摘要:

The operation of filters used to remove leukocytes from red cell concentrates may depend on the adhesion and mechanical trapping of leukocytes. If adhesion is a major component of filtration then filter materials which augment leukocyte adhesion will be useful. In previous leukocyte adhesion studies, done without flow, poly(ethyleneimene) (PEI) modified polyurethane (PU) films were shown to have greater adhesion when compared with unmodified PU. Since filtration is done under flow conditions, it was decided to study PMN adhesion at a number of flow rates using an established parallel plate flow cell. The influence of divalent cations, plasma and platelets were investigated in the presence of red cells, 40% Hematocrit. The number of adherent PMNs to the PEI modified films was always substantially higher than that for the unmodified ones when the shear rate was set at 30 s-1. When using Tyrode's solution containing albumin, with or without divalent cations, a maximum in PMN adhesion was found between the shear rates of 10 and 100 s-1. With Tyrode's solution containing albumin and with 10% (v/v) plasma in saline, the addition of platelets increased PMN adhesion when divalent cations were absent. Adhesion levels with 10% (v/v) plasma in saline were reduced when compared to Tyrode's solution containing albumin without divalent cations. These results support the use of filtration conditions where the concentration of plasma is reduced and the concentration of divalent cations is increased. Detailed evaluation of filter function with flow rate is also recommended. A cell adhesion promoting polymer coating, such as PEI, may be useful in improving filter efficiency.

ISSN:0920-5063    

DOI:10.1163/156856294X00013

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor

摘要:

Factors determining the thrombogenic response to particular artificial surfaces were investigated ex vivo in a canine shunt model. Methods using radioisotopic tracers made it possible to dynamically monitor the deposition of labelled blood cells and proteins on a NHLBI.DTB primary reference material polydimethylsiloxane (PRM.PDMS) and on a IUPAC reference material polyvinyl chloride (IUPAC.PVC). On the one hand, leukocyte affinity τs(leu)(number of deposited leukocytes mm-2S-1) was not significantly different between IUPAC.PVC (τs(leu)= 1.2-2.5) and PRM.PDMS (τs(leu)= 1.5-3.4) and the fibrinogen adsorption rate varied from 33 to 48.10-5μg mm-2s-1for both these materials. On the other hand, platelet affinity τs(plat)(number of deposited platelets mm-2s-1) was significantly different (p < 0.05) for IUPAC.PVC and PRM.PDMS (τs(plat)PVC= 683 ± 200 > τs(plat)PDMS- 327 ± 80). Scanning electron micrographs of adherent platelets, red cells and leukocytes after blood contact ex vivo were performed after each experiment. This preliminary work contributes not only to quantify the adsorption of different radiotracers, but also to evaluate the superficial distribution of the labelled biological species on the inner surface of the tested biomaterials.

ISSN:0920-5063    

DOI:10.1163/156856294X00022

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor

摘要:

We have developed DNA-carrying latex particles for the separation and purification of transcription factors. These particles consist of styrene (St), glycidyl methacrylate (GMA) and divinylbenzene (DVB). It was confirmed that the ethanolamine-treated surface of these particles suffered no nonspecific adsorption of proteins. To the latex particles sequence-specific DNA oligomers were immobilized via covalent coupling. A transcription factor, E4TF3, was efficiently purified to homogeneity using the latext particles. In contrast, the purification using DNA-carrying Sepharose gel yielded poor results. Compared to DNA-carrying Sepharose gel, the latex particles exhibited several times higher efficiency in the purification of E4TF3 from the crude nuclear extract.

ISSN:0920-5063    

DOI:10.1163/156856294X00031

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor

摘要:

Three water soluble copolymers based on N-(2-hydroxypropyl)methacrylamide were prepared. Copolymer I contains adriamycin, a chemotherapeutic agent, attached via enzymatically degradable oligopeptide (glycylphenylalanylleucylglycine; G-F-L-G) side chains. The other two copolymers contained the photosensitizer, meso-chlorin e6monoethylene diamine disodium salt (Mce6). In Copolymer II, the chlorin is attached via the degradable G-F-L-G sequence, and it was bound by the nondegradable glycyl spacer in Copolymer III. Initially, the copolymers were characterized separately in vitro and in vivo. Combinations of the copolymer bound chemotherapeutic agent and each of the copolymer bound photosensitizers were then assessed for antitumor effect in vivo. Localization/retention studies (A/J mice; Neuro 2A neuroblastoma solid tumor) were performed with the two copolymers containing Mce6as well as the free drug. Results of these experiments demonstrated a very different tumor uptake profile for the two copolymers. While the free drug was rapidly cleared from tumor tissue, the copolymer containing Mce6attached via the nondegradable bond was retained for an extended period; drug concentrations in the tumor were high even after 5 days. On the other hand, a high concentration of the copolymer containing Mce6bound via the degradable sequence was taken up by the tumor, yet its concentration in the tumor was substantially diminished at 48 h after administration. This shows indirect evidence of in vivo cleavage of Mce6from the copolymer in the lysosomal compartment which is supported by direct evidence of cleavage by cathepsin B (a lysosomal enzyme) in vitro. Antitumor effects were assessed on Neuro 2A neuroblastoma induced in A/J mice for all three copolymers. Photodynamic therapy (PDT) proved the copolymer with Mce6bound via the degradable oligopeptide sequence to be a more effective photosensitizer in vivo than the other chlorin containing copolymer. The difference in activity was consistent with the results obtained by photophysical analyses in which the free drug had a higher quantum yield of singlet oxygen generation than the polymer bound drug in buffer. The quantum yield of singlet oxygen generation increased with the enzymatic cleavage of the chlorin from the copolymer. Conditions were subsequently determined for which chemotherapy or PDT would show some antitumor effect, yet be incapable of curing tumors. Finally, combination therapy experiments were performed in which the copolymer bound adriamycin was mixed with either of the copolymer bound chlorin compounds and injected intravenously (i.v.) into the tail veins of mice. A time lag was allowed for optimal uptake in the tumor and for the adriamycin to begin to take effect, after which light (650 nm) was applied to activate the photosensitizer. Tumor cures were obtained with the combination therapy that could not be achieved by either chemotherapy or PDT alone.

ISSN:0920-5063    

DOI:10.1163/156856294X00040

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor

摘要:

The attachment of MRC-5 human fibroblasts was investigated on poly(γ-methyl L-glutamate) (PMLG), and upon cell adhesion peptides Arg-Gly-Asp-Ser (RGDS)- and Gly-Arg-Gly-Asp-Ser (GRGDS)-immobilized PMLG (RGDS-PMLG and GRGDS-PMLG). The peptides were immobilized by their N-terminal amine to activated PMLG surfaces. Prior to peptide immobilization, the aminolysis of PMLG surfaces was performed with hydrazine hydrate (HA), ethylenediamine (EDA), and hexamethylenediamine (HMDA) and was followed by the activation with hexamethylene diisocyanate. Surface characterization of these films was carried out by means of a Fourier transform IR (FT-IR) spectrometer equipped with an attenuated total reflectance (ATR) attachment. The amount of immobilized RGDS could be controlled by the reaction time of the aminolysis. The effects of HA, EDA, and HMDA as a spacer on the cell attachment were also investigated, and it was suggested that a longer spacer promoted the cell attachment via specific receptor-ligand interaction.

ISSN:0920-5063    

DOI:10.1163/156856294X00059

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor

摘要:

Novel, biodegradable controlled release systems were prepared from biodegradable microparticles of poly(lactic acid-co-glycolic acid) containing β-estradiol in the presence or absence of silicone. The release behavior of β-estradiol from free microparticles as well as from microparticles embedded within a silicone matrix was compared with the release behavior shown by nonencapsulated β-estradiol within a silicone matrix. It was found that incorporating biodegradable microparticles within a silicone matrix lessens the initial burst of release often seen with these types of formulations and provides a controlled rate of drug release. In addition, the release rate of β-estradiol from biodegradable microparticles within silicone is higher than for unencapsulated β-estradiol in silicone. This type of formulation may be useful in a number of instances such as release of drugs from implants for which a simple drug-silicone formulation does not yield desired release behavior, formulations which are currently developed for microparticles but which may need to be removed if necessary, and implant formulations containing drugs which will not diffuse through silicone.

ISSN:0920-5063    

DOI:10.1163/156856294X00068

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor

摘要:

Lysine terminated heparin, prepared by the nitrous acid partial depolymerization and reductive amination of heparin, failed to increase the active heparin content of a heparin-polyvinyl alcohol (heparin-PVA) hydrogel relative to the unmodified commercial heparin. The depolymerization of heparin resulted in a loss of biological activity which outweighed the increase in the terminal amine groups (produced by reductive amination), that were used for glutaraldehyde immobilization to the PVA. The loss in anti-thrombin activity (thrombin time or chromogenic substrate) paralleled the increase in anhydromannose end groups due to depolymerization making it necessary to optimize the loss of activity against the increase in terminal amine groups after amination. For example, depolymerization at a high sodium nitrite concentration (81 g/l) at pH4 and 25°C for 20 min, resulted in a loss of 22-40% of the biological activity but achieved an anhydromannose content of 600 nmoles/mg (~7 cleavage sites/ molecule). After the anhydromannose groups were reductively aminated by lysine, the anhydromannose content was reduced to 190 nmol/mg indicating a terminal lysine content of 410 nmol/mg. This resulted in an increase in heparin content of the final hydrogel by 53% on mass terms. However, given the reduction in biological activity, it was not surprising that the modified heparin-PVA hydrogel coated on a polyethylene tube was no better than the hydrogel with unmodified heparin in inactivating thrombin in a flow circuit. These results point out the need for care in interpreting heparin immobilization results and for new strategies to increase the active heparin content of this hydrogel.

ISSN:0920-5063    

DOI:10.1163/156856294X00077

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor

摘要:

A thermo-reversible poly(N-isopropylacrylamide) poly(NIPAAm) oligomer with a carboxyl functional end group has been synthesized by radical polymerization using β-mercaptopropionic acid as a chain transfer reagent. This polymer has been conjugated to an enzyme, β-D-glucosidase, to form a thermo-reversible water soluble-insoluble polymer-enzyme conjugate. This conjugate can be used for separation, recovery and recycle of an enzyme simply by applying small temperature changes to the reaction medium. In contrast to the random polymer-enzyme conjugates reported in the literature, in this study the enzyme is coupled to each polymer chain by a single end attachment. These preliminary studies show that the conjugated enzyme exhibits very high retention of activity ( > 90%) compared to the native enzyme and shows improved thermal stability.

ISSN:0920-5063    

DOI:10.1163/156856294X00086

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor