Biomedical subjects

Norio Yoshino

Publications and source records attributed to Norio Yoshino.

15 recordsLinked to original sources

PubMed2006

Preparation of thin polymer films with drug release and protein adsorption resistance.

Thin polymer films with the ability of both drug release and protein adsorption resistance were formed on silicon substrates and silica particles. The films were made of a block copolymer of poly(N-isopropylacrylamide) (p(AAm)) that can load and release drugs and poly(2-methoxyethyl methacrylate) (p(MEMA)) that can suppress protein adsorption. Aspirin and bovine serum albumin were respectively used as model substances for testing the abilities of the films to load and release drugs and to suppress protein adsorption. The films were immersed in a phosphate buffer saline (pH 7.4) for 100 days to evaluate their water resistance. The experimental results showed that the films have both drug release and protein adsorption resistance and are highly stable against PBS.

Acrylic Resins↗

PubMed2006

Protein adsorption and stability of poly(ethylene oxide)-modified surfaces having hydrophobic layer between substrate and polymer.

The materials covered with poly(ethylene oxide) (PEO) are of use in a wide variety of biomaterials due to blood compatibility of this polymer. The long-term sustainability of its blood compatibility strongly depends on the stability of the PEO layer against aqueous environment. An attempt was made in the present work to immobilize a PEO layer on the silicon surfaces using a silane coupling agent with the aim to improve the waterproof durability of the layer. Several kinds of PEO-modified substrates having a densely and closely packed hydrocarbon layer between substrate and PEO layer were prepared and the stability of the PEO layer against phosphate buffer saline (pH 7.4) was examined in terms of the density of hydrocarbon chains. Those substrates which have a dense hydrophobic chain layer showed a high waterproof durability and a good ability to suppress protein adsorption.

Adsorption↗

PubMed2006

Protein adsorption on polymer-modified silica particle surface.

Silicon substrate surface and silica particle surface were modified with five kinds of polymers, poly(2-methoxyethyl methacrylate) (pMEMA), poly(2-hydroxyethyl methacrylate) (pHEMA), poly(acrylamide) (pAAm), poly(methyl methacrylate) (pMMA), and poly(styrene) (pSt), using a combined polymerization of surface-initiated polymerization that gives dense polymer chain layers and atom transfer radical polymerization (ATRP) that yields polymers with a narrow molecular weight distribution. Measurements of water contact angle and polymer chain amount on the modified silicon substrate surface and adsorption amounts of proteins (albumin and fibrinogen) on the modified silica particle surface revealed that the amount of polymer on the modified surface greatly affects the suppression of protein adsorption on the surface.

Adsorption↗

PubMed2006

Surface modification of poly(oligoethylene oxide methacrylate) for resisting protein adsorption.

We prepare poly(2-methoxyethyl-, 2-(2-methoxyethoxy)ethyl-, 2-[2-(2-methoxyethoxy)ethoxy]ethyl methacrylate) (p(nEOMA), n=1, 2, and 3) brushed surfaces with varying the polymer density by surface initiated polymerization. The amount of bovine serum albumin (BSA) adsorbed on the surfaces is investigated. The mobility of the polymer chain in the polymer/water interfaces and the structure of adsorbed water on the surfaces are characterized by Electron Spin Resonance (ESR) and transmission-Fourier transform infrared (FT-IR) spectroscopy, respectively. This work reports the relationship between these surface properties and albumin adsorption. As a result, the surface having both a high molecular mobility and bulk-like water found to be very effective in preventing albumin adsorption.

Adsorption↗

PubMed2006

Mode of interaction of two fluorinated-hydrogenated hybrid amphiphiles with dipalmitoylphosphatidylcholine (DPPC) at the air-water interface.

Two-component Langmuir monolayers formed on 0.02 M Tris buffer solution (pH 7.4) with 0.13 M NaCl at 298.2K were investigated for two different fluorinated-hydrogenated hybrid amphiphiles (F6PH5PPhNa and F8PH5PPhNa or F6 and F8, respectively) with DPPC. Surface pressure (pi), surface potential (DeltaV) and dipole moment (mu( perpendicular)) as a function of molecular surface area (A) were measured by employing the Whilhelmy method and an ionizing electrode method. From the A- and DeltaV-X(F6) (or X(F8)) curves, partial molecular surface area (PMA) and apparent partial molecular surface potential (APSP) were determined as a function of surface mole fraction (X(Fn)) at discrete surface pressures. Then, the behavior of occupied surface areas and surface potentials of the respective components could be made clearer. Compressibility (C(s)), elasticity (C(s)(-1)), and excess Gibbs energy (DeltaG((ex))) as a function of X(F6) (or X(F8)) were estimated at definite pressures. These physico-chemical parameters were found to reflect the mechanical strength of monolayer films formed. The regular solution theory being applied to DeltaG((ex)), the activity coefficients (f) as well as the interaction parameter (I(p)) between DPPC and two hybrid amphiphiles in the binary monolayers were evaluated. I(p) values thus obtained indicated that F8 molecules interact more strongly with DPPC molecules than F6. Moreover, in order to better understand the morphological monolayer state, Langmuir-Blodgett (LB) films made from DPPC and fluorinated-hydrogenated hybrid amphiphiles were examined by atomic force microscopy (AFM). The miscibility of the two components in the monolayer state is evidenced by these thermodynamic quantities and AFM observations. Furthermore, AFM images demonstrated that F8 could more effectively disperse the ordered domains of DPPC than F6.

1,2-Dipalmitoylphosphatidylcholine↗

PubMed2006

Langmuir monolayer properties of the fluorinated-hydrogenated hybrid amphiphiles with dipalmitoylphosphatidylcholine (DPPC).

Surface pressure-area (pi-A), surface potential-area (DeltaV-A), and dipole moment-area (mu( perpendicular)-A) isotherms were obtained for the Langmuir monolayer of two fluorinated-hydrogenated hybrid amphiphiles (sodium phenyl 1-[(4-perfluorohexyl)-phenyl]-1-hexylphosphate (F6PH5PPhNa) and (sodium phenyl 1-[(4-perfluorooctyl)-phenyl]-1-hexylphosphate (F8PH5PPhNa)), DPPC and their two-component systems at the air/water interface. Monolayers spread on 0.02 M Tris buffer solution (pH 7.4) with 0.13M NaCl at 298.2K were investigated by the Wilhelmy method, ionizing electrode method and fluorescence microscopy. Moreover, the miscibility of two components was examined by plotting the variation of the molecular area and the surface potential as a function of the molar fraction for the fluorinated-hydrogenated hybrid amphiphiles on the basis of the additivity rule. The miscibility of the monolayers was also examined by construction of two-dimensional phase diagrams. Furthermore, assuming the regular surface mixture, the Joos equation for analysis of the collapse pressure of two-component monolayers allowed calculation of the interaction parameter (xi) and the interaction energy (-Deltaepsilon) between the fluorinated-hydrogenated hybrid amphiphiles and DPPC. The observations by a fluorescence microscopy also supported our interpretation as for the miscibility in the monolayer state. Comparing the monolayer behavior between the two binary systems, no remarkable difference was found among various aspects. Among the two combinations, the mole fraction dependence in monolayer properties was commonly classified into two ranges: 0 <or= X <or= 0.3 and 0.3 < X <or = 1. Dependence of the chain length of fluorinated part was reflected for the molecular packing and surface potential.

1,2-Dipalmitoylphosphatidylcholine↗

PubMed2006

Esophageal carcinoma: evaluation with high-resolution three-dimensional constructive interference in steady state MR imaging in vitro.

PURPOSE: To determine the usefulness of high-resolution three-dimensional (3D) constructive interference in steady state (CISS) MRI for evaluating mural invasion and morphologic features in esophageal carcinomas. MATERIALS AND METHODS: Twenty-four esophageal specimens with carcinomas were studied with a 1.5-T system using a 4-cm-diameter loop coil. High-resolution 3D-CISS MR images were obtained with a field of view (FOV) of 80 mm, matrix of 256 x 256, and section thickness of 0.5 mm (voxel size of 0.05 mm(3)). 3D-CISS MR images were compared with histopathologic findings, and virtual MR endoscopic images were compared with macroscopic findings at surgery. RESULTS: 3D-CISS MR images clearly depicted the normal esophageal wall as consisting of eight layers, which correlated well with the histologic layers. In 22 of 24 esophageal carcinomas (92%), the depth of mural invasion visualized with 3D-CISS MRI correlated well with the histopathologic staging. In all 24 carcinomas (100%), virtual MR endoscopic images clearly depicted the macroscopic types of the carcinomas, including adjacent lymph node swelling. CONCLUSION: High-resolution 3D-CISS MRI has a high diagnostic accuracy for evaluating mural invasion and macroscopic findings in esophageal carcinomas, and may be applicable to preoperative histopathologic staging and morphologic evaluation.

Aged↗

PubMed2006

Comparison of tongue volume/oral cavity volume ratio between obstructive sleep apnea syndrome patients and normal adults using magnetic resonance imaging.

Obstructive sleep apnea syndrome (OSAS) is a group of disorders in which breathing stops intermittently and repeatedly for 10 seconds or more during sleep. The causal site of the disorders is thought to be in the upper airway above the glottis. In order to understand the three-dimensional features of the oral and peripharyngeal structures involved in the disorders, we calculated the tongue volume/oral cavity volume ratio (TV/OCV ratio) in the oral cavity using magnetic resonance imaging (MRI) for both OSAS patients and normal controls. The study subjects comprised 20 male patients with OSAS (apnea-hypopnea index [AHI] > or = 5.0, with a diagnosis of OSAS) and 20 normal male adults (AHI<5.0, with no history of OSAS) as the controls. We performed MRI to acquire T1- and T2-weighted images. We estimated tongue volumes on the basis of the cross-sectional area of each image, then using the tongue volume data, we calculated TV/OCV ratios. In the normal control group, mean (+/- SD) body mass index (BMI) was 21.68 +/- 1.73 and the mean TV/OCV ratio was 86.98 +/- 3.16%, whereas these values were 25.0 +/- 15.94 and 90.56 +/- 2.15%, respectively, in the OSAS patient group. The TV/OCV ratio of the OSAS patient group was significantly higher than that of the normal control group (p<0.01).

Adult↗

PubMed2004

Control of viscoelasticity using redox reaction.

The viscoelasticity of a fluid was tuned with the Faradaic reaction of (11-ferrocenylundecyl)trimethylammonium bromide (FTMA), a "redox-switchable" surfactant. An aqueous solution of the reduced form of FTMA exhibited a remarkable viscoelasticity in the presence of sodium salicylate (NaSal) because of the formation of three-dimensional entanglement of wormlike micelles. Electrolytic oxidation of FTMA caused the viscosity of the system to dramatically decrease and the elasticity to disappear. This drastic decrease in viscoelasticity arose from the disruption of wormlike micelles. This novel electrorheological phenomenon is expected to be applicable to ink for inkjet printers, the electrochemically controlled release of substances entrapped in wormlike micelles of FTMA, and fluid flow rate control using electric signals.

Journal Article↗

PubMed2004

Template-directed patterning using phase-separated Langmuir-Blodgett films.

The structures of the mixed Langmuir-Blodgett (LB) films of conventional amphiphiles (CAs) and amphiphilic silane-coupling agents (SCAs) were investigated using IR spectroscopy, atomic force microscopy, and friction force microscopy. By using CAs having hydrogenated alkyl chains and SCAs having perfluorinated alkyl chains, phase-separated structures were formed with domains consisting of CAs surrounded by SCAs. The size and shape of the domains depended strongly on the mixed components, the mixing ratios, and the subphase temperature. In particular, usage of a CA having hydrogenated and perfluorinated portions in the hydrophobic group as one of the components led to the formation of nanothreads. When the phase-separated mixed LB films were heated, SCAs formed covalent bonds with the substrates having silanol groups whereas CAs did not have such ability. Rinsing the heat-treated LB films with ethanol selectively removed CAs with the SCA regions intact, resulting in the fabrication of templates. The structures of the templates reflected those of the original phase-separated LB films. LB transfer of amphiphiles on the templates led to the confinement of the amphiphiles in regions with the size and shape delineated by the templates. These results demonstrate that a variety of amphiphiles can be confined two-dimensionally in a designed manner.

Journal Article↗

PubMed2004

Interfacial properties of branch-tailed fluorinated surfactants yielding a water/supercritical CO2 microemulsion.

We have examined the interfacial properties of several fluorinated surfactants in a water/CO2 mixture with a pendant drop tensiometer and revealed the relationships between the interfacial properties, the surfactant structure, and the microemulsifying power. We employed the following Aerosol-OT analogue surfactants that have two fluorinated tails: bis(1H,1H,5H-octafluoropentyl)-2-sulfosuccinate (di-HCF4), sodium bis(1H,1H,9H-hexadecafluorononyl)-2-sulfosuccinate (di-HCF8), sodium bis(1H,1H,2H,2H-heptadecafluorodecyl)-2-sulfosuccinate (8FS(EO)2), and sodium bis((1H,1H,2H,2H-heptadecafluorodecyl)-oxyethylene)-2-sulfosuccinate (8FS(EO)4). To discuss the effect of the fluorocarbon/hydrocarbon ratio in single surfactant molecules, water/CO2 interfacial tension (IFT) of a hybrid surfactant with one fluorocarbon and one hydrocarbon tail, that of a surfactant with a single fluorinated tail, and that of a hydrocarbon surfactant, Aerosol-OT (AOT), were examined. The hybrid surfactant employed was sodium 1-oxo-1-[4-(tridecafluorohexyl)phenyl]-2-hexanesulfonate (FC6-HC4), and the single-tailed surfactant was perfluoropolyether ammonium carboxylate (PFPECOONH4, CF3CF2(CF2OCF(CF3))4COONH4). All of the fluorinated AOT analogue surfactants exhibited an excellent level of activity at the water/CO2 interface compared with other fluorinated surfactants and AOT. With a larger hydrocarbon chain number in the CO2-philic tails (i.e., from 0 to 2), the IFT of the AOT analogue surfactants was increased. The area occupied by one surfactant molecule at the water/CO2 interface, A, and the critical microemulsion concentration, cmicroc, were determined and used to examine the water-to-surfactant molar ratio within a reversed micelle, W0c, of the surfactants. The surfactants that form W/scCO2 microemulsions with a large W0c were found to lower the interfacial tension efficiently irrespective of increases in temperature. To achieve the most desirable W0C, the surfactant needs not only a high CO2-philicity of the tails but also a high Krafft point, properties which induce a low hydrophilic/CO2-philic balance.

Carbon Dioxide↗

PubMed2003

Trigeminal neuralgia: evaluation of neuralgic manifestation and site of neurovascular compression with 3D CISS MR imaging and MR angiography.

PURPOSE: To evaluate three-dimensional (3D) constructive interference in steady-state (CISS) magnetic resonance (MR) imaging and MR angiography with multiplanar reconstruction (MPR) for detection of neurovascular compression (NVC) in patients with trigeminal neuralgia and to evaluate the relationship between clinical symptoms related to trigeminal branches and those related to the site of trigeminal nerve compression. MATERIALS AND METHODS: Fifty-four consecutive patients with trigeminal neuralgia were examined at 3D CISS imaging and MR angiography with a 1.5-T MR system. Original transverse and four reformatted images were used for image interpretation. Vascular contact with the trigeminal nerve at the root entry zone (REZ) was determined, and the nature of the involved vessels was identified. The position of the blood vessel compressing the nerve was classified into cranial, caudal, medial, or lateral sites. Statistical analysis was performed with the chi2 test or the Fisher exact test between two groups and with the chi2 test among more than two groups. RESULTS: In 12 of 15 patients who underwent surgery, the artery that was considered a responsible vessel at 3D CISS imaging and MR angiography was confirmed as such. In the other three patients, the vein was the responsible vessel, which was detected only at 3D CISS imaging. Sixteen (89%) of 18 patients with symptoms related to the maxillary division had NVC at the medial site of the REZ, while 16 (76%) of 21 patients with symptoms related to the mandibular division had NVC at the lateral site (P <.001, chi2 test). CONCLUSION: 3D CISS MR imaging with MPR is useful in the detection of NVC in patients with trigeminal neuralgia, compared with MR angiography. A close relationship was found between the region of neuralgic manifestation and the site of trigeminal nerve compression.

Adult↗

PubMed2003

Visible-light induced hydrophilicity on nitrogen-substituted titanium dioxide films.

Nitrogen-substituted titanium dioxide thin films were found to undergo hydrophilic conversion under irradiation with visible light. The hydrophilicity was enhanced by increasing the degree of nitrogen substitution at oxygen sites. The water contact angle for the thin film with the greatest hydrophilicity, TiO1.9884N0.0116, changed from 20 degrees to 6 degrees following irradiation.

Journal Article↗

PubMed2002

First anionic micelle with unusually long lifetime: self-assembly of fluorocarbon-hydrocarbon hybrid surfactant.

The exchange of a fluorocarbon-hydrocarbon hybrid surfactant between monomer and micelle states in deuterium oxide has been investigated through 19F NMR and 1H NMR experiments. The CF3 group in the surfactant gives two kinds of 19F NMR signals corresponding to the monomer and micelle states, indicating slow surfactant exchange on NMR time scale. The lifetime (taumic) of micelle, estimated by line shape analysis of the signals, is 2.0 ms at cmc, 102 to 103 times longer than that of general surfactant micelles. Pulsed-gradient spin-echo (PGSE) experiments show that the hybrid surfactant forms considerably small micelles with a hydrodynamic radius of 0.6 nm. In contrast, at a higher concentration where no slow surfactant exchange is observed, the micelle radius increases to 1.1 nm. The interdigitation between the surfactant molecules in the micelle will contribute to the unusually long lifetime, in other words, slow surfactant exchange on the NMR time scale.

Journal Article↗

PubMed2002

Preoperative evaluation of neurovascular compression in patients with trigeminal neuralgia by use of three-dimensional reconstruction from two types of high-resolution magnetic resonance imaging.

OBJECTIVE: To assess the value of three-dimensional (3-D) images reconstructed from 3-D constructive interference in steady state (3-D-CISS) and 3-D fast inflow with steady-state precession (3-D-FISP) images for the visualization of neurovascular compression in patients with trigeminal neuralgia. METHODS: Twenty-four consecutive patients with trigeminal neuralgia underwent preoperative 3-D-FISP and 3-D-CISS imaging. 3-D reconstruction of nerves and vessels was performed with the use of a volume-rendering method. We compared the 3-D reconstructed images with intraoperative findings. RESULTS: 3-D-CISS and 3-D-FISP images scanned from the same position clearly delineated the trigeminal nerve and vessels. 3-D reconstructed images showed the spatial relationship between the trigeminal nerve and causative vessels. The responsible arteries were identified from the 3-D reconstructed images, which closely simulated the microscopic operative view. CONCLUSION: 3-D reconstructions from two types of high-resolution magnetic resonance images (3-D-CISS and 3-D-FISP) are very useful for creating preoperative simulations and in deciding whether to perform surgery in patients with trigeminal neuralgia.

Adult↗