This paper investigates the accuracy of surface-scanning measurement of a wireless magnetoelastic (ME) biosensor for direct pathogen detection on solid surfaces. The model experiments were conducted on the surface of a at polyethylene (PE) plate. An ME biosensor (1 mm x 0.2 mm x 30 µm) was placed on the PE surface, and a surface-scanning detector was aligned to the sensor for wireless resonant frequency measurement. The position of the detector was accurately controlled by using a motorized three-axis translation system (i.e., controlled X, Y, and Z positions). The results showed that the resonant frequency variations of the sensor were -125 to +150 Hz for X and Y detector displacements of ± 600 µm and Z displacements of +100 to +500 µm. These resonant frequency variations were small compared to the sensor's initial resonant frequency (˂ 0.007% of 2.2 MHz initial resonant frequency) measured at the detector home position, indicating high accuracy of the measurement. In addition, the signal amplitude was, as anticipated, found to decrease exponentially with increasing detection distance (i.e., Z distance). Finally, additional experiments were conducted on the surface of cucumbers. Similar results were obtained.
Foodborne illness is a common public health problem because food can be contaminated with pathogens at any point in the farm-to-table continuum. This paper presents a method of capturing a quantity of a specific bacterial pathogen in a large volume of liquid using a biomolecular recognition filter. The filter consists of support frames made of a soft magnetic material and solenoid coils for magnetization/demagnetization of the frames. This filter is a planar, multi-layered arrangement of strip-shaped, phage-immobilized magnetoelastic (ME) biosensors that are magnetically held and arrayed on the filter frames. As a large volume of liquid passes through the biomolecular filter, the pathogen of interest is captured by the phage immobilized ME biosensors. This biomolecular filter is designed to capture a specific pathogen and allow non-specific debris to pass, thus avoiding a common clogging issue in conventional bead filters. In this work, single layer, double layers and triple layers of filter were test to capture Salmonella Typhimurium in a large volume of water. The effects of multiplication of filter layers on Salmonella capture efficiency will be discussed.
In this paper, a novel device named as phage filter is designed and presented to capture and identify a small number of Salmonella Typhimurium cells from large volumes of water. This phage filter is constructed from a filter chamber, filter frames on a spindle, strip-shape magnetoelastic filter elements, and a spinning speed control unit. The filter elements are made from Metglas 2826MB and coated with a specifically designed phage that only binds with Salmonella Typhimurium. These phage-coated filter elements can be held and arranged on the filter frames by magnetic force produced from couples of permanent magnets in the frame. Layers of filter frames are fixed on the spindle. The spindle with filter frames and filter elements can spin in the filter chamber and the spinning speed can be continuously adjusted. When the filter works, the tested water passes through the filter frame, and Salmonella Typhimurium cells striking on the filter elements can be bound by the phage on the element surfaces and removed from the tested water.
To perform rapid sensing of pathogens on the surface of food or food preparing plates, ME wireless biosensing system was combined with surface swab sampling techniques in this research. The ME biosensors which consist of ME resonators E2 phage was generally used for Salmonella typhimurium direct detections on the surfaces. E2 phage used in this research was designed for Salmonella typhimurium specific binding. Instead of measuring one spot at a time, the desired area or the whole area of a target surface can be swabbed for the inexpensive, rapid and easy-to-use pathogen collections. In this study, we first investigated the efficiency of capture and release of a model pathogen, Salmonella Typhimurium, by swab sampling on wet or dry surfaces. Plate counting was used to identify the recovery rates. The efficiency of capture and release was calculated and compared between various kinds of swabs which were composed of different tip materials, including cotton, rayon, and nylon-flocked ones.
This paper investigates a phage-based biomolecular filter that enables the evaluation of large volumes of liquids for the presence of small quantities of bacterial pathogens. The filter is a planar arrangement of phage-coated, strip-shaped magnetoelastic (ME) biosensors (4 mm × 0.8 mm × 0.03 mm), magnetically coupled to a filter frame structure, through which a liquid of interest flows. This "phage filter" is designed to capture specific bacterial pathogens and allow non-specific debris to pass, eliminating the common clogging issue in conventional bead filters. ANSYS Maxwell was used to simulate the magnetic field pattern required to hold ME biosensors densely and to optimize the frame design. Based on the simulation results, a phage filter structure was constructed, and a proof-in-concept experiment was conducted where a Salmonella solution of known concentration were passed through the filter, and the number of captured Salmonella was quantified by plate counting.