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At least 253 records · Page 14Linked to original sources
PubMed2005

Development of a delivery system for the continuous endogenous release of an anti-idiotypic antibody against ovarian carcinoma.

The treatment of several cancers with anti-idiotype antibodies has shown promising results in animals and clinical trials. A common drawback of many anti-idiotypic antibodies is their low immunogenicity. The aim of this work was to construct a new delivery form for the anti-idiotypic antibody ACA125hFc, with the goal of improving its immunogenicity as vaccine against ovarian carcinoma. Designed on bioencapsulation technologies, we generated an in vitro depot that acts as a continuous delivery system for the anti-idiotypic antibody ACA125hFc. C2C12 myoblasts were transfected with the anti-idiotypic chimeric antibody ACA125hFc, which mimics the CA125 tumor antigen and which consists of variable regions of the monoclonal murine antibody ACA125 (currently in clinical trial) and the human IgG Fc domain. Recombinant myoblasts were encapsulated in 1-cm semipermeable, polyethersulfone (PES), or polyvinylidene difluoride (PVDF) hollow fibers, which differ in their molecular weight cutoff (MWCO). Encapsulated cells were evaluated in vitro for viability and antibody secretion over a period of 3 months. PES hollow fibers with a higher MWCO showed a twofold higher secretion rate of chACA125hFc compared to PES devices with a lower MWCO. No remarkable level of ACA125hFc could be detected for PVDF devices. The expression levels of the anti-idiotypic antibody ACA125hFc from capsules with a lower MWCO could be improved substantially, in both PES as well as PVDF, by inserting an internal polyethyleneterephtalate (PET) yarn. We conclude that murine recombinant C2C12 myoblasts encapsulated in PES as well as PVDF hollow fibers containing an internal PET matrix can act as a long-term secretion system for anti-idiotypic antibodies.

Animals↗
PubMed1983

The use of the mouse peritoneal cavity for screening for biocompatibility of polymers.

The mouse peritoneal cavity was evaluated as a possible model for the preliminary screening of polymeric implant materials. The phagocytic cells of the cavity were stimulated prior to implant insertion by intraperitoneal injection of thioglycollate, glycogen, or sodium caseinate. Small, cylindrical polymeric implants of polyethylene, polychlorotrifluoroethylene, silicone, nylon-12, ethylene-chlorotrifluoroethylene copolymer, and polyethylene-silicone blend, were inserted and then retrieved at 1, 2, and 3 week intervals. The implants with attached cells were subsequently stained and evaluated as to the amount and type of cellular adherence. Results indicate that cell adherence varies according to the type of material used and therefore the mouse peritoneal cavity is a rapid and inexpensive method to evaluate cellular response to polymeric implant materials.

Animals↗
PubMed2006

Ultrasonic monitoring of early-stage biofilm growth on polymeric surfaces.

Biofilm growth on polymeric surfaces was monitored using ultrasonic frequency-domain reflectometry (UFDR). The materials utilized for this study included nonporous polycarbonate (PC) sheets, polyamide (PA) nanofiltration composite membranes and porous polyvinylidene fluoride (PVDF) microfiltration membranes (nominal pore size: 0.65 microm). Coupons of each material were placed in a biologically active annular reactor for up to 300 days, and subjected to a constant shear field (0.12 N m(-2)), which induced sessile microbial growth from acetate amended municipal tap water. Acoustic monitoring was non-destructively executed by traversing coupons in a constant temperature water bath using a spherically focused 20-MHz immersion transducer. This semi-automated system was configured to obtain reflections from 50 regions (c.a. 120x10(3) microm2) distributed evenly near the centerline of each coupon. The resulting reflected power distributions were compared with standard biochemical and microscopic assays that described surface associated biofilms. When compared to clean (virgin) conditions, biofilms growing on coupons induced consistent attenuations in reflection amplitude, which caused statistically significant shifts in reflected power (p<0.01). Using exocellular polysaccharides as a surrogate measure of total biofilm mass, UFDR was able to detect biofilms developing on any of the materials tested at surface-averaged masses < or = 150 microg cm(-2). Above these threshold levels, increasing amounts of exocellular polysaccharides correlated with significant decreases in total reflected power (TRP). The distribution of biomass on the coupon surfaces determined by acoustic spectra was consistent with that observed using environmental scanning electron microscopy (ESEM). These results suggest that UFDR may be used as a non-destructive tool to monitor biofouling in a wide variety of applications.

Bacteriological Techniques↗
PubMedDate not supplied

Loss of LDH activity during membrane filtration.

Membrane filters rendered hydrophilic and composed of biphenyl polycarbonate, polyvinylidene fluoride (PVDF), acrylic copolymer, polysulfone, and mixed esters of cellulose were evaluated to determine which type of filter best can be used for the filtration of lactate dehydrogenase (LDH) solution. Also, the effect of the membrane pore size was evaluated. LDH solution was passed through the filters at a controlled flow rate, after which the filtrate was assayed for LDH activity and protein content using the Bradford method. Polycarbonate and PVDF filters generally showed low loss of protein, except 5 microns PVDF filters. Mixed esters of cellulose, acrylic copolymer, and polysulfone caused considerable loss of protein during passage of the LDH solution through the filter. Interestingly, it was also found that, generally, as the pore size increased the amount of protein loss decreased. However, 5 microns PVDF and mixed esters of cellulose filters showed more loss than their corresponding 0.65 microns and 3 microns pore size filters, respectively. In all cases, more protein was recovered in the filtrate fractions as the volume of LDH solution filtered was increased, suggesting that the mechanism of loss is adsorption and that the magnitude of loss is related to saturation of the matrix polymer surfaces.

Adsorption↗
PubMed1995

In vivo cultivation of tumor cells in hollow fibers.

Advancement of potential anti-cancer agents from "discovery" in an in vitro screen to pre-clinical development requires a demonstration of in vivo efficacy in one or more animal models of neoplastic disease. Most such models require considerable materials in terms of laboratory animals and test compound as well as substantial amounts of time (and cost) to determine whether a given experimental agent or series of agents have even minimal anti-tumor activity. The present study was initiated to assess the feasibility of employing an alternate methodology for preliminary in vivo evaluations of therapeutic efficacy. Results of experimentation to date demonstrate that a hollow fiber encapsulation/implantation methodology provides quantitative indices of drug efficacy with minimum expenditures of time and materials. Following further pharmacologic calibrations, the hollow fiber technique is anticipated (a) to identify compounds having moderate to prominent anti-cancer activity and (b) to facilitate the identification of sensitive tumor cell line "targets" and optimal or near-optimal treatment regimens for subsequent testing using standard in vivo solid tumor models. The potential suitability of this methodology is demonstrated with several standard anti-neoplastic agents.

Animals↗
PubMed2006

Human amniotic cell sheet harvest using a novel temperature-responsive culture surface coated with protein-based polymer.

Human amniotic epithelial (hAE) and mesenchymal (hAM) cells are believed to have the potential to differentiate into various functional cells, such as neurons, hepatocytes, cardiomyocytes, and pancreatic beta cells. However, cell transplantation has been performed by injection of cell suspensions, and thus it is difficult to control shape, size, location, and functions of differentiated cells. To overcome these problems, we developed a novel temperature-responsive culture surface coated with elastic protein-based polymer. By reducing the temperature using a polyvinylidene difluoride (PVDF) membrane, the primary hAE and hAM cell sheet can detach from the coated surface. The recovered cell sheet can be transferred and can re-adhere and re-proliferate on another surface. This represents the first report of harvesting of primary hAE and hAM cell sheets using the novel temperature- responsive polymer. These findings suggest that this new technique of cell sheet detachment from noncytotoxic, highly biocompatible protein-based polymer-coated surfaces may be useful in tissue engineering, as well as in the investigation of hAE and hAM cell sheets for transplantation.

Amnion↗
PubMed1991

Antimicrobial activity of polymers coated with iodine-complexed polyvinylpyrrolidone.

Polymer-associated infection is a problem of increasing importance in modern medicine. In a new approach to prevent such infections we have modified polyvinylfluoride (TEDLAR) films by graft copolymerization with N-vinylpyrrolidone to which iodine can be complexed. Grafting reaction was performed by the preirradiation technique using an electron accelerator. Grafted films were then treated in Lugol's solution for at least 24 h. Release of free iodine from the films was determined either by titration or using the agar disc diffusion test, showing an iodine release for up to 4-5 days. The antimicrobial activity of the films was tested in bacterial adhesion measurements. Bacterial and fungal cells in the range of 10(3) to 10(6) cfu/cm2 polymer were found on control samples without iodine, whereas on iodine-complexed films no viable cells could be detected at least for 5 days or even longer. Thus, microbial adhesion and growth can be inhibited by iodine-containing polymers.

Animals↗
PubMed2005

Surface-initiated atom transfer radical polymerization on poly(vinylidene fluoride) membrane for antibacterial ability.

Surface-active microporous membranes were prepared from the poly(vinylidene fluoride)-graft-poly(2-(2-bromoisobutyryloxy)ethyl acrylate) copolymer (PVDF-g-PBIEA copolymer) by phase inversion in water. The PBIEA side chains could function as initiators for the atom transfer radical polymerization (ATRP) of 2-(N,N-dimethylamino)ethyl methacrylate on the membrane surfaces to give rise to the PVDF-g-PBIEA-ar-PDMAEMA membranes. N-alkylation with hexyl bromide and nitromethane gave rise to the quanternized PVDF-g-PBIEA-ar-QPDMAEMA membranes with polycation chains chemically tethered on the membrane surface, including the pore surfaces. The changes in the surface morphology and the surface chemical composition were confirmed by scanning electron microscopy and X-ray photoelectron spectroscopy. The scanning electron microscopy revealed that, in comparison to the pristine PVDF-g-PBIEA membranes, not only could the PVDF-g-PBIEA-ar-QPDMAEMA membranes remove the Gram-negative bacterium Escherichia coli but also inhibited the bacterial reproduction on the membranes to a significant extent.

Acrylates↗
PubMedDate not supplied

Promotion of neovascularization around hollow fiber bioartificial organs using biologically active substances.

A limiting factor of the long-term function of bioartificial organs is oxygen delivery to the encapsulated tissue. This study determined whether incorporation of endothelial cell growth factor (ECGF) into the alginate core of a hollow fiber bioartificial organ will induce neovascularization around the hollow fiber. Polyethersulfone (PES) and polyvinylidine difluoride (PVDF) hollow fibers were examined. Endothelial cell growth factor was incorporated into sodium alginate, extruded into the lumen of hollow fibers, and cured in calcium chloride. Samples without ECGF were fabricated and used as controls. Hollow fibers were implanted into 16 rats. For each rat, two implants were placed subcutaneously and two intraperitoneally, one with and one without ECGF at each site. Implants were placed on opposite sides of each animal. Implants were removed 65 days later and examined using immunohistochemical methods and light microscopy to determine the extent of neovascularization. A total of 64 implants were used. Most intraperitoneal implants were found free floating but were encased within a 100-microm thick avascular fibrotic reaction. This finding was independent from the presence of ECGF. Hollow fibers without ECGF, implanted subcutaneously, also had an avascular fibrotic reaction surrounding each implant. Subcutaneous implants with incorporation of ECGF within the alginate core had marked neovascularization within the fibrotic overgrowth that surrounded these implants. This was most prevalent in hollow fibers, with the thin separation layer facing the fiber lumen irrespective of limiting pore size. Potent angiogenic factors, such as ECGF, incorporated into diffusion chamber bioartificial organs can promote neovascularization around the subcutaneously implanted hollow fiber and may improve oxygen delivery to the tissue encapsulated within devices based on this technology.

Animals↗
PubMedDate not supplied

Hollow fibers for hepatocyte encapsulation and transplantation: studies of survival and function in rats.

In this study, the feasibility of transplanting hepatocytes using hollow fibers (HF) was investigated. Experiments were carried out in vitro and in vivo to determine the viability and function of hepatocytes encapsulated in four different types of commercially available HF: regenerated cellulose HF (RCHF), polysulfone HF of two different sizes (PSHF-1 and PSHF-2), and polyvinylidine HF (PVDF). Hepatocytes remained viable in all types of HF for at least 1 wk in vitro as measured by light microscopy and their ability to synthesize protein and secrete albumin. However, the levels of protein synthesis and albumin secretion in these cells varied significantly between different HF (RCHF > PSHF-2 > PVDF approximately PSHF-1) and appeared to be inversely related to their internal diameters (215, 500, 1000, and 1100 microns for RCHF, PSHF-2, PVDF, and PSHF-1, respectively). While PSHF-2, PVDF, and PSHF-1 did not support long term viability in vivo, hepatocytes in RCHF survived after implantation in the mesentery. After 24 h in vivo, the hepatocytes appeared morphologically intact and exhibited a similar rate of protein synthesis when compared with cells cultured in parallel. The hepatocytes in RCHF also maintained the ability to synthesize protein after 7 days in vivo. These results suggest that HF of appropriate size may be useful for hepatocyte transplantation applications in which prevascularization is not possible.

Albumins↗
PubMed2003

pH effect of coagulation bath on the characteristics of poly(acrylic acid)-grafted and poly(4-vinylpyridine)-grafted poly(vinylidene fluoride) microfiltration membranes.

The poly(acrylic acid)-graft-poly(vinylidene fluoride) (PAAc-g-PVDF) and poly(4-vinylpyridine)-graft-poly(vinylidene fluoride) (P4VP-g-PVDF) copolymers were obtained by thermally induced molecular graft copolymerization of acrylic acid (AAc) and 4-vinylpyridine (4VP), respectively, with the ozone-pretreated poly(vinylidene fluoride) (PVDF) in N-methyl-2-pyrrolidone (NMP) solution. Microfiltration (MF) membranes were prepared from the respective copolymers by phase inversion in aqueous media. The effects of pH of the coagulation bath on the physicochemical and morphological characteristics of the membranes were investigated. The surface compositions of the membranes were determined by X-ray photoelectron spectroscopy (XPS). The surface graft concentration of the AAc polymer for the PAAc-g-PVDF MF membrane increased with decreasing pH value of the coagulation bath. Completely opposite pH-dependent behavior was observed for the surface graft concentration of the 4VP polymer in the P4VP-g-PVDF MF membranes. A substantial increase in mean pore size was observed for the PAAc-g-PVDF MF membranes cast in basic coagulation baths of increasing pH. In the case of the P4VP-g-PVDF MF membranes, a substantial increase in mean pore size was observed for membranes cast in low pH (acidic) baths. The permeation rate of aqueous solutions through the PAAc-g-PVDF and P4VP-g-PVDF MF membranes exhibited a reversible dependence on the pH of the solution, with the membranes cast near the neutral pH exhibiting the highest sensitivity to changes in permeate pH.

Acrylates↗
PubMed2004

Branched fluoropolymer-Si hybrids via surface-initiated ATRP of pentafluorostyrene on hydrogen-terminated Si(100) surfaces.

Linear, branched, and arborescent fluoropolymer-Si hybrids were prepared via surface-initiated atom transfer radical polymerization (ATRP) from the 4-vinylbenzyl chloride (VBC) inimer and ClSO(3)H-modified VBC that were immobilized on hydrogen-terminated Si(100), or Si-H, surfaces. The simple approach of UV-induced coupling of VBC with the Si-H surface provided a stable, Si-C bonded monolayer of "monofunctional" ATRP initiators (the Si-VBC surface). The aromatic rings of the Si-VBC surface were then sulfonated by ClSO(3)H to introduce sulfonyl chloride (-SO(2)Cl) groups and to give rise to a monolayer of "bifunctional" ATRP initiators. Kinetics study indicated that the chain growth of poly(pentafluorostyrene) from the functionalized silicon surfaces was consistent with a "controlled" or "living" process. The chemical composition and functionality of the silicon surface were tailored by the well-defined linear and branched fluoropolymer brushes. Atomic force microscopy images revealed that the surface-initiated ATRP of pentafluorostyrene (PFS) had proceeded uniformly on the Si-VBC surface to give rise to a dense and molecularly flat surface coverage of the linear brushes. The uniformity of surfaces with branched brushes was controlled by varying the feed ratio of the monomer and inimer (VBC in the present case). The living chain ends on the functionalized silicon surfaces were used as the macroinitiators for the synthesis of diblock copolymer brushes, consisting of the PFS and methyl methacrylate polymer blocks.

Fluorocarbon Polymers↗