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Biomedical subjects

R Mariella

Publications and source records attributed to R Mariella.

5 recordsLinked to original sources
PubMed1999

A minisonicator to rapidly disrupt bacterial spores for DNA analysis.

Concerns about the use of anthrax spores as a weapon of mass destruction have motivated the development of portable instruments capable of detecting and monitoring a suspected release of the agent. Optimal detection of bacterial spores by PCR requires that the spores be disrupted to make the endogenous DNA available for amplification. The entire process of spore lysis, PCR, and detection can take several hours using conventional methods and instruments. In this report, a minisonicator and prototype spore lysis cartridge were built to disrupt Bacillus spores in 30 s for rapid, real-time PCR analysis. Utilization of the minisonicator improved PCR analysis by decreasing the limit of detection, reducing the time of detection, and increasing the signal amplitude. Total time of spore disruption and detection using the minisonicator and a microchip PCR instrument was less than 15 min.

Bacillus anthracis↗
PubMed1998

Rapid pathogen detection using a microchip PCR array instrument.

An array of PCR microchips for rapid, parallel testing of samples for pathogenic microbes is described. The instrument, called the Advanced Nucleic Acid Analyzer (ANAA), utilizes 10 silicon reaction chambers with thin-film resistive heaters and solid-state optics. Features of the system include efficient heating and real-time monitoring, low power requirements for battery operation, and no moving parts for reliability and ruggedness. We analyzed cultures of Erwinia herbicola vegetative cells, Bacillus subtilis spores, and MS2 virions, which simulated pathogenic microbes such as Yersinia pestis, Bacillus anthracis spores, and Venezuelan equine encephalitis, respectively. Detection of microbes was achieved in as little as 16 min with detection limits of 10(5)-10(7) organisms/L (10(2)-10(4) organisms/mL).

Bacillus subtilis↗
PubMed1996

Flow-stream waveguide for collection of perpendicular light scatter in flow cytometry.

We report a new physical configuration for the detection of perpendicular light scatter or fluorescence in flow cytometry when using a fluid stream in air. This configuration increases the signal-to-noise ratio and narrows the coefficient of variation for uniformly sized latex spheres when compared to using a microscope objective to collect such light. The new technique views the scattered light that is trapped within the optical waveguide that is naturally formed by the flow stream in air. One efficient and simple way to detect the light trapped within this optical waveguide is to place one end of a fiber optic, with a conically polished tip and sufficiently large-core diameter, directly into the flow stream and to place an optical detector at the fiber's other end. For perpendicular light scatter, the flow-stream waveguide achieves high collection efficiency (NA = 0.88) as well as high efficiency of optical through put due to lack of surfaces between the light scatterers and the detector. We obtained 10-fold higher signals with this technique than with a long-working-distance microscope objective. The flow-stream waveguide is also much easier to align than traditional microscope-lens-based systems.

Fiber Optic Technology↗