Stretch-driven microfluidic chip for nucleic acid detection

Molecular diagnosis is an essential means to detect pathogens. The portable nucleic acid detection chip has excellent prospects in places where medical resources are scarce, and it is also of research interest in the field of microfluidic chips. Here, the paper developed a new type of microfluidic chip for nucleic acid detection where stretching acts as the driving force. The sample entered the chip by applying capillary force. The strain valve was opened under the action of tensile force, and the spring pump generated the power to drive the fluid to flow to the detection chamber in a specific direction. The detection of COVID-19 was realized on the chip. The RT-LAMP amplification system was adopted to observe the liquid color in the detection chamber to decide whether the sample tested positive or negative qualitatively.

A New Detection Chamber Design on Centrifugal Microfluidic Platform to Measure Hemoglobin of Whole Blood

Undoubtedly, microfluidics has been a focal point of interdisciplinary science during the last two decades, resulting in many developments in this area. Centrifugal microfluidic platforms have good potential for use in point-of-care devices because they take advantage of some intrinsic forces, most notably centrifugal force, which obviates the need to any external driving forces. Herein, we introduce a newly designed detection chamber for use on microfluidic discs that can be employed as an absorbance readout step in cases where the final solution has a very low viscosity and surface tension. In such situations, our chamber easily eliminates the air bubbles from the final solution without any interruption. One microfluidic disc for measuring the hemoglobin concentration was designed and constructed to verify the correct functioning of this detection chamber. This disc measured the hemoglobin concentration of the blood samples via the HiCN method. Then, the hemoglobin concentration of 11 blood samples was quantified and compared with the clinic’s data using the hemoglobin measurement disc, which included four hemoglobin measurement sets, and each set contained two inlets for the blood sample and the reagent, one two-part mixing chamber, and one bubble-free detection chamber. The measured values of the disc had good linearity and conformity compared with the clinic’s data, and there were no air bubbles in the detection step. In this study, the standard deviation and the turnaround time were ± 0.51 g/dL and 68 s, respectively.

A novel vertical flow assay for point of care measurement of iron from whole blood

We present a novel vertical flow assay to measure iron levels in whole blood from a finger-prick sample. The system leverages a sensor strip, detection chamber and in-house app that detects color change and outputs iron concentration in five minutes.

Miniaturized photoacoustic detection of organofluorine-based refrigerants

Due to the ban on hydrofluorocarbon and haloalkane refrigerants with a high global warming potential, such as R134a, in the automotive industry, the significance of reliable and precise measuring devices for these refrigerants has risen. We present a photoacoustic gas detector for monitoring the organofluorine-based refrigerants R134a and R1234yf. The idea for this sensor is based on the three-chamber concept (a detection chamber, absorption chamber, and filter chamber). The optimal parameters and dimensions of the photoacoustic sensor components were determined via simulations. The simulation results were the cornerstone of our hardware construction. The first measurements with the newly developed sensor showed a sufficient signal-to-noise ratio for a reliable 0.5 vol. % (0.005 m3 m−3) detection resolution. The influence and importance of the filter chamber were examined and validated.

A Portable Biosensing Device with Magnetic Separation and Quantum Dot Bead Labeling for Simple, Rapid, and Quantitative Detection of Salmonella Typhimurium

HighlightsA portable biosensing device was designed, fabricated, and evaluated for Salmonella detection.A mixing, separation, and detection chamber (MSDC) was developed and used for Salmonella detection.The disposable MSDC prevented cross-contamination and reduced costs.The device was mostly automated for Salmonella detection and feasible for in-field applications.Abstract. Foodborne pathogenic bacteria have caused numerous illnesses and economic losses in the U.S. and the world. It is highly important for food industries to conduct in-field screening for pathogenic bacteria to ensure food safety. The objective of this study was to convert our previously developed optical biosensing method into a portable biosensing device to achieve simple, rapid, and quantitative detection of Salmonella Typhimurium. The device consisted of a control module, a magnetic separation module, and a fluorescence detection module. The bacteria sample, immuno-magnetic nanoparticles, and immuno-quantum dot beads were added into a mixing, separation, and detection chamber and were fully mixed in the control module. The sample was then moved to the magnetic separation module to automatically separate and concentrate the target bacteria. Finally, the fluorescence intensity was measured with the fluorescence detection module to determine the concentration of the target bacteria. The device was able to perform separation and detection of Salmonella with minimal manual operation with a detection limit of 5.4 × 102 CFU mL-1 in 1 h. The device also showed good specificity against four selected non-target bacteria. Keywords: Biosensing device, Fluorescence biosensor, Foodborne bacteria detection, Magnetic separation.

Application of Sample6 DETECT™ HT/L Kit for the Detection of Listeria in Mixed Leafy Greens

Background: Early and accurate detection of Listeria in foods is vital. Current methods require 24 h enrichment for detection. Objective: This study aimed to demonstrate enhanced early detection of Listeria in mixed leafy greens using Sample6 DETECT™ HT/L, a phage-based detection system. Methods: A method comparison between the reference method (U.S. Food and Drug Administration Bacteriological Analytical Manual Chapter 10) for the detection of Listeria spp. and the Sample6 DETECT HT/L using a new proprietary R2 Medium was performed in mixed leafy greens. Results: Using the R2 Medium enrichment with Sample6 DETECT HT/L, detection of L. innocua was possible at 12 h (with a centrifugation step), and L. monocytogenes was detected by 18 h, with equivalent performance as the 24 h enrichments using the reference method detection. The Sample6 DETECT HT/L gave an equivalent performance for L. innocua at 15 h as the reference method at 24 h. Detection was accomplished by the addition of reagents in the kit, following the package insert, and reading results in a detection chamber using a 96-well plate reader that detects a fluorescent signal. Conclusions: Results indicate the new R2 Medium and Sample6 DETECT HT/L allowed for earlier detection of Listeria spp. in mixed leafy greens. Highlights: Sample6 DETECT HT/L with the new R2 Medium allowed the early detection of Listeria spp. and may be applied in other food matrices and environmental samples.

Carbon dioxide quantified by the infrared in respiratory activity evaluation in corn seeds

The respiratory activity is one of the first biological manifestations of vigor loss and detecting it can help the monitoring and quality control of seed production by seed industries. This research aimed to develop and validate the methodology of the carbon dioxide concentration in the evaluation of physiological quality of Zea mays (L.) seeds. The proposed method is grounded on the measurement of the CO2 content by infrared through a drag system and exhaustion of the gas released by the seed maintained in a closed system up to the detection chamber of the gas meter. Samples of 15, 20 and 25 seeds of 6 lots of cultivar CD 384 Hx were incubated at temperatures of 15, 25 and 40 °C. The CO2 content released after 1, 3, 6, 9, 12 and 24 h of incubation were quantified. In parallel, the percentage of normal seedlings emerged in the field were evaluated. The simple correlation coefficients among tests were calculated. After determining the reading conditions, the accuracy and precision of the proposed method were evaluated, using 15 seed lots. For the evaluation of the respiratory activity in Z. mays seeds, we recommend a sample of 25 seeds, incubated at 15 °C for a maximum of 12 h, which allows to classify lots with different levels of vigor and predict the establishment of seedlings in the field, being the appropriate method for measuring CO2 as it externalizes precision between successive measurements and agreement to the reference method.

Supernatant Decanting on a Centrifugal Platform

This work presents a novel approach to decant and meter supernatant on a centrifugal platform. Supernatant decanting, such as decanting plasma from the centrifuged whole blood, is an important sample preparation procedure for the whole blood bioassays. By manipulating the centrifugally induced pressure and the elastic deformation of the chamber’s plastic lid, fixed amounts of the supernatant can be decanted into the detection chamber. This approach has the advantages of low manufacturing cost and ease of operation.