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.     

两亲性寡聚体Gd(Ⅲ)配合物的合成及肝选择性磁共振造影

小分子造影剂在体内存留的时间较短,被注射到体内后,在较短的时间内就会排出体外,所以在进行造影检查时,需要多次注射造影剂．一般大分子造影剂,比小分子造影剂[如二乙三胺五乙酸(DTPA)钆的配合物等]有更好的弛豫效能,而且大分子造影剂在体内停留的时间较长,能满足造     

L-酪氨酸甲酯消旋及Alcalase 2.4L催化对映选择性水解制备D-酪氨酸

提出了一个5-硝基水杨醛催化L-酪氨酸甲酯消旋化的新方法并推测了L-酪氨酸甲酯的消旋机理.在乙腈/磷酸盐缓冲液(pH 7.5)中,5-硝基水杨醛催化L-酪氨酸甲酯消旋为DL-酪氨酸甲酯,消旋率100%,消旋收率93%.优化了Alcalase 2.4L催化DL-酪氨酸甲酯对映选择性水解的反应条件.30℃下,在叔丁醇/磷酸盐缓冲液(pH 7.5)中,Alcalase 2.4L催化DL-酪氨酸甲酯对映选择性水解为L-酪氨酸和D-酪氨酸甲酯.在酶催化水解过程中,L-酪氨酸形成沉淀,容易通过简单的过滤进行分离.D-酪氨酸甲酯在碱性条件下水解为D-酪氨酸,收率91%,ee97%.     

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.     

含罗丹明B基团的聚天冬酰胺荧光成像探针研究

以L-天冬氨酸为原料,在体积分数为85%的磷酸催化条件下采用热缩合方法合成了聚琥珀酰亚胺大分子,用罗丹明B与乙二胺反应生成的罗丹明-乙二胺衍生物的氨基以及乙醇胺上的氨基对聚琥珀酰亚胺进行开环反应,合成了含罗丹明B基团的聚天冬酰胺大分子.通过溴化与亲核取代反应将磺胺嘧啶基团接枝于聚天冬酰胺大分子上,从而制备具有肿瘤靶向功能的水溶性聚天冬酰胺大分子荧光探针(SD-PHEA-RhB).对所合成的荧光探针进行了核磁共振谱、红外光谱、紫外-可见光谱、凝胶渗透色谱和质谱等结构表征,进一步测试了其分子量及分布、粒径、荧光性能、体外细胞毒性与细胞摄取以及荧光成像性能.实验结果表明,所合成的聚天冬酰胺荧光成像探针具有良好的水溶性和荧光性能,对酸性环境敏感,对Hep G2和HeLa细胞均具有较低的体外细胞毒性,能被HeLa肿瘤细胞选择性摄取,且能获得较好的HeLa细胞红色荧光成像.     

基于同源建模和定点突变技术研究嗜热型L-阿拉伯糖异构酶与D-半乳糖的亲和作用

通过同源建模分析选取对Lactobacillus fermentum CGMCC2921来源的L-阿拉伯糖异构酶(简称L-AI酶)催化D-半乳糖生产D-塔格糖起重要作用的氨基酸位点进行突变,发现当Q16,M311,K423和Q438位点的氨基酸突变为丙氨酸时,突变酶Km值降低,其中突变酶M311A降至本体的51.6%,对D-半乳糖的转化率提高了18.7%.当K423位点的氨基酸残基分别突变为丙氨酸、天冬酰胺或精氨酸时,突变酶与底物的亲和力以及D-半乳糖的转化率随着423位点突变氨基酸侧链长度的增加而降低.运用计算机分子模拟技术分析表明,当M311位点氨基酸突变为丙氨酸以后,催化位点氨基酸残基与底物D-半乳糖之间的氢键作用增强,导致与底物亲和力增大,从而提高了酶活力.     

肝靶向性磁共振成像造影剂──含D-半乳糖基的DTPA双酰胺钆配合物的研究

通过二乙三胺五乙酸的双N-羟基琥珀酰亚胺活性酯与含氨基的乳糖或D-半乳糖衍生物反应,合成了8种含有D-半乳糖基的二乙三胺五乙酸非离子型配体,并进一步合成了其钆(Ⅲ)配合物. 配体及配合物的结构经IR、¹HNMR与元素分析表征,对配合物的体外弛豫性能和小鼠急性毒性作了初步研究. 家兔的磁共振成像实验表明这类造影剂具有肝靶向的特性.     

α,β-聚[N-(丁二酸基)-L-天冬酰胺]的合成及其顺铂大分子药物的细胞毒性

L-天冬氨酸在H2O/三乙胺混合溶剂中直接均相开环聚(L-天冬酰亚胺)(PSI), 合成α,β-聚[N-(丁二酸基)-L-天冬酰胺](PSAA). 研究了H2O和三乙胺的混合体积比对反应物溶解性能的影响, 并用FTIR和1H NMR表征了PSAA的结构. 以PSAA和α,β-聚(L-天冬氨酸)(PAsp)为载体, 与顺式二氯二氨合铂(Ⅱ)(CDDP)络合, 合成了PSAA-CDDP和PAsp-CDDP大分子药物. 结果表明, 载体PSAA和PAsp对Bel7402细胞的毒性均低于同浓度的聚赖氨酸; PSAA-CDDP的水溶性良好, 载药量较高, 达到了14.6%, 其药物控制释放性能较好; PSAA-CDDP和PAsp-CDDP的细胞毒性随着其浓度的增大而增大, 且细胞毒性PAsp-CDDP相似文献   

具有荧光探针的靶向肽/聚(醚-酰胺)制备及其肝癌细胞靶向性能研究

通过端氨基聚乙二醇PEG(Ⅰ)与二亚乙基三胺五乙酸二酐(DTPAA)开环合成新型端氨基聚(醚-酰胺)(PEG/DTPA)共聚物造影剂配体(Ⅱ)(Step1);Ⅱ的端氨基与偶联剂3-马来酰亚胺苯甲酸-N-琥珀酰亚胺酯(MBS)的活化端COOH反应,生成偶联剂/聚(醚-酰胺)MB/PEG/DTPA(Ⅲ′)(Step2);再通过Ⅲ′中MBS的CC双键与肝癌细胞靶向黏附肽FAM-AGKGTPSLETTPC-(SH)-COOH(FAM-13)上的巯基SH发生Michael加成反应(Step3),合成含有荧光探针FAM(5-carboxyfluorescein)的肝癌靶向肽/聚(醚-酰胺)(FAM-13/PEG/DTPA,Ⅲ).用1H-NMR和13C-NMR等方法对共聚物进行表征.Ⅲ对正常肝细胞L-02几乎观察不到荧光现象,而对肝癌细胞BEL-7404则有很强的黄绿色荧光,Ⅲ对肝癌细胞有很强的靶向性.大分子配体Ⅲ可望用于制备大分子造影剂及靶向载体负载药物.     

新型羧甲基壳聚糖水凝胶流变性能,药物释放及细胞相容性研究

羧甲基壳聚糖含有丰富的羧基和氨基, 通过1-乙基-(3-二甲基氨基丙基)碳二亚胺盐酸盐(EDC)和N-羟基琥珀酰亚胺(NHS)共催化交联羧甲基壳聚糖形成新型水凝胶. 调节EDC/NHS用量, 制备不同交联度的羧甲基壳聚糖水凝胶(CMCS hydrogels). 研究水凝胶的流变行为, 结果表明, 高交联度的水凝胶具有较好的弹性形变能力, 较高的储存模量, 这是因为随着交联度的升高, 羧甲基壳聚糖水凝胶化学交联网络结构趋于完善. 以胸腺五肽(TP-5)为模型药物, 初步评价CMCS水凝胶药物释放行为, 结果表明水凝胶交联度越高, 胸腺五肽释放速度越慢. MTT法初步评价了水凝胶细胞毒性, 细胞形态和细胞相对增值速率, 结果表明水凝胶毒性很低. 由此可见, 水凝胶具有良好的生物相容性, 在药物缓释和组织工程领域具有广阔的应用前景.     

二乙三胺五乙酸二氢吡啶衍生物的合成及Gd(Ⅲ),Fe(Ⅲ),Mn(Ⅱ)配合物的弛豫性能研究

用二乙三胺五乙酸(DTPA)酸酐与二氢吡啶类化合物反应,合成了4种新型的含二氢吡啶基的二乙三胺五乙酸非离子型配体,并进一步合成了其Gd(Ⅲ),Fe(Ⅲ),Mn(Ⅱ)的顺磁性金属配合物.配体和配合物的结构用IR,¹HNMR及元素分析表征.研究了配合物的体外弛豫性能,结果表明,Fe(Ⅲ)和Mn(Ⅱ)配合物弛豫效率R₁ 低于Gd(Ⅲ)配合物的R₁ ,Gd(Ⅲ)配合物的弛豫效率较高,具有作为MRI造影剂的条件.     

Conjugation effects of various linkers on Gd(III) MRI contrast agents with dendrimers: optimizing the hydroxypyridinonate (HOPO) ligands with nontoxic, degradable esteramide (EA) dendrimers for high relaxivity

One essential requirement for more sensitive gadolinium-based MRI contrast agents is to slow the molecular tumbling of the gadolinium(III) ion, which increases the gadolinium's relaxivity (i.e., its ability to speed up the NMR relaxation of nearby water molecules). One route to this is through conjugation to high-molecular-weight polymers such as dendrimers. In this work, amine-functionalized TREN-bis(1,2-HOPO)-TAM-ethylamine and TREN-bis(1-Me-3,2-HOPO)-TAM-ethylamine ligands have been synthesized and attached to biocompatible 40 kDa esteramide (EA)- and poly-l-lysine (PLL)-based dendrimers capable of binding up to eight gadolinium complexes. These conjugates have T(1) relaxivities of up to 38.14 ± 0.02 mM(-1) s(-1) per gadolinium at 37 °C, corresponding to relaxivities of up to 228 mM(-1) s(-1) per dendrimer molecule. This relaxivity expressed on a "per Gd" basis is several times that of the small-molecule complexes and an order of magnitude higher than that of current commercial agents. Because of their high performance and low toxicity, these macromolecules may constitute an attractive complement to currently available gadolinium(III)-based contrast agents.     

Synthesis and relaxivity of Gd(Ⅲ), Fe(Ⅲ) and Mn(Ⅱ)complexes with dihydropyridine derivative of diethylenetriaminepentaacetic acid

A novel ligand of DTPA-dihydropyridine derivative was synthesized by reaction of DTPA-dianhydride with 4-aniline-1,4-dihydropyridine. Its complexes of gadolinium, manganese and iron were prepared. Their spin-lattice relaxivities (T1) were investigated. The results show that the NMR T1 relaxivitives (R1) for complexes of Fe(Ⅲ), Mn(Ⅱ) are less than that of Gd(Ⅲ) complex,which has a high relaxivity (R1) on the surrounding water protons, indicating that the Gd(Ⅲ) complex possesses the precondition to be contrast agents for magnetic resonance imaging.     

Polymerizable Gd(iii) building blocks for the synthesis of high relaxivity macromolecular MRI contrast agents

A new synthetic strategy for the preparation of macromolecular MRI contrast agents (CAs) is reported. Four gadolinium(iii) complexes bearing either one or two polymerizable methacrylamide groups were synthesized, serving as monomers or crosslinkers for the preparation of water-soluble, polymeric CAs using Reversible Addition–Fragmentation Chain Transfer (RAFT) polymerization. Using this approach, macromolecular CAs were synthesized with different architectures, including linear, hyperbranched polymers and gels. The relaxivities of the polymeric CAs were determined by NMR relaxometry, revealing an up to 5-fold increase in relaxivity (60 MHz, 310 K) for the linear polymers compared with the clinically used CA, Gd-DOTA. Moreover, hyperbranched polymers obtained from Gd(iii) crosslinkers, displayed even higher relaxivities up to 22.8 mM⁻¹ s⁻¹, approximately 8 times higher than that of Gd-DOTA (60 MHz, 310 K). A detailed NMRD study revealed that the enhanced relaxivities of the hyperbranched polymers were obtained by limiting the local motion of the crosslinked Gd(iii) chelate. The versatility of RAFT polymerization of Gd(iii) monomers and crosslinkers opens the doors to more advanced polymeric CAs capable of multimodal, bioresponsive or targeting properties.

A new synthetic strategy for the preparation of efficient macromolecular MRI contrast agents is reported.     

Synthesis and relaxivity of Gd(III), Fe(III) and Mn(II) complexes with dihydropyridine derivative of diethylenetriaminepentaacetic acid

A novel ligand of DTPA-dihydropyridine derivative was synthesized by reaction of DTPA-dianhydride with 4-aniline-1,4-dihydropyridine. Its complexes of gadolinium, manganese and iron were prepared. Their spin-lattice relaxivities (T₁) were investigated. The results show that the NMR T₁ relaxivitives (R₁) for complexes of Fe(III), Mn(II) are less than that of Gd(III) complex, which has a high relaxivity (R₁) on the surrounding water protons, indicating that the Gd(III) complex possesses the precondition to be contrast agents for magnetic resonance imaging.     

Magnetic nanoparticles modified with DTPA-AMC-rare earth for fluorescent and magnetic resonance dual mode imaging

In the present study, we report new water-soluble cell fluorescence imaging and contrast agents that are based on DTPA-AMC(7-amino-4-methyl coumarin)-Eu(3+) and DTPA-AMC(7-amino-4-methyl coumarin)-Gd(3+) compounds conjugated to Fe(3)O(4) NPs via a PEG-NH(2) linker. The novel Fe(3)O(4) NP-conjugates present two main advantages for cell fluorescence labelling: water solubility and targeting ability. The in vitro experiments demonstrate that water-soluble Fe(3)O(4) NPs-DBI-PEG-NH-DTPA-AMC(7-amino-4-methyl coumarin)-Eu(3+) has excellent cell permeating activity. Moreover, the relaxation rate test of Fe(3)O(4) NPs-DBI-PEG-NH-DTPA-AMC(7-amino-4-methyl coumarin)-Gd(3+) shows a higher T1 relaxation effect than traditional DTPA-Gd(3+) MRI agents. According to in vivo liver MRI experiments, better contrast of the liver was achieved after addition of Fe(3)O(4) NPs-DBI-PEG-NH-DTPA-AMC(7-amino-4-methyl coumarin)-Gd(3+). The results will provide a significant guide for researchers exploring the biomedical applications of superparamagnetic Fe(3)O(4) NPs.     

Gd(DTPA-BIN)与人血清白蛋白作用的核磁共振研究

造影剂通常为Ｇｄ３＋、Ｍｎ２＋或Ｆｅ３＋的稳定化合物．它们能改变体内水分子氢核的弛豫速率,从而提高正常与病变组织的磁共振成像（ＭａｇｎｅｔｉｃＲｅｓｏｎａｎｃｅＩｍａｇｉｎｇ,ＭＲＩ）对比度或显示体内器官的功能状态．因此,开发新优ＭＲＩ造影剂具有重要...     

Liver-targeting macromolecular MRI contrast agents

Macromolecular ligands with liver-targeting group (pyridoxamine, PM) PHEA-DTPA-PM and PAEA-DTPA-PM were prepared by the incorporation of different amount of diethylenetria-minepentaacetic acid monopyridoxamine group (DTPA-PM) into poly-cc, p-[N-(2-hydroxyethyl)-L-aspartamide] (PHEA) and poly-α, β-[N-(2-aminoethyl)-L-aspartamide] (PAEA). The macromolecular ligands thus obtained were further complexed with gadolinium chloride to give macromolecular MRI contrast agents with different Gd(Ⅲ) contents. These macromolecular ligands and their gadolinium complexes were characterized by 1H NMR, 1R, UV and elementary analysis. Relaxivity studies showed that these polyaspartamide gadolinium complexes possess higher relaxation effectiveness than that of the clinically used Gd-DTPA. Magnetic resonance imaging of the liver in rats and experimental data of biodistribution in mice indicate that these macromolecular MRI contrast agents containing pyridoxamine exhibit liver-targeting property.     

二乙三胺五乙酸吡哆醇酯配体及其钆配合物的合成、弛豫率和肝靶向性研究

由维生素B₆族化合物吡哆醇及其衍生物与二乙三胺五乙酸(DTPA)双酸酐反应合成了一系列二乙三胺五乙酸吡哆醇酯配体.将这些配体与GdCl₃·6H₂O反应后得到了钆配合物.测定了这些配合物在水溶液中水质子的纵向弛豫率R₁.与母体配合物GdDTPA相比,R₁值略有提高.配体用放射性核素⁹⁹Tc标记,研究了其肝靶向性.结果表明,配体2和6的肝靶向性较为明显.动物核磁共振成像实验进一步证实由这两种配体合成的钆配合物对大鼠肝部的造影信号明显增强     

Structure, stability, dynamics, high-field relaxivity and ternary-complex formation of a new tris(aquo) gadolinium complex

The tripodal hexadentate picolinate ligand dpaa3- (H3dpaa=N,N'-bis[(6-carboxypyridin-2-yl)methyl]glycine) has been synthesised. It can form 1:1 and 1:2 lanthanide/ligand complexes. The crystal structure of the bis(aquo) lutetium complex [Lu(dpaa)(H2O)2] has been determined by X-ray diffraction studies. The number of water molecules was determined by luminescence lifetime studies of the terbium and europium complexes. The tris(aquo) terbium complex shows a fairly high luminescence quantum yield (22 %). The [Gd(dpaa)(H2O)3] complex displays a high water solubility and an increased stability (pGd=12.3) with respect to the analogous bis(aquo) complex [Gd(tpaa)(H2O)2] (pGd=11.2). Potentiometric and relaxometric studies show the formation of a soluble GdIII hydroxo complex at high pH values. A unique aquohydroxo gadolinium complex has been isolated and its crystal structure determined. This complex crystallises as a 1D polymeric chain consisting of square-shaped tetrameric units. In heavy water, the [Gd(dpaa)-(D2O)3] complex shows a quite high HOD proton relaxivity at high field (11.93 s(-1) mM(-1) at 200 MHz and 298 K) because of the three inner-sphere water molecules. The formation of ternary complexes with physiological anions has been monitored by relaxometric studies, which indicate that even under conditions favourable to the formation of adducts with oxyanions, the mean relaxivity remains higher than those of most of the currently used commercial contrast agents except for the citrate. However, the measured relaxivity (r1=7.9 s(-1) mM(-1)) in a solution containing equimolar concentrations of [Gd(dpaa)(D2O)3] and citrate is still high. The interaction with albumin has been investigated by relaxometric and luminescence studies. Finally, a new versatile method to unravel the geometric and dynamic molecular factors that explain the high-field relaxivities has been developed. This approach uses a small, uncharged non-coordinating probe solute, the outer-sphere relaxivity of which mimics that of the water proton. Only a routine NMR spectrometer and simple mathematical analysis are required.