A novel assay for monoacylglycerol hydrolysis suitable for high-throughput screening

A simple assay for monoacylglycerol hydrolysis suitable for high-throughput screening is described. The assay uses [(3)H]2-oleoylglycerol as substrate, with the tritium label in the glycerol part of the molecule and the use of phenyl sepharose gel to separate the hydrolyzed product ([(3)H]glycerol) from substrate. Using cytosolic fractions derived from rat cerebella as a source of hydrolytic activity, the assay gives the appropriate pH profile and sensitivity to inhibition with compounds known to inhibit hydrolysis of this substrate. The assay could also be adapted to a 96-well plate format, using C6 cells as the source of hydrolytic activity. Thus the assay is simple and appropriate for high-throughput screening of inhibitors of monoacylglycerol hydrolysis.     

Identification of new cytokine combinations for antigen-specific T-cell therapy products via a high-throughput multi-parameter assay

Infusion of viral-specific T cells (VSTs) is an effective treatment for viral infection after stem cell transplant. Current manufacturing approaches are rapid, but growth conditions can still be further improved. To optimize VST cell products, the authors designed a high-throughput flow cytometry-based assay using 40 cytokine combinations in a 96-well plate to fully characterize T-cell viability, function, growth and differentiation. Peripheral blood mononuclear cells (PBMCs) from six consenting donors were seeded at 100 000 cells per well with pools of cytomegalovirus peptides from IE1 and pp65 and combinations of IL-15, IL-6, IL-21, interferon alpha, IL-12, IL-18, IL-4 and IL-7. Ten-day cultures were tested by 13-color flow cytometry to evaluate viable cell count, lymphocyte phenotype, memory markers and interferon gamma (IFNγ) and tumor necrosis factor alpha (TNFα) expression. Combinations of IL-15/IL-6 and IL-4/IL-7 were optimal for the expansion of viral-specific CD3+ T cells, (18-fold and 14-fold, respectively, compared with unstimulated controls). CD8+ T cells expanded 24-fold in IL-15/IL-6 and 9-fold in IL-4/IL-7 cultures (P < 0.0001). CD4+ T cells expanded 27-fold in IL-4/IL-7 and 15-fold in IL-15/IL-6 (P < 0.0001). CD45RO+ CCR7– effector memory (CD45RO+ CCR7– CD3+), central memory (CD45RO+ CCR7+ CD3+), terminal effector (CD45RO– CCR7– CD3+), and naive (CD45RO– CCR7+ CD3+). T cells were the preponderant cells (76.8% and 72.3% in IL-15/IL-6 and IL-15/IL-7 cultures, respectively). Cells cultured in both cytokine conditions were potent, with 19.4% of CD3+ cells cultured in IL-15/IL-6 producing IFNγ (7.6% producing both TNFα and IFNγ) and 18.5% of CD3+ cells grown in IL-4/IL-7 producing IFNγ (9% producing both TNFα and IFNγ). This study shows the utility of this single-plate assay to rapidly identify optimal growth conditions for VST manufacture using only 10⁷ PBMCs.     

核黄素工业菌株高通量筛选方法的建立和应用

枯草芽孢杆菌是主要的核黄素工业生产菌之一,高通量筛选技术是选育获得高产核黄素菌株的关键环节。为实现工业菌种选育与高通量筛选技术相结合,对流式细胞分选、液滴微流控分选和96孔板筛选在核黄素工业菌株筛选中的应用进行了研究,并对96孔板筛选方法进行了优化。在流式细胞分析中,来源于同一株工业菌的低产菌株P1与高产菌株R1的细胞荧光与核黄素产量不成正相关。在液滴微流控分析中,P1和R1的发酵液上清荧光与核黄素产量成正相关,然而液滴分选后活细胞的数量很少。在96孔板筛选实验中,振荡培养后P1和R1的发酵液荧光分别为22 264 a.u.、28 647 a.u.;静置培养后荧光分别为7 095 a.u.、10 189 a.u.,核黄素产量与荧光成正相关,且二者荧光差异显著。利用96孔板静置培养的方法对工业菌株S1的突变体库进行筛选,得到的优选菌株核黄素产量为2.53 g/L,相比S1提高了15%。这些结果表明96孔板静置培养-荧光检测筛选可以应用于核黄素工业生产菌产量的提高。     

Fluorinert, an oxygen carrier, improves cell culture performance in deep square 96-well plates by facilitating oxygen transfer

In bioprocess development, the 96-well plate format has been widely used for high-throughput screening of production cell line or culture conditions. However, suspension cell cultures in conventional 96-well plates often fail to reach high cell density under normal agitation presumably due to constraints in oxygen transfer. Although more vigorous agitation can improve gas transfer in 96-well plate format, it often requires specialized instruments. In this report, we employed Fluorinert, a biologically inert perfluorocarbon, to improve oxygen transfer in 96-well plate and to enable the growth of a Chinese Hamster Ovary cell line expressing a recombinant monoclonal antibody. When different amounts of Fluorinert were added to the cell culture medium, a dose-dependent improvement in cell growth was observed in both conventional and deep square 96-well plates. When sufficient Fluorinert was present in the culture, the cell growth rate, the peak cell density, and recombinant protein production levels achieved in deep square 96-wells were comparable to cultures in ventilated shake flasks. Although Fluorinert is known to dissolve gases such as oxygen and CO(2), it does not dissolve nor extract medium components, such as glucose, lactate, or amino acids. We conclude that mixing Fluorinert with culture media is a suitable model for miniaturization of cell line development and process optimization. Proper cell growth and cellular productivity can be obtained with a standard shaker without the need for any additional aeration or vigorous agitation.     

An automated method for DNA preparation from thousands of YAC clones.

We describe an automated method for the preparation of yeast genomic DNA capable of preparing thousands of DNAs in parallel from a YAC library. Briefly, the protocol involves four steps: (1) Yeast clones are grown in the wells of 96-well microtiter plates with filter (rather than plastic) well-bottoms, which are embedded in solid growth media; (2) These yeast cultures are resuspended and their concentrations determined by optical density measurement; (3) Equal numbers of cells from each well are embedded in low-melting temperature agarose blocks in fresh 96-well plates, again with filter bottoms; and (4) DNA is prepared in the agarose blocks by a protocol similar to that used for preparing DNA for pulsed-field gels, with the reagents being dialyzed through the (filter) bottoms of the microtiter plate. The DNA produced by this method is suitable for pulsed-field gel electrophoresis, for restriction enzyme digestion, and for the polymerase chain reaction (PCR). Using this protocol, we produced 3000 YAC strain DNAs in three weeks. This automated procedure should be extremely useful in many genomic mapping projects.     

Nonradioactive assay of FLAG-tagged MAPK using ANTI-FLAG antibody-coated multiwell plates

We have developed a rapid, sensitive, and quantitative 96-well microplate-based nonradioactive immunoprecipitation/kinase assay to evaluate mitogen-activated protein kinase (MAPK) activity. Three quantitative nonradioactive imunoprecipitation/kinase assays of MAPK were demonstrated on a 96-well microplate coated with ANTI-FLAG M2 antibody (ANTI-FLAG M2 plate): (i) the capture of phosphorylated FLAG-tagged MAPK fusion protein (FLAG-MAPK) from phorbol esters-stimulated, FLAG-MAPK-transfected COS-7 cells, coupled with a very sensitive ELISA procedure to quantitate the level of phosphorylation of FLAG-MAPK; (ii) the in vitro kinase reaction of FLAG-MAPK activity with a substrate and ATP in the same well used to captured the phosphorylated FLAG-MAPK; and (iii) the in vitro kinase reaction of captured non-activated FLAG-MAPK by its upstream kinase from phorbol 12-myristate 13-acetate (PMA)-stimulated COS-7 cells. These results demonstrate that the ANTI-FLAG M2 plate allows for the rapid and quantitative determination of phosphorylation of FLAG-MAPK directly from stimulated, transfected cell lysate. Captured, phosphorylated FLAG-MAPK retains catalytic activity as demonstrated by the phosphorylation of Elk-1 in the same well. Furthermore, phosphorylation of captured FLAG-MAPK by the upstream kinases can be observed directly on the plate. These assays are sensitive, specific, and suitable for handling multiple samples. Thus, the ANTI-FLAG M2 plate forms the basis of a high-throughput screening platform in kinase analysis.     

A cost-effective,simple and high-throughput method for DNA extraction from insects

Abstract We present a high-throughput cost-effective method to extract DNA suitable for polymerase chain reaction (PCR) from insect tissue. The method uses standard 200 μL-deep 96-well plates in which samples are ground, digested and subsequently purified. The test extraction using four different insect species and controlling for potential contamination showed that the method yields good-quantity and quality DNA. PCR with mitochondrial and nuclear primers was reliable. The proposed extraction protocol combines the speed of commercial 96-well plate methods with the economies associated with readily available and cheap laboratory chemicals, consumables and equipment. Therefore, this method is particularly suitable for low-budget research projects and for laboratories with only basic equipment present.     

A magnetic bead-based protein kinase assay with dual detection techniques

A novel magnetic bead-based protein kinase assay was developed using MALDI-TOF mass spectrometry (MALDI-TOF MS) and immunochemifluorescence as two independent detection techniques. Abltide substrate was immobilized onto magnetic beads via noncovalent biotin–streptavidin interactions. This noncovalent immobilization strategy facilitated peptide release and allowed MALDI-TOF MS analysis of substrate phosphorylation. The use of magnetic beads provided rapid sample handling and allowed secondary analysis by immunochemifluorescence to determine the degree of substrate phosphorylation. This dual detection technique was used to evaluate the inhibition of c-Abl kinase by imatinib and dasatinib. For each inhibitor, IC₅₀ (half-maximal inhibitory concentration) values determined by these two different detection methods were consistent and close to values reported in the literature. The high-throughput potential of this new approach to kinase assays was preliminarily demonstrated by screening a chemical library consisting of 31 compounds against c-Abl kinase using a 96-well plate. In this proof-of-principle experiment, both MALDI-TOF MS and immunochemifluorescence were able to compare inhibitor potencies with consistent values. Dual detection may significantly enhance the reliability of chemical library screening and identify false positives and negatives. Formatted for 96-well plates and with high-throughput potential, this dual detection kinase assay may provide a rapid, reliable, and inexpensive route to the discovery of small-molecule drug leads.     

DEVDase detection in intact apoptotic cells using the cell permeant fluorogenic substrate, (z-DEVD)2-cresyl violet

Using a bisubstituted caspase-3 target sequence: aspartate-glutamate-valine-aspartate, (z-DEVD)2 peptide derivative of the fluorophore, cresyl violet, we have obtained a cell permeant, fluorogenic, caspase substrate capable of detecting the site-specific presence of functionally active, caspase-3 and caspase-7 up-regulation within intact apoptotic cells. Addition of this substrate to induced and noninduced cell culture populations allows for the rapid site-specific detection of caspase up-regulation without the requirement for a wash step. We demonstrate here the use of (z-DEVD)2-cresyl violet substrate for the detection of apoptosis induction in Jurkat, THP-1, and MCF-7 cells using fluorescence microscopy and 96-well fluorescence plate reader analysis. Intracellular up-regulated DEVDase activity, which was clearly visible by fluorescence microscopy and 96-well fluorescence plate reader measurements, showed greater than 6-fold increases in fluorescence output in induced versus noninduced Jurkat cell samples. A simple fluorogenic substrate conversion method is demonstrated here for detecting apoptosis induction within intact living cells.     

High-throughput plasmid mini preparations facilitated by micro-mixing.

We have developed a reliable high-throughput plasmid isolation system using a 96-well plate format. This system combines a novel glass bead micro-mixing method with modified alkaline lysis and Sephacryl S-500 DNA purification procedures. Mechanical forces generated by vortexing glass beads inside each well of the 96-well plates ensure that the bacterial pellets are homogeneously resuspended, the cells are completely lyzed, and the resulting bacterial lysates are thoroughly mixed with the potassium acetate solution. The vortexing speed and duration for glass bead mixing have been standardized to facilitate plasmid DNA yields without significant adjustments.     

Monoclonal antibodies to pregnanediol-3-glucuronide: application to a direct enzyme-linked immunosorbent assay of urine

Monoclonal antibodies to pregnanediol-3-glucuronide were produced and characterized. One of three clones investigated provided antibody suitable for a direct urinary enzyme-linked immunosorbent assay (ELISA). The ELISA uses a pregnanediol-thyroglobulin conjugate adsorbed onto the wells of a standard 96-well microtiter plate. Pregnanediol-3-glucuronide in standards or diluted urine competes with the immobilized steroid for antibody-binding sites. After washing, mouse monoclonal antibody bound to the plate is probed with antimouse immunoglobulin peroxidase. After further washing, o-phenylenediamine substrate is added and, finally, the absorbance is read at 492 nm. The ELISA shows excellent performance and agreement with the previous gas chromatographic method. The ELISA is ideal for aiding the assessment of ovarian function in the routine laboratory.     

A FlashPlate assay for the identification of PARP-1 inhibitors

A novel FlashPlate scintillation proximity assay has been developed for the high-throughput screening (HTS) of large compound libraries to identify inhibitors of poly(ADP-ribose) polymerase-1 (PARP-1), an important enzyme involved in DNA repair. The assay was originally developed for the 96-well FlashPlate but is easily transferred to a 384-well format. Moreover, the authors demonstrate that the assay is sufficiently sensitive to determine accurate IC(50) values and adaptable for kinetic evaluation of lead molecules. The mechanism of action of the assay requires the binding of PARP-1 to a double-stranded DNA oligonucleotide leading to the active enzyme. Using NAD(+) and (3)H-NAD(+) as substrate, activated PARP-1 synthesizes labeled poly(ADP-ribose) chains. Once the reaction is stopped, ADP-ribose polymers are brought into proximity with the pretreated FlashPlate walls, resulting in signal amplification. This signal is then detected by a TopCount scintillation plate reader. The developed assay is a robust and reproducible method of screening for PARP-1 inhibitors that is low maintenance and cost-effective and can easily be automated.     

Comparison of the three optical platforms for measurement of cellular respiration

We compared three optical platforms for measurement of cellular respiration: absolute oxygen consumption rates (OCRs) in hermetically sealed microcuvettes, relative OCRs measured in a 96-well plate with oil seal, and steady-state oxygenation of cells in an open 96-well plate. Using mouse embryonic fibroblasts cell line, the phosphorescent intracellular O₂ probe MitoXpress-Intra, and time-resolved fluorescence reader, we determined algorithms for conversion of relative OCRs and cell oxygenation into absolute OCRs, thereby allowing simple high-throughput measurement of absolute OCR values.     

Combinatory use of cell-free protein expression,limited proteolysis and mass spectrometry for the high-throughput protein domain identification

The structural domains of proteins have often been identified through the use of limited proteolysis. In structural genomics studies, it is necessary to carry this out in a high-throughput manner. Here, we constructed a novel high-throughput system, which consists of cell-free protein expression and one-step affinity purification, followed by limited proteolysis using a unique new method, referred to “on beads method”. All these steps were carried out on 96-well plate formats and completed in two days, even by manual handling. The merits of the new method versus the conventional one are as follows: (1) experimental times are reduced, (2) the sample preparation for limited proteolysis experiments is simplified, and (3) both protein purification and limited digestion can be performed “in situ” on the same sample plate. This preparation method is therefore suitable for highly automated, proteolytic analyses coupled to mass spectrometry techniques at a micro-scale protein expression level. The resulting protease-resistant fragments were analyzed by MALDI-TOF-MS and protein domains of 34 mouse cDNA products were identified with this system.     

Microtiter plate transformation using the LiAc/SS carrier DNA/PEG method

Here, we describe a protocol that has been adapted for the transformation of yeast cells in 96-well microtiter plates. This protocol can be tailored for multiple applications and is suitable for high-throughput applications. It can be completed in 2-3 h, once the yeast cells have been grown depending on the heat shock used.     

Chemiluminometric biochemical induction assay (CBIA) for the detection of DNA-damaging agents

A microbroth chemiluminometric version of the biochemical induction assay (BIA) was developed using a chemiluminescent substrate widely used to detect beta-galactosidase in high-throughput screening (HTS) laboratories. The assay was run in both 96-well and 384-well plate formats using the Zymark RapidPlate liquid handling system to transfer samples and reagents. Chemiluminescence was read using the Victor-2 multilabel counter. The new microbroth chemiluminometric method, the CBIA, allowed rapid screening of samples, crude extracts, and pure compounds for their DNA-damaging effects in bacteria. In screening a small subset of our natural products library samples by the agar plate BIA and the CBIA, the latter yielded a higher hit rate, suggesting it is more sensitive than the agar plate assay. The CBIA was unaffected by the colored samples often encountered during screening of crude natural products extracts.     

Investigation of high-throughput ultrafiltration for the determination of an unbound compound in human plasma using liquid chromatography and tandem mass spectrometry with electrospray ionization

A high-throughput ultrafiltration method with a direct injection assay has been developed to determine unbound concentrations of a high-protein binding compound, an alpha(v)beta(3) bone integrin antagonist (I), in human plasma for a clinical pharmacokinetic study. The 96-well MultiScreen filter plate with Ultracel-PPB membrane was evaluated for the separation of unbound from protein-bound compound I by ultrafiltration. The sample preparation was automated using a Packard MultiPROBE II EX liquid handling system to transfer the plasma samples to the 96-well PPB plate for centrifugation and to prepare ultrafiltrate samples for analysis. Using on-line extraction with a column-switching setup for sample clean-up and separation, the ultrafiltrate samples were directly injected onto a reversed-phase HPLC system and analyzed using a mass spectrometer interfaced with an electrospray ionization (ESI) source in the positive ionization mode (LC/ESI-MS/MS). The performance of the ultrafiltration using Ultracel-PPB 96-well plate for unbound I analysis was evaluated and optimized with respect to sample volume, centrifugation temperature, speed and time, and the relationship of the well positions of the PPB plate versus filtrate volumes and concentrations. The assay intraday accuracy and precision were between 93.9 and 104.8 and <7.3% (CV), respectively. The linear range of the calibration curve for the assay was 0.1-500 ng/mL on a Finnigan TSQ Quantum LC/ESI-MS/MS system. Evaluation and validation of the unbound plasma assay demonstrated it to be rapid, sensitive and reproducible.     

Soluble Interleukin-5 Receptor α-Chain Binding Assays: Use for Screening and Analysis of Interleukin-5 Mutants

Interleukin-5 (IL-5) is a key cytokine for the production, differentiation, and activation of eosinophils. IL-5 is a member of the four helical bundle family of cytokines, and in common with many members of the cytokine family it binds to a heterodimeric receptor composed of a ligand binding α-chain and a signal-transducing β-chain. We have established two receptor/ligand binding assays based on the extracellular domain of the receptor α-chain which we have produced as a fusion protein. One assay is based on scintillation proximity fluoromicrospheres and radiolabeled ligand and the other on detection of biotinylated ligand binding to immobilized receptor using a chemiluminescent substrate in a 96-well microtiter plate format. Both receptor binding assays have been optimized for high throughput screening for receptor antagonists. These assays were also used for analytical purposes and the binding of ligand to the receptor α-chain was compared directly to receptor binding assays performed on TF-1 cells which express the receptor αβ-heterodimer. These three assays have been used to study site-directed mutants of IL-5 to determine the important residues for interaction of the cytokine with each chain of the receptor (P. Graber et al. (1995) J. Biol. Chem. 270, 15762-15769).     

Towards automated production and drug sensitivity testing using scaffold-free spherical tumor microtissues

Although the relevance of three-dimensional (3-D) culture has been recognized for years and exploited at an academic level, its translation to industrial applications has been slow. The development of reliable high-throughput technologies is clearly a prerequisite for the industrial implementation of 3-D models. In this study the robustness of spherical microtissue production and drug testing in a 96-well hanging-drop multiwell plate format was assessed on a standard 96-well channel robotic platform. Microtissue models derived from six different cell lines were produced and characterized according to their growth profile and morphology displaying high-density tissue-like reformation and growth over at least 15 days. The colon cancer cell line HCT116 was chosen as a model to assess microtissue-based assay reproducibility. Within three individual production batches the size variations of the produced microtissues were below 5%. Reliability of the microtissue-based assay was tested using two reference compounds, staurosporine and chlorambucil. In four independent drug testings the calculated IC(50) values were benchmarked against 2-D multiwell testings displaying similar consistency. The technology presented here for the automated production of a variety of microtissues for efficacy testing in a standard 96-well format will aid the implementation of more organotypic models at an early time point in the drug discovery process.