Biomedical subjects

Finny P Mathew

Publications and source records attributed to Finny P Mathew.

3 recordsLinked to original sources

PubMed2005

Porous silicon-based biosensor for pathogen detection.

A porous silicon-based biosensor for rapid detection of bacteria was fabricated. Silicon (0.01 ohmcm, p-type) was anodized electrochemically in an electrochemical Teflon cell containing ethanoic hydrofluoric acid solution to produce sponge-like porous layer of silicon. Anodizing conditions of 5 mA/cm2 for 85 min proved best for biosensor fabrication. A single-tube chemiluminescence-based assay, previously developed, was adapted to the biosensor for detection of Escherichia coli. Porous silicon chips were functionalized with a dioxetane-Polymyxin B (cell wall permeabilizer) mixture by diffusion and adsorption on to the porous surface. The reaction of beta-galactosidase enzyme from E. coli with the dioxetane substrate generated light at 530 nm. Light emission for the porous silicon biosensor chip with E. coli was significantly greater than that of the control and planar silicon chip with E. coli (P<0.01). Sensitivity of the porous silicon biosensor was determined to be 101-102 colony forming units (CFU) of E. coli. The porous silicon-based biosensor was fabricated and functionalized to successfully detect E. coli and has potential applications in food and environmental testing.

Biosensing Techniques↗

PubMed2002

Competition of thermally injured listeria monocytogenes with a mesophilic lactic acid starter culture in milk for various heat treatments.

Overnight tryptose broth cultures of three L monocytogenes strains were combined, centrifuged, suspended in 200 ml of tryptose phosphate broth, and heated at 56 degrees C for 20 min and at 64 degrees C for 2 min to obtain low-heat-injured (LHI) and high-heat-injured (HHI) cells, respectively, showing >99.6% injury. Flasks containing 200 ml of raw, low-heat-treated (56 degrees C for 20 min), high-heat-treated (64 degrees C for 2 min), pasteurized, and ultrahigh-temperature (UHT) milk were tempered to 31.1 degrees C and inoculated to contain 10(4) to 10(6) CFU/ml of LHI, HHI, or healthy L. monocytogenes cells and a commercial Lactococcus lactis subsp. lactis-Lactococcus lactis subsp. cremoris starter culture at levels of 0.5, 1.0, and 2.0%. Numbers of healthy and injured L. monocytogenes cells and starter organisms were determined using tryptose phosphate agar with or without 4.0% NaCl at selected intervals during 24 h of incubation at 31.1 degrees C. The presence of L. monocytogenes did not adversely affect the growth of the starter culture at any inoculation level. Overall, L. monocytogenes survived the 24-h fermentation period and grew to some extent. In starter-free controls. 76 to 81% of LHI cells and 59 to 69% of HHI cells were repaired after 8 h of incubation, with the lowest repair rates being observed for raw rather than heat-treated or pasteurized milk. Increased injury was observed for healthy L. monocytogenes cells at the 1.0 and 2.0% starter levels, with less injury seen for LHI and HHI cells. Raw and subpasteurized milk allowed less of a decrease in the percentage of injury and also showed higher numbers of injured cells than did pasteurized and UHT milks. These findings may have important implications for the survival of Listeria spp. in certain cheeses that can be prepared from raw or heat-treated milk.

Animals↗

PubMedDate not supplied

Chemiluminescence detection of Escherichia coli in fresh produce obtained from different sources.

A chemiluminescence-based assay is developed for the rapid detection of Escherichia coli in fresh produce. The assay was based on the reaction of beta-galactosidase enzyme from E. coli with a phenylgalactosidase-substituted dioxetane substrate. Light emitted from the reaction was measured in a luminometer and data correlated with counts of E. coli enumerated on sorbitol-MacConkey agar plates. A strain of E. coli O157:H7 was used to inoculate samples of fresh produce to differentiate the inoculum from the natural E. coli potentially present on the produce. Fresh market samples were tested for generic E. coli and E. coli O157:H7. Significant differences in light emission were found in samples with high initial E. coli counts when market samples were compared to respective heat-treated samples. The assay was able to detect E. coli in all produce tested, particularly at higher contamination or inoculation levels. The sensitivity of the assay ranged between 10(2)-10(5) CFU within 30 min. The chemiluminescence assay provides a simple and rapid method for detection of viable E. coli, an important step towards enhancing food safety.

Escherichia coli↗