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Good antiinfection properties of medical polymers, especially those used in artificial organs, are crucial to the minimization of microbial attack in nosocomial treatments. However, medical polymers fabricated by conventional methods usually have unstable and short-lived antimicrobial effects because of unsteady out-diffusion of the antibacterial species from the organic matrix. Here, we introduce a dual plasma implantation process to enhance the properties. An inorganic antibacterial element, copper, is introduced into a medical polymer, polyethylene (PE), by means of copper plasma immersion ion implantation (PIII) and a subsequent nitrogen PIII process is used to regulate the release of the implanted Cu. X-ray photoelectron spectroscopy and transmission electron microscopy reveal that a relatively large amount of copper of about 11% is implanted into PE to a depth of several hundred nanometers. Chemical analyses confirm that the implanted Cu does not bond with the polymer matrix. However, the N(2) plasma treatment produces various functional bonds such as C=N, and C[triple bond]N which exert appreciable influence on regulating the out-diffusion rate of copper. The large amount of embedded Cu, coupled with controlled release of the element to the surface, gives rise to excellent and long-lasting surface antibacterial properties of the plasma-treated polymer. The capability of controlling the release and storing the antibacterial reagent in a buried layer leads to better antimicrobial polymeric materials for medicine., (Copyright 2007 Wiley Periodicals, Inc.)

A radio frequency (rf) inductively coupled plasma apparatus has been developed to simulate the atomic oxygen environment encountered in low Earth orbit (LEO). Basing on the novel design, the apparatus can achieve stable, long lasting operation, pure and high density oxygen plasma beam. Furthermore, the effective atomic oxygen flux can be regulated. The equivalent effective atomic oxygen flux may reach (2.289-2.984) x 10(16) at.cm(2) s at an oxygen pressure of 1.5 Pa and rf power of 400 W. The equivalent atomic oxygen flux is about 100 times than that in the LEO environment. The mass loss measured from the polyimide sample changes linearly with the exposure time, while the density of the eroded holes becomes smaller. The erosion mechanism of the polymeric materials by atomic oxygen is complex and involves initial reactions at the gas-surface interface as well as steady-state material removal.

Widespread applications of direct current (dc) cathodic arc deposition are hampered by macroparticle (MP) contamination, although a cathodic arc offers many unique merits such as high ionization rate, high deposition rate, etc. In this work, a flexible curvilinear electromagnetic filter is described to eliminate MPs from a dc cathodic arc source. The filter which has a relatively large size with a minor radius of about 85 mm is suitable for large cathodes. The filter is open and so the MPs do not rebound inside the filter. The flexible design allows the ions to be transported from the cathode to the sample surface optimally. Our measurements with a saturated ion current probe show that the efficiency of this flexible filter reaches about 2.0% (aluminum cathode) when the filter current is about 250 A. The MP density measured from TiN films deposited using this filter is two to three orders of magnitude less than that from films deposited with a 90 degrees duct magnetic filter and three to four orders of magnitude smaller than those deposited without a filter. Furthermore, our experiments reveal that the potential of the filter coil and the magnetic field on the surface of the cathode are two important factors affecting the efficacy of the filter. Different biasing potentials can enhance the efficiency to up to 12-fold, and a magnetic field at about 4.0 mT can improve it by a factor of 2 compared to 5.4 mT.

Fenton's oxidation is traditionally used to remove inorganic and organic pollutants from water in waster water treatment. It is an advanced oxidation process in which H2O2 is catalytically decomposed by ferrous irons into hydroxyl radicals (*OH) which have a higher oxidation potential (2.8V) than H2O2. In the work reported here, we for the first time use Fenton's oxidation to modify the surface of biomedical NiTi shape memory alloy (SMA). The influences of Fenton's oxidation on the surface microstructure, blood compatibility, leaching of harmful Ni ions and corrosion resistance in simulated body fluids is assessed using scanning electron microscopy, X-ray diffraction, X-ray photoelectron spectroscopy, inductively coupled plasma mass spectrometry, electrochemical tests, hemolysis analysis and the blood platelet adhesion test. The mechanical stability of the surface titania film produced by Fenton's oxidation as well as their effects on the shape memory behavior of the SMA are studied by bending tests. Our results show that Fenton's oxidation produces a novel nanostructured titania gel film with a graded structure on the NiTi substrate without an intermediate Ni-rich layer that is typical of high-temperature oxidation. Moreover, there is a clear Ni-free zone near the top surface of the titania film. The surface structural changes introduced by Fenton's oxidation improve the electrochemical corrosion resistance and mitigate Ni release. The latter effects are comparable to those observed after oxygen plasma immersion ion implantation reported previously and better than those of high-temperature oxidation. Aging in boiling water improves the crystallinity of the titania film and further reduces Ni leaching. Blood platelet adhesion is remarkably reduced after Fenton's oxidation, suggesting that the treated SMA has improved thrombo resistance. Enhancement of blood compatibility is believed to stem from the improved hemolysis resistance, the surface wettability and the intrinsic electrical characteristics of the titania film. The titania film produced by Fenton's oxidation has good mechanical stability and does not adversely impact the shape memory behavior of NiTi. Our work suggests that Fenton's oxidation is a promising low-temperature, low-cost surface modification method for improving the surface properties of biomedical NiTi SMA.

Stainless steel and titanium alloys are the most common metallic orthopedic materials. Recently, nickel-titanium (NiTi) shape memory alloys have attracted much attention due to their shape memory effect and super-elasticity. However, this alloy consists of equal amounts of nickel and titanium, and nickel is a well known sensitizer to cause allergy or other deleterious effects in living tissues. Nickel ion leaching is correspondingly worse if the surface corrosion resistance deteriorates. We have therefore modified the NiTi surface by nitrogen plasma immersion ion implantation (PIII). The surface chemistry and corrosion resistance of the implanted samples were studied and compared with those of the untreated NiTi alloys, stainless steel, and Ti-6Al-4V alloy serving as controls. Immersion tests were carried out to investigate the extent of nickel leaching under simulated human body conditions and cytocompatibility tests were conducted using enhanced green fluorescent protein mice osteoblasts. The X-ray photoelectron spectroscopy results reveal that a thin titanium nitride (TiN) layer with higher hardness is formed on the surface after nitrogen PIII. The corrosion resistance of the implanted sample is also superior to that of the untreated NiTi and stainless steel and comparable to that of titanium alloy. The release of nickel ions is significantly reduced compared with the untreated NiTi. The sample with surface TiN exhibits the highest amount of cell proliferation whereas stainless steel fares the worst. Compared with coatings, the plasma-implanted structure does not delaminate as easily and nitrogen PIII is a viable way to improve the properties of NiTi orthopedic implants.

NiTi shape memory alloy is one of the promising orthopedic materials due to the unique shape memory effect and superelasticity. However, the large amount of Ni in the alloy may cause allergic reactions and toxic effects thereby limiting its applications. In this work, the surface of NiTi alloy was modified by nitrogen plasma immersion ion implantation (N-PIII) at various voltages. The materials were characterized by X-ray photoelectron spectroscopy (XPS). The topography and roughness before and after N-PIII were measured by atomic force microscope. The effects of the modified surfaces on nickel release and cytotoxicity were assessed by immersion tests and cell cultures. The XPS results reveal that near-surface Ni concentration is significantly reduced by PIII and the surface TiN layer suppresses nickel release and favors osteoblast proliferation, especially for samples implanted at higher voltages. The surfaces produced at higher voltages of 30 and 40 kV show better adhesion ability to osteoblasts compared to the unimplanted and 20 kV PIII samples. The effects of heating during PIII on the phase transformation behavior and cyclic deformation response of the materials were investigated by differential scanning calorimetry and three-point bending tests. Our results show that N-PIII conducted using the proper conditions improves the biocompatibility and mechanical properties of the NiTi alloy significantly.

Porous NiTi shape memory alloys are one of the promising biomaterials for surgical implants because of their unique shape memory effects and porous structure with open pores. However, the complex surface morphology and larger area of porous NiTi compared to dense NiTi make it more vulnerable from the viewpoint of release of nickel, which can cause deleterious effects in the human body. It is also more difficult to modify the exposed surfaces of a porous structure using conventional surface modification technologies. In this work, oxidation in conjunction with postreaction heat treatment was used to modify the surfaces of porous single-phase NiTi prepared by capsule-free hot isostatic pressing to mitigate Ni leaching and enhance the surface properties. Differential scanning calorimetry thermal analysis, uniaxial compression tests, inductively-coupled plasma mass spectrometry, and cell cultures reveal that porous NiTi alloys oxidized at 450 degrees C for 1 h have an austenite transition temperature below 37 degrees C, excellent superelasticity, lower nickel release, and no cytotoxicity., ((c) 2007 Wiley Periodicals, Inc.)

Silicon has gradually been recognized to be an essential trace element in the normal metabolism of higher animals, and the role of silicon in the human body has aroused interests in the biomedical community. In fact, the interactions between silicon-based devices and the human body such as biosensors and microelectromechanical systems (MEMS) often suffer from poor biocompatibility. In this work, hydrogen plasma immersion ion implantation (H-PIII) is conducted to improve the bioactivity or bone conductivity of silicon. In order to investigate the formation mechanism of bone-like apatite on the surface of the hydrogen implanted silicon wafer, two comparative experiments, hydrogenation and argon bombardment, are performed. The H-PIII sample exhibits an amorphous surface consisting of Si-H bonds. After immersion in simulated body fluids, a negatively charged surface containing the functional group ([triple bond]Si-O-) is produced and bone-like apatite is observed to nucleate and grow on the surface. The surface of the H-PIII silicon wafer favors the adhesion and growth of osteoblast cells and good cytocompatibility may be inferred.

Using a Si-based porous anodic alumina membrane as a mask, we demonstrate a way to pattern Si surface. After removing the SiO(2) nanoislands formed during anodization of the Al/Si interface, we obtain a Si nanotip array on the surface of a Si wafer. This array shows an excellent field emission property with a low turn-on field of 8.5 V µm(-1). The Fowler-Nordheim plot obtained is linearly dependent, indicating that the emission current arises from the quantum tunnelling effect. The Si nanotip array can be expected to have important applications in nanoelectronic devices.

Good surface properties and biocompatibility are crucial to porous NiTi shape memory alloys (SMA) used in medical implants, as possible nickel release from porous NiTi may cause deleterious effects in the human body. In this work, oxygen plasma immersion ion implantation (O-PIII) was used to reduce the amount of nickel leached from porous NiTi alloys with a porosity of 42% prepared by capsule-free hot isostatic pressing. The mechanical properties, surface properties, and biocompatibility were studied by compression tests, X-ray photoelectron spectroscopy (XPS), and cell culturing. The O-PIII porous NiTi SMAs have good mechanical properties and excellent superelasticity, and the amount of nickel leached from the O-PIII porous NiTi is much less than that from the untreated samples. XPS results indicate that a nickel-depleted surface layer predominantly composed of TiO(2) is produced by O-PIII and acts as a barrier against out-diffusion of nickel. The cell culturing tests reveal that both the O-PIII and untreated porous NiTi alloys have good biocompatibility., ((c) 2006 Wiley Periodicals, Inc)

The antibacterial characteristics of triclosan- or bronopol-coated and plasma-modified polyethylene (PE) are investigated. The modified PE samples exhibit excellent bactericidal effects against Escherichia coli and Staphylococcus aureus even when the bacteria concentration in the suspension is 10(6) colony forming units (CFU)/mL. However, when the concentration exceeds 10(8) CFU/mL, the materials fail to develop noticeable resistance to large amount of bacteria because of the formation of a bacterial biofilm on their surfaces. The PE treated by this relatively simple technique possesses excellent antimicrobial properties and is useful in biomedical and disinfection applications because the bacteria concentrations in most situations are well below 10(6) CFU/mL., (Copyright 2006 Wiley Periodicals, Inc.)

Efficient resonant electron transfer from the surface bonding structure to the conduction band of quantum confined Si nanocrystals is observed by Si nanocrystals in a toluene suspension. Based on the electron transfer mechanism, the enhancement of photoluminescence originates from the band-to-band recombination in the p-type Si nanocrystals suspended in a toluene solution. The energy levels of the electrons in the Si nanocrystals chemisorbed with toluene molecules are calculated using the method of linear combination of atomic orbitals, and the characteristics of the obtained density of states is in good agreement with the observed photoluminescence properties.

111-oriented p-type Si wafer with a resistivity of 1-5 Omega cm was implanted with Fe+ and then annealed at 1100 degrees C in N2 for 60 min, followed by anodization in a solution of HF to form porous structure with beta-FeSi2 nanocrystallites. Photoluminescence (PL) spectral measurements show that a strong PL peak appears in the range of 610-670 nm. The position of the PL peak remains unchanged, but its intensity increases with the storage time in air until about three months and then saturates. C60 molecules were chemically coupled on the porous structure through a kind of silane coupling agent to form a nanocomposite. It is revealed that the stable PL peak monotonically shifts to a pinning wavelength at 570 nm. Experimental results from PL, PL excitation, Raman scattering, and x-ray diffraction measurements clearly show that the pinned PL originates from optical transition in C60-related defect states, whereas the photoexcited carriers occur in the beta-FeSi2 nanocrystallites formed during anodization. This work opens a new way to tailor nanometer environment for seeking optimal luminescent properties.

Zirconium oxide thin films were fabricated on silicon wafers using a filtered cathodic arc system in concert with oxygen plasma. The structure and phase composition of the zirconium oxide thin films were characterized by atomic force microscopy (AFM), X-ray diffraction (XRD), Rutherford backscattering spectrometry (RBS), and transmission electron microscopy (TEM). The bioactivity was assessed by investigating the formation of apatite on the film surface after soaking in simulated body fluids. Bone marrow mesenchymal stem cells (BMMSC) were used to further evaluate the cytocompatibility of the materials. The results indicate that the films are composed of stoichiometric ZrO(2) and the composition is quite uniform throughout the thickness. Bone-like apatite can be formed on the surface of the ZrO(2) thin film in our SBF immersion experiments, suggesting that the surface is bioactive. The outermost layer of the ZrO(2) thin film comprises nano-sized particles that can be identified by AFM images taken on the thin film surface and TEM micrographs obtained from the interface between the ZrO(2) thin film and apatite layer. The nanostructured surface is believed to be the key factor that apatite is induced to precipitate on the surface. Bone marrow mesenchymal stem cells are observed to grow and proliferate in good states on the film surface. Our results show that ZrO(2) thin films fabricated by cathodic arc deposition exhibit favorable bioactivity and cytocompatibility.

Photoluminescence (PL) measurements have been performed on the nanocomposites of higher fullerene-coupled porous silicon (PS) nanocrystals. For the C70PS and C76(78)PS nanocomposites, the PL spectra show a pinning wavelength at approximately 565 nm and for the C84PS and C94PS nanosystems the pinning wavelength is at approximately 590 nm. The PL pinning property is closely related to the sorts of the coupled fullerenes. A band mixing model of direct and indirect gaps in a nanometer environment consisting of nc-Si core, SiO2 surface layer, and coupled fullerene has been proposed for calculation of electronic states. Good agreement is achieved between the experiments and theory.

Ultra-long rutile tin dioxide nanowires and nanobelts are synthesized by thermal oxidation of tin powder using gold film as the catalyst. Nanowire or nanobelts can be selectively produced by tuning the reaction temperature. The vapour-liquid-solid growth mechanism is proposed. The band gaps of the nanowires and nanobelts are 3.74 and 3.81 eV respectively, determined from UV/visible absorption spectral results. The SnO2 nanowires show stable photoluminescence with two emission peaks centred at around 470 and 560 nm. Their wavelengths stay almost fixed while their intensities depend sensitively on the temperatures within the examination ranges from 10 to 300 K. The SnO2 nanobelts show similar photoluminescence behaviours and the origin of the luminescence is discussed.

Plasma immersion ion implantation (PIII) was used to modify medical-grade PVC coated by triclosan and bronopol to enhance the antibacterial properties. The surface was first activated by O2 plasma to produce more hydrophilic groups so that triclosan and bronopol could be coated more effectively on the surface. Subsequently, an argon plasma treatment was conducted under optimal conditions to improve the antibacterial properties of the triclosan and bronopol-coated PVC samples. The modified surfaces were characterized by XPS, ATR-FTIR, SEM, and contact angle measurements. The antibacterial properties were evaluated utilizing the method of plate-counting of Staphylococcus aureus (gram positive) and Escherichia coli (gram negative). Our experimental results show that the plasma-modified PVC with bronopol exhibits good antibacterial properties while the favorable bulk properties of PVC are retained. The plasma-modified PVC with triclosan has better antibacterial performance against E. coli than bronopol. The change in the antibacterial effect on the modified PVC with time was also investigated and the antibacterial effect was observed to decrease with time.

Nickel-titanium shape memory alloys are promising materials in orthopedic applications because of their unique properties. However, for prolonged use in a human body, deterioration of the corrosion resistance of the materials becomes a critical issue because of the increasing possibility of deleterious ions released from the substrate to living tissues. We have investigated the use of nitrogen, acetylene, and oxygen plasma immersion ion implantation (PIII) to improve the corrosion resistance and mechanical properties of the materials. Our results reveal that the corrosion resistance and mechanical properties such as hardness and elastic modulus are significantly enhanced after surface treatment. The release of nickel is drastically reduced as compared with the untreated control. In addition, our in vitro tests show that the plasma-treated surfaces are well tolerated by osteoblasts. Among the three types of samples, the best biological effects are observed on the nitrogen PIII samples.

Although some types of TiO(2) powders and gel-derived films can exhibit bioactivity, plasma-sprayed TiO(2) coatings are always bioinert, thereby hampering wider applications in bone implants. We have successfully produced a bioactive nanostructured TiO(2) surface with grain size smaller than 50 nm using nanoparticle plasma spraying followed by hydrogen plasma immersion ion implantation (PIII). The hydrogen PIII nano-TiO(2) coating can induce bone-like apatite formation on its surface after immersion in a simulated body fluid. In contrast, apatite cannot form on either the as-sprayed TiO(2) surfaces (both <50 nm grain size and >50 nm grain size) or hydrogen-implanted TiO(2) with grain size larger than 50 nm. Hence, both a hydrogenated surface that gives rise to negatively charged functional groups on the surface and small grain size (<50 nm) that enhances surface adsorption are crucial to the growth of apatite. Introduction of surface bioactivity to plasma-sprayed TiO(2) coatings, which are generally recognized to have excellent biocompatibility and corrosion resistance as well as high bonding to titanium alloys, makes them more superior than many current biomedical coatings.

We have investigated the surface bioactivity of titanium after water and hydrogen plasma immersion ion implantation. Plasma immersion ion implantation (PIII) excels in the surface treatment of components possessing a complicated shape such as medical implants. In addition, water and hydrogen PIII has been extensively studied as a method to fabricate silicon-on-insulator (SOI) substrates in the semiconductor industry and so it is relatively straightforward to transfer the technology to the biomedical field. In our investigation, water and hydrogen were plasma-implanted into titanium sequentially. Our objective is that water PIII introduces near-surface damages that trap hydrogen implanted in the subsequent step to improve the surface bioactivity while the desirable bulk properties of the materials are not compromised. Ti-OH functional groups can be detected on the (H(2)O+H(2))-implanted titanium surface by X-ray photoelectron spectroscopy (XPS) and Fourier transform infrared (FTIR) spectroscopy. After incubation in simulated body fluids (SBF) for cytocompatibililty evaluation in vitro, bone-like hydroxyapatite was found to precipitate on the (H(2)O+H(2)) implanted samples while no apatite was found on titanium samples plasma implanted with water or hydrogen alone. Human osteoblast cells were cultured on the (H(2)O+H(2))-implanted titanium surface and they exhibited good adhesion and growth. Our results suggest a practical means to improve the surface bioactivity and cytocompatibility of medical implants made of titanium.

A uniquely structured SiO(x)-capped (x = 0.5-0.8) Si nanowire array with strong blue emission, like a nanobeacon array, was fabricated using electroless metal (silver) deposition on a water plasma-treated Si wafer. Formation of the nanoscale light source array can be understood on the basis of a self-assembled localized microscopic electrochemical cell model and a diffusion-limited aggregation process. Photoluminescence spectral analysis reveals that the intensity of the broad blue-emitting luminescent band centred at around 435 nm strongly depends upon the irradiation of H(2)O(+), HO(+), and O(+) ions, which are present in the water plasma. We attribute the blue PL band to the optical transition of the self-trapped excitons at the surfaces of SiO(x) nanocaps.

Dicalcium silicate coating was deposited onto a Ti-6Al-4V substrate using plasma-spraying technology. The coating was immersed in simulated body fluid (SBF) for 1, 3, 6, 12, 24, and 48 h to investigate early apatite formation on the coating. Osteoblasts were also seeded onto the surface of the dicalcium silicate coating to evaluate its biocompatibility. Cold field-emission scanning electron microscopy and energy-dispersive X-ray spectrometry were used to evaluate the morphologies and determine the chemical composition of the coatings. The surface structural changes caused by immersion in SBF were analyzed using thin-film X-ray diffraction. After the dicalcium silicate coating was soaked in SBF solution 1-6 h, two types of particles containing calcium and phosphorus were formed on the surface. One type consisted of relatively larger particles (P1) precipitated on the surface of the coating from the precursor cluster formed in the SBF solution. The second type was composed of particles (P2) nucleated on the surface of the coating. With increasing immersion time, the particles coalesced to form a surface Ca-P layer. The Ca-P layer was composed of amorphous calcium phosphate that was not transformed to crystalline apatite until the immersion time in SBF exceeded 24 h. The formation mechanism of the Ca-P layer and apatite on the surface of the coating is believed to be involved in the formation of the Si 3-ring active surface site with negative charge. The cell-seeding test revealed that osteoblasts grew and proliferated very well on the surface of the dicalcium silicate coating., (Copyright (c) 2005 Wiley Periodicals, Inc.)

Bio-activation of titanium surface by Na plasma immersion ion implantation and deposition (PIII and D) is illustrated by precipitation of calcium phosphate and cell culture. The bioactivity of the plasma-implanted titanium is compared to that of the untreated, Na beam-line implanted and NaOH-treated titanium samples. Our data show that the samples can be classified into two groups: non-bioactive (untreated titanium and beam-line Na implanted titanium) and bioactive (Na-PIII and D and NaOH-treated titanium). None of the four types of surfaces exhibited major cell toxicity as determined by lactate dehydrogenase (LDH) release. However, the LDH release was higher on the more bioactive PIII and NaOH-treated surfaces. From a morphological point of view, cell adherence on the NaOH-treated titanium is the best. On the other hand, the cell activity and protein production were higher on the non-bioactive surfaces. The high alkaline phosphatase activity per cell suggests that the active surfaces support an osteogenic differentiation of the bone marrow cells at the expense of lower proliferation. The use of Na-PIII and D provides an environmentally cleaner technology to improve the bioactivity of Ti compared to conventional wet chemical processes. The technique is also particularly useful for the uniform and conforming treatment of medical implants that typically possess an irregular shape and are difficult to treat by conventional ion beam techniques.

Nickel-titanium (NiTi) shape memory alloys possess super-elasticity in addition to the well-known shape memory effect and are potentially suitable for orthopedic implants. However, a critical concern is the release of harmful Ni ions from the implants into the living tissues. We propose to enhance the corrosion resistance and other surface and biological properties of NiTi using carbon plasma immersion ion implantation and deposition (PIII&D). Our corrosion and simulated body fluid tests indicate that either an ion-mixed amorphous carbon coating fabricated by PIII&D or direct carbon PIII can drastically improve the corrosion resistance and block the out-diffusion of Ni from the materials. Our tribological tests show that the treated surfaces are mechanically more superior and cytotoxicity tests reveal that both sets of plasma-treated samples favor adhesion and proliferation of osteoblasts.

Nickel-titanium (NiTi) shape memory alloys are increasingly being used in orthopedic applications. However, there is a concern that Ni is harmful to the human body. We have recently investigated the use of nitrogen, or oxygen plasma immersion ion implantation to mitigate this deleterious effect. Our results reveal that the near-surface Ni concentration in all the treated samples is significantly suppressed. In addition, our in vitro tests show that the plasma-treated surfaces are cytologically compatible allowing the attachment and proliferation of osteoblasts. Among the two types of samples, the best biological effects are found on the samples with nitrogen implantation.

Using electrochemical etching of a polycrystalline 3C-SiC target and subsequent ultrasonic treatment in water solution, we have fabricated suspensions of 3C-SiC nanocrystallites that luminesce. Transmission electron microscope observations show that the 3C-SiC nanocrystallites, which uniformly disperse in water, have sizes in the range of 1-6 nm. Photoluminescence and photoluminescence excitation spectral examinations show clear evidence for the quantum confinement of 3C-SiC nanocrystallites with the emission band maximum ranging from 440 to 560 nm. Tunable, composite polystyrene/SiC film can be made by adding polystyrene to a toluene suspension of the 3C-SiC nanocrystallites and then coating the resulting solution onto a Si wafer.

A 58-yr-old male with a history of hepatitis C virus infection, presented with a 2-mo history of intractable left upper abdominal pain. He had fallen from a ladder 2 yr previously, landing on his left side. Abdominal computed tomography identified a large cystic mass in the spleen. The patient was brought to the operating room with a presumptive diagnosis of symptomatic, post-traumatic, false cyst of the spleen. Instead, at surgery, a splenic mass with dense adhesions to the diaphragm and stomach was found. On final histological analysis, it was diagnosed to be a large B-cell lymphoma. Despite its rarity, gastroenterologists and surgeons should be aware of large B-cell lymphoma when encountering cystic lesions of the spleen, because the management of benign cystic disease is usually nonsurgical.

Hydrogen in silicon has been widely applied in semiconductor fields. In this paper, the application of hydrogen-implanted silicon wafer in biomedical fields was explored by investigating its bioactivity. Hydrogen implanted silicon wafers were prepared using plasma immersion ion implantation. The surface structures of the 1.4 x 10(17) cm(-2) hydrogen-implanted silicon wafers were investigated using atomic force microscopy and transmission electron microscopy (TEM). The hydrogen depth profiles were acquired by SIMS and the crystal quality of the as-implanted silicon was studied by channeling Rutherford backscattering spectrometry (RBS). The bioactivity of the implanted silicon was evaluated using the biomimetic growth of apatite on its surface after it was soaked in simulated body fluid for a period of time. The TEM, SIMS and RBS results indicate the formation of an amorphous hydrogenated silicon (a-Si:Hx) layer has been formed on the surface of the hydrogen-implanted silicon wafer. After immersion in SBF for 14 days, bone-like apatite is observed to nucleate and grow on the surface. With longer soaking time, more apatite appeared on the surface of the hydrogen implanted silicon but our control experiments did not reveal any apatite formation on the surface of the un-implanted silicon wafer, hydrogenated crystalline silicon wafer (with hydrogen, but no amorphous surface), or argon-implanted silicon wafer (amorphous surface but without hydrogen). Our results indicated that the bioactivity of silicon wafer can be improved after hydrogen implantation and the formation of the amorphous hydrogenated silicon (a-Si:Hx) surface also plays a synergistic role to improve the bioactivity.

There is an increasing interest in developing new methods to reduce bacteria adhesion onto polymeric materials that are used in biomedical implants. The antibacterial behavior on polyethylene terephthalate (PET) treated by acetylene (C2H2) plasma immersion ion implantation-deposition (PIII-D) is investigated. The surface structure of the treated PET is determined by laser Raman spectroscopy, X-ray photoelectron spectroscopy (XPS) and attenuated total reflection Fourier transform infrared spectroscopy (ATR-FTIR). The results show that a thin amorphous polymer-like carbon (PLC) layer is formed on the PET surface. Atomic force micrographs (AFM) show that C2H2 PIII-D significantly changes the surface morphology of PET. The capacities of Staphylococcus aureus (SA) and Staphylococcus epidermidis (SE) to adhere onto PET are quantitatively determined by plate counting and Gamma-ray counting of 125I radio labeled bacteria in vitro. The results indicate that the adhesion of the two kinds of bacteria to PET is suppressed by PLC. The adhesion efficiency of SE on the coated surface is only about 14% of that of the untreated PET surface, and that of SA is about 35% of that of the virgin surface. The electrokinetic potentials of the bacterial cells and substrates are determined by zeta potential measurement. All the substrates as well as the bacterial strain have negative zeta potentials, and it means that bacterial adhesion is not mediated by electrostatic interactions. The surface energy components of the various substrates and bacteria are calculated based on measurements in water, formamide and diiodomethane. The surface free energies obtained are used to calculate the interfacial free energies of adhesion ( deltaFAdh ) of SA and SE onto various substrates, and it is found that bacterial adhesion is energetically unfavorable on the PLC deposited on PET by C2H2 PIII-D.

Amorphous hydrogenated carbon (a-C:H) has been shown to be a potential material in biomedical devices such as artificial heart valves, bone implants, and so on because of its chemical inertness, low coefficient of friction, high wear resistance, and good biocompatibility. However, the biomedical characteristics such as blood compatibility of doped hydrogen-free diamond-like carbon (DLC) have not been investigated in details. We recently began to investigate the potential use of nitrogen-doped, hydrogen-free DLC in artificial heart valves. In our experiments, a series of hydrogen-free DLC films doped with nitrogen were synthesized by plasma immersion ion implantation-deposition (PIII-D) utilizing a pulsed vacuum arc plasma source and different N to Ar (FN/FAr) gas mixtures in the plasma chamber. The structures and properties of the film were evaluated by Raman spectroscopy, Rutherford backscattering spectrometry (RBS), and X-ray photoelectron spectroscopy (XPS). To assess the blood compatibility of the films and the impact on the blood compatibility by the presence of nitrogen, platelet adhesion tests were conducted. Our results indicate that the blood compatibility of both hydrogen-free carbon films (a-C) and amorphous carbon nitride films are better than that of low-temperature isotropic pyrolytic carbon (LTIC). The experimental results are consistent with the relative theory of interfacial energy and surface tension including both dispersion and polar components. Our results also indicate that an optimal fraction of sp2 bonding is desirable, but an excessively high nitrogen concentration degrades the properties to an extent that the biocompatibility can be worse than that of LTIC., (Copyright 2004 Wiley Periodicals, Inc.)

The formation mechanism of apatite on the surface of wollastonite coating was examined. Plasma-sprayed wollastonite coatings were soaked in a lactic acid solution (pH=2.4) to result in the dissolution of calcium from the coating to form silanol (triple bond Si-OH) on the surface. Some calcium-drained samples were soaked in a trimethanol aminomethane solution (pH=10) for 24h to create a negatively charged surface with the functional group (triple bond Si-O(-)). These samples before and after treatment in a trimethanol aminomethane solution were immersed in simulated body fluids (SBF) to investigate the precipitation of apatite on the coating surface. The results indicate that the increase of calcium in the SBF solution is not the critical factor affecting the precipitation of apatite on the surface of the wollastonite coating and the apatite can only form on a negatively charged surface with the functional group (triple bond Si-O(-)). The mechanism of apatite formation on the wollastonite coating is proposed. After the wollastonite coatings are immersed into the SBF, calcium ions initially exchange with H(+) leading to the formation of silanol (triple bond Si-OH) on the surface of the layer and increase in the pH value at the coating-SBF interface. Consequently, a negatively charged surface with the functional group (triple bond Si-O(-)) forms on the surface. Due to the negatively charged surface, Ca(2+) ions in the SBF solution are attracted to the interface between the coating and solution, thereby increasing the ionic activity of the apatite at the interface to the extent that apatite precipitates on the coating surface.

Amorphous carbon films have attracted much attention recently due to their good biocompatibility. Diamond-like carbon (DLC), one form of amorphous carbon that is widely used in many kinds of industries, has been proposed for use in blood contacting medical devices. However, the blood coagulation mechanism on DLC in a biological environment is not well understood. Platelet adhesion and activation are crucial events in the interactions between blood and the materials as they influence the subsequent formation of thrombus. In this work, the behavior of platelets adhered onto hydrogenated amorphous carbon films (a-C:H) is investigated. Hydrogenated amorphous carbon films with different hydrogen contents, structures, and chemical bonds were fabricated at room temperature using plasma immersion ion implantation-deposition (PIII-D). The wettability of the films was investigated by contact angle measurements using several common liquids. Platelet adhesion experiments were conducted to examine the interaction of blood with the films in vitro and the activation of adherent platelets. The results show that the behavior of the platelets adhered on the a-C:H films is influenced by their structure and chemical bond, and it appears that protein interaction plays a key role in the activation of the adherent platelets.

Recent improvements in the antithrombogenic properties of blood contacting biomaterials permit a hybrid design of layers for biomedical applications such as artificial heart valves and stents. Using magnetron sputtering and thermal oxidation, titanium oxide thin films containing tantalum. Ti(Ta(+5))O2, are fabricated to meet the challenge of enhanced hemocompatibility. The blood compatibility is evaluated in vitro by clotting time and platelet adhesion measurement, and in vivo experiments are also conducted. The Ti(Ta(+5))O2 films exhibit attractive blood compatibility exceeding that of low isotropic pyrolytic carbon. Physical properties such as surface energy and semiconductivity are found to play important roles. Our calculated results reveal that the smaller surface force gamma(s) of the film and the smaller blood film interfacial tension gamma(c,blood) are partially responsible for the enhancement of the blood compatibility. Based on the optical bandgap model, the film possesses better hemocompatibility because its optical bandgap of 3.2 eV is wider than that of fibrinogen having a bandgap of 1.8 eV. These factors result in thinner protein layers on the film surface, less protein denaturing, and overall excellent antithrombogenic properties.

Quantitative errors (due to magnetic susceptibility artifacts) in the measurement of the cervical spinal neural foramina with fast gradient-echo (GRE) magnetic resonance imaging were assessed. Cylindric phantoms of different materials were used to demonstrate the nature of magnetic susceptibility artifacts, emphasizing the dependence of the artifact on tissue geometry. Neural foramina diameters measured on thin, sagittal GRE and spin-echo (SE) images through the neural foramina of a fresh human cervical spine specimen were then compared with direct measurements with calipers. The GRE images showed more apparent narrowing than did the SE images. The absolute distortion of seven neural foramina was rather constant (less than two pixels) on the GRE images; therefore, the relative distortion was inversely proportional to the size of the neural foramen, ranging up to 10% in the upper cervical region at a short TE. The absolute and relative distortion increased as TE increased. At a constant TE, the structural distortion did not change with different TRs or flip angles. The shortest possible TE is recommended in evaluation of the cervical spine.

The orbital area of 18 individuals was examined by using a combination of fat-suppression contrast-enhanced MR imaging to determine whether contrast between fat and surrounding tissues could be improved over that obtained with conventional fat-suppression techniques alone. We used a hybrid technique combining two independent methods of fat suppression. Subjects consisted of 16 patients and two normal volunteers. Fifteen individuals received gadopentetate dimeglumine, and conventional T1-weighted, T2-weighted, and fat-suppression T1-weighted images were obtained. The fat-suppressed T1-weighted images obtained after contrast administration provided more information than did the conventional MR images. Intraorbital and paraorbital lesions could be distinguished easily from intraorbital fat that had been suppressed. Cases of chorioretinitis and optic neuritis could be confidently diagnosed only by this technique. Cases of optic nerve meningioma and mixed conal lesions also were better appreciated. Because of sharp contrast between tissue planes, this technique was helpful for detecting any intraorbital invasion from paraorbital lesions. Fat-suppression MR imaging with paramagnetic contrast enhancement can significantly improve the delineation of both normal and abnormal structures and better define lesional margins in the orbit, where large amounts of fat are present. Our results support earlier findings, and we suggest that postcontrast fat-suppressed T1-weighted imaging be used instead of conventional T1-weighted postcontrast imaging in evaluating orbital and paraorbital lesions.

CT and MR scans of 29 immunocompromised patients (28 with AIDS or ARC, one with diabetes mellitus) who had documented intracranial cryptococcal infection were reviewed retrospectively. All patients had CT studies; 26 received iodinated contrast agent. CT findings included normal results in nine of 29, atrophy only in 13 of 29, nonenhancing lesions in three of 29, enhancing lesions in two of 20, and foci of leptomeningeal calcification in two of 29. Ten patients had both CT and MR studies, and four received gadopentetate dimeglumine. Among these 10 patients, five had normal CT studies and one showed moderate central atrophy. All 10, however, had abnormal MR findings. We observed four patterns: (1) parenchymal cryptococcoma (3/10); (2) numerous clustered tiny foci that were hyperintense on T2-weighted images and non-enhancing on postcontrast T1-weighted images, located relatively symmetrically in the basal ganglia bilaterally and in midbrain, representing dilated Virchow-Robin spaces (4/10); (3) multiple miliary enhancing parenchymal and leptomeningeal nodules (1/10); and (4) a mixed pattern, consisting of dilated Virchow-Robin spaces with mixed lesions such as cryptococcoma and miliary nodules (2/10). In the group of six patients with dilated Virchow-Robin spaces (patterns 2 and 4), two received gadopentetate dimeglumine, but the Virchow-Robin space lesions did not enhance; among the remaining four patients, two received gadopentetate dimeglumine (one with pattern 1 and one with pattern 3) and the lesions did enhance. Three patients in our study subsequently died and autopsies were performed. The postmortem results revealed dilated Virchow-Robin spaces filled with fungi in the basal ganglia, which correlated well with MR findings.(ABSTRACT TRUNCATED AT 250 WORDS)

Somewhat conflicting reports have appeared about the significance of linear meningeal thickening and enhancement adjacent to peripherally located cranial mass lesions on contrast enhanced magnetic resonance images. Some authors consider this finding nearly diagnostic of meningioma. In an attempt to determine the specificity of this so-called tail sign, particularly with respect to meningioma, we retrospectively reviewed 16 cases from institutional records. From our results, the tail sign appears to be highly suggestive but not specific for meningioma.

To compare conventional and fat suppression MR imaging in their ability to detect head and neck lesions, we prospectively studied 17 patients with head and neck tumors and one normal volunteer. Five patients had benign tumors (one mixed cell tumor, one hemangioma, one lipoma, and two plexiform neurofibromas), 10 had malignant tumors (six squamous cell carcinomas, two minor salivary gland carcinomas, one lymphoma, and one malignant fibrous histiocytoma), and two had nonspecific lymphadenopathy. All subjects were studied with standard spin-echo T1- and T2-weighted images (T2-weighted imaging was done with and without fat suppression technique). In addition, T1-weighted images with contrast enhancement and fat suppression were obtained in nine patients. A four-point grading system was used for comparison of the conventional and fat suppression images. Grades ranged from 0 (unsatisfactory, the lesion cannot be seen) to 3 (excellent, the lesion and its margins can be seen clearly with sharp contrast from surrounding normal tissue). We found that postcontrast fat suppression T1-weighted images and fat suppression T2-weighted images were most useful; these sequences obtained an average score close to grade 3 (2.77 and 2.85, respectively). On the other hand, the conventional T2-weighted images had an average score of about 2 (1.82) and the conventional T1-weighted image had a score of about 1 (1.33). Fat suppression T2-weighted sequences generally were superior in cases of lymphadenopathies. Postcontrast T1-weighted images were most useful in a case of plexiform neurofibroma, owing to their fibrous component and lower proton density.(ABSTRACT TRUNCATED AT 250 WORDS)

1. We have investigated the effect of intermittent doses of ammonia and octanoic acid on liver regeneration in the rat after partial hepatectomy. Regeneration was assessed by uptake of tritiated thymidine into liver deoxyribonucleic acid. 2. We have found a reduction in hepatic regenerative response in animals treated with ammonium acetate as a source of ammonia. 3. No inhibiting effect of octanoic acid on liver regeneration was found, at the dose used. 4. The implications of the results for management of fulminant hepatic failure are discussed.