超顺磁氧化铁纳米探针用于磁共振分子成像的研究进展

分子影像学是近年来分子生物学和影像学相结合而形成的新型交叉学科,磁共振分子成像技术是分子影像学的重要手段之一,为临床医学诊断提供重要依据。但是由于不同组织之间的弛豫时间相互重叠等问题,导致较小的病变难以显示,磁共振造影剂能提高对软组织的分辨率,其中超顺磁性氧化铁纳米探针作为近年来发展起来的一种新型磁共振分子造影剂。由于具有敏感性、安全性、大的比表面积、高稳定性、靶向性等优点,近年来已成为国内外研究的热点之一。本文就超顺磁性氧化铁纳米探针的增强原理、制备工艺及靶向作用做一综述,以期为该技术的应用与研究提供借鉴和启示。     

磁共振造影剂的研究进展

随着磁共振影像技术的快速发展,MRI在医学领域得到广泛应用,已成为目前临床常规影像诊断方法和手段之一.但MRI对信号探测的敏感性较低,因此需要某些介质在靶组织内大量聚集以达到信号扩增的目的,于是磁共振成像对比剂应用而生.磁共振造影剂(对比剂)可以提高成像分辨率,增加正常与病变组织的成像对比度,从而提高磁共振诊断疾病的敏感性和特异性,目前逐日成为众多学者研究关注的焦点之一.超顺磁性氧化铁纳米粒是一种新型的磁共振对比剂,它的有效成份为纳米级的Fe3O4或Fe2O3晶体核心,主要通过缩短组织中成像水质子的弛豫时间从而加快组织弛豫速率,得以提高正常组织和病灶组织的成像信号对比度,对肝、脾、淋巴结病变的成像效果好,安全性高,能够显著提高小病灶的检出,从而达到早期诊断发现疾病的目的.本文主要就磁共振造影剂的原理、分类及研究进展,尤其是超顺磁性氧化铁在肝脏疾病诊断中的应用进行了综述,并且对磁共振造影剂的未来发展趋势进行了展望.     

超顺磁性氧化铁微粒磁共振造影剂的制备研究

本文报道自制一种超顺磁性氧化铁微粒,探讨了各种制备条件对氧化铁颗粒大小、稳定性及弛豫增强性能的影响,分析了体外磁共振扫描时超顺磁性氧化铁的浓度——增强效果关系,初步提出了T_1W及T_2W成像时的最适造影浓度。     

RGD修饰包载超顺磁性氧化铁纳米粒用于脑胶质瘤的靶向研究

目的：采用PLGA-PEG为聚合材料,制备RGD修饰包载超顺磁性四氧化三铁纳米粒子（RGD-NP—Fe3O4）,用于脑胶质瘤细胞靶向核磁共振成像纳米探针。方法：采用沉淀法制备RGD修饰的栽超顺磁性纳米粒,考察纳米粒的粒径,电位等理化指标以及细胞毒性。通过细胞以及肿瘤球摄取实验,考察RGD．NP—Fe304的脑胶质瘤细胞靶向性。结果：制备得到的RGD-NP-Fe3O4粒径在85±7．5nm,电位为18＋1．15mV。纳米粒浓度在300μg/mL范围内,对脑胶质瘤细胞均无显著毒性。经过RGD修饰后脑胶质瘤细胞U87对纳米粒的摄取效率大大提高,纳米粒穿透肿瘤球能力显著增强。结论：RGD修饰包载超顺磁性氧化铁纳米粒是一种潜在的高效的脑胶质瘤细胞靶向诊断纳米探针和靶向给药系统。     

胃超声造影剂法对上消化道溃疡的诊断

目的：应用胃超声造影剂检测上消化溃疡。方法：采用“胃窗－８５超声造影剂化水量５００毫升口服后进行超声检查。结果：５６例超声检获胃溃疡２０例,十二指肠溃疡３６例。经手术病理,胃镜证实胃溃疡１７例,十二指肠溃疡３１例,Ｂ超误诊８例。Ｂ超诊断符合率分别赤８５％;８６％。结论：胃超声造影检查对上消化溃疡一定诊断价值     

无机纳米材料在神经胶质瘤诊疗中的应用与特点

神经胶质瘤是中枢神经系统中恶性程度与侵袭性最高的肿瘤之一,其难治性和高致死性亟需尽快开发新的诊疗方法。近年来,各种无机纳米材料独特的内在物化特性的探索应用,为神经胶质瘤的早期诊断和靶向治疗带来了新希望。该文系统地介绍了当前已应用于神经胶质瘤诊疗研究的一些重要无机纳米材料,包括纳米金、纳米银、超顺磁性氧化铁、石墨烯、碳纳米管、介孔硅、半导体量子点、上转换纳米材料、层状双氢氧化物以及二硫化钼。在神经胶质瘤诊断方面,超顺磁性氧化铁、量子点和上转换纳米材料等无机纳米材料,具有优异的肿瘤组织成像性能,能提高诊断的灵敏性,可实现对神经胶质瘤的早期诊断和实时监测;在治疗方面,大多数无机纳米材料进行功能性修饰后用作靶向药物载体,可加载多种抗癌的药物、基因和抗体等,提高靶向输送能力,以实现对胶质瘤的靶向治疗,延长药物在体内的半衰期,同时减少全身副作用;其中,纳米金和纳米银还可用于神经胶质瘤放射增敏治疗,碳纳米管和超顺磁性氧化铁可分别用于神经胶质瘤光热治疗和磁热治疗,达到安全特异的治疗效果。这些无机纳米材料尽管在体内降解、靶向可控性、个体化等技术性问题上还需要进一步解决,但其探索应用已为神经胶质瘤治疗研究提供了新的方向。     

纳米磁性粒子在DNA分离与纯化中的应用进展

纳米磁性粒子是一种新型的亲和纯析固相载体 ,其粒径小 ,具有超顺磁性 ,表面积大 ,表面可赋予多种反应基团如链霉亲和素、抗体等 ,或DNA片段 ,在磁场作用下可分离目的DNA ,已逐步应用于分子生物学领域中 ,有着极为广泛的应用前景。     

Fe3O4磁性纳米粒子在生物医学领域的应用

Fe_3O_4磁性纳米粒子由于其良好的磁学性能,被广泛应用到了化学、生物、物理、环境保护等各个领域。尤其是在生物医学领域中的应用越来越受到研究者的关注。由于其所具有的优秀的超顺磁性性质,Fe_3O_4磁性纳米粒子可以作为造影剂,增强核磁共振成像的对比度和成像效果;也可以结合到纳米载药系统内用于药物的靶向输送;也可以包埋到蛋白内部用于蛋白的磁性分离;也可以用于基因治疗,提高靶细胞的转染效率;由于其在近红外光的作用下具有很好的光热转换效果,使温度升高,展现出的良好热疗效果,Fe_3O_4磁性纳米粒子又可以用于癌细胞的热疗。本文针对其在该领域中作为药物的靶向传递,蛋白的磁分离,核磁共振成像,热疗,以及基因治疗的载体等方面的研究应用进行了系统性的总结,阐述了Fe_3O_4磁性纳米粒子在生物医学领域中各种应用进展和优势。     

超顺磁性氧化铁在吞噬细胞标记和示踪领域的研究进展

超顺磁性氧化铁(SPIO)颗粒在磁共振分子影像中发挥重要作用,SPIO可标记巨噬细胞或其它细胞从而能够追踪标记细胞在体内分布和转化,成为生物医学研究的重要部分。此外,细胞的SPIO标记及示踪可用于肿瘤及炎症诊断、评价及鉴别诊断等多方面。因此,本文汇总近年来SPIO在吞噬细胞标记和示踪领域的研究进展情况,现报道如下。     

纳米生物传感研究进展

纳米生物传感利用了新型纳米材料极佳的反应活性、催化效率、光谱效应、导电性、强度、韧性和超顺磁性等特有性质,因此具有灵敏度高、体积小、速度快、功耗小、多功能集成等诸多优势.近年来,纳米生物传感技术发展迅猛,应用广阔.本文归纳总结了纳米生物传感技术研究的历史和最新进展,为纳米生物传感技术的深入研究与应用提供了资料.     

^H磁共振波谱在脑胶质瘤的应用进展

磁共振波谱（magnetic resonance spectroscopy,MRS）技术的出现使活体检测组织的代谢和生化信息成为可能,随着其技术的不断成熟,其在临床的应用范围日益扩大。脑胶质瘤具有与正常脑组织不同的代谢特征,借助MRS技术一方面可以反映其代谢特征,另外可将其与正常脑组织区分,因此MRS技术特别是^1H-MRS在脑胶质瘤的诊断、鉴别诊断、分级及预后评估中应用日益广泛。本文就相关进展进行综述。     

磁生物学效应的研究进展

磁场作用于生物体后产生一系列的生物学效应,这种观点已被多年来的许多实验所证实。早在1896年,磁场对神经系统作用的研究就已被报道。后来,磁场抗炎,促进骨生成,促进血管神经再生等作用相继被发现。近几十年来,关于磁场对生物体的作用,从流行病学调查到实验室研究也都有了一定进展。如今,磁场的生物学效应研究已成为物理医学研究的热点。本文就近年来磁场生物学效应研究的热点与进展作一简要综述。     

The osmotic magnetometer: a new model for magnetite-based magnetoreceptors in animals

Homing pigeons and migratory birds are well known examples for animals that use the geomagnetic field for their orientation. Yet, neither the underlying receptor mechanism nor the magnetoreceptor itself is known. Recently, an innervated structure containing clusters of magnetite nanocrystals was identified in the upper beak skin of the homing pigeon. Here we show theoretically that such a cluster has a magnetic-field-dependent shape, even in fields as weak as the Earth's magnetic field; by converting magnetic stimuli into mechanical strain, the clusters can be assumed as primary units of magnetoperception in homing pigeons. Since the orientation of the strain ellipsoid indicates the direction of the external magnetic field, a cluster of magnetite nanocrystals also has the potential to serve as the basis of the so-called inclination compass of migratory birds. It is quantitatively demonstrated that the magnetic-field-induced shape change of a cluster can be amplified as well as counterbalanced by means of osmotic pressure regulation, which offers an elegant possibility to determine the magnetic field strength just by measuring changes in concentration. Received: 18 May 1998 / Revised version: 11 February 1999 / Accepted: 11 February 1999     

Investigation of the magnetic susceptibility properties of fresh and fixed mouse heart,liver, skeletal muscle and brain tissue

PurposeSeveral magnetic resonance imaging (MRI) techniques exploit the difference in magnetic susceptibilities between tissues, but systematic measurements of tissue susceptibility are lacking. Furthermore, there is the question as to whether chemical fixation that is used for ex vivo MRI studies, affects the magnetic properties of the tissue. Here, we determined the magnetic susceptibility and water content of fresh and chemically fixed mouse tissue.MethodsMass susceptibility of brain, heart, liver and skeletal muscle samples were determined on a vibrating sample magnetometer at room temperature. Measurements at 50, 125, 200 and 295 K were performed to assess the temperature dependence of susceptibility. Moreover, we measured water content of fresh and fixed samples.ResultsAll samples show mass susceptibilities between −0.068 and −1.929 × 10⁻⁸ m³/kg, compared to −9.338 × 10⁻⁹ m³/kg of double distilled water. Heart tissue has a more diamagnetic susceptibility than the other tissues. Compared to fresh tissue, fixed tissue has a less diamagnetic susceptibility. Fixed tissue was not different in water content to fresh tissue and showed no consistent dependence of susceptibility with temperature, whereas fresh tissue shows a decrease to at least 125 K, indicative of a paramagnetic component.ConclusionsBiological tissues are diamagnetic in comparison to water, where the heart is more diamagnetic than the other tissues, with paramagnetic contributions. Fixation rendered tissue less diamagnetic compared to fresh tissue. Our measurements revealed differences in tissue susceptibility between VSM and QSM, inviting more research to compare susceptibility-based MRI methods with physical measurements of tissue susceptibility.     

Brain Magnetic Resonance in the Diagnostic Evaluation of Mitochondrial Encephalopathies

Brain MR imaging techniques are important ancillary tests in the diagnosis of a suspected mitochondrial encephalopathy since they provide details on brain structural and metabolic abnormalities. This is particularly true in children where non-specific neurologic symptoms are common, biochemical findings can be marginal and genetic defects may be not discovered. MR imaging modalities include conventional, or structural, imaging (MRI) and functional, or ultrastructural, imaging (spectroscopy, MRS; diffusion, DWI-ADC; perfusion, DSCI––ASL). Among them MRI and MRS are the main tools for diagnosis and work up of MD, and this review will focus mainly on them. The MRI findings of MD are very heterogeneous, as they depend on the metabolic brain defects, age of the patient, stage and severity of the disease. No correlation has been found between genetic defects and neuroimaging picture; however, some relationships between MR findings and clinical phenotypes may be identified. Different combinations of MRI signal abnormalities are often encountered but the most common findings may be summarized into three main MR patterns: (i) non-specific; (ii) specific; (iii) leukodystrophic-like. Regarding the functional MR techniques, only proton MRS plays an important role in demonstrating an oxidative metabolism impairment in the brain since it can show the accumulation of lactate, present as a doublet peak at 1.33 ppm. Assessment of lactate should be always performed on brain tissue and on the ventricular cerebral spinal fluid. As for MRI, metabolic MRS abnormalities can be of different types, and two distinct patterns can be recognized: non-specific and specific. The specific metabolic profiles, although not frequent to find, are highly pathognomonic of MD. The un-specific metabolic profiles add value to structural images in allowing to define the lesion load and to monitor the response to therapy trials.     

Physical interactions of static magnetic fields with living tissues

Clinical magnetic resonance imaging (MRI) was introduced in the early 1980s and has become a widely accepted and heavily utilized medical technology. This technique requires that the patients being studied be exposed to an intense magnetic field of a strength not previously encountered on a wide scale by humans. Nonetheless, the technique has proved to be very safe and the vast majority of the scans have been performed without any evidence of injury to the patient. In this article the history of proposed interactions of magnetic fields with human tissues is briefly reviewed and the predictions of electromagnetic theory on the nature and strength of these interactions are described. The physical basis of the relative weakness of these interactions is attributed to the very low magnetic susceptibility of human tissues and the lack of any substantial amount of ferromagnetic material normally occurring in these tissues. The presence of ferromagnetic foreign bodies within patients, or in the vicinity of the scanner, represents a very great hazard that must be scrupulously avoided. As technology and experience advance, ever stronger magnetic field strengths are being brought into service to improve the capabilities of this imaging technology and the benefits to patients. It is imperative that vigilance be maintained as these higher field strengths are introduced into clinical practice to assure that the high degree of patient safety that has been associated with MRI is maintained.     

静磁场保健寝具磁参数的评价

基于对生物磁学效应的研究,磁疗成为替代医学和补充医学的一种有效的治疗方法,本文通过对现有静磁场（恒定磁场）保健寝具磁标准和磁剂量的评述,首次提出磁保健寝具三围空间磁场的概念,指出采用磁感应强度在空间的强度分布作为磁保健剂量标准。论述了三围空间磁场具体磁参数的评价,包括所用磁源的表面磁感应强度,寝具织物表面磁场的穿透力、梯度、有效磁通量和空间能量等磁场分布的描述性指标。指出了静磁场保健寝具磁参数的合理的评价参量：为确保织物表面磁感应强度在目前认知的400～1100Gs有效安全剂量内,依据使用时的织物厚度,磁保健寝具选用的磁体表磁应在1000-3000Gs左右．且磁场的梯度不宜过大,磁场的平均穿透力在25-30cm左右,以确保空间磁场能量的有效作用于人体深处。     

Impact of Low-Frequency Pulsed Magnetic Fields on Defensin and CRP Concentrations in Patients with Painful Diabetic Polyneuropathy and in Healthy Subjects

Aim. The aim was to assess whether magnetic field influences defensin and CRP concentrations in patients with diabetic polyneuropathy and in healthy subjects.

Methods. 61 diabetic patients were randomly divided into 2 groups: study group—32 patients exposed to low-frequency magnetic field; and control group—29 patients with sham exposure. Additionally, 20 healthy subjects exposed to low-frequency magnetic field. Exposures were performed during 3 weeks, 5 days in a week. Defensin and CRP concentrations were measured at baseline, after 3 weeks and at the end of the study.

Results. There were no significant changes in defensin concentration in patients with diabetes in both the real and sham exposure group. We observed increased concentration of defensin in healthy subjects in week 5 vs. baseline value (P<0.02).

Conclusions. Magnetic field has no impact on defensin concentration in diabetic patients but has positive influence on this parameter in healthy subjects.     

Electrochemical titrations and reaction time courses monitored in situ by magnetic circular dichroism spectroscopy

Magnetic circular dichroism (MCD) spectra, at ultraviolet–visible or near-infrared wavelengths (185–2000 nm), contain the same transitions observed in conventional absorbance spectroscopy, but their bisignate nature and more stringent selection rules provide greatly enhanced resolution. Thus, they have proved to be invaluable in the study of many transition metal-containing proteins. For mainly technical reasons, MCD has been limited almost exclusively to the measurement of static samples. But the ability to employ the resolving power of MCD to follow changes at transition metal sites would be a potentially significant advance. We describe here the development of a cuvette holder that allows reagent injection and sample mixing within the 50-mm-diameter ambient temperature bore of an energized superconducting solenoid. This has allowed us, for the first time, to monitor time-resolved MCD resulting from in situ chemical manipulation of a metalloprotein sample. Furthermore, we report the parallel development of an electrochemical cell using a three-electrode configuration with physically separated working and counter electrodes, allowing true potentiometric titration to be performed within the bore of the MCD solenoid.     

Application of Weak Sinusoidal Magnetic Field on Flavobacterium Species in the Treatment of Paper Mill Effluent

This paper presents the results of a preliminary study on the effects of sinusoidal magnetic fields on the growth and degradation potential of Flavobacterium species in paper mill effluents. The paper presents a brief account of the experimental set-up, protocol and the essential parameters employed. The study was carried out using a pure colony of Flavobacterium species and subjecting them to Sinusoidal Magnetic Fields (SMF) at different frequencies, intensities and duration of exposure in order to obtain the “frequency window” of optimum response. The organisms were subjected to 1 Hz (100 nT, 1500 nT and 4000 nT) for 5 hours per day for 3, 6, 9, 12, 15, 18 and 20 days and to 10 Hz (100 nT, 1500 nT and 4000 nT) for 5 hours per days for 3, 6, 9, 12, 15, 18 and 20 days. The organism has been primarily analyzed for its efficacy in the treatment of paper mill effluent by using a sinusoidal magnetic field. The growth kinetics of the bacterium with the application of sinusoidal magnetic fields was studied. As judged from the physico-chemical properties of the effluent, Flavobacterium species was found to have a four fold increase with respect to growth when exposed to SMF of 10 Hz, 100 nT for 30 hrs (5 hours per day for 6 days). The BOD, COD, lignin, phenol and protein content were found reduced in the effluent using SMF treated cells.

Pre-treatment of Flavobacterium species with Sinusoidal Magnetic Fields (SMF) appears to result in more effective degradation of the paper mill effluents.