A portable microfluidic analyzer for integrated bacterial detection using visible loop-mediated amplification

Sample-to-answer COVID-19 nucleic acid testing using a low-cost centrifugal microfluidic platform with bead-based signal enhancement and smartphone read-out

“…19 Thus, in the context of pathogen detection, several groups have been actively exploring the use of loop-mediated isothermal amplification (LAMP) as a potential alternative, requiring only a constant and relatively lower temperature of ∼65°C. 19 Concerning the miniaturization of LAMP towards integrated analytical platforms, its combination with centrifugal microfluidics [20][21][22][23][24][25] and/or smartphone-based signal readout [26][27][28][29][30][31][32][33] has been showing significant promise to achieve a true sample-toanswer operation. A few remarkable examples of LAMPbased miniaturized modules using either of these approaches are: (1) capture of LAMP amplification products with anti-DIG antibodies followed by generation of a TMB precipitate measured using a standard light source and a smartphone camera; 26 (2) digital microfluidic platform with temperature monitoring/control provided by a thermal imaging camera and SYBR Green I derived fluorescence transduction by naked eye or smartphone camera; 28 (3) microfluidic cartridge combining immune-capture, lysis and LAMP to detect viable bacteria using a reader platform comprising two light sources for fluorometric and/or turbidimetric analysis resorting to a smartphone camera; 31 (4) a hermetic container providing power-free chemicalbased heating for LAMP amplification followed by detection using a smartphone flashlight and camera for fluorometric detection; 33 (5) centrifugal platform combining silica-based DNA extraction and integrated LFA strips to multiplex the detection of multiple LAMP products using anti-DIG antibodies and colorimetric detection; 33 (6) centrifugal platform with automated bead-beating lysis followed by direct RT-LAMP by continuous measurement of fluorescence with UVC illumination and a standard camera; 22 and (7) centrifugal platform incorporating non-contact heating of the disc and colorimetric detection of LAMP products using a white LED for illumination and filtered photodiodes for signal acquisition.…”

“…A few remarkable examples of LAMPbased miniaturized modules using either of these approaches are: (1) capture of LAMP amplification products with anti-DIG antibodies followed by generation of a TMB precipitate measured using a standard light source and a smartphone camera; 26 (2) digital microfluidic platform with temperature monitoring/control provided by a thermal imaging camera and SYBR Green I derived fluorescence transduction by naked eye or smartphone camera; 28 (3) microfluidic cartridge combining immune-capture, lysis and LAMP to detect viable bacteria using a reader platform comprising two light sources for fluorometric and/or turbidimetric analysis resorting to a smartphone camera; 31 (4) a hermetic container providing power-free chemicalbased heating for LAMP amplification followed by detection using a smartphone flashlight and camera for fluorometric detection; 33 (5) centrifugal platform combining silica-based DNA extraction and integrated LFA strips to multiplex the detection of multiple LAMP products using anti-DIG antibodies and colorimetric detection; 33 (6) centrifugal platform with automated bead-beating lysis followed by direct RT-LAMP by continuous measurement of fluorescence with UVC illumination and a standard camera; 22 and (7) centrifugal platform incorporating non-contact heating of the disc and colorimetric detection of LAMP products using a white LED for illumination and filtered photodiodes for signal acquisition. 24 Here, LAMP, centrifugal microfluidics, smartphone-based detection and recent developments in RT-LAMP applied to the detection of SARS-CoV-2 RNA [34][35][36][37][38][39][40] are combined to develop a novel cost-effective and fully integrated platform for COVID-19 diagnostics directly from heat-inactivated nasopharyngeal samples. The direct detection from heatinactivated samples was achieved using (1) a one-pot combination of reverse transcriptase and polymerase enzymes for robust isothermal amplification and (2) an agarose bead-based signal enhancement strategy for improved fluorometric detection, thus avoiding the impact of collection media on weakly-buffered pH responsive colorimetric amplification mixtures.…”

Stretch‐driven microfluidic chip for nucleic acid detection

“…Xin et al developed a fully integrated nucleic acid detection system to achieve nucleic acid purification, separation, amplification, and detection by real‐time fluorescence monitoring (Ye et al, 2021). Liu et al presented a portable food source bacteria detection instrument to achieve sample input and result output (Liu et al, 2020). Although the above devices have reduced the complexity of detection by changing the detection equipment from tube to chip and automating the detection procedure, current methods are still not applicable to a wide range of residents because they (Ji et al, 2020; Strohmeier et al, 2014; B. Yang, Fan et al, 2020; X. Yang, Yao, et al 2020) require instruments as centrifuges to drive the fluid flow.…”

Mobile origami immunosensors for the rapid detection of urinary tract infections

“…14 They are also faster and easier to use than biosensors based on detecting nucleic acids. [22][23][24][25] Moreover, the biosensors provide more information about the type of pathogen causing the UTI compared to the traditional urine strip. While this information is limited to a single pathogen at the moment, it has the potential to be expanded into a multisensor design including multiple reservoirs with antibodydecorated nanoparticles against different types of pathogens.…”