Detailed dynamical features of the slow hydration water in the vicinity of poly(ethylene oxide) chains

Poly(ethylene oxide) (PEO) is a well-known biocompatible polymer and has widely been used for medical applications. Recently, we have investigated the dynamic behavior of hydration water in the vicinity of PEO chains at physiological temperature and shown the presence of slow water with diffusion coefficient one order of magnitude less than that of bulk water. This could be evidence for the intermediate water that is critical for biocompatibility; however, its detailed dynamical features were not established. In this article, we analyze the quasi-elastic neutron scattering from hydration water through mode distribution analysis and present a microscopic picture of hydration water as well as its relation to cold crystallization.

Altering the bio-inert properties of surfaces by fluorinated copolymers of mPEGMA

Hydrophilic materials display "bio-inert properties", meaning that they are less recognized as foreign substances by proteins and cells. Such materials are often water soluble; therefore, one general approach to enable the use of these materials in various applications deals with copolymerizing hydrophilic monomers with hydrophobic ones to facilitate such resulting copolymers water insoluble. However, reducing the hydrophilic monomer amount may reduce the bio-inert properties of the material. The decrease in bio-inert properties can be avoided when small amounts of fluorine are used in copolymers with hydrophilic monomers, as presented in this article. Even in small quantities (7.9 wt%), the fluorinated monomer, 1,1,1,3,3,3-hexafluoropropan-2-yl 2-fluoroacrylate (FAHFiP), contributed to the improved hydrophobicity of the polymers of the long side-chain poly(ethylene glycol) methyl ether methacrylate (mPEGMA) bearing nine ethylene glycol units turning them water insoluble. As evidenced by the AFM deformation image, a phase separation between the FAHFiP and mPEGMA domains was observed. The copolymer with the highest amount of the fluorinated monomer (66.2 wt%) displayed also high (82 %) FAHFiP amount at the polymer-water interface. In contrast, the hydrated sample with the lowest FAHFiP/highest mPEGMA amount was enriched of three times more hydrophilic domains at the polymer-water interface compared to that of the sample with the highest FAHFiP content. Thus, by adding a small FAHFiP amount to mPEGMA copolymers, water insoluble in the bulk too, could be turned highly hydrophilic at the water interface. The high content of intermediate water contributed to their excellent bio-inert properties. Platelet adhesion and fibrinogen adsorption on their surfaces were even more decreased as compared to those on poly(2-methoxyethyl acrylate), which is typically used in medical devices.

Prevalence and Risk Factors for Retropharyngeal and Retro-Styloid Lymph Node Metastasis in Hypopharyngeal Carcinoma

PURPOSE/OBJECTIVE(S)

We evaluated the prevalence and identified the risk factors for retropharyngeal and retro-styloid lymph node metastasis (LNM) in patients with hypopharyngeal carcinoma (HPC). This was achieved using a combination of MR and FDG-PET/CT images.

MATERIALS/METHODS

Two board-certified radiation oncologists, who experienced 16 and 18 years in the diagnosis and treatment of head and neck cancers retrospectively reviewed pretreatment FDG-PET/CT images and contrast-enhanced thin-slice CT and MR images of 155 patients with HPC who underwent radiotherapy. Observers assessed these images without prior knowledge of the patient's clinical information and disagreements were resolved by consensus. The radiological diagnostic criteria for lateral retropharyngeal LNM (RPLNM) and retro-styloid LNM (RSLNM) were a short-axis diameter of ≥5 mm and/or necrosis and/or abnormal FDG uptake. Any visible medial RPLN was defined as LNM.

RESULTS

RPLNM was confirmed in 20 (13%) patients. Of these, 10 (6%) had ipsilateral RPLNM, 5 (3%) had contralateral RPLNM, and 5 (3%) had bilateral RPLNM. No patients were diagnosed with medial RPLNM. Fisher's exact test revealed tumor site (p = 0.006), T category (p = 0.049), and cervical LNM (p < 0.001) to be significantly associated with RPLNM. Logistic regression analysis revealed posterior wall (PW) tumors (odds ratio [OR]: 4.128, 95% confidence interval [CI]: 1.339-12.727; p = 0.014) and bilateral or contralateral cervical LNM (OR: 11.577, 95% CI: 2.135-62.789; p = 0.005) to be significantly correlated with RPLNM. The RPLNM was found in 9 (32%) of the 28 patients with PW tumors. Of these 9 patients, 2 (7%) had ipsilateral RPLNM, 3 (11%) had contralateral RPLNM, and 4 (14%) had bilateral RPLNM. Fisher's exact test revealed the PW tumors to be significantly associated with contralateral RPLNM (p < 0.001). Retro-styloid LNM (RSLNM) was confirmed in two (1%) patients, both of whom had ipsilateral RSLNM with lymph nodes (LNs) of ≥15 mm in the upper limit of ipsilateral level II. Fisher's exact test revealed the LN of ≥15 mm in the upper limit of ipsilateral level II to be significantly associated with ipsilateral RSLNM (p = 0.001).

CONCLUSION

The RPLNM was identified in 13% of patients with HPC. The PW tumors and bilateral or contralateral cervical LNM were risk factors for RPLNM; particularly, PW tumors were a specific risk factor for contralateral RPLNM. Although the RSLNM was rare, LNs of ≥15 mm in the upper limit of ipsilateral level II were a risk factor for ipsilateral RSLNM.

Pulmonary lymphoepithelial cyst with no prior HIV infection: A case report

Most lymphoepithelial cysts (LECs) occur in the salivary glands and are considered one of the autoimmune syndromes caused by the human immunodeficiency virus (HIV). In this report, we present a case of pulmonary LEC without prior HIV infection, paying special attention to radiographic features. A chest radiograph revealed an oval mass with a smooth surface, localized in the left lower lung field, which was in direct contact with the diaphragm. Computed tomography showed an oval homogenous mass with a smooth surface in the lower left lobe. Further, magnetic resonance imaging demonstrated that the mass was a homogeneous internal structure with a smooth surface and a slightly high signal in T2-weighted images and a slightly low signal in T1-weighted images. Surgical resection was performed, and pathological examination confirmed the diagnosis of a pulmonary LEC. To the best of our knowledge, no cases of pulmonary LECs without prior HIV infection have been reported in the literature to date, therefore, the case presented here is considered very rare and informative.

Infrared Spectra and Hydrogen-Bond Configurations of Water Molecules at the Interface of Water-Insoluble Polymers under Humidified Conditions

Elucidating the state of interfacial water, especially the hydrogen-bond configurations, is considered to be key for a better understanding of the functions of polymers that are exhibited in the presence of water. Here, an analysis in this direction is conducted for two water-insoluble biocompatible polymers, poly(2-methoxyethyl acrylate) and cyclic(poly(2-methoxyethyl acrylate)), and a non-biocompatible polymer, poly(n-butyl acrylate), by measuring their IR spectra under humidified conditions and by carrying out theoretical calculations on model complex systems. It is found that the OH stretching bands of water are decomposed into four components, and while the higher-frequency components (with peaks at ∼3610 and ∼3540 cm^-1) behave in parallel with the C═O and C-O-C stretching and CH deformation bands of the polymers, the lower-frequency components (with peaks at ∼3430 and ∼3260 cm^-1) become pronounced to a greater extent with increasing humidity. From the theoretical calculations, it is shown that the OH stretching frequency that is distributed from ∼3650 to ∼3200 cm^-1 is correlated to the hydrogen-bond configurations and is mainly controlled by the electric field that is sensed by the vibrating H atom. By combining these observed and calculated results, the configurations of water at the interface of the polymers are discussed.

Experimental Evidence of Slow Mode Water in the Vicinity of Poly(ethylene oxide) at Physiological Temperature

In some synthetic polymers used for medical applications, hydration water in the vicinity of the polymer chains is known to play an important role in biocompatibility and is referred to as intermediate water. The crystallization of water below 0 °C observed during thermal analysis has been considered as evidence of the presence of intermediate water. However, the origin and physicochemical properties of intermediate water have not yet been elucidated. In this study, as a typical biocompatible polymer, poly(ethylene oxide) and its hydration water were investigated with the use of terahertz time-domain spectroscopy and quasi-elastic neutron scattering. The obtained results prove the existence of a significant amount of mobile water that interacts with the polymer chains even when the water content is low at physiological temperatures.

Hydration Mechanism in Blood-Compatible Polymers Undergoing Phase Separation

Interactions involving intermediate water are crucial for the design of novel blood-compatible materials. Herein, we use a combination of atomic force microscopy, quartz crystal microbalance measurements, and soft X-ray emission spectroscopy to investigate the local hydrogen-bonded configuration of water on blood-compatible poly(2-methoxyethyl acrylate) and non-blood-compatible poly(n-butyl acrylate) grafted on a gold substrate. We find that the initially incorporated water induces polymer-dependent phase separation, facilitating further water uptake. For the blood-compatible polymer, tetrahedrally coordinated water coexists with water adsorbed on C═O groups in low-density regions of the grafted polymer surface, providing a scaffold for the formation of intermediate water. The amount of intermediate water is determined by the type of functional groups, local polymer configuration, and polymer morphology. Thus, blood compatibility is governed by the complex water/polymer interactions.

Nanoscopic Analyses of Protein Adsorption on Poly(2-methoxyethyl acrylate) Surfaces for Tailoring Cell Adhesiveness

Regulation of protein adsorption on the surface of biomaterials is important for modulating cell adhesion. Two important proteins in this regard are fibrinogen and fibronectin. Poly(2-methoxyethyl acrylate) (PMEA) and its...

[A Case of Multiple Hepatic Metastases after Surgery for Low Differentiated Mucous Cancer of Sigmoid Colon with Notable Mesenteric Infiltration in Which Chemotherapy Was Effective]

Mucinous adenocarcinoma of the colon occasionally develops from the submucosa, depending on the pattern of onset; therefore, in many cases, it is already advanced at the time of diagnosis. This type of cancer is known to have a poor prognosis. We report the case of a 59-year-old woman who presented with abdominal pain on defecation for 1 month. A mass was palpable in the lower part of her abdomen. On computed tomography(CT), an extrinsic mass was seen in the sigmoid colon, and lower gastrointestinal endoscopy findings suggested an invasive tumor originating from another organ outside the intestinal wall. A high level of the tumor marker CEA(40.8 ng/mL)was observed. No findings suggestive of malignancy were present on biopsy examination, Colorectal cancer was suspected, for which a sigmoidectomy was performed. On histopathological examination, though there was little to indicate a primary colon tumor on HE staining, due to strong CDX2 positivity it was suspected to be an intestinal-type adenocarcinoma. The final clinical diagnosis was unclassifiable, poorly differentiated, mucinous adenocarcinoma of the colon. Multiple liver metastases appeared 4 months postoperatively, which were treated with XELOX plus BV and FOLFIRI plus BV. CT evaluation 24 months postoperatively showed a complete response radiographically. This case of mucinous adenocarcinoma of the colon, in which chemotherapy was successful and long-term survival of 5 years and 2 months was achieved postoperatively, is reported together with a discussion of the literature.

Local Dynamics of the Hydration Water and Poly(Methyl Methacrylate) Chains in PMMA Networks

The dynamic behavior of water molecules and polymer chains in a hydrated poly(methyl methacrylate) (PMMA) matrix containing a small amount of water molecules was investigated. Water molecules have been widely recognized as plasticizers for activating the segmental motion of polymer chains owing to their ability to reduce the glass transition temperature. In this study, combined with judicious hydrogen/deuterium labeling, we conducted quasi-elastic neutron scattering (QENS) experiments on PMMA for its dry and hydrated states. Our results clearly indicate that the dynamics of hydrated polymer chains are accelerated, and that individual water molecules are slower than bulk water. It is therefore suggested that the hydration water affects the local motion of PMMA and activates the local relaxation process known as restricted rotation, which is widely accepted to be generally insensitive to changes in the microenvironment.

Protein- and Cell-Resistance of Zwitterionic Peptide-Based Self-Assembled Monolayers: Anti-Biofouling Tests and Surface Force Analysis

Peptide-based self-assembled monolayers (peptide-SAMs) with specific zwitterionic amino acid sequences express an anti-biofouling property. In this work, we performed protein adsorption and cell adhesion tests using peptide-SAMs with repeating units of various zwitterionic pairs of amino acids (EK, DK, ER, and DR). The SAMs with the repeating units of EK and DK (EK and DK SAMs) manifested excellent bioinertness, whereas the SAMs with the repeating units of ER and DR (ER and DR SAMs) adhered proteins and cells. We also performed surface force measurements using atomic force microscopy to elucidate the mechanism underlying the difference in the anti-biofouling property. Our measurements revealed that water-induced repulsion with a range of about 8 nm acts between EK SAMs (immobilized on both probe and substrate) and DK SAMs, whereas such repulsion was not observed for ER and DR SAMs. The strength of the repulsion exhibited a clear correlation with the protein- and cell-resistance of the SAMs, indicating that the interfacial water in the vicinity of EK and DK SAMs is considered as a physical barrier to deter protein and cells from their adsorption or adhesion. The range of the repulsion observed for EK and DK SAMs is longer than 8 nm, indicating that the hydrogen bonding state of the interfacial water with a thickness of 4 nm is modified by EK and DK SAMs, resulting in the expression of the anti-biofouling property.

Effect of Branching Degree of Dendritic Polyglycerols on Plasma Protein Adsorption: Relationship between Hydration States and Surface Morphology

This study focuses on dendritic glycerols and investigates the construction of biocompatible surfaces by understanding how differences in the branching of these molecules change the interactions with the biological components. The two molecules, polyglycerol dendrimer (PGD), which has a completely branched structure, and hyperbranched polyglycerol (HPG), which has an incompletely branched structure, are compared and the differences in branching are evaluated. It is shown that PGD has a little bit more intermediate water than HPG, which reflects the differences in the branching. The effect of surface state on the adsorption of the plasma proteins, human serum albumin (HSA), fibrinogen (Fib), and fibronectin (FN), is discussed by modifying a glass surface using these molecules with different hydration states. The adsorption of HSA decreases to several percent for HPG and 10% for PGD compared to unmodified substrate. Although the adsorption of Fib decreases to 5% for HPG, an increase to 150% is observed for PGD. Since this specific Fib adsorption observed only onto PGD is suppressed in the cases of a mixed solution of HSA and Fib or sequentially using HSA solution and then Fib solution, it is thought that the Vroman effect is suppressed on the PGD-modified surface. Furthermore, when AFM measurements are performed in PBS to understand the surface roughness, PGD is found to be more highly non-uniform. Because of this, the nanometer scale roughness that is significantly observed only on the PGD-modified surface is thought to have an effect on the characteristic adsorption properties of Fib. Thus, although both PGD and HPG with different branching have intermediate water, the proportion differs between PGD and HPG. Therefore, it is found that differences occur in the plasma protein adsorption mechanisms depending on the coordinates and density of hydroxyl groups within the molecules.

First Observation of the Hydration Layer around Polymer Chain by Scattering and Its Relationship to Thromboresistance: Dilute Solution Properties of PMEA in THF/Water

Poly(2-methoxyethyl acrylate) (PMEA) is known to exhibit excellent thromboresistance, i.e., hardly causing blood-clot formation on its surface. Hence, PMEA and its analogues have been commercially used for blood-contacting materials in medical devices. In this study, we investigated the conformation and solvation state of PMEA in mixtures of tetrahydrofuran (THF) and water with various water volume fractions (ϕ_water) by viscosity, sedimentation equilibrium, small-angle X-ray scattering (SAXS), and dielectric relaxation measurements. We also comparatively investigated those of poly[2-(2-methoxyethoxy)ethyl methacrylate] (PMe2MA) and polystyrene (PS). For all of these, THF is a good solvent and water is a nonsolvent or poor solvent. PMe2MA and PMEA show equally good thromboresistance, while PS does not at all. The solution properties of PMe2MA and PMEA were found to be quite different from PS. There are clear attractive interactions (or correlation) between the PMEA chain (or PMe2MA) and the waters in the vicinity of the chain despite their water insolubility. These correlated waters give additional scattering and the angular dependence of SAXS was analyzed in terms of the hydration layer model that has been used in protein solution scattering. The hydration is related to increasing both the chain stiffness and excluded volume. These distinctive properties are likely related to the origin of its good thromboresistance.

Effect of interfacial structure based on grafting density of poly(2-methoxyethyl acrylate) on blood compatibility

An excellent blood-compatible polymer, poly(2-methoxyethyl acrylate) (PMEA), exhibits nanometer-scale phase-separated structures at the interface with water or phosphate-buffered saline (PBS), and fibrinogen adsorption is suppressed, especially on the water-rich region. To understand the correlation between the interfacial structure based on the grafting density of PMEA and blood compatibility, grafted PMEA (gPMEA) surfaces with controlled density were prepared by immobilizing thiol-terminated PMEA on a gold substrate. The amount of adsorbed fibrinogen and the number of adhered platelets on gPMEAs decreased first with the increasing grafting density (σ), but increased after showed minimum at σ of approximately 0.11 chains/nm². The interfacial structures of the gPMEA/PBS interface changed with grafting density, and the maximum area of water-rich region was obtained at σ = 0.11. The water contact angle at σ = 0.11 is smaller than that at the other grafting density. These results revealed that hydration to the polymer is very effective to suppress the platelet adhesion and water-rich region shows excellent blood compatibility on gPMEA surfaces. This work clearly indicated that the density of PMEA affects the interfacial structure and plays an important role in the blood compatibility of the material.

Understanding the Effect of Hydration on the Bio-inert Properties of 2-Hydroxyethyl Methacrylate Copolymers with Small Amounts of Amino- or/and Fluorine-Containing Monomers

Materials exhibiting "bio-inert properties" are essential for developing medical devices because they are less recognized as foreign substances by proteins and cells in the living body. We have reported that the presence of intermediate water (IW) with the water molecules loosely bound to a polymer is a useful index of the bio-inertness of materials. Here, we analyzed the hydration state and the responses to biomolecules of poly(2-hydroxyethyl methacrylate) (PHEMA) copolymers including small amounts of 2-(dimethylamino)ethyl methacrylate (DMAEMA) (N-series) or/and 2,2,2-trifluoroethyl methacrylate (TFEMA) (F-series). The hydration structure was analyzed by differential scanning calorimetry (DSC), the molecular mobility of the produced copolymers by temperature derivative of DSC (DDSC), and the water mobility by solid ¹H pulse nuclear magnetic resonance (NMR). Although the homopolymers did not show bio-inert properties, the binary and ternary PHEMA copolymers with low comonomer contents showed higher bio-inert properties than those of PHEMA homopolymers. The hydration state of PHEMA was changed by introducing a small amount of comonomers. The mobility of both water molecules and hydrated polymers was changed in the N-series nonfreezing water (NFW) with the water molecules tightly bound to a polymer and was shifted to high-mobility IW and free water (FW) with the water molecules scarcely bound to a polymer. On the other hand, in the F-series, FW turned to IW and NFW. Additionally, a synergetic effect was postulated when both comonomers coexist in the copolymers of HEMA, which was expressed by widening the temperature range of cold crystallization, contributing to further improvement of the bio-inert properties.

Primary bipolar hemiarthroplasty as a treatment option for unstable intertrochanteric fractures

OBJECTIVES

Management of unstable intertrochanteric fractures is challenging, especially in patients with osteoporosis. Comminuted unstable intertrochanteric fractures require postoperative immobilization. Several recent reports have recommended hemiarthroplasty for treatment of unstable intertrochanteric fractures to avoid various immobilization-associated complications. The purpose of this study was to evaluate the functional and clinical outcomes of bipolar hemiarthroplasty for unstable intertrochanteric fractures in older persons.

METHODS

Sixty patients aged over 75 years underwent hemiarthroplasty to treat unstable intertrochanteric fractures and were followed up over 12 months. All surgeries were performed by the same surgical team using the standard posterolateral approach. Wires, cables, and plates were used as required. Use of cemented protheses was considered when the lesser trochanter had been displaced. All patients were allowed full weight-bearing as tolerated. Clinical evaluation was based on Harris Hip Scores.

RESULTS

The cohort comprised 16 men and 44 women (aged 75-96 years). According to the Jensen classification, 24 fractures were type III, 14 type IV, and 22 type V. Cement was used in 24 patients. At 12 months follow-up, Harris Hip Scores were excellent in 18%, good in 42%, fair in 25%, and poor in 15%. No radiological abnormalities were detected.

CONCLUSIONS

Primary bipolar hemiarthroplasty for treating unstable intertrochanteric fractures eliminates the need for prolonged immobilization and permits early ambulation. As reported by others, hip hemiarthroplasty is an effective treatment choice for unstable intertrochanteric femoral fracture in older patients.

Donor-Acceptor Core-Shell Nanoparticles and Their Application in Non-Volatile Transistor Memory Devices

Donor-acceptor crosslinked poly[poly(ethylene glycol) methyl ether-methacrylate]-block-poly[1,1'-bis(2-ethylpentyl)-6-methyl-6'-(5-methyl-3-vinylthiophen-2-yl)-[3,3'-biindoline]-2,2'-dione] (poly(PEGMA)_m -b-poly(VTIID)_n ) nanoparticles with various vinylthiophene donor/isoindigo acceptor ratios are synthesized successfully. The prepared nanoparticles have uniform sizes and well-defined core-shell nanostructures. The intramolecular charge transfer is effectively enhanced due to the incorporation of acceptor groups after the crosslinking reaction. A transistor memory device is assembled using the synthesized polymer and has nonvolatile flash-type memory and amphiphilic trapping behavior. The optimized devices exhibit a significant memory window of approximately 38 V, a retention ability of over 10⁴ s, and an endurance of at least 100 cycles. This study examines multiple applications of crosslinked core-shell nanoparticles, which demonstrates their promise as charge-storage dielectric materials for use in organic memory devices.

Effect of the Molecular Weight of Poly(2-methoxyethyl acrylate) on Interfacial Structure and Blood Compatibility

The blood-compatible polymer poly(2-methoxyethyl acrylate) (PMEA) is composed of nanometer-scale interfacial structures because of the phase separation of the polymer and water at the PMEA/phosphate-buffered saline (PBS) interface. We synthesized PMEA with four different molecular weights (19, 30, 44, and 183 kg/mol) to investigate the effect of the molecular weight on the interfacial structures and blood compatibility. The amounts of intermediate water and fibrinogen adsorption were not affected by the molecular weight of PMEA. In contrast, the degree of denaturation of adsorbed fibrinogen molecules and platelet adhesion increased as the molecular weight increased. Atomic force microscopy observation revealed that the domain size of the microphase separation structures observed at the PMEA/PBS interfaces drastically (nearly 3 times in the mean area of a domain) changed with the molecular weight. PMEA with a lower molecular weight showed a smaller polymer-rich domain size, as expected on the basis of the microphase separation of polymer-rich and water-rich domains. The small domain size suppressed the aggregation and denaturation of adsorbed fibrinogen molecules because only a few fibrinogen molecules were adsorbed on a domain. Increasing the domain size enhanced the denaturation of adsorbed fibrinogen molecules. Controlling the interfacial structures is crucial for ensuring the blood compatibility of polymer interfaces.

Alcohol-Soluble Cross-Linked Poly( nBA) n- b-Poly(NVTri) m Block Copolymer and Its Applications in Organic Photovoltaic Cells for Improved Stability

In this study, a series of alcohol-soluble cross-linked block copolymers (BCPs) consisting of poly( n-butyl acrylate) (poly( nBA)) and poly( N-vinyl-1,2,4-triazole) (poly(NVTri)) blocks with different individual functions and lengths are designed and developed. These presynthesized cross-linked BCPs (PBA _n-Tri _m) were, for the first time, revealed to exhibit many advantages in serving as the electron-extraction layer (EEL) for organic photovoltaics (OPVs). The cross-linked BCPs possessed intense ionic functionality, showing well capability to form effective interfacial dipoles at the indium tin oxide interface to facilitate the charge extraction at the corresponding interface. Furthermore, it also consisted a core-shell structure, wherein the polar poly(NVTri) core was well protected by the poly( nBA) shell to endow improved robustness against solvent erosion and thermal/photo inputs. Consequently, the PBA₇₀-Tri₃₀ device yielded a decent power conversion efficiency of 8.03% with a V_oc of 0.83 V, much exceeding the performance of the control device without using any EEL. Moreover, this device showed superior thermal stability/photostability. More than 80% of its initial performance was retained after being heated at 60 °C for 1000 h or exposed under continuous illumination (1 sun) for 1000 h, greatly surpassing the lifetime of the control device and the reference device using a common poly[(9,9-bis(3'-( N, N-dimethylamino)propyl)-2,7-fluorene)-alt-2,7-(9,9-dioctylfluorene)] (PFN) EEL. The results revealed the merit of using cross-linked BCPs in improving the long-term stability of OPVs.

Analysis of Interaction Between Interfacial Structure and Fibrinogen at Blood-Compatible Polymer/Water Interface

The correlation between the interfacial structure and protein adsorption at a polymer/water interface was investigated. Poly(2-methoxyethyl acrylate)(PMEA), which is one of the best blood compatible polymers available, was employed. Nanometer-scale structures generated through the phase separation of polymer and water were observed at the PMEA/phosphate buffered saline interface. The interaction between the interfacial structures and fibrinogen (FNG) was measured using atomic force microscopy. Attraction was observed in the polymer-rich domains as well as in the non-blood compatible polymer. In contrast, no attractive interactions were observed, and only a repulsion occurred in the water-rich domains. The non-adsorption of FNG into the water rich domains was also clarified through topographic and phase image analyses. Furthermore, the FNG molecules adsorbed on the surface of PMEA were easily desorbed, even in the polymer-rich domains. Water molecules in the water-rich domains are anticipated to be the dominant factor in preventing FNG adsorption and thrombogenesis on a PMEA interface.

Thermosensitive Polymer Biocompatibility Based on Interfacial Structure at Biointerface

The interfacial structure of a thermosensitive biocompatible polymer, poly[2-(2-methoxyethoxy)ethyl methacrylate] (PMe2MA), at the polymer/phosphate-buffered saline (PBS) interface was investigated by atomic force microscopy. A number of nanometer scale protrusions appeared at 37 °C and disappeared at 22 °C, reversibly. This structural change occurred above the lower critical solution temperature of PMe2MA in PBS (19 °C), indicating that the formation of protrusions was explained by the microphase separation of polymer and water at the interfacial region. The protein adsorption and platelet adhesion onto PMe2MA interface were drastically restrained at 22 °C compared to that at 37 °C. Detachment of NIH3T3 cells accompanied by the dissipation of protrusions on the PMe2MA interface was also demonstrated. These results indicate that the protrusions act as the scaffold for the protein adsorption and cell adhesion.

Ambulatory Behavior Map, Physical Activity and Biosignal Monitoring System

In this study, we have developed an ambulatory human behavior map and physical activity monitoring system. This was accomplished by equipping our portable digital biosignal memory device developed previously with GPS sensors and piezoresistive accelerometers. Using this new system, we can get a subject’s behavior map, and estimate his physical activities and posture changes in daily life.

Wetting transition from the Cassie-Baxter state to the Wenzel state on textured polymer surfaces

The wetting transition from the Cassie-Baxter state to the Wenzel state on textured surfaces was investigated. Nano- to microscale hexagonal pillared lattices were prepared by nanoimprint lithography on fluorinated cycloolefin polymer substrates. The transition was clearly observed for water and some ionic liquids through contact angle measurements and optical microscopy. A simple model clearly demonstrated that the energy barrier in the wetting transition from the Cassie-Baxter state to the Wenzel state was dominated by the competition between the energy barrier and external forces, particularly the Laplace pressure in the present case.

Measurement of the electrostatic interaction between polyelectrolyte brush surfaces by optical tweezers

We demonstrated an optical tweezers method to measure the electrostatic interaction between the strong polyelectrolyte brushes, poly(2-(methacryloyloxy)ethyltrimethylammonium chloride) (PMTAC), grafted on silica particles in aqueous media. The weak electrostatic interaction was successfully detected with a resolution of less than 0.1 μN m(-1). The apparent Debye length, including the charge distribution in the polymer brush and the surface potential, decreased as the salt concentration in the medium increased. The experimentally obtained surface charge density was much smaller than that estimated from the amount of polyelectrolyte on the surface. Furthermore, the dissociation of ionic groups was enhanced by decreasing the grafting density of the polyelectrolyte brush. The results suggest that the majority of chloride counterions was immobilized in the dense polyelectrolyte brush layer to neutralize the high charge density.

Dynamical crossover between hyperdiffusion and subdiffusion of polymer-grafted nanoparticles in a polymer matrix

The dynamical behavior of polystyrene-grafted silica nanoparticles dispersed in an atactic polystyrene matrix was studied using x-ray photon correlation spectroscopy. The time-autocorrelation functions were subjected to fitting analyses based on continuous-time random walk models. The nanoparticles exhibited non-Brownian behavior, and as the temperature increased, the crossover from hyperdiffusion to subdiffusion occurred at 1.25T_{g}, where T_{g} is the glass transition temperature of the matrix polystyrene. Hyperdiffusive behavior is caused by the dynamical heterogeneity of the polymer matrix associated with the glass transition. When the temperature was higher than 1.25T_{g}, the interaction of the grafted polymers with the polymer matrix became relatively significant, and caused a dramatic change in the dynamical behavior of the nanoparticles.

Spreading and structuring of water on superhydrophilic polyelectrolyte brush surfaces

The wetting behavior of superhydrophilic polyelectrolyte brushes was investigated. Reflection interference contrast microscopy demonstrated that the contact angles of water on the polyelectrolyte brushes were extremely low but remained finite in the range of <3°. The presence of water molecules was evident, even outside the macroscopic water droplet. These water molecules were confined to the thin brush layers and contained a highly ordered hydrogen bond network, which was identified as structural water. The presence of the thin film and the structural water changed the surface energies, which prevented the complete wetting of the surface.

X-ray photon correlation spectroscopy using a fast pixel array detector with a grid mask resolution enhancer

The performance of a fast pixel array detector with a grid mask resolution enhancer has been demonstrated for X-ray photon correlation spectroscopy (XPCS) measurements to investigate fast dynamics on a microscopic scale. A detecting system, in which each pixel of a single-photon-counting pixel array detector, PILATUS, is covered by grid mask apertures, was constructed for XPCS measurements of silica nanoparticles in polymer melts. The experimental results are confirmed to be consistent by comparison with other independent experiments. By applying this method, XPCS measurements can be carried out by customizing the hole size of the grid mask to suit the experimental conditions, such as beam size, detector size and sample-to-detector distance.

Wettability and antifouling behavior on the surfaces of superhydrophilic polymer brushes

The surface wettabilities of polymer brushes with hydrophobic and hydrophilic functional groups were discussed on the basis of conventional static and dynamic contact angle measurements of water and hexadecane in air and captive bubble measurements in water. Various types of high-density polymer brushes with nonionic and ionic functional groups were prepared on a silicon wafer by surface-initiated atom-transfer radical polymerization. The surface free energies of the brushes were estimated by Owens-Wendt equation using the contact angles of various probe liquids with different polarities. The decrease in the water contact angle corresponded to the polarity of fluoroalkyl, hydroxy, ethylene oxide, amino, carboxylic acid, ammonium salt, sulfonate, carboxybetaine, sulfobetaine, and phosphobetaine functional groups. The poly(2-perfluorooctylethyl acrylate) brush had a low surface free energy of approximately 8.7 mN/m, but the polyelectrolyte brushes revealed much higher surface free energies of 70-74 mN/m, close to the value for water. Polyelectrolyte brushes repelled both air bubbles and hexadecane in water. Even when the silicone oil was spread on the polyelectrolyte brush surfaces in air, once they were immersed in water, the oil quickly rolled up and detached from the brush surface. The oil detachment behavior observed on the superhydrophilic polyelectrolyte brush in water was explained by the low adhesion force between the brush and the oil, which could contribute to its excellent antifouling and self-cleaning properties.