Current nucleic acid amplification methods to detect

A system for rapid point-of-use nucleic acid (NA) analysis based on PCR techniques is described. The extraction and concentration of DNA from test samples has been accomplished utilizing silicon fluidic microchips with high surface-area-to-volume ratios. Short (500 bp) and medium size (48,000 bp) DNA have been captured, washed, and eluted using the silicon dioxide surfaces of these chips. Chaotropic (GuHCl) salt solutions were used as binding agents. Wash and elution agents consisted of ethanol-based solutions and water, respectively. DNA quantities approaching 40 ng/cm2 of binding area were captured from input solutions in the 100-1000 ng/mL concentration range. For dilute samples of interest for pathogen detection, PCR and gel electrophoresis were used to demonstrate extraction efficiencies of about 50 percent, and concentration factors of about 10x using bacteriophage lambda DNA as the target. Rapid, multichannel PCR thermal cycling modules with integrated solid-state detection components have also been demonstrated. These results confirm the viability of utilizing these components as elements of a compact, disposable cartridge system for the detection of NA in applications such as clinical diagnostics, biowarfare agent detection, food quality control, and environmental monitoring.

A compact, real-time PCR instrument was developed for rapid, multiplex analysis of nucleic acids in an inexpensive, portable format. The instrument consists of a notebook computer, two reaction modules with integrated optics for four-color fluorescence detection, batteries, and a battery-charging system. The instrument weighs 3.3 kg, measures 26 x 22 x 7.5 cm, and can run continuously on the internal batteries for 4 h. Independent control of the modules allows differing temperature profiles and detection schemes to be run simultaneously. Results are presented that demonstrate rapid (1) detection and identification of Bacillus subtilis and Bacillus thuringensis spores and (2) characterization of a single nucleotide polymorphism for the hereditary hemochromatosis gene.

Disturbances in the stoichiometry of compound semiconductors which result from ion implantation are calculated using a Boltzmann transport equation approach. Results for 50-keV boron, 150-keV silicon, and 400-keV selenium implanted into silicon carbide, indium phosphide, and gallium arsenide are presented. Possible complications in the annealing of such implants are discussed.

Results of Boltzmann transport equation calculations are used to estimate what fraction of a crystalline silicon lattice must be displaced to cause a crystalline-to-amorphous transition during ion implantation. Comparison of these calculations with experimental MeV He channeling and backscattering results for 150-keV boron implantation at 77 °K indicates that the displacement of about 10% of the lattice will cause amorphization provided the substrate is at a temperature which inhibits self-annealing processes and defect diffusion. The calculations also indicate that the number of atoms displaced is proportional to the deposited energy density, one displacement occurring on average for each 200 eV of deposited energy. Experimental results for room-temperature silicon implantation confirm the fact that higher temperature substrates require a greater fractional displacement of the lattice before amorphization occurs.