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Biomedical subjects

Martin B McDonnell

Publications and source records attributed to Martin B McDonnell.

9 recordsLinked to original sources
PubMed2005

Spore and micro-particle capture on an immunosensor surface in an ultrasound standing wave system.

The capture of Bacillus subtilis var. niger spores on an antibody-coated surface can be enhanced when that coated surface acts as an acoustic reflector in a quarter wavelength ultrasonic (3 MHz) standing wave resonator. Immunocapture in such a resonator has been characterised here for both spores and 1 microm diameter biotinylated fluorescent microparticles. A mean spatial acoustic pressure amplitude of 460 kPa and a frequency of 2.82 MHz gave high capture efficiencies. It was shown that capture was critically dependent on reflector thickness. The time dependence of particle deposition on a reflector in a batch system was broadly consistent with a calculated time of 35 s to bring 95% of particles to the coated surface. A suspension flow rate of 0.1 ml/min and a reflector thickness of 1.01 mm gave optimal capture in a 2 min assay. The enhancement of particle detection compared with the control (no ultrasound) situation was x 70. The system detects a total of five particles in 15 fields of view in a 2 min assay when the suspending phase concentration was 10(4) particles/ml. A general expression for the dependence of minimum concentration detectable on; number of fields examined, sample volume flowing through the chamber and assay time shows that, for a practical combination of these variables, the threshold detection concentration can be two orders of magnitude lower.

Bacillus subtilis↗
PubMed2005

Improvement of immunodetection of bacterial spore antigen by ultrasonic cavitation.

Ultrasonic cavitation was employed to enhance sensitivity of bacterial spore immunoassay detection, specifically, enzyme-linked immunosorbent assay (ELISA) and resonant mirror (RM) sensing. Bacillus spore suspensions were exposed to high-power ultrasound in a tubular sonicator operated at 267 kHz in both batch and flow modes. The sonicator was designed to deliver high output power and is in a form that can be cooled efficiently to avoid thermal denaturation of antigen. The 30-s batch and cooled flow (0.3 mL/min) sonication achieved an approximately 20-fold increase in ELISA sensitivity compared to unsonicated spores by ELISA. RM sensing of sonicated spores achieved detection sensitivity of approximately 10(6) spores/mL, whereas unsonicated spores were undetectable at the highest concentration tested. Improvements in detection were associated with antigen released from the spores. Equilibrium temperature increase in the tubular sonicator was limited to 14 K after 30 min and was maintained for 6 h with cooling and flow (0.3 mL/min). The work described here demonstrates the utility of the tubular sonicator for the improvement in the sensitivity of the detection of spores and its suitability as an in-line component of a rapid detection system.

Antigens, Bacterial↗
PubMed2005

An integrated optical leaky waveguide sensor with electrically induced concentration system for the detection of bacteria.

An integrated, sensitive and rapid system was developed for the detection of bacteria. The system combined an optical metal-clad leaky waveguide (MCLW) sensor with an electric field. The electric field was used to concentrate Bacillus subtilis var. niger(BG) bacteria spores onto the immobilized anti-BG antibody on the MCLW sensor surface. This sensor combination has been characterised by detecting the scattering from bacterial spores, which are concentrated at the sensor surface, when they are illuminated at the coupling angle; and by detection of fluorescence from labelled antibodies added after the spores had been captured on the surface. The light scattering and fluorescence detection methods gave a detection limit of BG bacterial spores of 1 x 10(3) spores ml(-1) when the electric field was applied for 3 minutes.

Bacillus subtilis↗
PubMed2005

Optical leaky waveguide sensor for detection of bacteria with ultrasound attractor force.

An integrated, sensitive, and rapid system was developed for the detection of bacteria. The system combined an optical metal-clad leaky waveguide (MCLW) sensor with ultrasound standing waves (USW). The performance of a MCLW sensor for the detection of bacteria has been increased (>100 fold) by using USWs to drive bacteria onto the sensor surface. By forming the USW nodes at or within the surface of the MCLW, the diffusion-limited capture rate has been replaced by fast movement. Immobilized anti-BG antibody on the MCLW sensor surface was used to capture Bacillus subtilis var. niger (BG) bacterial spores driven to the surface. This combination of sensor and attractor force combination has been tested by detecting the evanescent scattering from bacterial spores at the sensor surface. Application of ultrasound for 3 min gave a detection limit for BG bacterial spores of 1 x 10(3) spores/mL.

Bacillus subtilis↗
PubMed2005

An integrated metal clad leaky waveguide sensor for detection of bacteria.

An integrated optical metal clad leaky waveguide (MCLW) sensor device has been developed for the detection of bacteria. This is more sensitive than waveguide sensors currently in use. The MCLW device has been fabricated to extend the evanescent field to provide significant light intensity over the entire volume of the bacteria bound on the chip surface within this field. This in turn increases the interaction of the light with the entire volume of the bacteria. MCLW devices have been used for detecting refractive index changes, scattering, and fluorescence from bacterial spores captured on an immobilized antibody. The detection limit of Bacillus subtilis var. niger bacterial spores using refractive index detection was 8 x10(4) spores/mL. The scattering intensity of the BG spores was found to be three times greater than the scattering intensity generated using surface plasmon resonance. The extended light propagation along the direction of flow for a few millimeters provides an effective interrogation approach to increase the area of detection to detect low concentrations down to 1 x 10(4) spores/mL. The sensor was then optimized by studying the key factors affecting sensor performance including changing the pH of the medium, type of antibody immobilization matrix, sensor surface regeneration approaches, and longevity of the sensor.

Bacteria↗
PubMed2004

Bacteria detection using disposable optical leaky waveguide sensors.

Novel disposable absorbing material clad leaky waveguide sensor devices (LWD) have been developed for the detection of pathogenic particles such as bacteria. These chips are tailored to give the maximum extension of the evanescent field at the sensor surface in order to place the entire volume of the bacteria captured by immobilized antibodies on the chip surface within this field. This in turn increases the interaction of the light with the bacteria's bulk volume. Disposable LWD chips were fabricated at room temperature and without the use of expensive fabrication equipment. These LWDs have been characterised by detecting refractive index (RI) changes, scattering and fluorescence from bacterial spores at the sensor surface when illuminated at the coupling angle. The detection limit of Bacillus subtilis var. niger (BG) bacterial spores was 10(4) spores/ml and the illumination intensity of the spores was found to be three times greater than the illumination intensity generated using the surface plasmon resonance (SPR).

Bacillus↗
PubMed2004

Ultrasonic deposition of cells on a surface.

Bacteria in water have been driven to a glass surface by an ultrasonic standing wave. On an antibody coated surface capture of Bacillus subtilis var niger (BG) spores (6.6 x 10(6) ml(-1)) was increased more than 200-fold over above the efficiency in the absence of ultrasound. In microfluidic (non-turbulent) systems detection of particles by sensors operating at a surface is diffusion limited. This results in very low detection abilities particularly for particles with diameters greater than 1 microm. Ultrasound is used here to drive bacterial spores to a wall and overcome this limitation. The results confirm: (1) pressure nodes can be formed close to the water-glass interface when the glass thickness is near half the ultrasonic wavelength; (2) the antibody used was able to capture spores in the presence of an ultrasonic standing wave.

Bacillus subtilis↗
PubMedDate not supplied

Affinity determination of ricinus communis agglutinin ligands identified from combinatorial O- and S-,N-glycopeptide libraries.

Two combinatorial glycopeptide libraries were synthesized on solid support via the "split-and-mix" method combined with the ladder synthesis strategy. The O-glycopeptide library contained Gal(beta1-O)Thr, whereas the S-,N-glycopeptide library contained both Gal(beta1-S)Cys and Gal(beta1-N)Asn. In this model study, the two libraries were screened against the fluorescently labeled lectin Ricinus communis agglutinin (RCA120). The screening results showed that both O- and S- or S-,N-glycopeptides were recognized by the lectin with similar amino acid recognition patterns. Surface plasmon resonance interaction studies demonstrated that both the selected S- or S-,N-glycopeptide hits and the O-glycopeptides bound to the lectin with a similar affinity. Structure 19, containing two glycosylated cysteine residues, bound to the receptor with the highest affinity (KA = 3.81 x 10(4) M(-1)), which is comparable to N-acetyllactosamine. Competition assays, in which some selected glycopeptides and methyl beta-d-galactopyranoside competed for the binding site of immobilized RCA120, showed that the glycopeptide-lectin interaction was carbohydrate-specific. Incubation of the O- and S-,N-glycopeptides with beta-galactosidase demonstrated the complete stability of S-,N-glycopeptides toward enzymatic degradation, whereas O-glycopeptides were not completely stable.

Chromatography, Affinity↗