The immobilization of urease using liquid-surfactant membranes

Nonisothermal bioreactors in the treatment of vegetation waters from olive oil: laccase versus syringic acid as bioremediation model

Laccase from Trametes versicolor was immobilized by diazotization on a nylon membrane grafted with glycidil methacrylate, using phenylenediamine as spacer and coupling agent. The behavior of these enzyme derivatives was studied under isothermal and nonisothermal conditions by using syringic acid as substrate, in view of the employment of these membranes in processes of detoxification of vegetation waters from olive oil mills. The pH and temperature dependence of catalytic activity under isothermal conditions has shown that these membranes can be usefully employed under extreme pH and temperatures. When employed under nonisothermal conditions, the membranes exhibited an increase of catalytic activity linearly proportional to the applied transmembrane temperature difference. Percentage activity increases ranging from 62% to 18% were found in the range of syringic acid concentration from 0.02 to 0.8 mM, when a difference of 1 degrees C was applied across the catalytic membrane. Because the percentage activity increase is strictly related to the reduction of the production times, the technology of nonisothermal bioreactors has been demonstrated to be an useful tool also in the treatment of vegetation waters from olive oil mills.

Preparation and evaluation of w/o/w type emulsions containing vancomycin

The objective of this contribution is to summarize the preparation and application of water-in-oil-in-water type multiple emulsions (w/o/w emulsions) entrapping vancomycin (VCM). Formulations of the emulsions (the composition of an oily phase or the type and concentrations of surfactants) and emulsification methods (a stirring method and a membrane method) or conditions (rotation rates, pore sizes of membrane or operation pressures) were evaluated in order to prepare stable w/o/w emulsions. The pharmaceutical properties of the w/o/w emulsions - particle sizes, viscosity, phase separation and drug entrapment efficiency were measured and evaluated. We prepared stable w/o/w emulsions with a particle size of about 3 micrometer and an entrapment efficiency of VCM of about 70%. When this emulsion was administered intravenously to rats, plasma concentrations of VCM were prolonged compared to the VCM solution alone. The results of this study show the potential of the w/o/w emulsions for several clinical applications as one of the drug delivery systems.

Artificial cells with emphasis on bioencapsulation in biotechnology

The most common use of artificial cells is for bioencapsulation of biologically active materials. Each artificial cell can contain combinations of materials. The permeability, composition and shape of an artificial cell membrane can be varied using different types of synthetic or biological materials. These possible variations in contents and membranes allow for large variations in the properties and functions of artificial cells. Artificial cells containing adsorbents have been a routine form of treatment in hemoperfusion for patients. This includes acute poisoning, high blood aluminum and iron, and supplement to dialysis in kidney failure. Artificial red blood cell substitutes based on modified hemoglobin are already in Phase I and Phase II clinical trials in patients. Artificial cell encapsulated cell cultures are being studied for the treatment of diabetes, liver failure, gene therapy and other conditions. Research on artificial cells containing enzymes includes their use for treatment in hereditary enzyme deficiency diseases and other diseases. Recent demonstration of extensive enterorecirculation of amino acids in the intestine has allowed oral administration to deplete specific amino acids. One example is phenylketonuria, an inborn error or metabolism resulting in high systemic phenylalanine levels. Preliminary clinical studies in patients using bioencapsulation of cells or enzymes have started. Artificial cells containing complex enzyme systems convert wastes like urea and ammonia into essential amino acids. Artificial cells are being used for the production of monoclonal antibodies, interferon and other biotechnological products. Other areas of biotechnological uses include drug delivery, and other areas of biotechnology, chemical engineering and medicine.

Multiple emulsions for the delivery of proteins

Multiple emulsions are unique in that a true liquid phase is maintained separate from an external aqueous phase. This may be especially important for bioactive molecules that cannot be appropriately stabilized in the solid state. In addition, the separation of aqueous phases enables highly specialized environments, conducive to protein activity, to be prepared. The physical instability of conventional systems remains a major factor limiting their wider application. Attempts to improve the physical stability of the aqueous dispersions through interfacial complexation and the use of micro-emulsions are improving the short-term stability. As an alternative approach, solid-state emulsions attempt to store the multiple emulsion as a solid. Although solid-state emulsions appear to have the potential to be useful protein delivery systems, a substantial experimental data base has yet to be generated.

Hemoglobin multiple emulsion as an oxygen delivery system

Multiple emulsion technology provides a mechanism for the encapsulation and in vivo delivery of drugs, proteins, and other materials which would otherwise be degraded, cleared rapidly, or toxic to the host. These feasibility studies were performed to evaluate a prototype Hb multiple emulsion as a stable oxygen delivery system. A concentrated solution of hemoglobin (Hb) was encapsulated in the form of a Hb-in-oil-in-water (Hb/O/W) multiple emulsion. Studies using mineral oil demonstrated that Hb multiple emulsions have several important characteristics that are compatible with utility as a blood substitute. These include: satisfactory rheological properties and good hydrodynamic stability compared to whole blood, high encapsulation concentration of Hb and high encapsulation efficiency with little met-hemoglobin generation, and satisfactory oxygen affinity and cooperativity compared to whole blood. Isovolemic exchange transfusions of Hb/O/W multiple emulsion can support life in rats whose hematocrit has been reduced to levels (5% or lower) that are incompatible with survival, and induces no acute toxicity. These results are consistent with the utility of Hb/O/W as an oxygen-carrying red blood cell substitute or organ perfusion media.

Experimental evaluation of the usefulness of equations describing the apparent maximum reaction rate and apparent Michaelis constant of an immobilized enzyme reaction

To determine the usefulness of equations previously proposed for the apparent maximum reaction rate and apparent Michaelis constant of an immobilized enzyme, starch hydrolysis by glucoamylase immobilized on a porous ceramic support was considered as a model system. Initial reaction rates, v0, were measured for a wide range of initial starch concentrations, Sb0, to make a nonlinear plot of Sb0/v0 versus Sb0, and the apparent kinetic parameters were determined from the slopes and intercepts of tangents to the nonlinear plot at given values of Sb0. The equations were found to accurately express the diffusional effect on the kinetic parameters.

Artificial cells in immobilization biotechnology

Artificial cells contain biologically active materials. Artificial cells containing adsorbents have been a routine form of treatment in hemoperfusion for patients. This includes acute poisoning, high blood aluminum and iron, and supplement to dialysis in kidney failure. Artificial cells are being tested for use as red blood cell substitutes. Artificial cells encapsulated cell culture are being tested in animals for the treatment of diabetes and liver failure. A novel 2 step method has prevented xenograft rejection. Artificial cells containing enzymes are being studied for treatment in hereditary enzyme deficiency diseases and other diseases. Recent demonstration of extensive enterorecirculation of amino acids in the intestine has allowed its oral administration to deplete specific amino acids. Artificial cells containing complex enzyme system convert wastes like urea and ammonia into essential amino acids. Artificial cell is being used for the production of monoclonal antibodies, interferons and other biotechnological products. It is also being investigated for drug delivery, and for use in other applications in biotechnology, chemical engineering and medicine.

Artificial cells in medicine and biotechnology

Since the feasibility of artificial cells was first demonstrated in 1957 [Chang (1, 2)], an increasing number of approaches to their preparation and use have become available. Thus artificial cell membranes can now be formed using a variety of synthetic or biological materials to produce desired variations in their permeability, surface properties, and blood compatibility. Almost any material can be included within artificial cells. These include enzyme systems, cell extracts, biological cells, magnetic materials, isotopes, antigens, antibodies, vaccines, hormones, adsorbents, and others. Since cells are the fundamental units of living organisms, it is not surprising that artificial cells can have a number of possible applications. This is especially so since artificial cells can be "tailor-made" to have very specialized functions. A number of potential applications suggested earlier have now reached a developmental stage appropriate for clinical trial or application. These clinical applications include the use of such cells as a red blood cell substitute, in hemoperfusion, in an artificial kidney or artificial liver, as detoxifiers, in an artificial pancreas, and so on. Artificial red blood cells based on lipid-coated fluorocarbon or crosslinked hemoglobin are being investigated in a number of centers. The principle of the artificial cells is also being used in biotechnology to immobilize enzymes and cells. Developments in biotechnology have also resulted in the use of the principle underlying the artificial cell to help produce interferons and monoclonal antibodies; to create immunosorbents; to develop an artificial pancreas; and to bring enzyme technology usefully into biotechnology and biomedical applications. Artificial cells are also being used as drug delivery systems based on slow release, on magnetic target delivery, on biodegradability, on liposomes, or other approaches. The present status and recent advances will be emphasized in this paper.

A newly prepared surface-treated oxystarch for removal of urea

There is an urgent need to develop an efficient technique to remove urea from the blood or gastrointestinal tract of uremic patients. Activated charcoals have a low sorption capacity for urea although they effectively remove other uremic toxic substances. To provide an urea-reactive adsorbent, a chemically modified oxystarch with albumin or gelatin has been prepared. Elemental analysis and Fourier transform infrared (FT-IR) spectroscopic analysis demonstrate that the reaction of a small amount of protein (albumin or gelatin) with oxystarch has taken place possibly by chemical combination. The influence of the dialdehyde content of the oxystarch on urea sorption, its sorption isotherm, and the adsorption rates have been investigated. It was found that the swelling factor of the oxystarch is closely related to the sorption activity under physiological conditions (pH 7.2-7.4 at 37 degrees C). Adsorption studies have shown that sorption capacity is increased by surface treatment and can reach 6-8.2 g urea/kg-dried adsorbent (initial urea concentration was 70 mg/dL). The oxystarch had 49.2% of glucose unit oxidized and was surface treated with albumin. These results suggest that the newly prepared surface-treated oxystarch would be utilized as an effective chemisorbent for urea removal under physiological conditions.