A portable immunosensor provides sensitive and rapid detection of Borrelia burgdorferi antigen in spiked blood.

There are no assays for detecting B. burgdorferi antigen in blood of infected Lyme disease individuals. Here, we provide proof-of-principle evidence that we can quantify B. burgdorferi antigen in spiked blood using a portable smartphone-based fluorescence microscope that measures immunoagglutination on a paper microfluidic chip. We targeted B. burgdorferi OspA to develop a working prototype and added examples of two antigens (OspC and VlsE) that have diagnostic value for discrimination of Lyme disease stage. Using an extensively validated monoclonal antibody to OspA (LA-2), detection of OspA antigen had a broad linear range up to 100 pg/mL in 1% blood and the limit of detection (LOD) was 100 fg/mL (= 10 pg/mL in undiluted blood), which was 1000 times lower than our target of 10 ng/mL. Analysis of the two other targets was done using polyclonal and monoclonal antibodies. OspC antigen was detected at LOD 100 pg/mL (= 10 ng/mL of undiluted blood) and VlsE antigen was detected at LOD 1-10 pg/mL (= 0.1-1 ng/mL of undiluted blood). The method is accurate and was performed in 20 min from sample to answer. When optimized for detecting several B. burgdorferi antigens, this assay may differentiate active from past infections and facilitate diagnosis of Lyme disease in the initial weeks of infection, when antibody presence is typically below the threshold to be detected by serologic methods.

Rapid, sensitive detection of PFOA with smartphone-based flow rate analysis utilizing competitive molecular interactions during capillary action.

Perfluorinated-alkyl substances (PFAS) pose an unmet threat to the public because they are not strictly monitored and regulated. Perfluorinated-carbon alkyl chains (PFOA), a type of PFAS, at 70 fg/µL is the current health and safety recommendation. Current testing methods for PFOA and PFAS chemicals include HPLC-MS/MS and molecularly imprinted polymers, which are expensive, time-consuming, and require training. In this work, PFOA and PFOS detection was performed on a paper microfluidic chip using competitive interactions between PFOA/PFOS, cellulose fibers, and various reagents (L-lysine, casein, and albumin). Such interactions altered the surface tension at the wetting front and, subsequently, the capillary flow rate. A smartphone captured the videos of this capillary action. The samples flowed through the channel in less than 2 min. Albumin worked the best in detecting PFOA, followed by casein. The detection limit was 10 ag/µL in DI water and 1 fg/µL in effluent (processed) wastewater. Specificity to other non-fluorocarbon surfactants was also tested, using anionic sodium dodecyl sulfate (SDS), non-ionic Tween 20, and cationic cetrimonium bromide (CTAB). A combination of the reagents successfully distinguished PFOA from all three surfactants at 100% accuracy. This low-cost, handheld assay can be an accessible alternative for rapid in situ estimation of PFOA concentration.

Biosensor detection of airborne respiratory viruses such as SARS-CoV-2.

Airborne SARS-CoV-2 transmission represents a significant route for possible human infection that is not yet fully understood. Viruses in droplets and aerosols are difficult to detect because they are typically present in low amounts. In addition, the current techniques used, such as RT-PCR and virus culturing, require large amounts of time to get results. Biosensor technology can provide rapid, handheld, and point-of-care systems that can identify virus presence quickly and accurately. This paper reviews the background of airborne virus transmission and the characteristics of SARS-CoV-2, its relative risk for transmission even at distances greater than the currently suggested 6 feet (or 2 m) physical distancing. Publications on biosensor technology that may be applied to the detection of airborne SARS-CoV-2 and other respiratory viruses are also summarized. Based on the current research we believe that there is a pressing need for continued research into handheld and rapid methods for sensitive collection and detection of airborne viruses. We propose a paper-based microfluidic chip and immunofluorescence assay as one method that could be investigated as a low-cost and portable option.