Microencapsulated genetically engineered E. coli cells can efficiently remove urea without any increase in the ammonia levels in the medium. A 100 mg. alginate encapsulated bacteria rapidly reduces urea in a 100 ml. solution. The original urea concentration 100.00 +/- 1.00 mg./dl. fell to 1.55 +/- 0.13 mg./dl. in 30 minutes. There was no increase in the ammonia in the reaction medium. Extrapolated results shows that urea depletion capacity of encapsulated bacteria is sufficient to remove urea during kidney failure. Using single pool model, 40 gm. of encapsulated genetically engineered E. coli can lower urea (100 mg./dl.) in 40 litres of the body water to 1.60 mg./dl. within 30 minutes. Also, 40.00 gm. bacteria can lower ammonia (758.00 microM/l), in 40 litres of body water, to 90.42 microM/l in 20 minutes. Further studies will be required for multi-compartmental models in the physiological conditions.
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.
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 C-10.
Combined use of plasma-exchange and dialysis therapy in 3 different cases of acute renal failure is presented. The first is a case of acute renal failure due to rhabdomyolysis caused by hemlock poisoning. Plasma-exchange was effective in improving the signs of rhabdomyolysis and renal failure. The second is a case of acute renal failure in an IgG-kappa myeloma. After 9 sessions of plasma-exchange, performed simultaneously with CAPD, a significant fall in the plasma and urine light chains levels was obtained. After the recovery of normal renal function, CAPD was prosecuted to remove light chains. The last is a case of acute renal failure in a patient with a mesangiocapillary nephritis and a high level of circulating immune complexes (CIC). He underwent steroid therapy and daily sessions of hemodialysis, followed by plasma-exchange, which permitted a fall of the CIC level, until a normal renal function was achieved. In conclusion, plasma-exchange combined with dialysis, is an useful tool for the management of acute renal failure caused by toxic proteins.
In this study we investigated the fate of microencapsulated hepatocytes following long-term (6 months) transplantation in Gunn rats. Isolated hepatocytes were microencapsulated with a collagen matrix within an alginate-poly L-lysine composite membrane. Isolated, encapsulated hepatocytes (IEH) or free (unencapsulated) isolated hepatocytes were intraperitoneally transplanted into homozygous Gunn rats that exhibit congenital hyperbilirubinemia. Control Gunn rats received empty microcapsules. Total serum bilirubin was measured at weekly intervals for one month post-IEH transplantation, every two weeks for the next month, and monthly thereafter for up to six months. IEH samples were biopsied from the Gunn rats at monthly intervals and analyzed by light and electron microscopy. A significant (p < 0.01) decrease in total serum bilirubin was observed in IEH transplanted animals during the first month of transplantation. Thereafter, total serum bilirubin levels gradually returned to pre-transplantation levels. A mild, transient decrease in total serum bilirubin was seen in animals transplanted with free (unencapsulated) hepatocytes. No decrease in total serum bilirubin levels was seen in the Gunn rats transplanted with control (empty) microcapsules. Transplanted IEH retained its normal ultrastructure for up to one month and intact microcapsules showed no evidence of hepatocyte rejection, at this time. Degenerative changes observed in the IEH beginning at 2 months post-transplantation, suggests that repeated transplantations may be necessary for long-term effectiveness of IEH therapy.
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.
Rat islets encapsulated in the immuno-isolated membrane were transplanted intraperitoneally into 11 streptozotocin induced diabetic mice. The effective rate was 91% while all rejected in the 11 nonencapsulated xenograft group. 4 mice showed complete remission and longest normoglycemic period in those mice was 360 days. The pathological changes of islets of the long-term successful xenograft group were studied and showed atrophy. It proved that the immuno-isolated membrane can protect rejection during xeno-transplantation.
ESA (European Space Agency) decision in 1987 to acquire the capability needed to support man living and working in space, was the trigger for initiating the development of space life support technologies in Europe. The discipline of life support covers basically all the techniques that ensure the biological autonomy of man when isolated from his original biosphere. Biological life support technologies are presently under development at ESA either for their intrinsic ability to better achieve specific tasks than the currently available physico-chemical processes, or because only they can achieve these tasks. Moreover, a global integration of these biotechnologies leads us to the important notion of closed ecological life support system (CELSS). Indeed, a CELSS is the ultimate form of life support system we currently foresee for long-term space missions (over 2 years). Among those biotechnologies, immobilisation processes such as bioencapsulation are considered as potentially potent tools. They are detailed and presented in their life support context as they are currently standing along with their possible future time course in the ESA life support space program.
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.
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.
Methods to encapsulate biological materials are now widely used. Sometimes bioencapsulation is considered as a universal technique conducting to identical results independently on the biological material used. For instance, a similar behavior is frequently waited for different strains of immobilized microorganisms without taking into account substantial differences in its physiological and morphological characteristics. Often interactions with the matrix support are also neglected. Thus, some concepts developed throughout all these years working in bioencapsulation merits to be revisited.
Ammonia plasma generated by electrical discharge at low pressure was employed for the surface modification of PTFE and ePTFE. A new chemistry at the plasma treated surfaces is reported. X-ray photoelectron spectroscopy studies showed the incorporation of C-N, C-O, C = O etc functional groups on the plasma treated surfaces. Human endothelial cells derived from umbilical veins (HUEC) were used to seed the plasma treated PTFE and ePTFE surfaces to assess the attachment and growth. Enhanced attachment and growth of HUEC was observed on the plasma treated surfaces. In addition, the performance of these surfaces in this respect was found to be considerably superior to human collagen or human fibronectin or collagen-fibronectin coated PTFE. HUEC attachment and growth on these plasma treated surfaces was further enhanced by immobilizing collagen or fibronectin or collagen-fibronectin. Ammonia plasma treated and untreated ePTFE vascular graft samples were seeded with 3.6 X 10(4) cells/sample. At 24 hrs after seeding, HUEC cell attachment was studied. Although, HUEC attachment on collagen or fibronectin coated ePTFE was improved, but there was no significant difference between the number of cells attached to these surfaces when compared with those adhered to plasma treated ePTFE without collagen or fibronectin coating. Collagen or fibronectin coated plasma treated surfaces showed better performance over their respective controls.
After first adventurous attempts to apply perfusion techniques to the treatment of liver diseases, more extensive experiences have been acquired in the last twenty years, not only in acute hepatic failure but also in some chronic liver diseases (mainly in CAH:chronic active hepatitis, and in primary biliary cirrhosis) and in a severe complication of them, that is cryoglobulinemia. Some experiences on this field that are found in literature, using both plasma exchange and hemoperfusion, are reviewed and some personal data are reported: 15 patients with acute viral liver failure (survival rate: 33%) and 5 patients with a CAH-linked (3 viral and 2 autoimmune) cryoglobulinemia, in whom a good control of the disease parameters was obtained.
Liposomes represent for amphotericin B (AmB) a promising delivery system that may reduce the important toxicity of the drug. Liposomal AmB has a higher therapeutic index than AmB alone and allows to use larger doses, The mechanism of reduced toxicity may be related to a better targeting ability, a protective effect, and a selective transfer of liposomes. Anyway the liposomes intercalated AmB tends to be uptaken by organs that belong to the reticuloendothelial system, where fungi, the target cells, are localized.
In this work a new type of polyelectrolyte complex capsules is introduced as an artificial housing for liver cells. Male Wistar rat hepatocytes were encapsulated using cellulose sulphate and polydimethyldiallylammonium chlorid as polyelectrolytes. Amino acid metabolism rate and urea synthesis of the cells increased over the investigation period in contrast to the decrease observed in control monolayer cultures. The encapsulated cells were morphologically characterized. The described procedure represents a sufficient method for the cultivation of living cells in mechanically stable semipermeable microcapsules.
In summary the therapeutic use of affinity chromatography, the immunapheresis with LDL-Therasorb columns, Baxter, has been shown to be a safe, specific and efficacious extracorporeal treatment. Following GMP rules LDL-Therasorb is produced in a constant quality. Beyond the treatment of hypercholesterolemia the versatility of antibodies opens this technology to the treatment of other diseases.
One of the criteria for the Dental Restorative Material is to not to evoke sensitization reaction when used clinically. The newly synthesized BIS-GMA based Chitra's Dental Material intended for such application was tested for skin sensitization as per the international protocol of test i.e. skin Maximization test in G. Pig. Result of this test showed conclusively that the material is devoid of sensitization potential and fit for clinical application.
"Bioencapsulation Research GROUP and its Activities." Biomaterials, Artificial Cells and Immobilization Biotechnology, 21(3), p. vii
