Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

General Protocol for the Synthesis of Functionalized Magnetic Nanoparticles for Magnetic Resonance Imaging from Protected Metal–Organic Precursors

The development of magnetic nanoparticles (MNPs) with functional groups has been intensively pursued in recent years. Herein, a simple, versatile, and cost‐effective strategy to synthesize water‐soluble and amino‐functionalized MNPs, based on the thermal decomposition of phthalimide‐protected metal–organic precursors followed by deprotection, was developed. The resulting amino‐functionalized Fe₃O₄, MnFe₂O₄, and Mn₃O₄ MNPs with particle sizes of about 14.3, 7.5, and 6.6 nm, respectively, had narrow size distributions and good dispersibility in water. These MNPs also exhibited high magnetism and relaxivities of r₂=107.25 mM^?1 s^?1 for Fe₃O₄, r₂=245.75 mM^?1 s^?1 for MnFe₂O₄, and r₁=2.74 mM^?1 s^?1 for Mn₃O₄. The amino‐functionalized MNPs were further conjugated with a fluorescent dye (rhodamine B) and a targeting ligand (folic acid: FA) and used as multifunctional probes. Magnetic resonance imaging and flow‐cytometric studies showed that these probes could specifically target cancer cells overexpressing FA receptors. This new protocol opens a new way for the synthesis and design of water‐soluble and amino‐functionalized MNPs by an easy and versatile route.     

Biotin-Conjugated Poly(Acrylic Acid)-Grafted Ultrasmall Gadolinium Oxide Nanoparticles for Enhanced Tumor Imaging

Herein, biotin (Bio)-conjugated poly(acrylic acid) (PAA)-grafted ultrasmall gadolinium oxide nanoparticles (Bio-PAA-Gd₂O₃ NPs) were synthesized for enhanced tumor imaging using Bio as a tumor-targeting ligand. The average particle diameter of Gd₂O₃ NPs was 2.1 nm. The Bio-PAA-Gd₂O₃ NPs exhibited excellent colloidal stability (i. e., no precipitation) and a high longitudinal water proton spin relaxivity (r₁) of 23.8 s⁻¹ mM⁻¹ (r₂/r₁=1.6 and r₂=transverse water proton spin relaxivity), which was ∼6 times higher than those of commercial Gd-chelated magnetic resonance imaging (MRI) contrast agents. Cytotoxicity tests using two cell lines showed that the Bio-PAA-Gd₂O₃ NPs were almost non-toxic up to the measured concentration of 500 μM Gd. The enhanced tumor imaging of the Bio-PAA-Gd₂O₃ NPs was demonstrated through their higher positive contrasts and longer contrast retention at the tumor after intravenous injection in T₁ MR images, compared with those of the control PAA-Gd₂O₃ NPs.     

Amino-phenol complexes of Fe(III) as promising T1 accelerators

Iron(III) complexes with N,O-ligands are compounds of high interest because they can be applied in catalysis and play an important role in living organisms, e.g., as models of catechol dioxygenase. Several N,O-ligands were studied: their synthesis, iron(III) complexation and the potential of the latter as T₁-MRI contrast agents. A route to the tetrapodal N₃O₂-naphthyl ligand was investigated. The resulting iron complex was obtained in 26% total yield and its relaxivity value was moderate (r₁ = 1.03 in water and 2.54 s^?1 mM^?1 in serum). Thus, phenyl isomeric salan complexes were obtained. These complexes differed in charge (positive and neutral) and in the presence of polar hydrogen-bonding substituents. The highest relaxivities (r₁ = 2.39 in water and 5.37 s^?1 mM^?1 in serum) were obtained for the Fe(III) cationic complex with MeO groups in the ligand. EPR studies confirmed a high spin configuration of rhombically distorted Fe(III) complexes.     

Multifunctional nanoprobe for cancer cell targeting and simultaneous fluorescence/magnetic resonance imaging

Multifunctional nanoprobes with distinctive magnetic and fluorescent properties are highly useful in accurate and early cancer diagnosis. In this study, nanoparticles of Fe₃O₄ core with fluorescent SiO₂ shell (MFS) are synthesized by a facile improved Stöber method. These nanoparticles owning a significant core-shell structure exhibit good dispersion, stable fluorescence, low cytotoxicity and excellent biocompatibility. TLS11a aptamer (Apt1), a specific membrane protein for human liver cancer cells which could be internalized into cells, is conjugated to the MFS nanoparticles through the formation of amide bond working as a target-specific moiety. The attached TLS11a aptamers on nanoparticles are very stable and can't be hydrolyzed by DNA hydrolytic enzyme in vivo. Both fluorescence and magnetic resonance imaging show significant uptake of aptamer conjugated nanoprobe by HepG2 cells compared to 4T1, SGC-7901 and MCF-7 cells. In addition, with the increasing concentration of the nanoprobe, T₂-weighted MRI images of the as-treated HepG2 cells are significantly negatively enhanced, indicating that a high magnetic field gradient is generated by MFS-Apt1 which has been specifically captured by HepG2 cells. The relaxivity of nanoprobe is calculated to be 11.5 mg⁻¹s⁻¹. The MR imaging of tumor-bearing nude mouse is also confirmed. The proposed multifunctional nanoprobe with the size of sub-100 nm has the potential to provide real-time imaging in early liver cancer cell diagnosis.     

Purification, Characterization, and Specificity Determination of a New Serine Protease Secreted by Penicillium waksmanii

The purpose of this work was to purify a protease from Penicillium waksmanii and to determine its biochemical characteristics and specificity. The extracellular protease isolated that was produced by P. waksmanii is a serine protease that is essential for the reproduction and growth of the fungus. The protease isolated showed 32 kDa, and has optimal activity at pH 8.0 and 35 °C towards the substrate Abz-KLRSSKQ-EDDnp. The protease is active in the presence of CaCl₂, KCl, and BaCl, and partially inhibited by CuCl₂, CoCl₂ and totally inhibited by AlCl₃ and LiCl. In the presence of 1 M urea, the protease remains 50 % active. The activity of the protease increases 60 % when it is exposed to 0.4 % nonionic surfactant-Triton X-100 and loses 10 % activity in the presence of 0.4 % Tween-80. Using fluorescence resonance energy transfer analysis, the protease showed the most specificity for the peptide Abz-KIRSSKQ-EDDnp with k _cat/K _m of 10,666 mM^?1?s^?1, followed by the peptide Abz-GLRSSKQ-EDDnp with a k _cat/K _m of 7,500 mM^?1?s^?1. Basic and acidic side chain-containing amino acids performed best at subsite S₁. Subsites S₂, S₃, S^′ ₂, and S^′ ₁, S^′ ₃ showed a preference for binding for amino acids with hydrophobic and basic amino acid side chain, respectively. High values of k _cat/K _m were observed for the subsites S₂, S₃, and S^′ _2. The sequence of the N-terminus (ANVVQSNVPSWGLARLSSKKTGTTDYTYD) showed high similarity to the fungi Penicillium citrinum and Penicillium chrysogenum, with 89 % of identity at the amino acid level.     

A Chemical Strategy for the Relaxivity Enhancement of GdIII Chelates Anchored on Mesoporous Silica Nanoparticles

Functionalised MCM‐41 mesoporous silica nanoparticles were used as carriers of Gd^III complexes for the development of nanosized magnetic resonance imaging contrast agents. Three Gd^III complexes based on the 1,4,7,10‐tetraazacyclododecane scaffold (DOTA; monoamide‐, DOTA‐ and DO3A‐like complexes) with distinct structural and magnetic properties were anchored on the silica nanoparticles functionalised with NH₂ groups. The interaction between Gd^III chelates and surface functional groups markedly influenced the relaxometric properties of the hybrid materials, and were deeply modified passing from ionic ? NH₃⁺ to neutral amides. A complete study of the structural, textural and surface properties together with a full ¹H relaxometric characterisation of these hybrid materials before and after surface modification was carried out. Particularly for the anionic complex 2 attached to MCM‐41, an impressive increase in relaxivity (r_1p) was observed (from 20.3 to 37.8 mM ^?1 s^?1, 86.2 % enhancement at 20 MHz and 310 K), mainly due to a threefold faster water exchange rate after acetylation of the surface ? NH₃⁺ ions. This high r_1p value, coupled with the large molar amount of grafted 2 onto the silica nanoparticles gives rise to a value of relaxivity per particle of 29 500 mM ^?1 s^?1, which possibly allows it to be used in molecular imaging procedures. Smaller changes were observed for the hybrid materials based on neutral 1 and 3 complexes. In fact, whereas 1 shows a weak interaction with the surface and acetylation induced only some decrease of the local rotation, complex 3 appears to be involved in a strong interaction with surface silanols. This results in the displacement of a coordinated water molecule and in a decrease of the accessibility of the solvent to the metal centre, which is unaffected by the modification of ammonium ions to neutral amides.