Magnetic Nanoparticles Enhanced Surface Plasmon Resonance Biosensor for Rapid Detection of Salmonella Typhimurium in Romaine Lettuce

Salmonella is one of the major foodborne pathogens responsible for many cases of illnesses, hospitalizations and deaths worldwide. Although different methods are available to timely detect Salmonella in foods, surface plasmon resonance (SPR) has the benefit of real-time detection with a high sensitivity and specificity. The purpose of this study was to develop an SPR method in conjunction with magnetic nanoparticles (MNPs) for the rapid detection of Salmonella Typhimurium. The assay utilizes a pair of well-characterized, flagellin-specific monoclonal antibodies; one is immobilized on the sensor surface and the other is coupled to the MNPs. Samples of romaine lettuce contaminated with Salmonella Typhimurium were washed with deionized water, and bacterial cells were captured on a filter membrane by vacuum filtration. SPR assays were compared in three different formats—direct assay, sequential two-step sandwich assay, and preincubation one-step sandwich assay. The interaction of flagellin and MNPs with the antibody-immobilized sensor surface were analyzed. SPR signals from a sequential two-step sandwich assay and preincubation one-step sandwich assay were 7.5 times and 14.0 times higher than the direct assay. The detection limits of the assay were 4.7 log cfu/mL in the buffer and 5.2 log cfu/g in romaine lettuce samples.

Detection of Oenological Polyphenols via QCM-D Measurements

Polyphenols are a family of compounds present in grapes, musts, and wines. Their dosage is associated with the grape ripening, correct must fermentation, and final wine properties. Owing to their anti-inflammatory properties, they are also relevant for health applications. To date, such compounds are detected mainly via standard chemical analysis, which is costly for constant monitoring and requires a specialized laboratory. Cheap and portable sensors would be desirable to reduce costs and speed up measurements. This paper illustrates the development of strategies for sensor surface chemical functionalization for polyphenol detection. We perform measurements by using a commercial quartz crystal microbalance with dissipation monitoring apparatus. Chemical functionalizations are based on proteins (bovine serum albumin and gelatin type A) or customized peptides derived from istatine-5 and murine salivary protein-5. Commercial oenological additives containing pure gallic tannins or proanthocyanidins, dissolved in water or commercial wine, are used for the analysis. Results indicate that selected functionalizations enable the detection of the two different tannin families, suggesting a relationship between the recorded signal and concentration. Gelatin A also demonstrates the ability to discriminate gallic tannins from proanthocyanidins. Outcomes are promising and pave the way for the exploitation of such devices for precision oenology.

Improving the Detection Accuracy of an Ag/Au Bimetallic Surface Plasmon Resonance Biosensor Based on Graphene

A theoretical study was conducted with the aim of improving the detection accuracy of graphene-based surface plasmon resonance (SPR) biosensors. We studied the effect of applying a bias voltage to the sensor surface on its detection accuracy. The optimum thicknesses of silver and gold layers in the biosensor of 47 nm and 3 nm, respectively, were determined. Graphene layers deposited on these thin silver and gold films formed a sensor surface system, on which the surface plasmons were excited. The real and imaginary parts of the refractive index of graphene were controlled by the bias voltage. When the chemical potential was increased from 36 meV to 8 eV, the detection accuracy of the sensor was correspondingly increased by 213%.

Label-free detection of single nanoparticles with disordered nanoisland surface plasmon sensor

We report sensing of single nanoparticles using disordered metallic nanoisland substrates supporting surface plasmon polaritons (SPPs). Speckle patterns arising from leakage radiation of elastically scattered SPPs provides a unique fingerprint of the scattering microstructure at the sensor surface. Experimental measurements of the speckle decorrelation are presented and shown to enable detection of sorption of individual gold nanoparticles and polystyrene beads. Our approach is verified through bright-field and fluorescence imaging of particles adhering to the nanoisland substrate.

Magnetically propelled Carreau fluid flow over Penetrable Sensor Surface Influenced by Thermal Radiation, Joule Heating and Heat Generation

This examination emphasizes the analysis of thermal transmission of Carreau fluid flow on a permeable sensor surface equipped with radiation, Joule heating, internal heat source, and magnetic field. With the above effects and assumptions, the equations that administer the flow are formulated. Configured system of equations is productively reduced to system of ordinary differential equations. The reduced system is then dealt with the Runge-Kutta-Fehlberg 4th -5th order tool equipped by shooting technique. Derived numerical solutions are utilized to plot graphs and tables. The study concluded with some important findings such as power law index, thermal radiation parameter and heat source parameter enhance the thermal panel whereas Weissenberg number deescalates the same. The power law index and permeable velocity decrease the velocity panel significantly. Diagrammatic representation of streamlines of the flow has been given to strengthen the study. A detailed description has been produced about the results obtained in the study

Detection of Foreign Bodies in Soft Foods Employing Tactile Image Sensor

In the inspection work involving foodstuffs in food factories, there are cases where people not only visually inspect foodstuffs, but must also physically touch foodstuffs with their hands to find foreign or undesirable objects mixed in the product. To contribute to the automation of the inspection process, this paper proposes a method for detecting foreign objects in food based on differences in hardness using a camera-based tactile image sensor. Because the foreign objects to be detected are often small, the tactile sensor requires a high spatial resolution. In addition, inspection work in food factories requires a sufficient inspection speed. The proposed cylindrical tactile image sensor meets these requirements because it can efficiently acquire high-resolution tactile images with a camera mounted inside while rolling the cylindrical sensor surface over the target object. By analyzing the images obtained from the tactile image sensor, we detected the presence of foreign objects and their locations. By using a reflective membrane-type sensor surface with high sensitivity, small and hard foreign bodies of sub-millimeter size mixed in with soft food were successfully detected. The effectiveness of the proposed method was confirmed through experiments to detect shell fragments left on the surface of raw shrimp and bones left in fish fillets.

Manufacturing Process of Polymeric Microneedle Sensors for Mass Production

In this work, we present a fabrication process for microneedle sensors made of polylactic acid (PLA), which can be utilized for the electrochemical detection of various biomarkers in interstitial fluid. Microneedles were fabricated by the thermal compression molding of PLA into a laser machined polytetrafluoroethylene (PTFE) mold. Sensor fabrication was completed by forming working, counter, and reference electrodes on each sensor surface by Au sputtering through a stencil mask, followed by laser dicing to separate individual sensors from the substrate. The devised series of processes was designed to be suitable for mass production, where multiple microneedle sensors can be produced at once on a 4-inch wafer. The operational stability of the fabricated sensors was confirmed by linear sweep voltammetry and cyclic voltammetry at the range of working potentials of various biochemical molecules in interstitial fluid.

Surface Functionalization of Silicon MEMS Biochemical Sensors for the Detection of Foodborne Pathogens

This work presents the surface modification of silicon chips as a platform for silicon-based biosensors with applications aiming for the detection of foodborne bacteria in aqueous solution. The detection requires high selectivity as the solution may contain a variety of biological species, which affect the outcome of the sensing process. The silicon surface is functionalized by a self-assembled monolayer (SAM) with thiol groups followed by immobilizing a thiol-linked DNA aptamer. The DNA aptamer used in this work has reported to recognize a biological species, E. coli ATCC 25922. The presence of DNA aptamer on the sensor surface allows the capture of the specific E. coli cells on the surface, while other potential biological (and chemical) species would not attach to the sensor surface, thus improving the selectivity of the sensor. The uniform formation of the SAM on the surface is an important step toward uniformly coating the sensor surface with the desired DNA aptamer. The SAM is created on the silicon surface by surface modification with the MPTS (3-mercaptopropyl trimethoxy silane) solution. Then the aptamer DNA solution is applied as droplets on the chip followed by a cure process. The attachment of the SAM and DNA aptamers are verified by atomic force microscopy (AFM). The surface functionalization presented in this work can be used for sensors made of silicon coated with a thin layer of native oxide, and can be adopted for detection of other cells and biological agents using the proper SAM and DNA aptamer.

Electrode Modified with Tin(IV) Oxide Nanoparticles and Surfactants as Sensitive Sensor for Hesperidin

Tin(IV) oxide nanoparticles in combination with surfactants were used as a sensitive layer in a sensor for hesperidin. The effect of the surfactant’s nature and concentration on the hesperidin response was evaluated. The best parameters were registered in the case of 500 µM cetylpyridinium bromide (CPB) as a dispersive agent. The SEM and electrochemical data confirmed the increase in sensor surface effective area and electron transfer rate. The sensor gave a linear response to hesperidin in the ranges of 0.10–10 and 10–75 µM with a detection limit of 77 nM. The approach was successfully tested on orange juices and validated using ultra-HPLC.