Biomaterials, artificial cells, and immobilization biotechnology : official journal of the International Society for Artificial Cells and Immobilization Biotechnology最新文献

Safety test of modified hemoglobin in animals does not always reflect safety in human. We have earlier reported an in-vitro preclinical screening test based on in-vitro complement activation of human plasma In this test, modified hemoglobin is added to human plasma in a test tube. Complement activation is followed by the C3a levels. Since this directly measures the effect of modified hemoglobin on human plasma, this could be an important bridge before clinical use in patients. The use of plasma is suitable for research, development and industrial applications. However, there are many extra steps involved and may not be convenient for population or patient screening on a large scale bases. The present study shows that it is possible to use small sample of whole blood obtained directly from finger pricks and use immediately for analysing complement activation using an ELISA enzyme immunoassay method.

A method for the coupling of polyacrylamide beads to polyethylene terephthalate (PET) vascular prostheses is described. The reactional procedure used is performed along several steps; acrylic acid grafting on PET textile fibres, in order to introduce reactive carboxylic groups, introduction of terminal primary amine groups onto the beads, and then, attachment method which consists in coupling carboxylic groups of prostheses with amine groups of modified beads. The relative weight increase of the samples before and after the coupling reaction and, microscopic observations of beads distribution onto the prostheses surface demonstrate the binding feasibility of polyacrylamide matrices to PET prostheses. In the near future, authors expect to replace these beads by microcapsules with polyacrylamide wall and containing active compounds to improve the vascular prostheses biocompatibility.

Human oxyhemoglobin reacts with mellitic dianhydride to produce a modified protein which shows a reduced oxygen affinity over a wide pH range, a reduced but significant cooperativity, a reduced Bohr effect and no response to the allosteric effectors: chloride, clofibric acid or inositol hexaphosphate. The amount of crosslinking in the modified hemoglobin is approximately 22% suggesting promise as a blood substitute. Reaction of deoxyhemoglobin with mellitic dianhydride produces a modified protein with reduced response to clofibric acid and a decrease in oxygen affinity in the presence of inositol hexaphosphate.

Inhibition of cell growth is the most commonly used endpoint for in vitro toxicity of biomaterials. The use of several different endpoints might however generate more information concerning the nature of the toxicity. Thus, we examined the toxicity of two biomaterials, Polyvinylchloride (PVC) and Polyoximethene (POM), with different selected endpoints. The influence of cell growth on these endpoints was also investigated. Water extracts from the polymeric materials were tested on the continuous cell line L-929. Cell density, total protein, total protein per cell, fraction of cells in G0/G1- or S-phase, the concentration of ATP, ADP and AMP were used as endpoints. The PVC material did not significantly influence any of these endpoints until after 72 hours of exposure and the main part of the toxicity at 72 hours was related to higher proliferation rate in control cultures. After the cells had been incubated for 8 hour with POM the main toxic effect was on the energy parameters. In conclusion the PVC material was less toxic than the POM material. Our results also implies that the choice of endpoint will influence the evaluation of cytotoxicity.

Poly (lactic/glycolic) acid (PLGA) microspheres containing 20% norethisterone (NET) were prepared and the preparation methodology was optimised. The microspheres showed a slow and steady release pattern up to more than 96 hours in 27.5 wt% ethanol solution. In vivo performance of the microspheres indicated that a single intramuscular injection of 80 mg of microspheres could significantly prolong the duration of estrus suppression up to 45 days in rats. In addition, the studies on the stability of microspheres showed that there was no significant change both in the NET content of microspheres and the NET release rate in vitro after storage for one year.

Semifluorinated alkanes are useful for blood-substitutes in two different ways: as co-surfactant to stabilize emulsions with perfluorocarbons as oxygen-carrier and as oxygen-carrier instead of perfluorocarbons. Semifluorinated alkanes act as co-surfactants in low concentrations because they are enriched at the interface perfluorodecalin/water. Emulsions with semifluorinated alkanes dissolve about the same amount of oxygen as emulsions with perfluorocarbons. The stability of these emulsions depends on the nature of the alkyl and the perfluoroalkyl chain. Semifluorinated alkanes do not eliminate hydrogen fluoride under clean-up conditions of perfluorocarbons. According to toxicity tests against human carcinoma cells semifluorinated alkanes with alkyl chains are harmless in the examined range from C6 to C10.

Rifamycin oxidase from Curvularia lunata var. aeria was immobilized on kappa-carrageenan gel where the enzyme showed excellent catalyzing activity and operational stability. Factors affecting the activity of immobilized enzyme preparation such as pH and temperature were investigated. Thermostability of the immobilized enzyme preparation was checked at 30 and 40 degrees C and it was found that the thermostability of the immobilized rifamycin oxidase activity has increased compared to free enzyme. Transformation of rifamycin B to rifamycin S was also carried out with the immobilized enzyme preparation. Kappa-carrageenan immobilized rifamycin oxidase was also reused several times for the transformation of rifamycin B to rifamycin S.

We developed improved immobilization conditions which permitted (i) to immobilize neuroblastoma cells (N18) in calcium-alginate gel beads, (ii) to test the function of ionic channels using patch-clamp electrophysiological techniques and (iii) to quantitatively analyze ligand interactions with voltage-dependent sodium channels in neurons inside the beads. These results qualify this immobilization technique for the isolation and/or purification of ligands specific for neuronal cells.