γ-Cyclodextrin-polyurethane copolymer adsorbent for selective removal of endotoxin from DNA solution.

Copolymer particles for removal of endotoxins (lipopolysaccharides, LPSs) were prepared by suspension copolymerization of γ-cyclodextrin (CyD) and 1,6-hexamethylenediisocyanate. The LPS-removing activity of the copolymer particles was compared with that of poly(ε-lysine)-immobilized Cellufine (cationic adsorbent) or polystyrene particles (hydrophobic adsorbent) by a batch method. When DNA was present in solution with LPSs under physiological conditions (pH 6.0, ionic strength of µ = 0.05-0.8), LPS-removing activity of the cationic or hydrophobic adsorbent was unsatisfactory because both the DNA and the LPSs were adsorbed onto each adsorbent. By contrast, the copolymer particles with γ-CyD cavity (CyD content: 14-20 mol%) could selectively remove LPSs from a DNA solution (50 µg ml(-1), pH 6.0, and µ = 0.05-0.2) containing LPSs (15 EU ml(-1)) without the adsorption of DNA. The residual concentration of LPSs in the treated DNA solution was below 0.1 EU ml(-1), and the recovery of DNA was 99%.

Selective removal of endotoxin from a DNA solution by cross-linked cyclodextrin beads.

The removal of lipopolysaccharide (LPS) from a contaminated DNA solution was achieved using cross-linked cyclodextrin (CyD polymer) beads as LPS adsorbents. The LPS-removing activity of the ß- and γ-CyD polymer beads was compared with that of common cationic LPS adsorbents. The γ-CyD polymer beads selectively removed LPS from a DNA solution (50 µg mL(-1), pH 6, ionic strength µ = 0.2) containing natural LPS (15 EU mL(-1)), without the adsorption of DNA. The adsorptions of LPS and DNA were 85% and <1%, respectively.

Limulus amebocyte lysate assay for endotoxins by an adsorption method with polycation-immobilized cellulose beads.

To assay lipopolysaccharides (LPSs) in solutions containing Limulus amebocyte lysate (LAL)-inhibiting or LAL-enhancing compounds, we developed a selective endotoxin (LPS) assay using poly(epsilon-lysine)-immobilized cellulose beads (PL-Cellufine) and LAL. The PL-Cellufine can adsorb LPSs in a solution containing certain compounds (NaCl, proteins and amino acids) at an ionic strength of mu = 0.05-0.4 at neutral pH. The LPSs adsorbed on the PL-Cellufine were separated from the compounds by centrifugation and then the PL-Cellufine was suspended in LPS-free water. The LPS activities of the suspension are directly assayed by a turbidimetric time assay with the LAL reagent. The accuracy of the adsorption method was high compared with those of common solution methods. As for the common method, the apparent recovery of LPS from the compounds was 40-95%. This suggests that these compounds inhibit the LAL procedure. By contrast, the adsorption method showed good LPS recovery (88-120%) in all cases, without being inhibited or enhanced by the compounds.

Selective assay for endotoxin using poly(epsilon-lysine)-immobilized Cellufine and Limulus amoebocyte lysate (LAL).

We developed a selective endotoxin (lipopolysaccharide; LPS) assay using poly(epsilon-lysine)-immobilized cellulose beads (PL-Cellufine) and Limulus amoebocyte lysate (LAL). First, LPS was selectively adsorbed on the beads in a solution containing various LAL-inhibiting or LAL-enhancing compounds (e.g., amino acids, enzymes) and the LPS adsorbed on the beads was separated from the compounds by centrifugation. Second, the LPS adsorbed on the beads directly reacted with the LAL reagent, and the LPS concentration was determined by a turbidimetric time assay. The accuracy of the adsorption method with PL-Cellufine was high compared with that of a common solution method. Apparent recovery of LPS from compound solution was 88-120%.

Fullerene adlayers on various single-crystal metal surfaces prepared by transfer from L films.

Fullerene adlayers prepared by the simple Langmuir-Blodgett (LB) method onto various well-defined single-crystal metal surfaces were investigated by in situ scanning tunneling microscopy (STM). The surface morphologies of fullerene adsorbed onto metal surfaces depended largely on the adsorbate-substrate interactions, which are governed by the types of surfaces. Too weak adsorption of C60 molecules onto iodine-modified Au(111) (I/Au(111)) allows surface migration of the molecules, and then, STM cannot visualize the C60 molecules. Stronger and appropriate adsorption onto bare Au(111) leads to highly ordered arrays relatively easily due to the limited surface migration of C60. On iodine-modified Pt(111) (I/Pt(111)) and bare Pt(111) surfaces, which have stronger adsorption, randomly adsorbed molecular adlayers were observed. Although C60 molecules on Au(111) were visualized as a featureless ball due to the maintenance of the rapid rotational motion (perturbation) of C60 on the surface at room temperature, those on I/Pt(111) revealed the intramolecular structures, thus indicating that the perturbation motion of molecules on the surface was prohibited.

Selective removal of DNA from protein solution with copolymer particles derived from N,N-dimethylaminopropylacrylamide.

To remove nucleic acids from cellular products as drugs, cross-linked N,N-dimethylaminopropylacrylamide (DMP) particles with cationic functional groups were prepared. The particle's hydrophobicity and its anion-exchange capacity were easily adjusted by changing the cross-linking agent and the DMP ratio in the cross-linking, respectively. When divinylbenzene (DVB) was used as a cross-linking agent and the DMP ratio (in the cross-linking) was adjusted to 90 mol%, the particles (DMP-DVB, 90:10) showed the highest adsorbing activity of DNA (salmon spermary). Its adsorption capacity was 54 mg/ml adsorbent. On the other hand, the adsorption of bovine serum albumin (BSA) to the DMP-DVB extremely increased with increase in the adsorbent's pore size (molecular mass exclusions; M(lim)) from 2 x 10(3) to 1 x 10(4), but decreased with increase in the buffer's ionic strength (mu) to 0.2 or stronger. As a result, when the DMP-DVB (80:20) with M(lim) 2 x 10(3) was used as adsorbent by a column method at pH, 7.2 and mu = 0.17, it only selectively removed DNA from a BSA solution, including 1000 microg/ml of BSA and 10 microg/ml of DNA. The adsorbent decreased the concentration of DNA in the BSA solution to < 10 ng/ml, and the recovery rate of BSA was more 98%.

2D-supramolecular arrangements of dibenzo-18-crown-6-ether and its inclusion complex with potassium ion by potential controlled adsorption.

The construction of self-organized adlayers of dibenzo-18-crown-6 and its inclusion complex with potassium ion on a Au(111) surface was independently achieved by potential-controlled adsorption. Highly-ordered adlayers both for the metal-free state and the complex were visualized by in-situ STM with sub-molecular visualization. The potassium ions in the complex were also clearly visualized.

The design of polymer microcarrier surfaces for enhanced cell growth.

A variety of neutral and cationic polymers based on polyamino acids were prepared and investigated as microcarriers for cell attachment and growth. Among neutral polymer particles including the alkylated poly(gamma-methyl L-glutamate) (PG) particles, in which the hydrophobicity changes as a function of the length of the alkyl groups, and hydroxy terminal PG particles, the PG particle with the longest alkyl chain (PG-C12) demonstrated the highest cell attachment rate and highest rate of cell growth. Moreover, the introduction of hydroxyl groups (PG-OH) led to a deterioration of cell growth. Cell growth on cationic particles having primary amino groups was drastically dependent upon the anion exchange capacity (AEC). A higher AEC for aminated PG microcarriers inhibited cell growth. In contrast, a higher AEC for cross-linked poly( epsilon -lysine) (PL) microcarriers facilitated cell growth. Cell growth on cationic particles clearly showed a good correlation with the pK(a,app) of the microcarriers, but not with their AEC. The particles with low and high pK(a) values possessed toxically acidic and basic pH microenvironments near the surface, respectively. These microenvironments had cytotoxic effects. On the other hand, no correlation between attachment rate constants and high cell growth was observed. The aminated particles, in which pK(a) were controlled at neutral pH, and PG-C12 produced obviously higher cell growth than did a commercially available microcarrier.

Poly(ethyleneimine)-immobilized-cloth enzyme immunoassay for the detection of Salmonella lipopolysaccharide.

Poly(ethyleneimine) (PEI) was immobilized on non-woven polyester cloth and examined for application on a simple, rapid and economical "cloth enzyme immunoassay (CEIA)" which was developed originally as polymyxin-CEIA for the detection of Salmonella lipopolysaccharide (LPS). PEI-cloth regardless of the PEI molecular weight, but with the amine group contents of 0.1 to approximately 0.35 meq/g immobilized either in a physisorption-like or chemisorption-like manner, adsorbed LPS rapidly, preferentially and effectively. The captured LPS was then able to be detected qualitatively and quantitatively as an antigen by enzyme immunoassay. PEI-CEIA had a detection limit for Salmonella LPS of 10 ng/ml, which was equivalent to 1.6 x 10(5) cell/ml and was ten times more sensitive than polymyxin-CEIA. It was possible to detect Salmonella LPS in the presence of a 100-fold excess of E. coli LPS. PEI-CEIA was found to be more sensitive and much easier to carry out than polymyxin-CEIA but had the same advantages as polymyxin-CEIA.

Comparison of nanotube structures constructed from alpha-, beta-, and gamma-cyclodextrins by potential-controlled adsorption.

"Nanotube" structures of the alpha-, beta-, and gamma-cyclodextrins (CyD's), which are similar to that of CyD-polyrotaxane, were constructed by potential-controlled adsorption onto Au(111) surfaces in sodium perchlorate solution without a threaded polymer. CyD molecules adsorbed randomly on bare Au(111) surfaces without potential control and the desorption of CyD's from Au surfaces was observed at a negative potential of less than -0.60 V versus SCE. On the other hand, in the specific range between these potentials, ordered molecular arrays with "nanotube" structures of the CyD's (alpha-, beta-, and gamma-CyD) were observed on Au(111). The range of potentials for formation of the "nanotube" structures of alpha-, beta-, and gamma-CyD was from -0.15 to -0.20 V, from -0.25 to -0.45 V, and from -0.22 to -0.45 V, respectively. beta- and gamma-CyD require a more negative potential for adsorption-induced self-organization (AISO) than alpha-CyD in order to weaken adsorption and induce self-organization. Furthermore, we have succeeded in the visualization of the dynamic process in solution, such as the self-ordering, and the destruction of the nanotube structure. These results indicate that control of the electrode potential facilitates management of the delicate balance of various interactions, resulting in the formation of two-dimensional supramolecular structures on the substrates.

Chromatographic removal of endotoxin from protein solutions by polymer particles.

Endotoxins, constituents of cell walls of gram-negative bacteria, are potential contaminants of the protein solutions originating from biological products. Such contaminants have to be removed from solutions used for intravenous administration, because of their potent biological activities causing pyrogenic reactions. Separation methods used for decontamination of water, such as ultrafiltration, have little effect on endotoxin levels in protein solutions. To remove endotoxin from a solution of high-molecular-mass compounds, such as proteins, the adsorption method has proven to be most effective. In this review, we first introduce endotoxin-specific properties in an aqueous solution, and then provide various methods of chromatographic separation of endotoxins from cellular products using polymer adsorbents. We also provide the design of novel endotoxin-specific polymer adsorbents.

Permselective monolayer membrane based on two-dimensional cross-linked polysiloxane LB films for hydrogen peroxide detecting glucose sensors.

Novel two-dimensional (2D) cross-linked polysiloxane LB films were prepared and applied for glucose sensing as H2O2-permselective films in order to block other electroactive interferences, such as L-ascorbic acid, L-cysteine, uric acid and acetaminophen; the 2D cross-linked polysiloxane monolayers were remarkably effective in eliminating interfering responses and had a rapid response for glucose, even though the films were only a monolayer thick.

A two-dimensional molecular network structure of trimesic acid prepared by adsorption-induced self-organization.

A two-dimensional molecular network of trimesic acid on Au(111) was visualized by in situ scanning tunneling microscopy with submolecular resolution. The supramolecular structures including an 'order to order' phase transition were constructed by precise potential-controlled adsorption based on adsorption-induced self-organization.