Rapid Detection of Salmonella typhimurium in Drinking Water by a White Light Reflectance Spectroscopy Immunosensor

Abstract

Biosensors represent an attractive approach for fast bacteria detection. Here, we present an optical biosensor for the detection of Salmonella typhimurium lipopolysaccharide (LPS) and Salmonella bacteria in drinking water, based on white light reflectance spectroscopy. The sensor chip consisted of a Si die with a thin SiO2 layer on top that was transformed into a biosensor through the immobilization of Salmonella LPS. The optical setup included a reflection probe with seven 200 μm fibers, a visible and near-infrared light source, and a spectrometer. The six fibers at the reflection probe circumference were coupled with the light source and illuminated the biosensor chip vertically, whereas the central fiber collected the reflected light and guided it to the spectrometer. A competitive immunoassay configuration was adopted for the analysis. Accordingly, a mixture of LPS or bacteria solution, pre-incubated for 15 min, with an anti-Salmonella LPS antibody was pumped over the chip followed by biotinylated secondary antibody and streptavidin for signal enhancement. The binding of the free anti-Salmonella antibody to chip-immobilized LPS led to a shift of the reflectance spectrum that was inversely related to the analyte concentration (LPS or bacteria) in the calibrators or samples. The total assay duration was 15 min, and the detection limits achieved were 4 ng/mL for LPS and 320 CFU/mL for bacteria. Taking into account the low detection limits, the short analysis time, and the small size of the chip and instrumentation employed, the proposed immunosensor could find wide application for bacteria detection in drinking water.

Near-Infrared-Fluorescent Probe for Turn-On Lipopolysaccharide Analysis Based on PEG-Modified Gold Nanorods with Plasmon-Enhanced Fluorescence

“…With the as-prepared plasmonenhanced probe, the detection limit was 3.85 ng/mL. Compared with the previously reported immunoassay method 15,16 with an antibody as the recognition component or colorimetry method, 42,43 as well as the fluorescence probe 10,44,45 (Table S1), our as-prepared probe with a peptide as the recognition component showed a shorter detection time, wider linear range, and a lower detection limit. And the antibody in the immunoassay method is easy to denature and showed lower stability than the peptide or aptamer.…”

“…And presence of glucose can lead to false-positive results, greatly limiting its application in the biomedical field. Therefore, biosensors independent of Limulus reagent have been widely studied. − Wang et al developed a colorimetric and fluorometric probe based on 3-phenylthiophene-based water-soluble copolythiophenes, with the emission wavelength of 600 nm, which can detect LPS at the picomolar level . Liedberg et al developed an LPS sensor by assembling tetramethylrhodamine-labeled LPS-binding peptides on graphene oxide, which can be used as a turn-on fluorescence probe .…”

A Novel Prototype Biosensor Array Electrode System for Detecting the Bacterial Pathogen Salmonella typhimurium

“…were used, as compared with the response when the same number of Salmonella cells was used, implies that the sensor surface with immobilized mouse anti- Salmonella monoclonal antibody (MCA) is specific for binding of Salmonella cells and will not permit non-selective binding of nonspecific bacterial cells that do not possess epitopes complementary to the immobilized antibody ( Figure 12 ). The results clearly show that a specific response signal is generated in the presence of more than 30 Salmonella cells, which represents an improvement in sensitivity over existing sensors currently on the market [ 4 , 45 , 46 , 47 , 48 , 49 , 50 ]. Statistical one-way analysis of variance (ANOVA) was computed for pairs of data.…”

Theragnostic application of nanoparticle and CRISPR against food-borne multi-drug resistant pathogens

“…A detecting system was established based on immune-magnetic NPs that incorporated magnetic and thermal properties of MNPs to allow efficient capturing, high sensitivity thermal sensor detection, and sterilization of Salmonella typhimurium . The spike in Salmonella typhimurium in drinking water can be detected with a detection limit of as low as 300 ​CFU/mL under ideal conditions [ 133 ].…”