Carbon Negative-ion Implantation Research Articles

Surface modification of silica glass by CHF 3 plasma treatment and carbon negative-ion implantation for cell pattern adhesion

We have investigated a method for the patterning of cell adhesion on a silica glass by using two-steps of surface modification processes of CHF 3 plasma treatment and negative-ion pattern implantation. For the first step, exposure of CHF 3 plasma to silica glass (SG) was used to obtain hydrophobic surface, leading to eliminate cell-adhesion property. After treatment with RF power of 20 W and exposure time of 120 s, the hydrophobicity was occurred from the increase in contact angle of SG from 43° to 88° and its reason based on XPS analysis was due to formations of C―F, C―F 2, and C―F 3 bonds, so-called fluorocarbonated bonds. Culture of mesenchymal stem cells (MSC) and rat adrenal pheochromocytoma cells (PC12h) showed the degradation of cell adhesion property on the plasma-treated SG surface. For the second step, carbon negative-ion implantation into the hydrophobic fluorocarbonated-SG surface was used to pattern the hydrophilic region, leading to enhance cell adhesion property. The contact angle of C-modified surface decreased to 76° at conditions of 15 keV and 1 × 10 15 ions/cm 2. XPS showed that the hydrophilicity was due to reduction of C―F x bonds and formation of C―O and C═O bonds. After 3 days culture of MSC and PC12h on the C-implanted surface of the plasma-treated SG, a fairly good adhesion patterning of both cells was obtained on the ion-implanted regions.

Line-width of ion beam-modified polystyrene by negative carbon ions for fine adhesion pattern of mesenchymal stem cells

The fine adhesion pattern of mesenchymal stem cells (MSCs) on polytyrene (PS) was investigated by carbon negative-ion implantation with decreasing the implanted line-width. The carbon negative ions with certain ion fluence of 3 × 10 14 ions/cm 2 and ion energy of 10 keV were implanted through the ridge-pattern mask having slit aperture from 0 to 40 μm. After 2 days of culture of rat MSCs on the modified PS, the MSCs elongated and adhered along the implanted region due to the lowering of contact angle after the ion implantation. The cells stained with fluorescent dye of DAPI were used to observe the position of cell adhesion on the modified line-width. By decreasing the line-width from 40 to 3 μm, we found the adhesion arrangements from the gathering cells to the individual cells. The most probable adhesions of the gathering cells in a lateral direction of the line were found at a wider width than 20 μm, while that of the individual cells were found at a width of about 10 μm. The adhesion arrangement of individual cells helped to increase the distances of cell-to-cell due to the elongated adhesion of cells along the narrowed implanted line-width. The number of adhered cells decreased with a decrease in the implanted line-width, and almost all of them had the same direction of their nucleus at the narrower line-width than 12 μm. Therefore, the controls of the individual cell-adhesion arrangement in a line and the nuclei direction could be achieved by decreasing the implanted line-width to about 10 μm.

Degradation of Proteins for Neural Cell Adhesion Patterning by Carbon Negative-Ion Implantation

Degradation of Proteins for Neural Cell Adhesion Patterning by Carbon Negative-Ion Implantation

Irradiation effect of carbon negative-ion implantation on polytetrafluoroethylene for controlling cell-adhesion property

We have investigated the irradiation effect of negative-ion implantation on the changes of physical surface property of polytetrafluoroethylene (PTFE) for controlling the adhesion property of stem cells. Carbon negative ions were implanted into PTFE sheets at fluences of 1 × 10 14–1 × 10 16 ions/cm 2 and energies of 5–20 keV. Wettability and atomic bonding state including the ion-induced functional groups on the modified surfaces were investigated by water contact angle measurement and XPS analysis, respectively. An initial value of water contact angles on PTFE decreased from 104° to 88° with an increase in ion influence to 1 × 10 16 ions/cm 2, corresponding to the peak shifting of XPS C1s spectra from 292.5 eV to 285 eV with long tail on the left peak-side. The change of peak position was due to decrease of C–F 2 bonds and increase of C–C bonds with the formation of hydrophilic oxygen functional groups of OH and C O bonds after the ion implantation. After culturing rat mesenchymal stem cells (MSC) for 4 days, the cell-adhesion properties on the C −-patterned PTFE were observed by fluorescent microscopy with staining the cell nuclei and their actin filament (F-actin). The clear adhesion patterning of MSCs on the PTFE was obtained at energies of 5–10 keV and a fluence of 1 × 10 15 ions/cm 2. While the sparse patterns and the uncontrollable patterns were found at a low fluence of 3 × 10 14 ions/cm 2 and a high fluence of 3 × 10 15 ions/cm 2, respectively. As a result, we could improve the surface wettability of PTFE to control the cell-adhesion property by carbon negative-ion implantation.

Negative ion implantation for pattering mesenchymal-stem cell adhesion on silicone rubber and differentiation into nerve cells with keeping their adhesion pattern

Adhesion properties of mesenchymal stem cells (MSC) from a rat bone marrow on silicone rubber (SR) surface modified by carbon negative-ion implantation through a pattern mask have been investigated in order to application in development of an advanced silicone guide tube for nerve regeneration. Then, the MSC cells cultured on C-implanted SR was also tested to their differentiation into neurons. Silicone rubber sheet (SR) was implanted with carbon negative ions. The surface wettability of the SR was improved by the implantation with fluence more than 1 × 10 14 ions/cm 2 for the energy range of 5–20 keV. After samples implanted with carbon negative ions through a patterning mask were sterilized and placed on a culture dish, MSC cells were cultured on them for 10 days with serum culture medium in a CO 2-incubator. The MSC clearly adhered over the C-implanted SR surface along the mask pattern for fluence of 3 × 10 15–1 × 10 16 ions/cm 2, at 10–15 keV. The differentiation into neuron was induced by the method using β-mercaptoethanol proposed by Woodbury et al. The MSC on C-implanted SR completely differentiated with remaining the previous adhesion pattern. The differentiation into neuron was confirmed by neuron specific enolase (NSE).

Adhesion patterning of mesenchymal stem cells on polystyrene surface by carbon negative-ion implantation and neuron differentiation on the position

We have tried to make patterning adhesion of mesenchymal stem cells (MSC) from a rat bone marrow on polystyrene (PS) surface modified by carbon negative-ion implantation through a pattern mask. Then the MSCs patterned on PS have been induced their differentiation into neurons. Spin-coated polystyrene film (SCPS) on a glass was implanted with carbon negative ions through a pattern mask. After the modified samples were sterilized and placed on a culture dish, MSC cells were cultured on them for 16 days with serum culture medium in a CO2-incubator. The MSC adhesion along the mask pattern was obtained with 5–20keV and 3×1014–1×1015ions/cm2. The MSC differentiation into neuron was examined using β-mercaptoethanol method proposed by Woodbury et al. The adhered MSC on C-implanted SCPS completely differentiated and maintained the adhesion pattern. The differentiation into neuron was confirmed by neuron specific enolase (NSE) after culturing for 6 days. The nerve cells can be cultured for more than 10 days.

Extension of lifetime of silicon field emitter arrays in oxygen ambient by carbon negative ion implantation

Extension of lifetime of silicon field emitter arrays (Si-FEAs) in oxygen ambient was achieved by implanting carbon negative ions into the emitter surface. The authors examined three samples, each of which has 1024 field emission tips and implanted with 5keV carbon negative ions to the doses of 1×1016, 3×1016, and 1×1017ionscm−2. The lifetime, the time when the emission current becomes half the maximum value after starting operation, was extended in accordance with the implantation dose. The lifetime of the sample which was dosed with 1×1017ionscm−2 was 50h, which was about 17 times as long as that of as-fabricated Si-FEA.

Nerve-cell attachment properties of polystyrene and silicone rubber modified by carbon negative-ion implantation

The surfaces of spin-coated polystyrene (PS) on glass and silicone rubber (SR) were modified by carbon negative ion implantation with various ion doses from 0.1 to 10 × 10 15 ions/cm 2 at various ion energies from 5 to 30 keV. The implantation conditions with and without a pattering mask were for investigation of cell attachment properties and for evaluation of surface physical properties of contact angle, respectively. The contact angles of modified surfaces were investigated by pure water drop as implanted and after dipping in pure water for 2 h. In case of SR, the contact angle decreases with increasing ion dose and ion energy. For the case of PS, the optimum decreasing value is about 3–5 × 10 15 ions/cm 2 at 10 keV implantation, and at 25 keV at 3 × 10 15 ions/cm 2 implantation. Nerve-cell attachment properties of modified surfaces were investigated using nerve-like cells of rat adrenal pheochromocytoma (PC12h) in vitro. As implanted at the mean implantation conditions of dose and energy which are 3 × 10 15 ions/cm 2 with 10 keV for PS and SR, the cells attached only on the implanted region. However, for C-implanted SR at 30 keV, the cells were abnormal in shape and of very large size.

Mesenchymal Stem Cell Attachment Properties on Silicone Rubber Modified by Carbon Negative-Ion Implantation

Mesenchymal Stem Cell Attachment Properties on Silicone Rubber Modified by Carbon Negative-Ion Implantation

Effect of C−implantation on Nerve-Cell Attachment to Polystyrene Films

The surfaces of the polystyrene films spin-coated on glass were modified by carbon negative-ion implantation with various ion doses from 1×1014 to 3×1016 ions/cm2 at 5 and 10 keV. The implantation conditions with and without a pattering mask were for investigation of the cell-attachment properties and for evaluation of surface physical properties of contact angle, respectively. The contact angles of modified surface were investigated by pure water drop and air bubble method. The lowest angle value of the implanted films at 5 and 10 keV were approximately 72° at 3×1015 ions/cm2 after dipping in the de-ionized water for 2 hours. The lowering of contact angles on C-implanted surfaces when increase the ion dose is due to formation of the OH and C-O bonds. Nerve-cell-attachment properties of modified surface were investigated by the nerve-like cell of rat adrenal pheochromocytoma (PC12h) in vitro. After 2 days culture of the PC12h cells, no cells attached on the polystyrene films implanted with low ion dose from 1×1014 to 3×1014 ions/cm2. On the polystyrene films implanted with the dose order of 1015 ions/cm2, the cells selectively attached only on the implanted region. Whereas on the surfaces implanted with high dose such as 1×1016 and 3×1016 ions/cm2 mostly cells attached on the implanted region, and some attached on the unimplanted region, as well as cells were abnormal in shape and large size. Therefore, the suitable dose implantation for the selective-attachment of nerve-cells on the polystyrene films implanted at 5 and 10 keV were obtained around the dose order of 1015 ions/cm2, and the best condition for the selective attachment properties was at 3×1015 ions/cm2 corresponding to the lowest contact angle.

炭素負イオン注入処理を施した高分子材料上におけるタンパク質吸着性の評価

Selective cell attachment on carbon-negative-ion implanted region of polystyrene was already reported by the authors. However, the selectivity and adhesion strength in the cell pattering were partially insufficient. The adhesive proteins called extracellular matrix (ECM), in general, intervene between cell and substrate surface in the cell attachment on the solid surface. Therefore, we considered to obtain clearer selective cell attachment with tighter binding strength on the implanted region of polystyrene when these adhesive proteins precedently adsorbed on the implanted region of polystyrene. In this paper, we have investigated adsorption properties of three kinds of adhesive proteins (gelatin, fibronectin, laminin) and cell attachment properties on precedent protein adsorbed surface of polystyrene modified by carbon negative-ion implantation. Carbon negative ions were implanted into polystyrene at energy of 10 keV with dose in a range of 1×1014~1×1016 ions/cm2. After implantation, the samples were dipped in the protein solutions for 2 hours. Then, the protein adsorption ratio between implanted and unimplanted regions was evaluated by detecting amount of nitrogen atoms on the surface by X-ray photoelectron spectroscopy (XPS). As a result, the protein-precedently-absorbed sample implanted at dose more than 3×1015 ions/cm2 showed the large gelatin adsorption ratio of more than 2, where the much densely populated cell-attachment was observed more than that on the implanted region of polystyrene without precedent adsorption of protein after cell culture.

Protein Adsorption Properties on Silicone Rubber Modified by Carbon Negative-Ion Implantation

The adsorption properties of proteins such as laminin (LN), fibronectin (FN) and gelatin on the carbon negative-ion implanted silicone rubber sheet (SR) including their effects of these protein-coated modified SR on patterning nerve-cell culture were investigated. The implantation conditions were fixed at 3x10^15 ions/cm^2 and 10 keV. The concentrations of LN in PBS, FN in PBS and gelatin in de-ionized water (DIW) were 0.5-50, 0.5-10 and 5-10^3 micro g/ml, respectively. The adsorption properties of proteins on SR sheet implanted as a half moon shape were evaluated by XPS. After 4-day in vitro culture of the nerve-like cell of rat adrenal pheochromocytoma (PC12h) on the protein-coated surfaces of SR implanted through the micro-pattern mask with slits of 50-f..l,m width, the phase contrast micrographs show that the suitable protein for patterning the attachment of nerve cell was FN at 1 micro g/ml of concentration, corresponding to high ratio of nitrogen adsorption between implanted and unimplanted regions that was 1.9. As coated with 1 micro g/ml of LN, cells attached over all areas. While coating with 1 mg/ml of gelatin, no cell attached.

Modification Limit in Line Width of Carbon Negative-Ion Implantation to Polystyrene Surface for Nerve-Cell Adhesion and Neurite Outgrowth

Modification Limit in Line Width of Carbon Negative-Ion Implantation to Polystyrene Surface for Nerve-Cell Adhesion and Neurite Outgrowth

Surface treatment of silicone rubber by carbon negative-ion implantation for nerve regeneration

Surface treatment of silicone rubber by carbon negative ion-implantation was investigated for nerve regeneration by “tubulation”. Silicone rubber had its surface property altered to be more hydrophilic by carbon negative-ion implantation. The extracellular matrices of proteins in culture medium adsorbed on the implanted surface rather than unimplanted ones. These improvements in wettability and adsorption properties of proteins were respected to contribute to the regeneration of a nerve-lacking system. An in vivo regeneration test of rat sciatic nerves with silicone-rubber tubes was performed. Using a tube in which the inner surface was implanted with carbon negative ions, the sciatic nerve was regenerated through the inter-stump gap of 15 mm between the proximal and distal nerve stumps and electrical stimulation was transported through the regenerated nerve. Thus, the nerve system was recovered. However, with the unimplanted tube, the nerve was not regenerated at all.

Improvement of polydimethylsiloxane guide tube for nerve regeneration treatment by carbon negative-ion implantation

Modification of polydimethylsiloxane (PDMS) rubber by negative ion-implantation was investigated for improvement of nerve regeneration property. The PDMS rubber surface was found to have more hydrophilic property after carbon negative-ion implantation than before. At the conditions of 10 keV and 3.0 × 10 15 ions/cm 2, the contact angle decreased to 83° from 100°. The reason of the hydrophilic modification is due to hydrophilic functional groups such as hydroxyl formed at the surface by radiation effect of ion implantation. The in vivo regeneration test of rat sciatic nerve was performed by using 18-mm-long PDMS rubber tubes with inner diameter of 2 mm, the inner surface of which was implanted with carbon negative ions at the above conditions. At 24 weeks after the clinical surgery, the sciatic nerve was regenerated through the tube between the proximal and distal nerve stumps.

炭素負イオン注入により改質した生分解性ポリ乳酸表面の神経細胞接着特性

We have investigated nerve cell-attachment properties of Poly-Lactic-Acid (PLA) surface modified by carbon negative-ion implantation. PLA is one of the absorbable polymers used in medical surgery. PLA sheets were implanted with carbon negative-ions at an energy in a range of 5-30 keV with dose in 1 × 1014-1 × 1016 ions/cm2. Contact angle for the PLA implanted at 5 keV showed a large value of 94° at a dose of 1 × 1014 ions/cm2, and then it decreased with an increase in dose to 80°. For the samples at 3 × 1015 ions/cm2, the contact angle slightly decreased from 82° to 78° as increasing in ion energy. In the nerve cell culture experiment with nerve cells of PC 12h cell (rat adrenal pheochromocytoma), selective cell attachment properties were obtained. The nerve cells attached on the unimplanted area in Carbon-implanted PLA samples at 5 and 10 keV, on the other hand, they attached on only implanted area for 30 keV C-implanted PLA sample.

Carbon negative ion implantation into silicon

We constructed a negative ion implanter with a sputter-type negative ion source, with which negative ion implantation was available in an energy range under 50 keV. Carbon negative ions were implanted into silicon substrates for investigating fundamental phenomena, such as ion projected range and profile, and also properties of implanted layers. The experimental results indicated that the depth profile of C atoms implanted at a single energy of 50 keV was in a good agreement with the LSS theory. In a synthesis of SiC by carbon negative ion implantation into silicon with multienergies, a SiC layer whose composition almost satisfied SiC stoichiometry was obtained. Although the β-SiC bonds were weakly observed in the SiC layer as implanted which was amorphous, the polycrystal β-SiC was certainly formed after annealing over 925°C for a substrate of Si(100) and 900°C for Si(111).