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PubMed2003

The in vitro biocompatibility performance of a 25 mmol/L bicarbonate/10 mmol/L lactate-buffered peritoneal dialysis fluid.

UNLABELLED: The in vitro biocompatibility performance of a 25 mmol/L bicarbonate/10 mmol/L lactate-buffered peritoneal dialysis fluid. BACKGROUND: The biocompatibility profile of a new peritoneal dialysis (PD) solution (Physioneal 35) was determined using a selection of in vitro assay systems. Physioneal 35 is buffered by a combination of 25 mmol/L bicarbonate and 10 mmol/L lactate, thereby providing a solution with a total of 35 mmol/L of alkali to complement the currently available 25 mmol/L bicarbonate and 15 mmol/L lactate combination solution, Physioneal 40. In addition, the new solution contains a calcium concentration of 1.75 mmol/L rather than 1.25 mmol/L present in Physioneal 40. Physioneal 35 and 40 are manufactured in double chamber bag systems that permit separation of glucose from the buffer during sterilization. When the two chambers are mixed just before patient use, the resulting solution has a neutral pH and reduced glucose degradation content. Physioneal 35 was evaluated for its cytotoxicity potential using a murine fibroblast assay, its acute effect on human neutrophil and human peritoneal mesothelial cell function, and its in vitro potential to form advanced glycation end products (AGE). The biocompatibility characteristics of this new formulation were compared with that of a conventional, lactate-based solution and to that of its parent formulation, Physioneal 40. METHODS: Proliferation of murine fibroblasts was determined after exposure to dialysis fluids for 72 hours. Cell viability was assayed by the ability to take up neutral red dye. Human neutrophils were exposed for 15 minutes to dialysis fluids, and their ATP content and phorbol 12-myristate 13-acetate (PMA) stimulated chemiluminescence response was determined as a measure of viability and respiratory burst activity, respectively. Cellular interleukin (IL)-1beta-driven IL-8 synthesis by human mesothelial cells following acute exposure to dialysis fluids was also assessed. Advanced glycation end product formation in the dialysis fluids was measured after 5 and 20 days of incubation with human serum albumin (HSA) as the model protein. RESULTS: In all assays employed, the biocompatibility profile of Physioneal 35 was similar to that of the Physioneal 40 parent formulation. Physioneal 35 showed a significant improvement in biocompatibility performance compared to a pH neutralized conventional lactate-buffered peritoneal dialysis solution in the murine fibroblast assay. In the acute exposure assays, human neutrophil viability and respiratory burst were significantly improved compared with the acidic, conventional solution; however, no statistically significant improvement were seen in mesothelial cells. AGE formation, which is thought to be an important mechanism by which glucose and glucose degradation products cause structural and functional changes of the peritoneal membrane, was significantly lower in Physioneal 35 compared with the conventional dialysis solution. CONCLUSION: The biocompatibility profile of Physioneal 35 was similar to that of the original Physioneal 40 bicarbonate/ lactate-buffered dialysis solution, confirming that differences in both buffer content and calcium concentration do not affect biocompatibility performance. Both bicarbonate/lactate formulations (Physioneal 35 and Physioneal 40) were more biocompatible than a conventional lactate-buffered dialysis solution in this in vitro biocompatibility assessment.

Adenosine Triphosphate↗
PubMed2005

In vitro regulation of single collagen fibril length by buffer compositions and temperature.

An understanding of collagen ultrastructure is very important for designing biopolymers mimicking collagen functions in tissue engineering, or for diagnosing abnormal collagen structure in clinical study. The present study examined formation of a large population of type I collagen single fibrils under different buffer compositions and temperatures. Fibril structures were investigated by dark-field microscopy and atomic force microscopy (AFM). In the phosphate buffered saline (PBS) buffer, the average lengths of single fibrils were 4.8+/-2.2, 5.0+/-1.9 and 9.2+/-5.0 microm for 37 degrees C, 33 degrees C and 29 degrees C, respectively. The differences were significant (P < 0.05) between 37 degrees C and 29 degrees C and between 33 degrees C and 29 degrees C. In the sodium phosphate (SP) buffer, the average lengths of single fibrils were 10.6+/-5.4, 11.1+/-4.5 and 19.6+/-11.7 microm for 37 degrees C, 33 degrees C and 29 degrees C, respectively. Similarly, the differences were significant (P < 0.05) between 37 degrees C and 29 degrees C and between 33 degrees C and 29 degrees C. While at the same temperature, the average lengths of single fibrils differed significantly (P < 0.05) between PBS and SP buffers. Single fibrils formed in SP buffer were found to have greater average length than those formed in PBS buffer.

Biocompatible Materials↗
PubMed2006

[Buffering effects of plaque solid, Streptococcus mutans and glucans].

OBJECTIVE: To investigate the buffer capacity of insoluble plaque mass including bacteria and glucans matrix. METHODS: Plaque samples (starved or incubated 1 h with 10% sucrose), Streptococcus mutans (S. mutans) mass, and insoluble/soluble glucans were titrated with 1 mmol/L HCl. Meanwhile, the density of bacteria was counted and related to buffer capacity. RESULTS: The bacteria density had significant effects on acid buffer capacity in dental plaque, but the effect reduced with consuming sugar. S. mutans mass with no sucrose incubating contributed to the buffer capacity of (0.609 +/- 0.202) mmol/L, and S. mutans mass with 2% sucrose had only the buffer capacity of (0.099 +/- 0.047) mmol/L. In the mean time, glucans had no effect on acid buffering (0.028 - 0.032 mmol/L). CONCLUSIONS: The bacteria including S. mutans may be the main contributor to acid buffering in plaque solid.

Acids↗
PubMed1996

Buffer may be the critical factor in measurement of anti-prothrombin antibody on a gamma-ray-irradiated plate by enzyme-linked immunosorbent assay.

We investigated the influence of different buffers (Tris-buffer and phosphate buffered saline (PBS)/Tween-20 buffer) on anti-prothrombin antibody (aPT) measurement by enzyme-linked immunosorbent assay (ELISA), employing a gamma-ray-irradiated plate. We found considerable discrepancies in aPT positivity between each buffer, and we suggest that the use of Tris-buffer is not suitable for aPT measurement with a gamma-ray-irradiated plate to measure aPT.

Autoantibodies↗
PubMed1998

The effects of different buffers on the oxidation of DNA by thiols and ferric iron.

Because buffers can act as metal ligands, they can effect several reactions necessary for DNA oxidation by ferric iron and thiols, such as iron reduction. Therefore, these reactions were studied in Hepes and phosphate buffers and unbuffered NaCl. Reduction of Fe3+ by dithiothreitol (DTT) and cysteine was observed in either Hepes or NaCl solutions, but not in phosphate buffer. Thiyl radicals were observed in Hepes, but there was much less thiyl radical production in the saline or phosphate solutions. Redox cycling between either DTT or cysteine and Fe3+ also resulted in dioxygen consumption in Hepes buffer. Reduction of Fe3+ and O2 resulted in the formation of an oxidant capable of producing 8-hydroxy-2'-deoxyguanosine (8-OHdG) in calf-thymus DNA. The highest levels of 8-OHdG were detected when DTT or cysteine and Fe3+ were incubated in Hepes, while much less DNA oxidation was detected when the experiment was done in a saline solution, and almost no DNA oxidation occurred in the phosphate buffer. These results demonstrate that the use of different buffers can greatly affect the ability of thiols to promote iron-dependent oxidations.

8-Hydroxy-2'-Deoxyguanosine↗
PubMed2000

Indirect photomeric detection of anions in capillary electrophoresis using dyes as probes and electrolytes buffered with an isoelectric ampholyte.

The use of highly absorbing anionic dyes as probes and isoelectric ampholytes as buffers in background electrolytes (BGEs) combined with the use of a light emitting diode (LED) as a light source has been studied for ultrasensitive indirect photometric detection in capillary electrophoresis (CE). Potential dyes and buffers were evaluated based on characteristics relevant to indirect photometric detection principles, such as the electrophoretic mobility of the probe dye, its solubility and adsorption behaviour, and the isoelectric point and buffering capacity of the ampholytic buffer. Two dyes, tartrazine and naphthol yellow S, and histidine as the ampholytic buffer, were selected for detailed investigation. Purification of the probes was vital to avoid anionic impurities interfering with the detection. For the electrolytes containing a purified probe (0.5 mM) and histidine as the isoelectric buffer (p/ 7.7), hydroxypropylmethyl cellulose (approximately 0.05%) was effective in suppression of the electroosmotic flow (EOF). Analytical method performance characteristics were determined. For both probes, experimentally determined mobilities were generally close to literature values, excellent peak shapes and separation efficiencies of up to 298 000 theoretical plates were obtained, and detection limits were generally at the sub-microM level. For the naphthol yellow S-histidine BGE, linearity and reproducibility were also evaluated, with excellent linearity being observed over a range of 5-500 microM, and reproducibility (relative standard deviation, RSD) less than 1% for migration times and 2-8% for normalised peak areas. The approach developed was applied successfully to several real samples including tap water, mineral waters, and beer.

Anions↗
PubMed2000

DNA and buffers: the hidden danger of complex formation.

The free solution electrophoretic mobility of DNA differs significantly in different buffers, suggesting that DNA-buffer interactions are present in certain buffer systems. Here, capillary and gel electrophoresis data are combined to show that the Tris ions in Tris-acetate-EDTA (TAE) buffers are associated with the DNA helix to approximately the same extent as sodium ions. The borate ions in Tris-borate-EDTA (TBE) buffers interact with DNA to form highly charged DNA-borate complexes, which are stable both in free solution and in polyacrylamide gels. DNA-borate complexes are not observed in agarose gels, because of the competition of the agarose gel fibers for the borate residues. The resulting agarose-borate complexes increase the negative charge of the agarose gel fibers, leading to an increased electroendosmotic flow of the solvent in agarose-TBE gels. The combined results indicate that the buffers in which DNA is studied cannot automatically be assumed to be innocuous.

Acetates↗
PubMed2000

The greater negative charge density of DNA in tris-borate buffers does not enhance DNA condensation by multivalent cations.

As indicated by recent measurements of the electrophoretic free solution mobility, DNA appears to have a greater helical charge density in Tris-borate-EDTA (TBE) buffers than in Tris-acetate-EDTA (TAE) buffers. Since electrostatic forces play a major role in DNA packaging processes, we have investigated the condensation of closed circular plasmid DNA using total intensity and dynamic light scattering in Tris-borate, Tris-acetate, and Tris-cacodylate buffers with cobaltic hexa-amine (III) [Co(NH(3))(3+)(6)]. We find that neither the critical concentration of Co(NH(3))(3+)(6) nor the hydrodynamic radii of the resulting condensates vary significantly in the buffer systems studied here despite the prediction that DNA condensation should occur at significantly lower Co(NH(3))(3+)(6) concentrations in Tris-borate buffers. Assuming a persistence length behavior similar to B-DNA in the presence of multivalent cations, a decrease in the attractive counterion correlation pressure decay length in Tris-borate buffers does not account for our observations. It is possible that the binding of multivalent cations to DNA may hinder borate association with the DNA double helix.

Amines↗
PubMedDate not supplied

The effect of buffers and chelators on the reaction of luminol with Fenton's reagent near neutral pH.

The chemiluminescence of the system luminol +Fe2+ +H2O2 was measured in aqueous buffer at pH 7.2. In veronal (5,5-diethybarbiturate) buffer, the luminescence is strongly quenched by ethanol and mannitol, but only weakly by t-butanol, benzoate and superoxide dismutase (SOD); complexing Fe2+ with 1,20-phenanthroline or 2,2'-dipyridyl causes a decrease of light production that can be partially obviated by the simultaneous addition of SOD. In phosphate buffer, the luminescence is higher than in veronal and it is efficiently quenched by all four OH. quenchers and by SOD. In Tris buffer, no light production is observed as long as the Fe2+ is not complexed. When Fe2+ is complexed by pyrophosphate or phytate, there is a strong chemiluminescence in all three buffers, which is quenched by all four OH. quenchers and by SOD. When Fe2+ is complexed by EDTA or DTPA, very little luminescence is observed. The luminol analogue phthalhydrazide, which was suggested by Merényi and Lind as a reliable OH. detector, can replace luminol only in phosphate buffer, and thus turns out to be very specific indeed for free OH..

Buffers↗
PubMed1993

On the use of dimensionless parameters in acid-base theory. V. Buffers composed of binary mixtures of monovalent weak acids and bases.

A general theory for buffers consisting of one weak acid and one weak base is developed, particular interest being devoted to the special case of doubly weak salts. The pH course as it varies with the acid/base concentration ratio is presented in equations and graphs. The influence of delta pK' = pK'b-pK'a, which can be negative as well as positive, is discussed and visualized in graphs. The buffer capacity is deduced as a function of pH. The buffer range is, at a maximum, 2.67 times that of a monovalent weak protolyte for delta pK' = 2.7 pH units. The buffer capacity curve has two maxima for delta pK' values bigger than 0.77. For negative delta pK' values the buffer capacity curve has only one maximum, and the buffer range is not better than that of a monovalent protolyte. A general equation for the ionic concentrations is deduced, and as a corollary the degree of hydrolysis of the doubly weak salt is obtained as a function of delta pK'. For solutions of this salt, the relation between concentration and pH is elucidated by equations and graphs.

Acids↗
PubMed1998

Synthesis of zwitterionic acrylic acid buffers for isoelectric focusing in immobilized pH gradients.

A range of zwitterionic acrylic acid derivatives, buffering in the neutral and basic pH ranges, have been synthesized by the Mannich reaction of malonic acid, formaldehyde and a secondary amine. These compounds include 2-(4-morpholinomethyl)propenoic acid pK2 7.59 +/- 0.03 (23 degrees C), 2-[bis(2-hydroxyethyl)aminomethyl]propenoic acid pK2 approximately 8.6 (20 degrees C), 2-[bis(2-hydroxypropyl) aminomethyl]propenoic acid PK2 approximately 8.7 (20 degrees C), 2-[N-(2-hydroxyethyl)-N-methylaminomethyl]propenoic acid pK2 9.22+/-0.08 (22 degrees C), 2-[N-ethyl-N-(2hydroxyethyl)aminomethyl]-propenoic acid pK2 approximately 9.6 (20 degrees C), and 2-[4-(2-carboxyprop-2-enyl)piperazinylmethyl]propenoic acid, which has a sigmoidal buffering profile over the pH range 3-10. These zwitterionic acrylic acid buffers were successfully copolymerized with acrylamide to prepare immobilized pH gradients (IPGs) in the neutral to alkaline portion of the pH range. Bovine erythrocyte carbonic anhydrase isozymes were resolved on a pH 5-8 IPG prepared using 2-[4-(2-carboxyprop-2-enyl)piperazinylmethyl]propenoic acid as the immobilized buffer, and horse heart myoglobin was focused on pH 7.1-8.1 and pH 7.5-7.7 IPGs, using 2-(4-morpholinomethyl)propenoic acid as the immobilized buffer. In both cases the pK 9.3 Immobiline compound was used as the strongly basic titrant. These new compounds, besides possessing more hydrophilic residues than the corresponding commercial basic acrylamido buffers (Immobilines), resist hydrolysis at alkaline pH values.

Acrylates↗
PubMed2005

Effect of buffer flow on DNA separation in a microfabricated electrophoresis system.

An adequate buffer reservoir is one essential component of an electrophoresis system, providing current carrying ions and maintaining constant pH. In a microfabricated DNA separation system with on-chip electrodes, the amount of buffer used is limited by the design of the device; the buffer continuity can be easily disturbed by the production of bubbles. Continuously flowing 1 x Tris-borate-EDTA (TBE) buffer over the electrodes at the cathodic end solves both problems. This flow increases the resolution for ssDNA primer separations (21 and 25 bases) to a maximum value of 1.4 within a distance of 1.2 cm, about four times higher than that without flow. Similar improvement has been achieved for dsDNA separation (20 bp ladder; BioRad) at a distance of only 0.4 cm, giving baseline resolution for bands from 20 to 240 bp. We have also investigated the effect of buffer concentration on resolution, and no similar improvement can be obtained by merely increasing the buffer concentration without flow.

Buffers↗
PubMed2006

Origin of peak asymmetry and isotherm nonlinearity in micellar electrokinetic chromatography: variation of peak shape with buffer concentration.

The diffuse fronts and sharp rears of peaks of nitrobenzene (nbz) solubilized at high concentrations in 50 mM SDS and 2.5, 25, and 50 mM sodium tetraborate buffers were modeled in MEKC by measurements of, and fits to, concave upward isotherms, and by numerical solution of the continuity equation. The isotherms varied with buffer concentration, with the smallest limiting slope and largest curvature found for the 50 mM tetraborate buffer. The Brunauer, Emmett, and Teller isotherm described the peak profiles in all buffers, with symmetrical peaks observed at sub- and low-mM levels of nbz, anti-Langmuirian peaks observed at 10-20 mM levels, and aquiline peaks resembling curved noses observed at 20-30 mM levels. The variation of the partition coefficient with nbz and buffer concentrations was shown to result from nonideal thermodynamics. High-buffer concentrations salt out nbz from the mobile phase, as quantified by a mobile-phase activity coefficient related to the Setchenov constant of nbz in sodium tetraborate. The activity coefficient of nbz in SDS micelles was shown to resemble that measured by other researchers for benzene in micelles of sodium octyl sulfate, i.e. it decreases with increasing solute concentration and increases with electrolyte concentration. Many examples from the literature are discussed, in which the variation of the intramicellar activity coefficient with solute mole fraction is consistent with peaks having diffuse fronts and sharp rears.

Buffers↗
PubMed1993

Stability of respiratory syncytial virus antigen due to buffer treatment for direct detection in nasopharyngeal specimens with enzyme immunoassay.

We developed an enzyme immunoassay (direct EIA; Enzygnost RSV[Ag]) for the direct detection of respiratory syncytial virus (RSV) antigen in nasopharyngeal specimens (NPS). The test procedure is the same as our recently described direct EIA for detection of influenza A and B virus antigens in NPS. For practical purposes it is of advantage to differentiate respiratory viruses on the same microtitration plate in the same run. The test shows no limitations by sample consistency, and results are obtained within 4 hr. In contrast to other test systems, sonification is not necessary. This is due to the sample buffer STD. We studied the influence of sample buffer STD on the stability of RSV (strain Long) antigen at different temperatures over a period of 7 days. PBS-BSA-buffer served as control. The treatment and storage of RSV (strain Long) with sample buffer STD at room temperature or at 4 degrees C showed no decrease of antigen detectability. The antigen is very stable in contrast to the storage of RSV (strain Long) in PBS-BSA buffer during the observation period of 7 days. Consequently, when NPS are stored in sample buffer STD, results of direct EIA are independent from the time of transport and temperature within 7 days. Thirty-eight NPS from infants with confirmed RSV infection were investigated. Confirmation was performed by virus isolation (n = 29) or with commercially available enzyme immunoassays or immunofluorescence test (n = 9). The direct EIA showed a specificity of 99.3% (n = 140) and a sensitivity of 95% (n = 38).

Antigens, Viral↗
PubMed1980

Effects of different buffer species on partition coefficients of drugs used in quantitative structure-activity relationships.

A study was conducted in which the same organic solvent, 1-octanol, and different buffer systems were used to obtain intercorrelations among log Pcorr values given by log P (octanol-water) = a log P (octanol-buffer) + b, where a and b are different constants for the different systems used. The range of a was 0.418-1.156 and that of b was -1.962-1.176 for the four buffer systems examined. Only with neutral drugs was the slope (a) close to 1.0 and the intercept (b) close to 0.0 for the three buffer systems studied. For acidic drugs, only 1-octanol-phosphate buffer gave a 1:1 correlation with 1-octanol-water partition coefficients. Acetate and bicarbonate buffer systems gave different correlations. For basic drugs, none of the three systems examined gave a 1:1 correlation with 1-octanol-water partition coefficients.

Buffers↗
PubMed1981

Kinetics of aspirin, salicylic acid, and salicyluric acid following oral administration of aspirin as a tablet and two buffered solutions.

Twelve fasting normal volunteers received three aspirin dosage forms in a single-dose, complete crossover study; the plasma and urine levels of aspirin, salicylic acid, and salicyluric acid were measured for 10 hr. The three dosage forms were an unbuffered tablet, an effervescent solution with 16 mEq of buffer, and an effervescent solution with 34 mEq of buffer. Significant differences in the absorption rate were observed, with the solution having 16 mEQ of buffer being fastest, the solution having 34 mEq of buffer being intermediate, and the tablet being slowest. These differences are attributed to gastric emptying rates and tablet dissolution. Urine pH and renal clearance for all three acid compounds are influenced by the buffer during the first 2 hr following dosing but not later. Area under the curve comparisons suggest that approximately 20% more aspirin reaches the general circulation intact following the tablet but that the total amount of salicylate absorbed is not different. Further studies are required to select the optimal buffer content to provide rapid absorption with minimal sodium dose and urine alkalinization.

Absorption↗
PubMed1984

Comparative aspirin absorption kinetics after administration of sodium- and potassium-containing buffered solutions.

Twelve fasting normal volunteers received three aspirin dosage forms in a single 325-mg dose in a complete crossover study; the plasma aspirin and salicylic acid levels and the urine salicylic acid and salicyluric acid levels were measured over 10 h. The three dosage forms included an unbuffered tablet and two effervescent solutions, one with sodium bicarbonate-citrate buffer and the other with potassium bicarbonate-citrate buffer. A significantly faster absorption rate was observed with the sodium bicarbonate-citrate buffer, when compared with the potassium bicarbonate-citrate buffer and the unbuffered tablets, which were equivalent. These differences were attributed primarily to gastric emptying rate differences. Urine pH and salicylate renal clearance were significantly affected by the single dose of antacid buffer. The area under the curve and urine accumulation comparisons suggested that approximately 25% more aspirin reaches the general circulation intact after administration of the unbuffered tablet than the two solutions, but that the total salicylate absorbed is equivalent for all three dosage forms. This difference in aspirin bioavailability is probably due to the fact that the two buffered solutions are predominantly absorbed through the intestine, in which presystemic hydrolysis occurs, whereas a significant portion of the tablet dose is absorbed through the gastric mucosa.

Adult↗
PubMed1984

Kinetics of aspirin absorption following oral administration of six aqueous solutions with different buffer capacities.

Fifteen volunteers each received two of six aspirin solutions in a balanced incomplete block design. The solutions contained 0, 3, 6, 10, 16, and 34 mEq of sodium bicarbonate-citric acid buffer and 650 mg of aspirin. Plasma aspirin levels were measured in blood samples collected frequently during the first 2.5 h, and the accumulation of aspirin, salicylic acid, and salicyluric acid were measured over 2 and 24 h. The most rapid absorption rates occurred with solutions which contained small quantities of the antacid buffer. The 3- and 6-mEq antacid buffers had mean maximal aspirin concentrations of 17.3 and 17.8 micrograms/mL, respectively. In the absence of the buffering agent, the 650 mg of aspirin failed to dissolve completely and gave a mean maximal plasma concentration of 13.4 micrograms/mL. With 34 mEq of a buffering agent, a delay in the onset of absorption occurred and the presystemic hydrolysis increased. This was probably because more aspirin was emptied into and absorbed from the small intestine with higher concentrations of the buffering agent.

Adult↗