Herng Er Horng

Designing optical-fiber modulators by using magnetic fluids.

To reduce interface loss between optical fibers and devices in telecommunication systems, the development of an optical-fiber-based device that can be fused directly with fibers is important. A novel optical modulator consisting of a bare fiber core surrounded by magnetic fluids instead of by a SiO2 cladding layer is proposed. Applying a magnetic field raises the refractive index of the magnetic fluid. Thus we can control the occurrence of total reflection at the interface between the fiber core and the magnetic fluid when light propagates along the fiber. As a result, the intensity of the outgoing light is modulated by variation in field strength. Details of the design, fabrication, and working properties of such a modulator are presented.

Time-Evolution contrast of target MRI using high-stability antibody functionalized magnetic nanoparticles: an animal model

In this work, high-quality antibody functionalized Fe3O4 magnetic nanoparticles are synthesized. Such physical characterizations as particle morphology, particle size, stability, and relaxivity of magnetic particles are investigated. The immunoreactivity of biofunctionalized magnetic nanoparticles is examined by utilizing immunomagnetic reduction. The results show that the mean diameter of antibody functionalized magnetic nanoparticles is around 50 nm, and the relaxivity of the magnetic particles is 145 (mMċs)-1. In addition to characterizing the magnetic nanoparticles, the feasibility of using the antibody functionalized magnetic nanoparticles for the contrast medium of target magnetic resonance imaging is investigated. These antibody functionalized magnetic nanoparticles are injected into mice bearing with tumor. The tumor magnetic-resonance image becomes darker after the injection and then recovers 50 hours after the injection. The tumor magnetic-resonance image becomes the darkest at around 20 hours after the injection. Thus, the observing time window for the specific labeling of tumors with antibody functionalized magnetic nanoparticles was found to be 20 hours after injecting biofunctionalized magnetic nanoparticles into mice. The biopsy of tumor is stained after the injection to prove that the long-term darkness of tumor magnetic-resonance image is due to the specific anchoring of antibody functionalized magnetic nanoparticles at tumor.

Magnetochromatics of the magnetic fluid film under a dynamic magnetic field

The structure and the corresponding magnetochromatics of homogeneous magnetic fluid films under dynamic magnetic fields perpendicular to the film surfaces are investigated in this letter. During the application of a magnetic field from 0 up to 200 Oe, the structure in the magnetic fluid film evolves from a monodispersed state to a disordered-column state, and then to an ordered hexagonal structure. The column spacing for the instant hexagonal structure during the dynamic process was measured and found to vary from 2.41 to 1.83 μm when the field strength was raised from 60 to 200 Oe. Within this range, the hexagonal structure diffracts the visible light like an optical grating. Due to the dynamic variation of the column spacing with the increasing field strength, the color of the diffracted light changed unceasingly from red to blue when observed from a fixed point above the film. The results strongly suggest the possibility that optical devices may be developed by utilizing the magnetochromatics of magnet...

Combined Plasma Biomarkers for Diagnosing Mild Cognition Impairment and Alzheimer’s Disease

A highly sensitive immunoassay, the immunomagnetic reduction, is used to measure several biomarkers for plasma that is related to Alzheimers disease (AD). These biomarkers include Aβ-40, Aβ-42, and tau proteins. The samples are composed of four groups: healthy controls (n=66), mild cognitive impairment (MCI, n=22), very mild dementia (n=23), and mild-to-serve dementia, all due to AD (n=22). It is found that the concentrations of both Aβ-42 and tau protein for the healthy controls are significantly lower than those of all of the other groups. The sensitivity and the specificity of plasma Aβ-42 and tau protein in differentiating MCI from AD are all around 0.9 (0.88-0.97). However, neither plasma Aβ-42 nor tau-protein concentration is an adequate parameter to distinguish MCI from AD. A parameter is proposed, which is the product of plasma Aβ-42 and tau-protein levels, to differentiate MCI from AD. The sensitivity and specificity are found to be 0.80 and 0.82, respectively. It is concluded that the use of combined plasma biomarkers not only allows the differentiation of the healthy controls and patients with AD in both the prodromal phase and the dementia phase, but it also allows AD in the prodromal phase to be distinguished from that in the dementia phase.

Enhancement of nuclear magnetic resonance in microtesla magnetic field with prepolarization field detected with high-Tc superconducting quantum interference device

We applied prepolarization field and high-Tc superconducting quantum interference device (SQUID) detector to enhance nuclear magnetic resonance signal in a microtesla magnetic field. The minimum measuring magnetic field is 8.9μT at which the proton resonance frequency is 380Hz. The specificity instrumentation and the difficulty of using a high-Tc SQUID with prepolarization field were investigated. We applied gradient field to perform one-dimensional proton imaging in a microtesla magnetic field. Additionally, low field high-Tc SQUID-based NMR systems are promising in biomagnetic research due to its use, for example, in imaging with hyperpolarized noble gas.

Magnetochromatic effects in magnetic fluid thin films

A homogeneous ferrofluid composition capable of reversiblyforming ordered crystalline two-dimensional hexagonal lattices ofmagnetic particle columns in a thin film under the influence ofexternal magnetic fields has been synthesized. We can manipulatethe spacings between the particles columns by adjusting parameters suchas external magnetic field strength, film thickness, rate of change ofthe field strength, and concentration of magnetic particles in theferrofluid. These spacings between particle columns are of theorder of several micrometers and are capable of diffracting visiblelight to produce monochromatic interference colors. We can changethe resulting colors by altering the lattice spacing to exhibit thefeasibility of generating monochromatic colors.

Plasma tau as a window to the brain—negative associations with brain volume and memory function in mild cognitive impairment and early alzheimer's disease

Neurofibrillary tangles are associated with cognitive dysfunction, and hippocampal atrophy with increased CSF tau markers. However, the plasma tau levels of Alzheimers disease (AD) have not been well studied. We investigated plasma tau by using an immunomagnetic reduction assay in 20 patients with mild cognitive impairment (MCI) due to AD, 10 early AD dementia, and 30 healthy elders (HE). All received a 3D‐brain MRI scan and a set of cognitive function test. We explored their relationships with both brain structure and cognitive functions. Images were analyzed to determine the brain volumes and gray matter densities. Patients with MCI or early AD had significantly increased plasma tau levels compared with HE. Plasma tau levels were negatively associated with the performance of logical memory, visual reproduction, and verbal fluency; also negatively associated with volume of total gray matter, hippocampus, amygdala; and gray matter densities of various regions. Regression analyses indicated that logical memory explained 0.394 and hippocampus volume predicted .608 of the variance of plasma tau levels, both P < 0.001. Education years were negatively associated with the gray matter densities of the supramarginal (r = −0.407), middle temporal gyrus (r = −0.40) and precuneus (r = −0.377; all P < 0.05) in HE; and negatively associated with plasma tau levels in patients (r = −0.626). We propose that plasma tau may serve as a window to both structure and function of the brain. Higher education is a protective factor against AD and is associated with lower plasma tau levels in patients. Hum Brain Mapp 35:3132–3142, 2014.

Biofunctionalized Magnetic Nanoparticles for Specifically Detecting Biomarkers of Alzheimer’s Disease in Vitro

Magnetic nanoparticles biofunctionalized with antibodies against β-amyloid-40 (Aβ-40) and Aβ-42, which are promising biomarkers related to Alzheimers disease (AD), were synthesized. We characterized the size distribution, saturated magnetizations, and stability of the magnetic nanoparticles conjugated with anti-Aβ antibody. In combination with immunomagnetic reduction technology, it is demonstrated such biofunctionalized magnetic nanoparticles are able to label Aβs specifically. The ultralow-detection limits of assaying Aβs in vitro using the magnetic nanoparticles via immunomagnetic reduction are determined to a concentration of ∼10 ppt (10 pg/mL). Further, immunomagnetic reduction signals of Aβ-40 and Aβ-42 in human plasma from normal samples and AD patients were analyzed, and the results showed a significant difference between these two groups. These results show the feasibility of using magnetic nanoparticles with Aβs as reagents for assaying low-concentration Aβs through immunomagnetic reduction, and also provide a promising new method for early diagnosis of Alzheimers disease from human blood plasma.

Ex vivo magnetofection with magnetic nanoparticles: a novel platform for nonviral tissue engineering.

Several methods have been described to introduce DNA expression vectors into mammalian cells both in vitro and in vivo. Each system has benefits and limitations, and to date there is still no ideal method for gene transfer. In this study, we introduced a novel method of gene transfer by using Fe3O4 nanoparticles. The magnetic nanoparticles composed of Fe3O4, and the transfected genes used are Lac Z and enhanced green fluorescence protein gene (EGFG). Four different groups of preparations included in this study were homemade liposome-enveloped EGFP-DNA/Fe3O4, homemade liposome EGFP-DNA gene without magnetic Fe3O4 nanoparticles, lipofectamine 2000-enveloped EGFP-DNA, and EGFP-DNA gene only. Mice osteoblast and He99 lung cancer cell line were used as host cells for gene transfection. The time-dependent EGFP gene expression was monitored and analyzed. The results showed that the diameter of the complex was less than 100 nm. There was no cytotoxicity observed at any of the magnetic Fe3O4 nanoparticle concentrations tested. In the presence of magnetic field, the liposome-enveloped EGFP-DNA/Fe3O4 complex exhibited a much higher efficiency for transfecting EGFP-DNA into osteoblast cells under external magnetic fields. The gene can be transfected into cells with an aid of magnetic vectors and magnetic force. Under a gradient magnetic field, the efficiency of magnetofection is enhanced as compared to that without magnetic field.

Evidence of multiple states of ordered structures and a phase transition in magnetic fluid films under perpendicular magnetic fields

When a magnetic fluid thin film is subjected to a perpendicular magnetic field H, the particles in the film agglomerate and form particle columns. With the increasing H, the columns evolve from a disordered column phase to the first-level hexagonal structural pattern and finally reach the second-level hexagonal structural pattern through a phase transition. During the transition phase, each column split into two columns. The split of a column may be attributed to the further alignment of the magnetic particles in each column under higher H’s. Hence the dipolar repulsive force in each column becomes dominant and causes the split of a column. The formation of the second-level hexagonal structure reveals that the minimum energy of the equilibrium system of magnetic fluid thin films under perpendicular magnetic fields has multiple local minima when H varies.