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Biomedical subjects

Jaromir Ruzicka

Publications and source records attributed to Jaromir Ruzicka.

14 recordsLinked to original sources
PubMed2006

Bead injection for biomolecular assays: Affinity chromatography enhanced by bead injection spectroscopy.

Selective capture of target biomolecules by ligands immobilized on a solid support is a cornerstone of two seemingly unrelated techniques: micro-Affinity Chromatography (microAC) and micro-Bead Injection Spectroscopy (microBIS). This work shows, for the first time, how these techniques can be carried out using the same instrument and how the data obtained this way complement each other, yielding complete information on retention and elution of target biomolecules. Biomolecular association and dissociation were investigated by microAC and microBIS, using computer-controlled programmable flow and the same instrument for automated bead transport, packing of a micro-column, assay of the analyte, and bead disposal. The absorbance of the analyte was monitored within the fiber optic flow cell configured either for monitoring directly on the beads or post-column after elution. The separation, binding, and elution of immunoglobulins (human IgG, rabbit IgG, and horse IgG) on protein G-coated Sepharose beads were studied as model systems. The limit of detection of the microAC technique was determined to be 5 ng microL(-1) IgG, and that of the microBIS technique was 50 ng microL(-1) IgG.

Animals↗
PubMed2006

Automated method, based on micro-sequential injection, for the study of enzyme kinetics and inhibition.

A micro-reactor system with continual spectrophotometric detection has been operated in Sequential Injection lab-on-valve (SI-LOV) mode and applied to enzyme kinetics and inhibition studies, using acetylcholinesterase (AChE) and angiotensin-converting enzyme (ACE) as model systems. With the advantages of automation, real-time kinetic measurement, and thorough mixing, the SI-LOV micro-reactor system allows for the monitoring of initial reaction rates and determination of reactant concentrations in the reaction mixture, both of which are essential for the determination of kinetic constants for enzymes and inhibitors. Enzyme, substrate, and inhibitor are precisely metered by the syringe pump and delivered to a stirred micro-reactor, followed by a reference scan that establishes the baseline for the following reaction rate measurement. Michaelis constants (Km) for AChE and ACE were determined to be 0.16 mM and 0.30 mM, respectively, which are consistent with literature values. The type of inhibition (competitive, uncompetitive, or mixed), the dissociation constants for the inhibitors, and the inhibitor dose-response curves were also determined.

Acetylcholinesterase↗
PubMed2005

Atomic absorption spectroscopy for mercury, automated by sequential injection and miniaturized in lab-on-valve system.

Sodium borohydride-based hydride generation was automated by using programmable flow within the lab-on-valve module. Mercury vapor, generated in the reaction mixture, was extracted in a gas/liquid separator. The gas-expansion separator was miniaturized and compared with the performance of a novel gas separator that exploits the combination of Venturi effect and reduced pressure. Cold vapor atomic spectroscopy was used as a model system, with detection of mercury by absorption at 254 nm and limit of detection of 9 microg of Hg/L, using 300 microL of sample and 100 microL of borohydride. This work introduces, for the first time, sequential injection technique for hydride generation, highlights advantages of using programmable flow, and outlines means for miniaturization of assays based on spectroscopy of volatile species.

Journal Article↗
PubMed2004

Accelerated micro-sequential injection in lab-on-valve format, applied to enzymatic assays.

The assay cycle of sequential injection (SI) analysis has been greatly accelerated by simultaneously processing two sample injections within the same manifold. This is achieved through micro-miniaturization of the SI system using the lab-on-valve format (LOV), and by optimizing the assay protocol for stopped-flow reaction rate measurements. The approach has been tested on enzymatic assays of glucose and ethanol, but it is, in principle, applicable to all SI reagent-based assays. The average assay time for a single run has been shortened from 200 s to approximately 30 s. Assays were carried out at 22 degree C and 37 degree C using commercially available reagent kits. For glucose, at 22 degree C, the calibration had a linear response (r(2)= 0.9999) for the concentration range of 100-1000 ppm. At 37 degree C, the calibration was linear (r(2)= 0.9996) for 100-600 ppm glucose, but was a second order polynomial curve (r(2)= 0.9996) for 100-1000 ppm. For ethanol, at both 22 degree C and 37 degree C, the calibrations were linear for the concentration range of 50-250 ppm. The r(2) at two temperatures was 0.9994 and 0.9995, respectively. For both the glucose and ethanol assays, the relative standard deviations were below 3%. Factors affecting sampling frequency are discussed. In this work, sequential injection is shown, for the first time, to achieve sampling frequency comparable to flow injection (FI), while retaining the advantages of small reagent consumption (typically microlitres per assay), minimized waste production, full automation of assay protocols, and zero carryover.

Journal Article↗
PubMed2004

A novel approach for monitoring extracellular acidification rates: based on bead injection spectrophotometry and the lab-on-valve system.

Monitoring extracellular acidification rates (ECARs) is important for the study of cellular activities, since it allows for the evaluation of factors that alter metabolic function, such as stimulants, inhibitors, toxins as well as receptor and non-receptor mediated events. While the light addressable potentiometric sensor (Cytosensor Microphysiometer) has been the principal tool for ECARs measurement in the past, this work introduces a novel method that exploits an immobilized pH indicator on the surface of microcarrier beads (Sephadex) and is probed with a fiber optic coupled spectrophotometer. Likewise, live cells under investigation were also immobilized on microcarrier beads (Cytopore). These beads are metered, transported and monitored within a microfluidic system, termed as the Lab-on-Valve (LOV). Use of carrier beads in conjunction with Bead Injection Spectrophotometry and a Lab-on-Valve module (BIS-LOV), makes ECAR measurements reliable and automated. The feasibility of the BIS-LOV approach is demonstrated measuring ECARs of the mouse hepatocyte cell line, TABX.2S, grown on Cytopore beads packed within the central channel of the LOV system. These immobilized cells were perfused in a phosphate buffer carrier solution (capacity: 1 mmol L(-1), pH 7.4). Protons extruded from 10(5) to 10(6) cells were accumulated during a stopped flow period of 220 s followed by a pH measurement, detected by changes in absorbance of the pH indicator bonded to the microcarrier beads. Addition of metabolic inhibitors (sodium azide, oxamic acid) to the carrier buffer solution can induced an increase or decrease of the basal proton extrusion rate in a very reproducible manner. Comparison of the BIS-LOV technique to the Cytosensor microphysiometer and literature confirms the validity of this novel approach, highlighting its advantages and suggesting future improvements that will make the BIS-LOV a practical tool for routine ECARs measurement.

Animals↗
PubMed2004

On-line flow cytometry for real-time surgical guidance.

OBJECTIVE: This study tests the feasibility of using on-line analysis of tissue during surgical resection of brain tumors to provide biologically relevant information in a clinically relevant time frame to augment surgical decision making. For the purposes of establishing feasibility, we used measurement of deoxyribonucleic acid (DNA) content as the end point for analysis. METHODS: We investigated the feasibility of interfacing an ultrasonic aspiration (USA) system with a flow cytometer (FC) capable of analyzing DNA content (DNA-FC). The sampling system design, tissue preparation requirements, and time requirements for each step of the on-line analysis system were determined using fresh beef brain tissue samples. We also compared DNA-FC measurements in 28 nonneoplastic human brain samples with DNA-FC measurements in specimens of 11 glioma patients obtained from central tumor regions and surgical margins after macroscopically gross total tumor removal to estimate the potential for analysis of a biological marker to influence surgical decision making. RESULTS: With minimal modification, modern FC systems are fully capable of real-time, intraoperative analysis of USA specimens. The total time required for on-line analysis of USA specimens varies between 36 and 63 seconds; this time includes delivery from the tip of the USA to complete analysis of the specimen. Approximately 60% of this time is required for equilibration of the DNA stain. When compared with values for nonneoplastic human brain samples, 50% of samples (10 of 20) from macroscopically normal glioma surgical margins contained DNA-FC abnormalities potentially indicating residual tumor. CONCLUSION: With an interface of existing technologies, DNA content of brain tissue samples can be analyzed in a meaningful time frame that has the potential to provide real-time information for surgical guidance. The identification of DNA content abnormalities in macroscopically normal tumor resection margins by DNA-FC supports the practical potential for on-line analysis of a tumor marker to guide surgical resections. The development of such a device would provide neurosurgeons with an objective method for intraoperative analysis of a clinically relevant biological parameter that can be measured in real time.

Aneuploidy↗
PubMed2003

Micro sequential injection: automated insulin derivatization and separation using a lab-on-valve capillary electrophoresis system.

Automated sampling and fluorogenic derivatization of islet proteins (insulin, proinsulin, c-peptide) are separated and analyzed by a novel lab-on-valve capillary electrophoresis (LOV-CE) system. This fully integrated device is based on a micro sequential injection instrument that uses a lab-on-valve manifold to integrate capillary electrophoresis. The lab-on-valve manifold is used to perform all microfluidic tasks such as sampling, fluorogenic labeling, and CE capillary rejuvenation providing a very reliable system for reproducible CE separations. Fluorescence detection was coupled to an epiluminescence fluorescence microscope using a customized capillary positioning plate. This customized plate incorporated two fused-silica fiber optic probes that allow for simultaneous absorbance and fluorescence detection, extending the utility of this device. Derivatization conditions with respect to the sequence of addition, timing, injection position, and volumes were optimized through iterative series of experiments that are executed automatically by software control. Reproducibility in fluorogenic labeling was tested with repetitive injections of 3.45 mM insulin, yielding 1.3% RSD for peak area, 0.5% RSD for electromigration time, and 2.8% RSD for peak height. Fluorescence detection demonstrated a linear dynamic range of 3.43 to 6.87 microM for insulin (r2 = 0.99999), 0.39 to 1.96 pM for proinsulin (r2 = 0.99195) and 260 to 781 nM for c-peptide (r2 = 0.99983). By including hydrodynamic flushing immediately after the detection of the last analyte, the sampling frequency for islet protein analysis was increased. Finally, an in vitro insulin assay using rat pancreatic islet excretions was tested using this lab-on-valve capillary electrophoresis system.

Autoanalysis↗
PubMed2003

Bead injection ELISA for the determination of antibodies implicated in type 1 diabetes mellitus.

This work introduces a novel analytical method for the detection and study of GAD65 autoantibodies, which have been implicated in the onset of type 1 diabetes. There is a clinical need for a rapid and automated assay for GAD65 autoantibodies. Therefore, this method was designed to exploit the advantages of bead injection (BI) analysis for enzyme-linked immunosorbent assays (ELISA). BI ELISA is a microscale technique that uses enzyme labeled secondary antibodies to detect the capture of target antibodies on immobilized antigen in the flow cell of the lab-on-valve (LOV) manifold. A detection limit of 20 ng mL(-1) of GAD65 monoclonal antibody 144 compares favorably with the sensitivity and precision of a standard ELISA currently employed to detect GAD65 autoantibodies. Compared to the standard ELISA protocol, BI ELISA offers a significantly reduced assay time and complete automation of solution handling and detection.

Autoanalysis↗
PubMed2002

Microsequential injection: anion separations using 'lab-on-valve' coupled with capillary electrophoresis.

Microsequential injection (microSI) has been successfully coupled with capillary electrophoresis (CE). Presented is the microSI-CE system, interfaced with an integrated Lab-on-Valve (LOV) manifold that provides an efficient sample delivery conduit and a versatile means of sample pretreatment along with total automation of the separation process. Programmable microSI protocols control all critical system peripherals to perform various types of CE sample injections automatically such as electrokinetic (EK) injection, hydrodynamic (HD) injection, and head column field amplification (HCFA) sample stacking injection. Novel features of the microSI-CE technique are demonstrated on assays of samples containing 10 anions that had been used previously as a model system. Calibration studies by EK sample injection yielded linear concentration ranges of 0.5-3.0 mM with linear regression responses of r2 = 0.9999 for both chloride and sulfate using conductivity corrected peak area (CCPA) as concentration responses. Calibration using an internal standard was studied at the same concentration range giving r2 = 0.9992 for both chloride and sulfate and r2 = 0.9997 for both when CCPA correction was deployed. With HCFA sample stacking injection, a linear concentration dynamic range of 0.034-3.419 mM for chloride and 0.014-1.408 mM for sulfate were produced with linear regression responses of r2 = 0.9999 for chloride and r2 = 0.9998 for sulfate.

Anions↗
PubMed2002

Label dilution method: a novel tool for bioligand interaction studies using bead injection in the lab-on-valve format.

This work introduces a novel method, label dilution, which is analogous to the well-established isotope dilution method. The principle is tested on a model system of commercially available antibodies and protein-coated Sepharose beads and implemented using micro-bead injection in the lab-on-valve format. This micro-scale method uses a labeled form of the target molecule as an internal standard. Label dilution employs ratiometric measurements using the absorbance signals from the label and the target molecules for quantitative determination of an analyte. The label dilution method is shown to discriminate between selective and non-selective binding and provides a means for monitoring bioligand interactions in real time. With a detection limit of 470 ng of IgG, this method provides a sensitive, automated technique for the determination of low-level analytes in complex samples. This technique has been developed with the aim of using it to facilitate diabetes research in which the interactions between autoantibodies and the molecules they target are a central focus.

Autoantibodies↗
PubMed2002

Real-time determination of glucose consumption by live cells using a lab-on-valve system with an integrated microbioreactor.

This paper describes a microquantitative method for glucose determination in situ of living cells in real-time. In this novel technique adherent cells are cultured onto microcarrier beads and packed into a renewable microcolumn within a microsequential injection lab-on-valve system (microSI-LOV). Glucose sensing is performed through the use of a two-step, NAD-linked enzymatic process. The course of the assay is monitored in real-time, by absorbance of NADH at 340 nm. The microsequential assay based on plug/nozzle design has a linear dynamic range for glucose of 0.1 to 5.6 mM. The design of the (microSI-LOV) system allows the assay to be carried out using only 40 microL of the enzyme reagent and 3 microL of sample. The technique was tested on a murine hepatocyte cell line (TABX2S) adhered to Cytopore beads. Rapid cellular glucose consumption, in this technique, is facilitated by a high cell density, which allows a large number of cells (10(4)-10(5)) to be retained in a very small volume (3 microL). In turn, this cell density results in the rapid depletion of glucose from the cell medium over short time periods (< 2 min). In conjunction with the assay development, the plug/nozzle design and its ramifications on mixing in general are presented and discussed.

Animals↗
PubMed2002

Real-time monitoring of lactate extrusion and glucose consumption of cultured cells using a lab-on-valve system.

Microsequential injection (microST) provides microfluidic operations that are ideally suited for cellular function studies and as a means of validating targets for drug discovery. MicroSI carried out within the lab-on-valve (LOV) manifold, is an ideal platform for spectroscopic studies on living cells that are grown on microcarrier beads and kept thermostated while their metabolism is probed in real-time. In this paper a microbioreactor is integrated into the LOV manifold allowing measurement of cellular lactate extrusion and glucose consumption rates of a cell culture that is automatically renewed prior to each measurement. Glucose consumption and lactate extrusion are monitored using NAD-linked enzymatic assays. The microSI-LOV setup has demonstrated a linear analysis range of 0.05-1.00 mM for lactate and 0.1-5.6 mM for glucose. These assays were conducted in a serial fashion requiring 3 microL of cellular perfusate and 10 s for glucose determination and 30 s for the lactate assay. Overall waste generated per lactate/glucose assay is < 200 microL. This work was performed using two different transfected hepatocyte cell lines, which adhere to Cytopore microcarrier beads. This novel approach to metabolic screening allows for the rapid evaluation of the effects of dosing cells with chemical agents.

Animals↗