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PubMed2006

Paclitaxel poliglumex (PPX-Xyotax) and concurrent radiation for esophageal and gastric cancer: a phase I study.

OBJECTIVES: To determine the maximal tolerated dose (MTD) and dose limiting toxicities of poly(l-glutamic acid)-paclitaxel (PPX) and concurrent radiation (PPX/RT) for patients with esophageal and gastric cancer. METHODS: Patients with esophageal or gastric cancer receiving chemoradiation for loco-regional, adjuvant, or palliative intent were eligible. The initial dose of PPX was 40 mg/m2/wk, for 6 weeks with 50.4 Gy radiation. Dose levels were increased in increments of 10 mg/m2/wk of PPX. RESULTS: Twenty-one patients were enrolled over 5 dose levels. Sixteen patients had esophageal cancer and 5 had gastric cancer. Twelve patients received PPX/RT as definitive loco-regional therapy, 4 patients had undergone resection and received adjuvant PPX/RT, and 5 patients had metastatic disease and received PPX/RT for palliation of dysphagia. Dose limiting toxicities of gastritis, esophagitis, neutropenia, and dehydration developed in 3 of 4 patients treated at the 80 mg/m2 dose level. Four of 12 patients (33%) with loco-regional disease had a complete clinical response. CONCLUSIONS: The maximally tolerated dose of PPX with concurrent radiotherapy is 70 mg/m2/wk for patients with esophageal and gastric cancer.

Adenocarcinoma↗
PubMed1996

A new biological glue from gelatin and poly (L-glutamic acid).

This study describes the potentiality of hydrogels composed of gelatin and poly(L-glutamic acid) (PLGA) as a biological glue for soft tissues and compares its effectiveness with that of a conventional fibrin glue. Water-soluble carbodiimides (WSC) were used to crosslink the aqueous mixture of gelatin and PLGA. The mixed aqueous solution of gelatin and PLGA set to a hydrogel by use of WSC as rapidly as BOLHEAL fibrin glue. An addition of PLGA to gelatin aqueous solution reduced not only its gelation time but also the WSC concentration necessary for hydrogel formation. The cured hydrogel exhibited firm adhesion to the mouse skin and other soft tissues with a higher bonding strength than BOLHEAL fibrin glue. Cohesive failure in the hydrogel was observed when the gel-tissue bond was broken, in contrast to BOLHEAL fibrin glue. The bonding strength of the gelatin-PLGA hydrogel became higher with the increasing PLGA concentration. The inflammatory reaction around the gelatin-PLGA hydrogel subcutaneously implanted in mice was mild, and the hydrogel was gradually absorbed with time in vivo. A toxicity test demonstrated that the concentration of WSC necessary as a biological glue was low enough not to induce its toxicity.

Adhesives↗
PubMed2007

Preparation and characterization of nanoparticles shelled with chitosan for oral insulin delivery.

Nanoparticles (NPs) composed of chitosan (CS) and poly(gamma-glutamic acid) (gamma-PGA) were prepared by a simple ionic-gelation method for oral insulin delivery. Fourier transform infrared (FT-IR) spectra indicated that CS and gamma-PGA were ionized at pH 2.5-6.6, while X-ray diffractograms demonstrated that the crystal structure of CS was disrupted after it was combined with gamma-PGA. The diameters of the prepared NPs were in the range of 110-150 nm with a negative or positive surface charge, depending on the relative concentrations of CS to gamma-PGA used. The NPs with a positive surface charge (or shelled with CS) could transiently open the tight junctions between Caco-2 cells and thus increased the paracellular permeability. After loading of insulin, the NPs remained spherical and the insulin release profiles were significantly affected by their stability in distinct pH environments. The in vivo results clearly indicated that the insulin-loaded NPs could effectively reduce the blood glucose level in a diabetic rat model.

Administration, Oral↗
PubMed1982

Nature of the antigenic complex recognized by T lymphocytes. VIII. Specific inhibition of the stimulatory capacity of antigen-pulsed hapten-modified peritoneal exudate cells by anti-hapten antibody.

When macrophages which were pulsed with soluble protein antigens and then modified with 2,4,6-trinitrobenzenesulfonic acid (TNBS) were cultured with primed T cells in the presence of anti-2,4,6-trinitrophenyl (TNP) antiserum, a marked inhibition of the T cell proliferative response specific for the soluble protein antigen under study was observed. Inhibition of the proliferative response required that the protein antigen under study be easily susceptible to conjugation with TNBS. A lag period of 1-3 h must elapse following pulse exposure to the protein antigen and prior to TNP modification for anti-TNP antibody to exert an inhibitory effect, which suggests that processing of antigen in an intracellular site might occur with subsequent reexpression of antigen on the macrophage surface. It was hypothesized that anti-TNP antibody inhibits T cell proliferation by capping and shedding of TNP-modified determinants of the nominal antigen as well as TNP-modified cell surface proteins from the macrophage membrane. The failure of others to demonstrate an effect of anti-antigen antibody on T cell activation can best be explained as secondary to the low density of antigenic determinants on the macrophage membrane with resultant low-affinity binding of antibody to antigen.

Animals↗
PubMed2003

Targeting doxorubicin to epidermal growth factor receptors by site-specific conjugation of C225 to poly(L-glutamic acid) through a polyethylene glycol spacer.

PURPOSE: Targeted delivery of chemotherapeutic agents through antibody-polymer conjugates has met with limited success. One of the limiting factors is the loss of antibody's binding affinity upon conjugation with polymeric carriers because of lack of control over the number and site of attachment. This study aims to synthesize monovalent polymeric immunoconjugates through site-specific conjugation and to evaluate the in vitro binding activities of the resulting construct. METHODS: Antibody C225 against epidermal growth factor receptors was coupled to the terminus of a doxorubicin-bound block copolymer, poly(L-glutamic acid)-co-polyethylene glycol (PG-PEG). Western blot analysis, confocal fluorescent microscopy, and cytotoxicity assay were performed to confirm the specific binding of C225-PEG-PG-Dox to EGFR. RESULTS: C225 was conjugated to PEG-PG-doxorubicin conjugates by reacting sulfhydryl group introduced to C225 with vinylsulfone group introduced at the terminus of PEG-PG block copolymer. Polymeric immunoconjugate C225-PEG-PG-Dox, but not control (i.e., conjugate without antibody), selectively bound to human vulvar squamous carcinoma A431 cells that overexpress epidermal growth factor receptors. Receptor-mediated uptake of C225-PEG-PG-Dox occurred rapidly (within 5 min), whereas nonspecific uptake of PEG-PG-Dox required an extended period of time (24 h) to internalize. Binding of C225-PEG-PG-Dox to A431 cells could be blocked by pretreatment with C225 antibody. C225-PEG-PG-Dox was more potent than free doxrubicin in inhibiting the growth of A431 cells after a 6-h exposure period. CONCLUSION: Site-specific conjugation of a monoclonal antibody to the terminus of a polymeric carrier enhances receptor-mediated delivery of anticancer agents.

Antibodies, Monoclonal↗
PubMed2006

Levan (beta-2, 6-fructan), a major fraction of fermented soybean mucilage, displays immunostimulating properties via Toll-like receptor 4 signalling: induction of interleukin-12 production and suppression of T-helper type 2 response and immunoglobulin E production.

BACKGROUND: Products from the fermentation process of soybeans by Bacillus subtilis (natto) have been shown to possess anti-tumour and immunomodulatory activities. However, the formulations previously examined were not chemically pure, and this is a major limitation for elucidation of the molecular mechanisms for their activities. OBJECTIVE: In order to determine which components in soybean mucilage exert immunostimulatory activities, we examined the activities of their purified forms in vitro and in vivo in mice. METHODS: B. subtilis (natto) and fractions including levan and poly-gamma-glutamic acid (gamma-PGA) from fermented soybean mucilage were prepared. Levels of cytokine production by mouse macrophage cells after treatment with the fractions were measured by means of ELISA. In vivo effect of levan delivered intragastrically on ovalbumin (OVA)-specific T-helper type 2 (Th2) response with IgE production was examined in BALB/c mice that had been immunized intraperitoneally with OVA. Results Levan but neither gamma-PGA nor killed B. subtilis (natto) was found to exert strong activity to induce production of IL-12 p40 and TNF-alpha by macrophage cell lines in vitro. RESULTS: of experiments using Toll-like receptor (TLR) 4-deficient mice and TLR4-transfected human cell line indicated that TLR4 is involved in pattern recognition of levan. Oral administration of levan in vivo significantly reduced the serum levels of OVA-specific IgE and Th2 response to OVA in mice immunized with OVA. CONCLUSION: Levan is an immunostimulatory moiety in products from the fermentation process of B. subtilis (natto) and may be useful for prevention of allergic disorders with IgE production.

Adjuvants, Immunologic↗
PubMed2006

Administration of poly-D-glutamic acid induces proliferation of erythropoietin-producing peritubular cells in rat kidney.

Erythropoietin (EPO), a 34-kDa glycoprotein, is produced predominantly by peritubular interstitial cells (PIC) in the renal cortex and is physiologically released when ambient oxygen pressure falls. However, the exact nature of EPO-producing cells in the kidney is not well understood. We discovered that brief administration of a low-molecular-weight synthetic peptide, poly-D-glutamic acid (PDG), induced prompt and robust expansion of EPO-producing PIC in rat kidney, without evidence of tubular cell necrosis/apoptosis or fibrotic reaction. Proliferating PIC in PDG-treated rats were noninflammatory, alpha-smooth muscle actin negative, and specifically expressed CD73 (ecto-5'-nucleotidase), EPO mRNA, and protein. Increased numbers of EPO-positive PIC persisted even after the cessation of PDG treatment. No erythropoietic effects of EPO were detected, potentially suggesting maintained physiological control of EPO secretion in this normoxic model. We showed previously that PDG is readily filtered and is rapidly taken up and stored in lysosomes of proximal tubular cells (PTC), resulting in an apparently nonnoxious lysosomal storage condition by virtue of its nonhydrolyzable nature (Kishore BK, Maldague P, Tulkens PM, Courtoy PJ. Lab Invest 74: 1013-1023, 1996). Based on these findings, we suggest that unknown signaling molecules, produced by PTC in response to lysosomal PDG storage, appear to specifically stimulate the proliferation of EPO-producing PIC. We conclude that this model is uniquely suited to investigate the biology of EPO production by PIC and may thus facilitate the development of novel and more economical therapies of anemias and other EPO-responsive conditions.

Animals↗
PubMed1992

Comparative assessment of poly-L-aspartic and poly-L-glutamic acids as protectants against gentamicin-induced renal lysosomal phospholipidosis, phospholipiduria and cell proliferation in rats.

Coadministration of poly-L-aspartic acid (poly-L-Asp) protects rats against all measured signs of aminoglycoside nephrotoxicity. Based on in vitro and acute in vivo models, previously we hypothesized that poly-L-Asp protects by forming complexes with the drug in lysomes of proximal tubular cells. However, another closely related peptide, poly-L-glutamic acid (poly-L-Glu), could not protect against gentamicin-induced phospholipidosis and nephrotoxicity, presumably because it is susceptible to rapid hydrolysis in sysosomes in vivo. The present study expands the in vivo comparison between these two polyanions to a subacute model of rats and examines in detail the influence of these polymers on the qualitative and quantitative morphological alterations of lysosomes, phospholipiduria and proliferation of cortical cells induced by gentamicin. Our results not only demonstrated that despite a significantly higher drug cortical accumulation, the coadministration of poly-L-Asp almost completely protects against the development of all these early renal alteration but also pointed to the possibility of a mild, albeit apparently nonlethal, lysosomal thesaurismosis to develop under these conditions. In contrast, poly-L-Glu could not protect against these early renal alterations, though cortical drug accumulation was not significantly higher; however, it induced a conspicuous proliferation of peritubular interstitial cells. Therefore, the present work, taken together with the earlier results of ours as well as that of others, tends to strengthen the hypothesis that the site of action of poly-L-Asp must be in lysosomes, which are also the organelles that sequester and accumulate the drug.

Animals↗
PubMed1994

Local treatment of pressure sores in the elderly: amino acid copolymer membrane versus hydrocolloid dressing.

OBJECTIVE: To compare the clinical effectiveness and wound management properties of a copolymer membrane, Inerpan (Synthélabo), and a hydrocolloid dressing, Comfeel (Coloplast), in the treatment of decubitus ulcers in the elderly. DESIGN: Open, randomized, multicentric French study, with two parallel groups of patients. PATIENTS: 168 in-patients aged more 65 years (mean age: 82 years) suffering from grade II to grade IV (in the Shea classification) pressure sores. TRIAL PERIOD: Either 8 weeks or until the ulcer healed, whichever occurred first. MEASUREMENTS: In addition to a complete physical examination, patients were evaluated at baseline for nutritional status and risk factors. The wounds were described, their depth scored, and the areas traced at Weeks 0, 1, 2, 4, 6, and 8. The number of dressings used was recorded. RESULTS: Thirty-one Inerpan-treated patients and 23 Comfeel-treated patients achieved healing (P = 0.089), with respective median healing times of 32 and 38 days. Healing times were compared using survival curves (in the whole population) adjusted for ulcer depth effect and showed a significant difference in favor of Inerpan (P = 0.044 and 0.014). Progress of healing (percentage of ulcer healed) was calculated in the two groups. Clinically assessed the treatment performance scored at the completion of the study showed better results with Inerpan (P < 0.05). Both groups were similar in terms of granulation/exudation scores, surrounding skin, and ease of care. CONCLUSION: It is concluded that Inerpan is easy to use, safeguards the healing process, and is of particular value in the management of pressure sores.

Age Factors↗
PubMed1990

Mechanism of protection afforded by polyaspartic acid against gentamicin-induced phospholipidosis. II. Comparative in vitro and in vivo studies with poly-L-aspartic, poly-L-glutamic and poly-D-glutamic acids.

Poly-L-aspartic acid (poly-L-Asp) protects rats against gentamicin (GM)-induced nephrotoxicity (functional and pathological changes) and early cortical alterations (phospholipidosis and increase in cell turnover) without decreasing, but actually increasing, the renal accumulation of the drug. We suggested that this protection occurs through the complexation of GM by poly-L-Asp, after their pinocytosis and accumulation in the lysosomes of the renal cortex (Kishore et al., J. Pharmacol. Exp. Ther. 867-874, 1990). Here we examine further our proposal by comparatively assessing poly-L-Asp (as provided by the Sigma Chemical Co., St. Louis, MO; MW 9-11,000), with two other polyanionic peptides, viz, poly-L-glutamic (poly-L-Glu; MW 14,300) and poly-D-glutamic (poly-D-Glu; MW 20,000) acids obtained from the same supplier. In vitro, all three polyanions showed a similar capacity to bind GM, to displace it from anionic phospholipids at acid pH and thereby to decrease the inhibitory potency of GM toward lysosomal phospholipase A1. In vivo, however, only poly-L-Asp and poly-D-Glu were able to prevent the development of GM-induced renal lysosomal phospholipidosis as assessed by key biochemical criteria (increase in lipid phosphorus and decrease of acid sphingomyelinase activity) and by examination of the lysosomal content in the electron microscope (accumulation of myeloid bodies). Based on these criteria, poly-L-Glu completely failed to protect. In vitro, poly-L-Glu was 13- to 17-fold more susceptible to hydrolysis by liver lysosomal extracts at pH 5.4 after 48 hr incubation, as compared to poly-L-Asp and poly-D-Glu, respectively. Assuming that all three polyanions tested are transported and accumulated in lysosomes of renal cortex to the same extent and that their respective rates of hydrolysis therein compare to that measured in vitro, these results suggest that stability of polyanions in lysosomes is an essential requisite for protection against GM-induced phospholipidosis and thus strengthens our earlier proposal that the site of action of poly-L-Asp must be in lysosomes. Although protecting from phospholipidosis, poly-D-Glu, however, caused a so far undescribed lysosomal storage disorder consisting of the accumulation of osmiophilic, nonlamellar material. This study, therefore, also demonstrates that not all polyanions resistant to lysosomal enzymes can be used as nephroprotectants, inasmuch as these, as is the case for poly-D-Glu, may cause renal alterations on their own.

Animals↗
PubMed2003

Cytochrome c is transformed from anti- to pro-oxidant when interacting with truncated oncoprotein prothymosin alpha.

Many apoptotic signals are known to induce release to cytosol of cytochrome c, a small mitochondrial protein with positively charged amino acid residues dominating over negatively charged ones. On the other hand, in this group, it was shown that prothymosin alpha (PT), a small nuclear protein where 53 of 109 amino acid residues are negatively charged, is truncated to form a protein of 99 amino acid residues which accumulates in cytosol during apoptosis [FEBS Lett. 467 (2000) 150]. It was suggested that positively charged cytochrome c and negatively charged truncated prothymosin alpha (tPT), when meeting in cytosol, can interact with each other. In this paper, such an interaction is shown. (1) Formation of cytochrome cz.ccirf;tPT complex is demonstrated by a blot-overlay assay. (2) Analytical centrifugation of solution containing cytochrome c and tPT reveals formation of complexes of molecular masses higher than those of these proteins. The masses increase when the cytochrome c/tPT ratio increases. High concentration of KCl prevents the complex formation. (3) In the complexes formed, cytochrome c becomes autoxidizable; its reduction by superoxide or ascorbate as well as its operation as electron carrier between the outer and inner mitochondrial membranes appear to be inhibited. (4) tPT inhibits cytochrome c oxidation by H(2)O(2), catalyzed by peroxidase. Thus, tPT abolishes all antioxidant functions of cytochrome c which, in the presence of tPT, becomes in fact a pro-oxidant. A possible role of tPT in the development of reactive oxygen species- and cytochrome c-mediated apoptosis is discussed.

Animals↗
PubMed1987

Analysis of T cell responses to poly-L(GluLys) at the clonal level. I. Presence of responsive clones in nonresponder mice.

The synthetic random copolymer of L-glutamic acid and L-lysine (GL) is weakly or nonimmunogenic in all inbred strains of mice. Theories proposed to account for nonresponsiveness to GL include a deficient T cell repertoire, failure of antigen-presenting cells to present the antigen and/or the presence of suppressor cells. In this study we examine mechanisms for nonresponsiveness to GL. We demonstrate the existence of GL-reactive T cells which can be isolated with a relatively high frequency. These clones, which were derived following immunization of H-2d mice with poly(LGluLLysLTyr), also respond to several GL-containing polypeptides including the terpolymers of GL with phenylalanine, alanine (GLA) or leucine. Although recognition of GLA by heterogeneous T cell populations usually occurs in association with I-A determinants, these clones recognize GLA, as well as the other GL-containing polymers, in association with I-E determinants. Analysis of the antigen and alloreactivity patterns of these clones indicated that they expressed distinct antigen receptors. These studies imply that the T cell repertoire of "nonresponder" H-2d mice includes multiple GL-reactive T cell clones and that the antigen-presenting cells of these mice are effective in processing and presenting GL.

Animals↗
PubMed2001

Controlled release of clot-dissolving tissue-type plasminogen activator from a poly(L-glutamic acid) semi-interpenetrating polymer network hydrogel.

With the aim of developing an effective therapeutic modality for treatment of thrombosis, a tissue-type plasminogen activator (t-PA)-loaded porous poly(L-glutamic acid) (PLGA) semi-interpenetrating polymer network (semi-IPN) hydrogel was developed as a possible local drug delivery system. Porous structure of hydrogel was essential in this system to yield a large surface area so that t-PA release could be facilitated. This semi-IPN hydrogel was prepared using the method of free-radical polymerization and crosslinking of polyethylene glycol (PEG)-methacrylate through the PLGA network. Sodium bicarbonate (NaHCO(3)) was added to function as a foaming agent under acidic conditions, rendering the semi-IPN hydrogel to be porous. While the added NaHCO(3) provided gas foam in the reaction mixture, the pH in the hydrogel increased to about 7 to 8, which stimulated the polymerization. The porous structure that was presented at both the surface and sublayer was stabilized during hydrogel formation and freeze-drying. The hydrogel thus prepared possessed a porous structure of 10-20 microm in diameter, as determined by scanning electron microscopy. Results showed that the above hydrogel preparation process did not significantly alter the specific activity of the entrapped t-PA with regard to plasminogen activation and fibrin clot lysis ability. The t-PA release from this semi-IPN hydrogel was examined by measuring the plasmin activity using the chromogenic substrate S-2251. Findings in this paper demonstrated that the porous structure of the hydrogel facilitated t-PA release when compared to the dense structure. Aside from the porous structure, other factors including the content of the crosslinker, PLGA and t-PA could all be varied to regulate t-PA release from the hydrogel. These results suggest that a porous PLGA semi-IPN hydrogel could potentially be a useful local delivery system to release active t-PA primarily at the site of a thrombus.

Blood Coagulation↗
PubMed2006

Poly(gamma,L-glutamic acid)-cisplatin conjugate effectively inhibits human breast tumor xenografted in nude mice.

An easily administered cis-dichlorodiammineplatinum (II) (CDDP) formulation with less toxicity and greater antitumor effect would be extremely valuable. We describe PGA-CDDP, a water-soluble CDDP derivative. The hydrolyzed gamma-PGA has a molecular weight between 45 and 60 kDa, and is a water-soluble, biodegradable, and nontoxic polymer produced by microbial fermentation. CDDP can be released from the resulting conjugate in PBS: there was initially a burst release during the first 6h, followed by sustained release. In vitro, PGA-CDDP was less potent than free CDDP at inhibiting cell growth in the Bcap-37 cell line. PGA-CDDP was given as 3 doses at an equivalent CDDP dose of 4 or 12 mg/kg with 2-day intervals between injections to Bcap-37-grafted mice. This treatment showed stronger antitumor activity and was less toxic than CDDP in vivo. Antitumor activity assays demonstrated that the PGA-CDDP conjugate treatment had significantly higher antitumor activity than control PBS treatment (P<0.01). PGA-CDDP also increased the survival of mice bearing Bcap-37 cells with reference to PBS treatment or free CDDP treatment. Furthermore, mice treated with PGA-CDDP (4 mg/kg, administered on day 0 and 5) showed no body weight loss (P>0.05 with respect to PBS treatment), whereas free CDDP treatment at the same dose caused a body weight loss of 20-30% (P<0.001). These findings suggest that PGA produced by microbial fermentation may be used as an effective drug carrier for CDDP and that PGA-CDDP may have potential applications in the treatment of human breast cancer.

Animals↗
PubMed2006

In vitro and in vivo metabolism of paclitaxel poliglumex: identification of metabolites and active proteases.

BACKGROUND: The efficacy and tolerability of paclitaxel is limited by its low solubility, high systemic exposure, and a lack of selective tumor uptake. Paclitaxel poliglumex (PPX; XYOTAX) is a macromolecular drug conjugate that was developed to overcome these limitations; the 2' hydroxyl group of paclitaxel is linked to a biodegradable polymer, poly-L: -glutamic acid, to form an inactive polymeric conjugate. PPX was previously shown to accumulate in tumor tissue, presumably by taking advantage of the hyperpermeable tumor vasculature and suppressed lymphatic clearance in tumor tissue. METHODS: Because anti-tumor activity requires the release of paclitaxel from the polymer-drug conjugate, the current report characterizes PPX biodegradation and release of paclitaxel as determined by quantitative HPLC/mass spectral analysis. RESULTS: The identification of monoglutamyl-paclitaxel metabolites in tumor tissue confirmed the in vivo metabolism of PPX in a panel of mouse tumor models. In vitro characterization of the metabolic pathway suggests that PPX can enter tumor cells, and is metabolized to form both mono- and diglutamyl-paclitaxel cleavage products. The intracellular formation of these intermediate metabolites is at least partially dependent on the proteolytic activity of the lysosomal enzyme cathepsin B; PPX metabolism is inhibited by a highly selective inhibitor of cathepsin B, CA-074. Reduced metabolism of PPX in livers and spleens from cathepsin B deficient mice confirms that cathepsin B is an important mediator of PPX metabolism in vivo; however, other proteolytic enzymes may contribute as well. CONCLUSIONS: The cathepsin B-mediated release of paclitaxel may have therapeutic implications as cathepsin B is upregulated in malignant cells, particularly during tumor progression.

Animals↗
PubMedDate not supplied

Alkaline phosphatase activatable polymeric cross-linkers and their use in the stabilization of proteins.

We report the synthesis of polymeric cross-linking agents, poly(glutamic acid) poly(phosphorothioates), and their use in the cross-linking and stabilization of proteins upon treatment with alkaline phosphatase. We have shown that poly(phosphorothioates) are excellent substrates of alkaline phosphatase, yielding thiolated polymers which react covalently with electrophilic groups introduced into the proteins. Three proteins of different structure and function were cross-linked using this method: calf intestinal alkaline phosphatase, glucose oxidase (Aspergillus niger), and (R)-phycoerythrin. The cross-linking of alkaline phosphatase is self-catalyzed since this enzyme catalyzes the hydrolysis of phosphates, unmasking thiolates which react with the maleimide prederivatized alkaline phosphatase. Incubation of buffered solutions of native alkaline phosphatase at 45 degreesC for 7-14 days resulted in a 35% higher loss of enzymatic activity compared to that of cross-linked enzyme. The effect of cross-linking glucose oxidase is even more notable, ranging from 800% stabilization at 37 degrees C and pH 9.0 to 3000% at 37 degrees C and pH 7.4. (R)-Phycoerythrin cross-linked with 1-3 equiv of poly(phosphorothioates) and incubated at 45 degrees C for 45 days was 20% more fluorescent than the native (R)-phycoerythrin subjected to the same conditions. The stabilizing effect of cross-linking was confirmed by comparing the rate of loss of quaternary structure of the cross-linked (R)-phycoerythrin with that of the native protein.

Alkaline Phosphatase↗
PubMed2005

Flocculating activity of cross-linked poly-gamma-glutamic acid against bentonite and Escherichia coli suspension pretreated with FeCl3 and its interaction with Fe3+.

Cross-linked poly-gamma-glutamic acid (C-L gamma-PGA) at 5 microg/ml flocculated bentonite suspension pretreated with polyaluminum chloride (PAC) at 2 microg/ml Al3+-PAC to a transparency of approximately 30% after 30 min and more than 90% after 4 h, while Al3+ concentration in the upper phase of the suspension decreased with incubation time. When pretreated with FeCl3 at 16 microg/ml Fe3+-FeCl3, similar results were obtained. In the case of Escherichia coli suspension, the combination of C-L gamma-PGA and FeCl3 demonstrated a more marked flocculating activity with a satisfactory transparency occurring after 30 min of treatment, accompanied by a decrease in residual Fe3+ concentration. In the above two suspensions pretreated with FeCl3, small visible floats appeared in the early stage of incubation. These floats were found to be due to the direct interaction between FeCl3 and C-L gamma-PGA, indicating the formation of a water-insoluble complex. After allowing the suspension to stand for a long time, elemental analysis and inductively coupled plasma spectroscopy of the precipitates produced suggested that not only the complex was formed due to the interaction between Fe3+ in FeCl3 and COO- in the C-L gamma-PGA molecule, but also Fe2O3 and Fe(OH)3 might be entrapped in this complex. This could be applied to scavenge metal ions including Fe3+ from polluted water.

Bentonite↗
PubMed2001

The effects of heparin on the adhesion of human peripheral blood mononuclear cells to human stimulated umbilical vein endothelial cells.

1. The effects of unfractionated heparin (UH) and a selectively O-desulphated derivative of heparin (ODSH), lacking anticoagulant activity, on the adhesion of human peripheral blood mononuclear cells (HPBMNC) to human stimulated umbilical vein endothelial cells (HUVECs), were investigated. 2. For comparison, the effects of poly-L-glutamic acid (PGA), a large polyanionic molecule without sulphate groups and two different molecular weight sulphated dextrans (DS 5 k and DS 10 k) were studied. 3. UH (50 - 1000 u ml(-1)) significantly (P<0.05) inhibited the adhesion of HPBMNC to HUVECs, stimulated with IL-1beta (100 u ml(-1)), TNF-alpha (1000 u ml(-1)) or LPS (100 microg ml(-1)), when the drugs were added together with stimuli to HUVECs and coincubated for 6 h. Such effects on adhesion occurred with limited influence on expression of relevant endothelial adhesion molecules (ICAM-1 and VCAM-1). 4. UH (100 - 1000 u ml(-1)), when added to prestimulated HUVECs, significantly (P<0.05) increased adhesion of mononuclear cells to endothelium at the higher concentrations tested, without any effect on adhesion molecule expression. In contrast, the opposite effect was observed when human polymorphonuclear leucocyte adhesion was examined, under the same experimental conditions, suggesting that the observed potentiation of HPBMNC adhesion is cell specific. 5. The effects of UH on HPBMNC adhesion were shared by the non-anticoagulant ODSH (600 - 6000 microg ml(-1)) but not by sulphated dextrans or PGA (300 - 6000 microg ml(-1)). 6. Heparin affects the adhesion of HPBMNC to stimulated endothelium, in both an inhibitory and potentiating manner, effects which are unrelated to its anticoagulant activity and not solely dependent on molecular charge characteristics.

Cell Adhesion↗