[Show abstract][Hide abstract] ABSTRACT: Background: In our previous study that characterized different human CD4+ lymphocyte preparations, it was found that both commercially available cryopreserved peripheral blood mononuclear cells (PBMC) and a commercially available lyophilized PBMC (Cyto-Trol™) preparation fulfilled a set of criteria for serving as biological calibrators for quantitative flow cytometry. However, the biomarker CD4 protein expression level measured for T helper cells from Cyto-Trol was about 16% lower than those for cryopreserved PBMC and fresh whole blood using flow cytometry and mass cytometry. A primary reason was hypothesized to be due to steric interference in anti- CD4 antibody binding to the smaller sized lyophilized control cells.
[Show abstract][Hide abstract] ABSTRACT: The scientific community has responded to the misidentification of human cell lines with validated methods to authenticate these cells; however, few assays are available for nonhuman cell line identification. We have developed a multiplex polymerase chain reaction assay that targets nine tetranucleotide short tandem repeat (STR) markers in the mouse genome. Unique profiles were obtained from seventy-two mouse samples that were used to determine the allele distribution for each STR marker. Correlations between allele fragment length and repeat number were determined with DNA Sanger sequencing. Genotypes for L929 and NIH3T3 cell lines were shown to be stable with increasing passage numbers as there were no significant differences in fragment length with samples of low passage when compared to high passage samples. In order to detect cell line contaminants, primers for two human STR markers were incorporated into the multiplex assay to facilitate detection of human and African green monkey DNA. This multiplex assay is the first of its kind to provide a unique STR profile for each individual mouse sample and can be used to authenticate mouse cell lines.
[Show abstract][Hide abstract] ABSTRACT: Cancer is a heterogeneous disease characterized by changes in the levels and activities of important cellular proteins, including oncogenes and tumor suppressors. Genetic mutations cause changes in protein activity and protein expression levels that result in the altered metabolism, proliferation, and metastasis seen in cancer cells. The identification of the critical biochemical changes in cancer has led to advances in its detection and treatment. An important example of this is the measurement of human epidermal growth factor receptor 2 (HER2), where increased expression occurs in approximately 20-30% of breast cancer tumors. HER2 is a member of the epidermal growth factor receptor family and is an important biomarker expressed on the cell surface. Measurement of the HER2 levels in tumor cells provides diagnostic, prognostic, and treatment information, because a targeted therapeutic is available. The most common methods to measure HER2 levels are immunohistochemistry and in situ hybridization assays. The accurate and reliable measurements of the specific changes in protein biomarkers for detection and treatment of cancer are important challenges. This review is focused on efforts to improve the quantitation and reliability of cancer biomarkers by using standards and reference materials.
[Show abstract][Hide abstract] ABSTRACT: The ability to detect spore contamination and inactivation is relevant to developing and determining decontamination strategy success for food and water safety. This study was conducted to develop a systematic comparison of nondestructive vibrational spectroscopy techniques (Surface-Enhanced Raman Spectroscopy, SERS, and normal Raman) to determine indicators of Bacillus thuringiensis physiology (spore, vegetative, outgrown, germinated and inactivated spore forms). SERS was found to provide better resolution of commonly utilized signatures of spore physiology (dipicolinic acid at 1006 cm−1 and 1387 cm−1) compared to normal Raman and native fluorescence indigenous to vegetative and outgrown cell samples was quenched in SERS experiment. New features including carotenoid pigments (Raman features at 1142 cm−1, 1512 cm−1) were identified for spore cell forms. Pronounced changes in the low frequency region (300 cm−1 to 500 cm−1) in spore spectra occurred upon germination and inactivation (with both free chlorine and by autoclaving) which is relevant to guiding decontamination and detection strategies using Raman techniques.
European Physical Journal Plus 12/2012; 127(12). DOI:10.1140/epjp/i2012-12151-6 · 1.38 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: To transform the linear fluorescence intensity scale obtained with fluorescent microspheres to an antibody bound per cell (ABC) scale, a biological cell reference material is needed. Optimally, this material should have a reproducible and tight ABC value for the expression of a known clinical reference biomarker. In this study, we characterized commercially available cryopreserved peripheral blood mononuclear cells (PBMCs) and two lyophilized PBMC preparations, Cyto-Trol and PBMC-National Institute for Biological Standard and Control (NIBSC) relative to freshly prepared PBMC and whole blood samples. It was found that the ABC values for CD4 expression on cryopreserved PBMC were consistent with those of freshly obtained PBMC and whole blood samples. By comparison, the ABC value for CD4 expression on Cyto-Trol is lower and the value on PBMC-NIBSC is much lower than those of freshly prepared cell samples using both conventional flow cytometry and CyTOF™ mass cytometry. By performing simultaneous surface and intracellular staining measurements on these two cell samples, we found that both cell membranes are mostly intact. Moreover, CD4(+) cell diameters from both lyophilized cell preparations are smaller than those of PBMC and whole blood. This could result in steric interference in antibody binding to the lyophilized cells. Further investigation of the fixation effect on the detected CD4 expression suggests that the very low ABC value obtained for CD4(+) cells from lyophilized PBMC-NIBSC is largely due to paraformaldehyde fixation; this significantly decreases available antibody binding sites. This study provides confirmation that the results obtained from the newly developed mass cytometry are directly comparable to the results from conventional flow cytometry when both methods are standardized using the same ABC approach.
Cytometry Part A 07/2012; 81(7):567-75. DOI:10.1002/cyto.a.22060 · 2.93 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Bacillus spores are resistant to disinfection methods and they represent a potential threat that requires improved methods to ensure water safety. Bacillus thuringiensis (BT) and B. anthracis Sterne (BA) spores were used to investigate the effectiveness of the electrochemical (EC) disinfection process. We tested the quaternary metal oxide (TiO 2-Sb 2O 5-SnO 2-RuO 2) as the anode material in an EC cell for the inactivation of the spores. The presence of chloride ions at low concentrations was found to be critical for the effective inactivation of BT spores. Active chlorine was produced in-situ by anodic oxidation of chloride in the solutions. Local tap water used as a realistic test solution was found to contain average chloride concentrations of 1.2 mM. High concentrations of active chlorine were generated in the range of 0.35 to 0.5 mM (25 to 35 mg/L) to ensure that the high concentrations of spores were inactivated. We showed that the amount of active chlorine produced in the EC cell can be readily controlled by the operating conditions, including potential, flow rate and chloride content. Scanning electron images of the EC treated spores indicate damage to the outer membranes resulting in disruption and leakage of the spore contents. EC water disinfection processes using inexpensive electrode materials are a promising alternative as shown by inactivation of challenging biological threats such as Bacillus spores.
Water Science & Technology Water Supply 12/2011; 11(6):719. DOI:10.2166/ws.2011.103 · 0.39 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: A discussion on affinity liquid chromatographic systems is presented. In affinity chromatography the ligand, which is capable of reversible binding and specific recognition of the compund to be purified, is attached to the solid chromatographic matrix and packed into a column. The basic components required in affinity liquid chromatography system are pump, injector, detector, recorder and fraction collector.
[Show abstract][Hide abstract] ABSTRACT: Tools for authenticating cell lines are critical for quality control in cell-based biological experiments. Currently there are methods to authenticate human cell lines using short tandem repeat (STR) markers based on the technology and procedures successfully used in the forensic community for human identification, but there are no STR based methods for authenticating nonhuman cell lines to date. There is significant homology between the human and vervet monkey genome and we utilized these similarities to design the first multiplex assay based on human STR markers for vervet cell line identification.
The following STR markers were incorporated into the vervet multiplex PCR assay: D17S1304, D5S1467, D19S245, D1S518, D8S1106, D4S2408, D6S1017, and DYS389. The eight markers were successful in uniquely identifying sixty-two vervet monkey DNA samples and confirmed that Vero76 cells and COS-7 cells were derived from Vero and CV-1 cells, respectively. The multiplex assay shows specificity for vervet DNA within the determined allele range for vervet monkeys; however, the primers will also amplify human DNA for each marker resulting in amplicons outside the vervet allele range in several of the loci. The STR markers showed genetic stability in over sixty-nine passages of Vero cells, suggesting low mutation rates in the targeted STR sequences in the Vero cell line.
A functional vervet multiplex assay consisting of eight human STR markers with heterozygosity values ranging from 0.53-0.79 was successful in uniquely identifying sixty-two vervet monkey samples. The probability of a random match using these eight markers between any two vervet samples is approximately 1 in 1.9 million. While authenticating a vervet cell line, the multiplex assay may also be a useful indicator for human cell line contamination since the assay is based on human STR markers.
[Show abstract][Hide abstract] ABSTRACT: Cardiac troponin I (cTnI) is considered the 'gold standard' cardiac biomarker. However, the result comparability of commercial cTnI immunoassays is still lacking despite the availability of NIST Standard Reference Material, SRM 2921 (human cardiac troponin). To facilitate the standardization of the cTnI immunoassays, a secondary reference material consisting of a panel of three cTnI-positive human serum pools is proposed by the IFCC Working Group on Standardization of Troponin I. The objective of this study is to develop measurement procedures for the characterization of the future secondary reference material using a pooled cTnI-positive serum sample as a development model.
We used magnetic beads coupled with 6 different anti-cTnI monoclonal antibodies that bind specifically to different amino acid sequence regions of the cTnI molecule to immunoprecipitate cTnI proteins from the pooled cTnI-positive serum sample followed by sensitive detection using a fluorescent Western blot.
The degradation of cTnI in the pooled sample was detected and the concentration of cTnI was determined.
We demonstrated the utility of this measurement procedure in support of the development of the proposed secondary cTnI-positive, serum-based reference material.
Clinica chimica acta; international journal of clinical chemistry 01/2011; 412(1-2):107-11. DOI:10.1016/j.cca.2010.09.017 · 2.82 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: In this study, the first steps in the development of a secondary reference measurement procedure (RMP) 'higher metrological order measurement procedure' to support the cardiac troponin I (cTnI) standardization initiative is described. The RMP should be used to assign values to serum-based secondary reference materials (RMs) without analytical artifacts causing bias. A multiplexed bead-based assay and sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE) were used to identify the optimum monoclonal antibody pair (clones 560 and 19C7) for the RMP. Using these antibodies, an ELISA-based procedure was developed to accurately measure the main cTnI forms present in blood. The proposed RMP appears to show no bias when tested on samples containing various troponin complexes, phosphorylated and dephosphorylated forms, and heparin. The candidate assay displayed suitable linearity and sensitivity (limit of detection, 0.052 μg/L) for the measurement of the proposed cTnI secondary RMs. Preliminary comparison data on patient samples with a commercial cTnI assay are also provided to support the suitability of RMP for value assignment to RMs. Full validation and final assessment of the RMP will be performed through transferability and inter-comparison studies.
Clinical Chemistry and Laboratory Medicine 11/2010; 48(11):1603-10. DOI:10.1515/CCLM.2010.316 · 2.71 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Virus reference materials are needed to develop and calibrate detection devices and instruments. We used electrospray differential mobility analysis (ES-DMA) and quantitative amino acid analysis (AAA) to determine the particle concentration of three small model viruses (bacteriophages MS2, PP7, and phiX174). The biological activity, purity, and aggregation of the virus samples were measured using plaque assays, denaturing gel electrophoresis, and size-exclusion chromatography. ES-DMA was developed to count the virus particles using gold nanoparticles as internal standards. ES-DMA additionally provides quantitative measurement of the size and extent of aggregation in the virus samples. Quantitative AAA was also used to determine the mass of the viral proteins in the pure virus samples. The samples were hydrolyzed and the masses of the well-recovered amino acids were used to calculate the equivalent concentration of viral particles in the samples. The concentration of the virus samples determined by ES-DMA was in good agreement with the concentration predicted by AAA for these purified samples. The advantages and limitations of ES-DMA and AAA to characterize virus reference materials are discussed.
Journal of Chromatography A 07/2009; 1216(30):5715-22. DOI:10.1016/j.chroma.2009.05.083 · 4.17 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Cell-based assays for measuring ribosome inhibition by proteins such as the plant toxin ricin are important for characterizing decontamination strategies and developing detection technologies for field use. We report here an assay for ricin that provides a response that is relevant to the mechanism of ricin activity and permits a much faster readout than the commonly used assays for cytotoxicity. The assay relies on the response of an engineered reporter cell line that was produced by stably transfecting Vero cells to express green fluorescent protein (GFP) under the control ofa cytomegalovirus (CMV) promoter. The results of the GFP-based assay were compared with the assay results from three commercially available cytotoxicity assays. The GFP assay reports a sensitive response to ricin after 6 h of treatment while the other assays require a 24-h incubation. Unlike the other assays, monitoring cellular GFP on a per-cell basis allows detection of reduced ribosome activity before significant cell death occurs, and the results are not convoluted by the numbers of cells being assayed.
Assay and Drug Development Technologies 07/2009; 7(4):356-65. DOI:10.1089/adt.2009.192 · 1.53 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Contact with germinant solutions followed by commonly used disinfectants as a means to decontaminate Bacillus spores in a model drinking water system was investigated. Biofilms composed of indigenous water system bacteria were accumulated on materials commonly used for residential plumbing, polyvinyl chloride (PVC), and copper, in a continuously stirred tank reactor for controlled shear. Once the biofilms were established, Bacillus thuringiensis kurstaki or B. anthracis Sterne spores were added to the reactor. Pipe surfaces were studied for biofilm accumulation, spore adhesion, and disinfectant (chlorine and monochloramine) susceptibility before and after germinant (1 mM inosine and 8 mM L-alanine) addition. High disinfectant concentrations (up to 100 mg/L free chlorine and 10 mg/L monochloramine) yielded less than a 2 log(10) reduction in biofilm-associated viable spores after 60 min. A 4 log(10) reduction in the associated spores was observed when coupons were contacted with germinants (24 h) prior to sampling. Germinant contact followed by heat (50 degrees C, 25 min) or disinfection resulted in a greater than 4 log(10) reduction in the associated viable spores. Contact with germinants resulted in dramatically enhanced susceptibility of surface-associated spores to elevated water temperature and disinfectants.
[Show abstract][Hide abstract] ABSTRACT: The objective of this work was to elucidate the disinfectant susceptibility of Bacillus anthracis Sterne (BA) and a commercial preparation of Bacillus thuringiensis (BT) spores associated with a simulated drinking water system. Biofilms composed of indigenous water system bacteria were accumulated on copper and polyvinyl chloride (PVC) pipe material surfaces in a low-flow pipe loop and uniformly mixed tank reactor (CDC biofilm reactor). Application of a distributed shear during spore contact resulted in approximately a 1.0 and 1.6 log10 increase in the number of spores associated with copper and PVC surfaces, respectively. Decontamination of spores in both free suspension and after association with biofilm-conditioned pipe materials was attempted using free chlorine and monochloramine. Associated spores required 5- to 10-fold higher disinfectant concentrations to observe the same reduction of viable spores as in suspension. High disinfectant concentrations (103 mg/L free chlorine and 49 mg/L monochloramine) yielded less than a 2-log10 reduction in viable associated spores after 60 min. Spores associated with biofilms on copper surfaces consistently yielded higher Ct values than PVC.
Water Research 10/2008; 42(20):5011-21. DOI:10.1016/j.watres.2008.09.012 · 5.53 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: It is important to develop rapid and reliable processes to monitor the decontamination of toxins released to the environment. The inactivation of the protein toxin ricin by the disinfectants bleach (sodium hypochlorite) and monochloramine was measured by the effect on mammalian cell cytotoxicity. The effect of the disinfectants on the native fluorescence (due mainly to tryptophan and to a lesser extent tyrosine) of ricin was also measured in parallel. Reactions of the disinfectants resulted in a decrease in the native fluorescence that was measured in real time in a noninvasive manner. We compared the inactivation of two well-characterized model enzymes to the behavior of ricin. The model enzymes studied were lysozyme, a small basic enzyme stabilized with internal disulfide bonds, and heart-muscle-type lactate dehydrogenase (LDH), a large protein composed of four subunits. The biological activities of the model enzymes were measured in parallel with their fluorescence. Gel electrophoresis showed a large number of modifications of the proteins caused by the disinfectants reflected in changes in mobility and the formation of higher-order aggregates. Size-exclusion chromatography showed that the disinfectants did not break down the subunit structure of ricin but instead resulted in an increased size and heterogeneity of the protein. Size-exclusion chromatography of LDH indicated that the subunits were dissociated and that higher-order aggregates were also formed. Bleach caused a rapid inactivation of biological activity correlated with a rapid decrease in the fluorescence. Monochloramine required much higher concentrations for significant effects and the kinetics of the reactions were slow, with half-life values of the decrease on the order of minutes. Each protein showed individual differences in responses to the disinfectants, but there was a consistent correlation between the loss of fluorescence and the decrease in biological activity. These results indicate that the monitoring the fluorescence is a useful process with limitations that can be used to monitor the inactivation of toxins using disinfectants.
[Show abstract][Hide abstract] ABSTRACT: To determine the stability and variability in concentration of spore suspensions of Bacillus anthracis (BA) spore suspensions by comparing different methods of enumeration and to detect changes, if any, under different storage conditions.
Plate and microscope counts were compared to measuring the genomic equivalents based on DNA content BA spore suspensions. We developed chemical methods to extract spore DNA and extra-spore (ES) DNA. DNA mass was determined by gel electrophoresis and QPCR assays were developed using the markers on the chromosome (rpoB) and the pXO1 plasmid (pag). The plate counts and microscope counts were very stable (for up to 900 days). The effect of freezing and the presence of additives in samples were tested for up to 300 days, and the results indicated that the additives tested and freezing did not decrease the viability or microscope counts.
Bacillus anthracis spore suspensions can be stored for long periods of time without significant loss of viability or clumping. The content of ES DNA was variable and changed with time.
The study shows that BA spore suspensions can be developed for reference materials providing a uniform basis for comparing detection equipment and results from different laboratories.
[Show abstract][Hide abstract] ABSTRACT: A recombinant mouse interleukin-4 (IL-4) and three different purified rat antimouse IL-4 monoclonal antibodies (Mab) with different clonalities were employed as a model system. This system was used to examine monoclonal antibody effectiveness using both conventional and high-throughput measurement techniques to select antibodies for attaining the most sensitive detection of the recombinant IL-4 through the "sandwich-type" immunoassays. Surface plasmon resonance (SPR) measurements and two high-throughput methods, suspension arrays (also called multiplexed bead arrays) and forward-phase protein microarrays, predicted the same capture (BVD4-1D11) and detection (BVD6-24G2) antibody pair for the most sensitive detection of the recombinant cytokine. By using this antibody pair, we were able to detect as low as 2 pg/mL of IL-4 in buffer solution and 13.5 pg/mL of IL-4 spiked in 100% normal mouse serum with the multiplexed bead arrays. Due to the large amount of material required for SPR measurements, the study suggests that the multiplexed bead arrays and protein microarrays are both suited for the selection of numerous antibodies against the same analyte of interest to meet the need in the areas of systems biology and reproducible clinical diagnostics for better patient care.
Journal of Proteome Research 01/2008; 6(12):4720-7. DOI:10.1021/pr070535s · 4.25 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: The molar absorption coefficient of ricin in phosphate-buffered saline (PBS) at 279 nm was measured as (93 900 ± 3300) L mol−1 cm−1. The concentration of ricin was determined using amino acid analysis. The absorption spectrum of ricin was interpreted in terms of 69% contribution from absorption by tryptophan residues and 31% contribution from absorption by tyrosine residues. The total dipole strength of the ricin band at 280 nm was determined to be (147 ± 8) D2 and was consistent with the combined dipole strengths of 10 tryptophan ([11.7 ± 1.0] D2) and 23 tyrosine ([1.4 ± 0.2] D2) residues. The structure of ricin was used to determine the coupling of the tryptophan residues in ricin. The maximum interaction energy was found to be 424 cm−1/ɛ while the average interaction between any two pairs of tryptophan residues was approximately 18 cm−1/ɛ. In this study, ɛ is the dielectric constant inside the protein. The fluorescence from ricin, excited at 280 nm, was dominated by fluorescence from tryptophan residues suggesting the presence of energy transfer from tyrosine to tryptophan residues. The absorbance and fluorescence of ricin increased slightly when ricin was denatured in a high concentration of guanidine. Irreversible thermal unfolding of ricin occurred between 65°C and 70°C.
(D = 3.3364*10−30 Cm, not SI unit, convenient unit for the magnitude of the electric dipole moment of molecules.)
Photochemistry and Photobiology 09/2007; 83(5):1149-56. DOI:10.1111/j.1751-1097.2007.00091.x · 2.27 Impact Factor