Field deployable technique for 90Sr emergency bioassay.

Rapid bioassay is very important for immediate and near-term consequence management, which includes identifying contaminated individuals and providing necessary medical intervention during a radiological or nuclear emergency. This paper reports the application of a newly developed bioassay technique for (90)Sr in urine on a field deployable instrument, the Triathler. Performance of this field technique for sensitivity, accuracy and repeatability is evaluated against bioassay criteria (ANSI N13.30). This field technique offers the following analytical merits: (1) minimum detectable activity of 121 Bq l(-1) when 20 ml of urine is used; (2) relative bias of 11.1 % and relative precision of 3.2 % at the level of 45 Bq per 20 ml of urine and (3) sample turnaround time of less than 1 h. The technique meets the requirements for emergency bioassay when a committed effective dose of 0.5 Sv is used as the action dose threshold for medical intervention. Sample throughput can be significantly improved if this technique is automated.

Release of chemicals from polyurethane foam in the Même breast implant.

Samples of polyurethane (PU) foam from the Même breast implant were incubated at 37 degrees C in either 0.3-3.0 N sodium hydroxide (NaOH) solutions, normal saline, or methanol. The chemicals released were analyzed by gas chromatography (GC), gas chromatography/mass spectrometry (GC/MS), and Fourier-transform infra-red (FT-IR) spectroscopy. The surfaces of the treated and untreated foam samples were studied by scanning electron microscopy (SEM). The NaOH solutions hydrolysed the foam, releasing toluene diamine (TDA). Incubating the foam in methanol washed out trace quantities of anti-oxidant, 2,4-dimethyl-6-t-butylphenol (DBP). When the foam was incubated in normal saline at 37 degrees C no TDA was detectable but another compound with a mass ion of 173 was detected. Further GC/MS studies confirmed that this compound was polyol, one of the reagents used to manufacture the PU foam. Repeatedly incubating or washing the foam in normal saline or methanol eliminated the release of polyol. SEM studies of the foam samples before and after incubation experiments, showed no evidence of polymer degradation. These findings indicated that polyol was present in the PU foam only as an impurity or residue and did not originate from the breakdown of the foam itself.

Effects of temperature and viscosity on prothrombin times of blood.

Accurate prothrombin time tests are important because they are frequently performed on presurgical patients to evaluate their blood-clotting status. We studied the effect of temperature (27-47 degrees C) on PTs obtained with eight different brands of thromboplastin. We also compared the sensitivities of two types of coagulation timers to changes in blood viscosities between 1 and 16 mPa/s. Viscosities were measured with the Brookfield Digital Viscometer. The MLA Eletra 800 and the BBL fibrometer were used to measure PTs. All eight thromboplastins gave convex curves of PT versus temperature, with optimum values lying between 38 and 39 degrees C. The curves were fitted to 4th-degree polynomials which showed that a mean temperature bias of 2 degrees C can increase PTs. Ortho Brain (7.8% change) was affected the most, while thromboplastin C (4.4% change) was affected the least. Plots of PT versus viscosity showed that the BBL fibrometer, which uses an electromechanical sensor, was more affected by viscosity than the MLA Electra 800, with an optical detector. However, above 8.2 mPa/s, all PTs were significantly elevated. Hence, patients with macroglobulinemia, whose plasma viscosities sometimes exceed 8.2 mPa/s, may have falsely elevated PTs. We conclude that temperature and viscosity are critical factors in the test and significantly contribute to within and between laboratory variations in PT measurements.

Bilirubin removal by the pseudoperoxidase activity of free and immobilized hemoglobin and hemoglobin co-immobilized with glucose oxidase.

We report a process for oxidizing bilirubin. Hemoglobin in the presence of an oxidizing agent can effectively oxidize bilirubin. Hemoglobin can be used either in free form or immobilized. Immobilisation includes microencapsulation, covalent linkage to carriers, intermolecular crosslinking into polyhemoglobin and others. The oxidizing agent can be added in the form of a peroxide. However, no external peroxide is required when hemoglobin is co-immobilized with glucose oxidase. In this case, the oxidation reaction takes place in the presence of glucose which is normally available in the blood stream and the presence of other oxidizing agents becomes unnecessary. In cases where bilirubin is conjugated to large proteins such as albumin, oxidation can be accomplished by using hemoglobin either in free form, adsorbed or bound on a suitable surface. Polyhemoglobin or cross-linked hemoglobins can also be used as oxidation catalysts in this case.

Immobilization and kinetics of lactate dehydrogenase at a rotating nylon disk.

Lactate dehydrogenase (LDH) was covalently attached to an impervious nylon surface by an improved technique. The procedure allowed the kinetics of the rotating enzyme disk reactor to be successfully explored. This enzyme-disk configuration has potential applications in assays for lactic acid or pyruvic acid in fluids of biological importance (e.g., urine). In order to evaluate and understand the physics and chemistry underlying the kinetics of the heterogeneous biocatalyst, a mathematical model based on the von Karman-Levich theories of rotating electrodes, was developed. It applied well to LDH attached to a disk, under variable NADH concentrations and fixed pyruvic acid. The new theory, leads to the conclusion that the apparent Michaelis constant K(m)(app), varies linearly with f(-1/2), where f is the speed of rotation of the disk. Extrapolation of f(-1/2) to zero gives the Michaelis-Menten constant, K(m), corresponding to the diffusion-free behavior. With immobilized LDH, the diffusion-free K(m) for NADH obtained at 25 degrees C, in phosphate buffer (pH 7.5) using the extrapolation method was 84 muM. This value was in good agreement with the previously published value of 87 muM, obtained with LDH attached to the inner surface of a nylon tubing. However, when compared to the K(m) for a free enzyme system, the 84 muM was about nine times larger, indicating an inherent reduction in the activity of the bound LDH. Since, at extrapolated infinite rotation speeds, diffusion effects were assumed eliminated, the drop in the activity was thought to be due to sterric hinderances imposed on the substrate NADH as a result of having LDH bound to another polymer.

Immobilization of enzymes on polypropylene bead surfaces by anhydrous ammonia gaseous plasma technique.

Anhydrous ammonia gaseous plasma technique was used for the surface modification of polypropylene beads. Amino groups were added onto the surfaces of beads by exposing them to ammonia plasma. Through these amino groups covalent immobilization of glucose oxidase and peroxidase were carried out. The total amounts of immobilized glucose oxidase and immobilized peroxidase were found to be 52 and 43 micrograms/cm2, respectively. To assess the stability of enzyme-polypropylene linkage, beads with covalently immobilized glucose oxidase and peroxidase were washed with phosphate buffer. It was found that after the removal of the adsorbed enzymes, the concentration of covalently immobilized enzymes tended to reach a steady state. After additional washing with buffer for 5 to 6 h, 40-55% of the immobilized enzymes were found to be in the active form.