Biomedical subjects

Akon Higuchi

Publications and source records attributed to Akon Higuchi.

At least 19 recordsLinked to original sources

PubMed2006

Separation of CD34+ cells from human peripheral blood through polyurethane foaming membranes.

Cell separation from peripheral blood was investigated using polyurethane (PU) foaming membranes and PU membranes (pore size, 5 or 12 mum) at different blood permeation speeds. Permeation ratio of hematopoietic stem cells (CD34(+) cells) through the PU membranes was the lowest among the blood cells at any blood permeation speed. This is thought to be because CD34(+) cells are more adhesive than red blood cells (RBCs), platelets, T cells, and B cells. Primitive hematopoietic stem and progenitor cells tend to adhere to the surface of mature blood cells, because of the high expression of cell-adhesion molecules on the surface of the cells. Human serum albumin solution was exposed to PU-COOH membranes to detach adhered cells from the surface of the membranes, allowing isolation of CD34(+) cells and reduction of RBCs in the permeate solution. Most purified CD34(+) cells (high recovery ratio of CD34(+) cells divided by recovery ratio of RBCs) were obtained in the recovery process using PU-COOH membranes (pore size, 5.2 microm) at a permeation speed of 0.3-1 mL/min.

Adult↗

PubMed2006

A tris(2,2'-bipyridine)ruthenium(II) derivative tethered to a cis-PtCl2(amine)2 moiety: syntheses, spectroscopic properties, and visible-light-induced scission of DNA.

A tris(2,2'-bipyridine)ruthenium(II) derivative having two N-(3-ammoniopropyl)carbamoyl pendant units has been prepared and reacted with cis-PtCl2(DMSO)2 (DMSO = dimethyl sulfoxide) to give a heteronuclear Ru(II)Pt(II) dimer having a cis-Pt(II)Cl2(aliphatic amine)2 unit, [Ru(bpy)2(mu-bridge)PtCl2](PF6)2 (bpy = 2,2'-bipyridine, bridge = 4,4'-bis(N-(3-aminopropyl)carbamoyl)-2,2'-bipyridine). The ESI-TOF mass spectrum of the Ru(II)Pt(II) dimer shows a set of signals corresponding to {[Ru(bpy)2(mu-bridge)PtCl2](PF6)}(+) (m/z 1181.1). The MLCT (metal-to-ligand charge transfer) luminescence intensity is enhanced upon the platination of two amine units, presumably due to the formation of a relatively rigid metallocycle. More interestingly, the luminescence intensity is further enhanced by the complexation of the Ru(II)Pt(II) dimer with either 5'-GMP (guanosine 5'-monophosphate disodium salt) or calf thymus DNA. Visible-light-induced scission of supercoiled pBR322 DNA is found to be efficiently enhanced in the presence of the title Ru(II)Pt(II) dimer.

Antineoplastic Agents↗

PubMed2006

Temperature-induced cell detachment on immobilized pluronic surface.

The Pluronic F68 and F127, a triblock copolymer of ethylene oxide and propylene oxide, was activated using carbonyldiimidazole (CDI), and CDI-activated Pluronic F68 and F127 was subsequently immobilized on the surface of a poly-L-lysine-coated polystyrene tissue culture flask. Cell culture was performed on the Pluronic-immobilized flask. The morphology of fibroblasts (L929 cells) on the Pluronic F127-immobilized flask was mainly spherical, and showed less spreading behavior than that on the Pluronic F68-immobilized flask and conventional tissue culture flask. This observation indicates that L929 cells on Pluronic F127-immobilized flasks were cultured in a bio-inert environment. L929 cells were successively detached from both Pluronic F127-immobilized flask and Pluronic F68-immobilized flask by cooling the flask to 4-15 degrees C. This detachment is due to the hydration and dehydration properties of Pluronic, depending on the temperature. Umbilical cord blood was cultured in the Pluronic F127-immobilized and conventional polystyrene tissue culture flasks at 37 degrees C. The expression ratio of surface markers on hematopoietic stem cells (CD34 and CD133) cultured in the Pluronic F127-immobilized flask was significantly higher than that of the cells in polystyrene tissue culture flask.

AC133 Antigen↗

PubMed2006

Synthesis and performance of amphiphilic copolymers for blood cell separation.

Three types of amphiphilic copolymers using n-butylmethacrylate (BMA) as a hydrophobic monomer, and each of N,N'-dimethylacrylamide (DMA), N-acryloylmorpholine (AMO), and N-vinylpyrrolidone (VP) as hydrophilic comonomers were synthesized for coating filters used to remove leukocytes. The influence of the amphiphilic property of the resulting filters, which were composed of nonwoven fabrics coated with the above copolymers, on leukocyte removal and platelet permeation through the filters from whole blood was investigated. The platelet permeation ratio through hydrophobic noncoated filters was only 0.2%, because platelets in whole blood adhered easily to the hydrophobic filter material. However, filters coated with poly(AMO-co-BMA) of high AMO content showed a much higher platelet permeation ratio (nearly 90%). Further, the filters coated with poly(DMA-co-BMA) also showed high permeation ratios of platelets (more than 78%) over a broad range of DMA content in the copolymer. On the other hand, the coated filters showed slightly a higher permeation ratio of leukocytes than did the noncoated filters, resulting from the increase in hydrophilicity of the surface of the filters. Moreover, the coating of the amphiphilic copolymers on the surface of the nonwoven fabrics may have affected the pore size of the filters, affecting the permeation ratio of leukocytes more strongly than that of platelets. The coated filters effectively improved platelet permeation through the filters, with a slight increase in the permeation ratio of leukocytes.

Adsorption↗

PubMed2006

Bioinert surface of pluronic-immobilized flask for preservation of hematopoietic stem cells.

The bioinert materials on which cells do not proliferate, differentiate, nor de-differentiate should be useful for the culture and preservation of stem cells. The Pluronic F127, a triblock copolymer of ethylene oxide, and propylene oxide was activated using carbonyldiimidazole (CDI), and CDI-activated Pluronic was subsequently immobilized on the surface of a lysine-coated polystyrene tissue culture flask. The morphology of fibroblasts (L929 cells) on the Pluronic-immobilized flask was spherical, and did not show spreading behavior. This observation indicates that L929 cells on the Pluronic-immobilized flask were cultured in a bioinert environment. The expression ratio of surface markers on hematopoietic stem cells (CD34 and CD133) cultured in the Pluronic-immobilized flask was significantly higher than that in polystyrene tissue culture flask and commercially available bioinert flask (i.e., low cell binding cultureware). This is caused by the existence of hydrophilic segments of Pluronic F127 on the Pluronic-immobilized flask.

Animals↗

PubMed2006

Alginate/galactosylated chitosan/heparin scaffold as a new synthetic extracellular matrix for hepatocytes.

Formation of multicellular hepatocyte spheroids in the three-dimensional culture is a potential approach for enhancing liver-specific functions in bioartificial liver (BAL) devices. In this study, as a synthetic extracellular matrix (ECM) for hepatocytes, a highly porous hydrogel (sponge-like) scaffold, 150-200 microm pore size in diameter, was fabricated with alginate (AL), galactosylated chitosan (GC), and heparin through electrostatic interaction. We attempt to select the best condition of AL/GC/heparin sponges for coculture with NIH3T3, as well as compare the liver-specific functions with monoculture. Cell adhesion to GC based on AL film was significantly increased with increasing GC concentration, but not to chitosan regardless of its concentration. The optimal concentration of GC and heparin in AL/GC/heparin sponges to perform the best liver-specific function was 1 and 6 wt% to AL contents, respectively, where albumin secretion were maintained with maximal rates. The mechanical properties in tensile strength of three types of sponges were very slightly different from one another. Cell viabilities performed on AL, AL/GC, and AL/GC/heparin sponges were 68.5, 83.3, and 90.4 % of control, respectively, after 15 days of incubation. Hepatocyte spheroids were more rapidly formed in the AL/GC and AL/GC/heparin sponges, with diameter enlarged to about 100 microm, than in AL sponges. Connexin32 and E-cadherin genes correlated with cell-to-cell adhesion were expressed in hepatocytes within AL/GC and AL/GC/heparin sponges at 36 h after incubation, but not in AL sponges. Treatment of a gap junctional intercellular communication (GJIC) inhibitor, 18beta-glycyrrhetinic acid, indicates that cell aggregation without GJIC does not perform the liver-specific functions for long periods. In the presence of HGF, the level of albumin secretion in AL/GC/heparin sponges was markedly elevated compared to that in AL/GC sponges. Coculture of hepatocytes in AL/GC/heparin sponges with NIH3T3 in a transwell insert resulted in significant increase of liver-specific functions, such as improved albumin secretion rates, ammonia elimination rates, and ethoxyresorufin-O-deethylase activity by cytochrome P4501A1 compared to those in hepatocyte monoculture. The results suggest that hepatocytes as stable spheroids enhance liver-specific functions in AL/GC/heparin sponges, providing a new synthetic ECM to design BAL devices.

Alginates↗

PubMed2005

Regulation of neurite outgrowth by intermittent irradiation of visible light.

The effect of neurite outgrowth of PC12 cells on collagen-coated glass plates under intermittent light irradiation at 525 nm and 0.4 mW/cm2 of intensity was investigated. Neurite outgrowth of PC12 cells was significantly suppressed when PC12 cells were cultivated under intermittent light irradiation with a total irradiation time of more than 2 min/h. No temperature increase was observed in the culture medium under either continuous or intermittent light irradiation. Therefore, suppression of neurite outgrowth under light irradiation was not due to the increase of temperature in the culture medium, but rather the effect of light on the PC12 cells, especially the signal transmittance of light to PC12 cells. The light irradiation interval also affected the neurite outgrowth of PC12 cells when the total irradiation time was constant. A high extension ratio of neurite outgrowth was observed under a long time interval of nonirradiation between light irradiations (1 min of irradiation every hour) as compared with frequent light irradiation intervals (5 s of irradiation every 5 min) with the same total irradiation period per hour. The neurite outgrowth ratio was thought to be dependent on the light intensity, the total time of light irradiation in the intermittent light irradiation, and the interval of light irradiation in the intermittent light irradiation.

Animals↗

PubMed2005

Cell separation between mesenchymal progenitor cells through porous polymeric membranes.

This study investigates the separation of two types of marrow stromal cells, KUSA-A1 osteoblasts and H-1/A preadipocytes, by filtration through various porous polymeric membranes. It was found that KUSA-A1 permeates better than H-1/A cells through 12-microm polyurethane foaming membranes. This appears to be due to the relatively smaller cell size of KUSA-A1 cells. In addition, when feed solutions containing suspensions of either cell type or a mixture of the two were used, the permeation ratio was relatively low (< 6%) through polyurethane and surface-modified polyurethane foaming membranes. It was also found that there was some degree of separation between KUSA-A1 and H-1/A cells (separation factor = 1.8) with nylon-net filter membranes, but no separation was obtained when filters made of nonwoven fabrics or silk screens were used. This ability of the nylon-net filter membranes to separate the two cell types was due to a sieving effect that results from an optimal pore size. Finally, permeation of a solution of human serum albumin through the membrane following filtration of the cells did not result in a separation of cells in the recovery solution.

Adipocytes↗

PubMed2005

Albumin and urea production by hepatocytes cultured on extracellular matrix proteins-conjugated poly(vinyl alcohol) membranes.

Production of albumin and urea by mouse hepatocytes on poly(vinylalcohol-co-ethylamine) (PVA-EA) membranes containing immobilized extracellular matrix (ECM) proteins was investigated for 7 days. The amount of ECM proteins (collagen, vitronectin and laminin) immobilized on PVA-EA and PVA-ECM membranes was determined to range from 1.09 microg/cm2 to 1.60 microg/cm2. Hepatocytes cultured on PVA-ECM membranes in serum-free media showed higher albumin production than those cultured on PVA-EA membranes after a 7-day incubation under the conditions in this study. Urea production by hepatocytes on PVA-ECM membranes was also determined to be higher than that on PVA-EA membranes up until day 5 of incubation in serum-free media, whereas no difference of urea production by hepatocytes on different PVA-ECM membranes and PVA-EA membranes was observed at 7 days of incubation. The effect of ECM proteins in PVA-ECM membranes on hepatocyte function (such as albumin and urea production) was observed in hepatocytes cultured in serum-free media up to day 5 of incubation. The ECM proteins immobilized on the PVA-ECM membranes contributed not only to the long-term stable production of albumin and urea by hepatocytes, but also the improved surviVal (viability) of hepatocytes on PVA-ECM membranes.

Albumins↗

PubMed2004

Cell separation of hepatocytes and fibroblasts through surface-modified polyurethane membranes.

The separation of fibroblast cells (L929 cells) and hepatocytes was investigated by using unmodified and surface-modified polyurethane (PU) foaming membranes (pore size of 12 microm) by the incorporation of various functional groups. L929 cells permeated more readily than hepatocytes, and very few populations of hepatocytes (<5%) permeated through the membranes. This result was thought to be due to the smaller cell size of the L929 cells (5-10 microm) relative to the hepatocytes (15-30 microm). The larger hepatocytes were thought to plug the pores of the membranes. A good cell separation between L929 cells and hepatocytes was achieved when the cell mixture permeated through the negatively charged PU membranes. The negatively charged membranes were thought to enhance the permeation of L929 cells because of the electrostatic repulsion between the membranes and negatively charged cells. On the other hand, the hepatocytes were unable to permeate through the membranes because of the sieve effect caused by their large cell size. The separation of hepatocytes isolated from mice at different ages was also accomplished by permeating the cell mixture through unmodified and surface-modified PU membranes.

Animals↗

PubMed2004

Peripheral blood cell separation through surface-modified polyurethane membranes.

Cell separation from peripheral blood was investigated using surface-modified polyurethane (PU) membranes with different functional groups. Both red blood cells and platelets could pass through unmodified PU and PU-SO(3)H membranes, whereas the red blood cells preferentially passed through PU-N(C(2)H(5))(2) and PU-NHC(2)H(4)OH membranes. The permeation ratio of T and B cells was <25% for the surface-modified and unmodified PU membranes. CD34(+) cells have been recognized as various kinds of stem cells including hematopoietic and mesenchymal stem cells. The adhesiveness of CD34(+) cells on the PU membranes was found to be higher than that of red blood cells, platelets, T cells, or B cells. Overall, the adhesiveness of blood cells on the PU membranes increased in the following order: red blood cells </= platelets < T cells </= B cells < CD34(+) cells. Treatment of PU-COOH membranes with a human albumin solution to detach adhered blood cells, allowed recovery of mainly CD34(+) cells in the permeate, whereas both red blood cells and platelets could be isolated in the permeate using unmodified PU membranes. The PU membranes showed different permeation and recovery ratios of specific cells depending on the functional groups attached to the membranes.

Antigens, CD↗

PubMed2004

Serum protein adsorption and platelet adhesion on aspartic-acid-immobilized polysulfone membranes.

Polysulfone (PSf) membranes that covalently conjugated with aspartic acid (ASP-PSf) were prepared and analyzed for hemocompatability. Compared to PSf or other types of surface-modified PSf membranes, the ASP-PSf membranes had a reduced ability to adsorb protein from either a plasma solution or a mixed solution of albumin, globulin and fibrinogen. This appears to be due to the creation of a hydrophilic surface by the aspartic acid zwitterion immobilized on the ASP-PSf membranes. Furthermore, the analyses of membrane protein adsorption showed that a mixed protein solution recapitulates the cooperative adsorption of proteins that occurs in plasma. We also found that the number of adhering platelets was the lowest on the ASP-PSf membranes and, in general, that platelet adhesion decreased in parallel with fibrinogen adsorption. In summary, aspartic acid immobilized on the ASP-PSf membranes, which have zwitterions with a net zero charge, effectively contributes to the hydrophilic and hemocompatible sites on the surface of the hydrophobic PSf membranes.

Adsorption↗

PubMed2003

Production of interferon-beta by fibroblast cells on membranes prepared with RGD-containing peptides.

The production of interferon-beta by NB1-RGB fibroblast cells cultured on protein and peptide membranes prepared from silk fibroin, motif peptides of silk fibroin [(AG)(n)] containing arginine-glycine-aspartic acid (RGD) peptide, and Pronectin was investigated. The cell density on various protein and peptide membranes was approximately the same, although the production of interferon-beta depended significantly on the membranes where the cells were cultured. The highest production of interferon-beta was observed when the cells were cultured on (AG)(6)RGD(AG)(7) membranes prepared with hexafluoroacetone (HFA) as the casting solvent. On RGD-containing peptide membranes more centrally located in the peptides, the cells produced more interferon-beta when the peptide membranes were prepared with HFA as the casting solvent. However, there was no enhanced production of interferon-beta by cells on (AG)(6)RGD(AG)(7) membranes prepared with 9 mol/L LiBr or 4.5 mol/L LiClO(4) solution as the casting solvent. Therefore, both the chemical composition and the secondary and higher order structure of the peptide membranes are important for enhanced production of interferon-beta. The blocking of integrin beta(1) on the cells by anti-integrin beta(1) antibody prevented the enhanced production of interferon-beta on (AG)(6)RGD(AG)(7) membranes prepared with HFA. We suggest that the cells must bind to the RGD sequence having the appropriate conformation through their integrin beta(1) for enhanced production of interferon-beta.

Amino Acid Sequence↗

PubMed2003

Serum protein adsorption and platelet adhesion on pluronic-adsorbed polysulfone membranes.

We examined plasma protein adsorption and platelet adhesion to polysulfone (PSf) flat membranes coated with Pluronic with varying polyethylene oxide (PEO) block length. Adsorption of albumin, globulin and fibrinogen to Pluronic-coated PSf membranes was independent of plasma dilution when concentrations of human blood plasma above 20% were applied. Increasing coating concentrations of aqueous Pluronic solution resulted in decreased protein adsorption by the PSf membranes. Pluronic F68, which was more hydrophilic than Pluronic L62 or L64 and had 80% of PEO content, was the most effective at suppressing the adsorption of plasma proteins and platelet adhesion to PSf membranes. We developed a mixed protein solution containing human albumin, gamma-globulin and fibrinogen to attempt to mimic the competitive and cooperative binding effects found in plasma. Fibrinogen adsorption from plasma could be recapitulated by the mixed protein solution. The number of platelets adhering to the PSf membranes decreased as the coating concentration of Pluronic solution was increased, and platelet adhesion decreased in parallel with fibrinogen adsorption. These results suggest that the bioinert property of PEO segments in the Pluronic, which is ascribed to their high flexibility in aqueous media, suppresses the adsorption of plasma proteins and platelets to the Pluronic-coated PSf membranes.

Adsorption↗

PubMed2003

Enhanced production of carcinoembryonic antigen by CW-2 cells cultured on polymeric membranes immobilized with extracellular matrix proteins.

Cell growth and the production of carcinoembryonic antigen (CEA) were investigated in human colorectal adenocarcinoma tumor (CW-2) cells cultured on extracellular matrix (ECM) protein membranes, heat-treated poly(vinyl alcohol-co-ethylamine) (PVA-EA) membranes, and PVA-EA membranes containing immobilized ECM proteins. The highest concentration of CEA was found in the cell culture media of CW-2 cells on collagen (COL)-immobilized PVA-EA membranes. This is explained by the flexible mobility of COL on the COL-immobilized PVA-EA membranes causing a specific cell response for the production of CEA. An inverse relationship was observed between either the cell density or the CEA concentration in the cell culture media and the amount of fibronectin (FN) adsorbed on the COL-immobilized membranes. The CEA concentration in the cell culture media was directly related to the cell density, which, in turn, is inversely related to the amount of FN secreted by CW-2 cells. These findings indicate that cells tend to attach to the surface by secreting ECM proteins such as FN when they are grown on substrates that provide weak cell attachment.

Adenocarcinoma↗

PubMed2003

Visible light is able to regulate neurite outgrowth.

The pheochromocytoma cell line PC12 displays neuronal characteristics. PC12 cells differentiate their phenotype from a proliferating cell to a neurite-bearing neuron upon treatment with nerve growth factor (NGF). The neurite outgrowth of PC12 cells on polystyrene tissue culture flasks and extracellular matrix protein-adsorbed glass plates was reversibly controlled using visible light. The percentage of cells with neurites decreased with increasing light intensity. Furthermore, neurite outgrowth was dramatically suppressed with light intensities over 300 Lux (approximately 130 microW). Neurite outgrowth occurred in the absence of irradiation by visible light, but did not occur or was limited with irradiation, depending on the membranes on which PC12 cells were cultured. These results hold promise for the creation of patterned neuronal networks corresponding to patterned irradiation of visible light on nerve cells.

Animals↗

PubMed2002

Chemically modified polysulfone hollow fibers with vinylpyrrolidone having improved blood compatibility.

Hydrophilic polysulfone membranes (PVP-PSf) were prepared from polysulfone membranes covalently conjugated with polyvinylpyrrolidone (PVP) on the surface. The immobilized amount of vinylpyrrolidone on PVP-PSf membranes was controlled by the amount of vinylpyrrolidone monomer in the reaction solution and the reaction time. The PVP-PSf membranes were found to be the most hydrophilic membranes among the polysulfone and surface-modified polysulfone membranes prepared in this study. This is explained by the long hydrophilic side chain of polyvinylpyrrolidone on the PVP-PSf membranes which contributes to the hydrophilic wiper on the hydrophobic PSf membranes. It was found that PVP-PSf membranes gave lower protein adsorption from a plasma solution than polysulfone and other surface-modified membranes (p < 0.01). This is attributed to the hydrophilic surface of the PVP-PSf membranes, because the hydrophilic surface is known to reduce the protein adsorption on the membranes. The PVP-PSf membranes showed a much suppressed number of adhering platelets on the surface than polysulfone and other surface-modified membranes (p < 0.01). It is suggested that the hydrophilic surface of the PVP-PSf membranes without ionic groups causes the suppression of platelet adhesion on the PVP-PSf membranes and that the long hydrophilic side chain of polyvinylpyrrolidone on PVP-PSf membranes contributes to the hydrophilic and hemocompatible wipers on the surface of the hydrophobic PSf membranes.

Adsorption↗

PubMed2002

Difference in the attachment of hepatocytes between a poly(gamma-benzyl L-glutamate) (PBLG)/poly(N-isopropylacrylamide) (PNIPAAm) diblock copolymer cast surface and a PBlg/PNIPAAm Langmuir-Blodgett one.

The effects of temperature on the monolayer behavior of the poly(gamma-benzyl L-glutamate) (PBLG)/poly(N-isopropylacrylamide) (PNIPAAm) diblock copolymer at the air-water interface were examined. Differences in the adhesion and morphology of hepatocytes between Langmuir-Blodgett (LB) films and cast surfaces of the PBLG/PNIPAAm diblock copolymer were investigated. The surface pressure (pi)-area (A) curve of the block copolymer had a tendency to expand with the temperature, due to a change in the conformation of PNIPAAm with the temperature change. Attachment of hepatocytes onto the PBLG/PNIPAAm block copolymer LB surface decreased slightly with an increase of the PNIPAAm content in the block copolymer, whereas that onto the cast surface decreased rapidly with an increase of the PNIPAAm content, due to the hydrophilic property of PNIPAAm in the microphase-separated structure. Rapid morphological changes of the hepatocytes adhered to the LB surfaces, from round shapes to spreading ones, were observed, compared with the cast films. The hepatocytes that adhered to the block copolymer LB surfaces showed less flattened and spread shapes than those that adhered to the PBLG one. Also, the spheroid formation of the hepatocytes increased with an increase of the PNIPAAm content in the block copolymer cast films.

Acrylic Resins↗