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1. Protein-based lateral flow assays for COVID-19 detection

   https://doi.org/10.1093/protein/gzab010  

   Mahmoudinobar, Farbod ; Britton, Dustin ; Montclare, Jin Kim ( January 2021 , Protein Engineering, Design and Selection)

   null (Ed.)

   Abstract To combat the enduring and dangerous spread of COVID-19, many innovations to rapid diagnostics have been developed based on proteinprotein interactions of the SARS-CoV-2 spike and nucleocapsid proteins to increase testing accessibility. These antigen tests have most prominently been developed using the lateral flow assay (LFA) test platform which has the benefit of administration at point-of-care, delivering quick results, lower cost, and does not require skilled personnel. However, they have gained criticism for an inferior sensitivity. In the last year, much attention has been given to creating a rapid LFA test for detection of COVID-19 antigens that can address its high limit of detection while retaining the advantages of rapid antibodyantigen interaction. In this review, a summary of these proteinprotein interactions as well as the challenges, benefits, and recent improvements to protein based LFA for detection of COVID-19 are discussed. 

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2. PCB-Based Magnetometer as a Platform for Quantification of Lateral-Flow Assays

   https://doi.org/10.3390/s19245433  

   Khodadadi, Mohammad ; Chang, Long ; Trabuco, João R. ; Vu, Binh V. ; Kourentzi, Katerina ; Willson, Richard C. ; Litvinov, Dmitri ( December 2019 , Sensors)

   This work presents a proof-of-concept demonstration of a novel inductive transducer, the femtoMag, that can be integrated with a lateral-flow assay (LFA) to provide detection and quantification of molecular biomarkers. The femtoMag transducer is manufactured using a low-cost printed circuit board (PCB) technology and can be controlled by relatively inexpensive electronics. It allows rapid high-precision quantification of the number (or amount) of superparamagnetic nanoparticle reporters along the length of an LFA test strip. It has a detection limit of 10−10 emu, which is equivalent to detecting 4 ng of superparamagnetic iron oxide (Fe3O4) nanoparticles. The femtoMag was used to quantify the hCG pregnancy hormone by quantifying the number of 200 nm magnetic reporters (superparamagnetic Fe3O4 nanoparticles embedded into a polymer matrix) immuno-captured within the test line of the LFA strip. A sensitivity of 100 pg/mL has been demonstrated. Upon further design and control electronics improvements, the sensitivity is projected to be better than 10 pg/mL. Analysis suggests that an average of 109 hCG molecules are needed to specifically bind 107 nanoparticles in the test line. The ratio of the number of hCG molecules in the sample to the number of reporters in the test line increases monotonically from 20 to 500 as the hCG concentration increases from 0.1 ng/mL to 10 ng/mL. The low-cost easy-to-use femtoMag platform offers high-sensitivity/high-precision target analyte quantification and promises to bring state-of-the-art medical diagnostic tests to the point of care. 

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3. Smartphone-read phage lateral flow assay for point-of-care detection of infection

   https://doi.org/10.1039/d2an01499h  

   Chabi, Maede ; Vu, Binh ; Brosamer, Kristen ; Smith, Maxwell ; Chavan, Dimple ; Conrad, Jacinta C. ; Willson, Richard C. ; Kourentzi, Katerina ( February 2023 , The Analyst)

   The COVID-19 pandemic has highlighted the urgent need for sensitive, affordable, and widely accessible testing at the point of care. Here we demonstrate a new, universal LFA platform technology using M13 phage conjugated with antibodies and HRP enzymes that offers high analytical sensitivity and excellent performance in a complex clinical matrix. We also report its complete integration into a sensitive chemiluminescence-based smartphone-readable lateral flow assay for the detection of SARS-CoV-2 nucleoprotein. We screened 84 anti-nucleoprotein monoclonal antibody pairs in phage LFA and identified an antibody pair that gave an LoD of 25 pg mL −1 nucleoprotein in nasal swab extract using a FluorChem gel documentation system and 100 pg mL −1 when the test was imaged and analyzed by an in-house-developed smartphone reader. The smartphone-read LFA signals for positive clinical samples tested ( N = 15, with known Ct) were statistically different ( p < 0.001) from signals for negative clinical samples ( N = 11). The phage LFA technology combined with smartphone chemiluminescence imaging can enable the timely development of ultrasensitive, affordable point-of-care testing platforms for SARS-CoV-2 and beyond. 

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4. Review of HIV Self Testing Technologies and Promising Approaches for the Next Generation

   https://doi.org/10.3390/bios13020298  

   Bacon, Amanda ; Wang, Weijing ; Lee, Hankeun ; Umrao, Saurabh ; Sinawang, Prima Dewi ; Akin, Demir ; Khemtonglang, Kodchakorn ; Tan, Anqi ; Hirshfield, Sabina ; Demirci, Utkan ; et al ( February 2023 , Biosensors)

   The ability to self-test for HIV is vital to preventing transmission, particularly when used in concert with HIV biomedical prevention modalities, such as pre-exposure prophylaxis (PrEP). In this paper, we review recent developments in HIV self-testing and self-sampling methods, and the potential future impact of novel materials and methods that emerged through efforts to develop more effective point-of-care (POC) SARS-CoV-2 diagnostics. We address the gaps in existing HIV self-testing technologies, where improvements in test sensitivity, sample-to-answer time, simplicity, and cost are needed to enhance diagnostic accuracy and widespread accessibility. We discuss potential paths toward the next generation of HIV self-testing through sample collection materials, biosensing assay techniques, and miniaturized instrumentation. We discuss the implications for other applications, such as self-monitoring of HIV viral load and other infectious diseases. 

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5. Enhancing the sensitivity of colorimetric lateral flow assay (CLFA) through signal amplification techniques

   https://doi.org/10.1039/C8TB01603H  

   Ye, Haihang ; Xia, Xiaohu ( November 2018 , Journal of Materials Chemistry B)

   Colorimetric lateral flow assay (CLFA) is one of a handful of diagnostic technologies that can be truly taken out of the laboratory for point-of-care testing without the need for any equipment and skilled personnel. Despite its simplicity and practicality, it remains a grand challenge to substantially enhance the detection sensitivity of CLFA without adding complexity. Such a limitation in sensitivity inhibits many critical applications such as early detection of significant cancers and severe infectious diseases. With the rapid development of materials science and nanotechnology, signal amplification techniques that hold great potential to break through the existing detection limit barrier of CLFA have been developed in recent years. This article specifically highlights these emerging techniques for CLFA development. The rationale behind and advantages and limitations of each technique are discussed. Perspectives on future research directions in this niche and important field are provided. 

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