Measurement of hemoglobin A1c (A1C) has long been accepted as the best indicator of glucose control over time. Assays for A1C use technologies based on either charge differences (high-pressure liquid chromatography) or structure (boronate affinity or immunoassay combined with general chemistry). These technologies are generally employed in expensive laboratory instruments. More recently, A1C technology has been incorporated into point of care (POC) devices, allowing for immediate availability of A1C measurements, greatly facilitating diabetes care in both specialist and general practices. POC A1C tests should have acceptable performance, standardization to national reference, National Glycohemoglobin Standardization Program (NGSP) certification, simple operation without need for costly instrumentation, and Clinical Laboratory Improvement Amendments (CLIA) waiver. CLIA-waived POC technology includes Bio-Rad MicroMat II (distributed by Cholestech as GDX) and the Axis-Shield Afinion, both of which utilize boronate affinity. The DCA 2000(R)+ utilizes combined immunoassay and general chemistry. These instruments cost $1000 to $3000 and require regular maintenance, making them appropriate only for high-volume physician offices. The newly improved A1CNow+ also utilizes combined immunoassay and general chemistry, but the small, inexpensive, disposable monitor can be used by patients as well as by health care professionals. The new version of A1CNow+ has improved performance through recent introduction of automated solid state chemistry manufacturing, improved fluidics and automated assembly of the test cartridge, error-correcting software, and unitary meter calibration with factory calibration directly to the NGSP reference standard.

In order to probe the factors which affect the interaction between the surface of a multiphase polyurethane material and blood, a series of butanediol-chain-extended polyetherurethanes was synthesized. These polyurethanes contained different levels of phase separation, produced by systematically varying the hard segment chemical structure by grafting ethyl and octadecyl groups to the urethane nitrogen atom. Surface characterization using high vacuum, air-equilibrated, and water-equilibrated methods was performed. A canine ex vivo arteriovenous series shunt was used to monitor initial platelet and fibrinogen deposition on these polymers. The ex vivo response to these materials, along with contact angle and ESCA surface chemistry, was found to vary with the degree of alkyl derivatization. This study demonstrated that an increase in the degree of phase separation and also the incorporation of long chain (C18) alkyl groups can affect surface properties and improve the short-term blood compatibility of the underivatized polyurethane.

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Despite the use of polyurethanes in a number of blood-contacting applications, little is known about the contributing effects of the various polyurethane components in thrombogenesis. In order to investigate blood-polyurethane interactions, a number of different polyurethanes were examined in an acute canine ex vivo series shunt experiment. Multiprobe surface characterization techniques, including contact angle measurements, ESCA, ATR-IR, and SEM were used to obtain surface property information on the materials studied. The polyurethanes examined included several with different soft segment types, a series of materials with different hard segment diisocyanates and chain extenders, a series consisting of the same polymer cast from different solvents, a zwitterionomer, and a hard segment analog. Two commercial urethanes were also examined, and the effect of methanol extraction on these materials was studied. The blood-contact and surface characterization results indicated that both the surface concentration and type of hard segment were of importance in determining blood response. The relative concentration of hard segment on the polymer surface was found to affect the observed blood-material interaction, although the extent of this effect was found to depend on the hard and soft segment components of the copolymer system. Both the surface properties and thrombogenicity of a particular polyurethane were changed by casting from different solvents, indicating the need to optimize and control fabrication conditions. Methanol extraction was found to improve the thromboresistance of the commercial polyurethanes.

Defined minimal media conditions were used to assess and subsequently enhance the production of subtilisin by genetically characterized Bacillus subtilis strains. Subtilisin production was initiated by the exhaustion or limitation of ammonium in batch and fed-batch cultures. Expression of the subtilisin gene (aprE) was monitored with a chromosomal aprE::lacZ gene fusion. The beta-galactosidase production driven by this fusion reflected subtilisin accumulation in the culture medium. Subtilisin gene expression was temporally extended in sporulation-deficient strains (spoIIG), relative to co-genic sporogenous strains, resulting in enhanced subtilisin production. Ammonium exhaustion not only triggered subtilisin production in asporogenous spoIIG mutants but also shifted carbon metabolism from acetate production to acetate uptake and resulted in the formation of multiple septa in a significant fraction of the cell population. Fed-batch culture techniques, employing the spoIIG strain, were investigated as a means to further extend subtilisin production. The constant provision of ammonium resulted in linear growth, with doubling times of 11 and 36 h in each of two independent experiments. At the lower growth rate, the responses elicited (subtilisin production, glucose metabolism, and morphological changes) during the feeding regime closely approximated the ammonium starvation response, while at the higher growth rate a partial starvation response was observed.