CHAPTER 1. Introduction
1.3 Lab-on-a-disc
1.3.3 Applications
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Figure 1.6. Examples of sample preparations on a centrifugal microfluidics. (a) Plasma separation from small volume of blood (5 µL) by applying the decanting structure with hydrophobic valve,7 (b) plasma separation from large volume of blood (2 mL) by use of siphone valve,18 (c) research on the investigation of the effect of various geometric variables on the blood cell separation rate,30 (d) a fully integrated bacterial DNA extraction from whole blood to detect Hepatitis B virus (HBV) and E.Coli.35
Figure 1.7. Examples of nucleic acid analysis on a disc. (a) An automated on-disc real-time PCR achieved by adapting the robust pre-amplification without cross-contamination,40 (b) ddPCR on a disc,44 (c) fully integrated food-borne pathogen detection on a disc.45
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chamber of a disc that is composed of a disposable cartridge suitable for mass production. By using the ddPCR disc, the mutation p.Phe508del, which is related to the cause of cystic fibrosis, was detected with a limit of detection in the order of 5 copies/µL.
Kim et al. described a micro total analysis system for the molecular analysis of the food-borne pathogen, Salmonella.45 The main steps of pathogen detection, including DNA extraction, isothermal recombines polymerase amplification (RPA), and detection, were integrated on a single disc, and the process could be completed within 30 min in a fully automated manner. The detection limit of the device, which used lateral flow strips, was 10 cfu/mL and 102 cfu/mL in PBS and milk, respectively.
Immunoassays
Immunoassays, the quantitative analysis of protein biomarkers, plays a crucial role in biomedical diagnostics. Conventional immunoassays, such as the sort of enzyme-linked immunosorbent assay (ELISA), are mostly performed in certain 96-well plates by a lot of manual handling. Therefore, integrated and automated immunoassays are desired for adapting an advanced immunoassay into point-of-care testing (POCT) (Figure 1.8). Park et al. reported a cost-effective, rapid, and fully automated lab-on-a-disc for the simultaneous detection of multiple protein biomarkers from whole blood or whole saliva.6 The protein markers of cardiovascular disease (CVD), which are high- sensitive C-reactive protein (hsCRP), cardiac troponin I (cTnI), N-terminal pro-B type natriuretic peptide (NT-proBNP), were simultaneously detected by performing a bead-based sandwich ELISA integrated on a disc. Kim et al. presented a novel lab-on-a-disc for target antigen capture from biological samples by fully integrating a bead-based ELISA and a flow-enhanced electrochemical detection.19 It took less than 20 min to detect the C-reactive protein (CRP) with a limit of detection of 4.9 pg/mL that is a 17-fold improvement over optical quantification. Lee et al. developed a highly efficient lab-on-a- disc that enables the detection of the cardiac markers (CRP, cTnI) from only 10 µL of whole blood within 30 min.31 Its advantages are derived from the high surface area of the TiO2 nanofibrous mat it uses as a substrate that is coated with a large amount of antibodies, which amplifies the target signal.
The device provides a wide dynamic range of six orders of magnitude from 1 pg/mL to 100 ng/mL for CRP spiked in CRP-free serum, and a dynamic range of 10 pg/mL to 100 ng/mL for cTnI spiked in whole blood.
Other applications
Obviously, a lab-on-a-disc system provides a beneficial platform for biomedical applications, but it also has the ability to conduct various academic or industrial applications (Figure 1.9). In the case of environmental monitoring, Hwang et al. described a novel platform based on lab-on-a-disc system
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Figure 1.8. Integration of the immunoassays on a disc. (a) A fully automated lab-on-a-disc for simultaneous detection of multiple biomarkers (CRP, cTnI, NT-proBNP),6 (b) integration of a bead- based ELISA and flow-enhanced electrochemical detection on a disc,19 (c) cardiac marker (CRP, cTnI) detection from small volume (10 µL) of whole blood on a disc. A large surface area of TiO2
nanofiber enhanced the sensitivity of the detection.31
Figure 1.9. Various applications of a lab-on-a-disc system. (a) Simultaneous determination of nutrients from seawater samples on a disc,36 (b) quality monitoring of river water on a disc with wireless paired emitter detector diode device (PEDD),41 (c) detection of residues in vegetable and soil samples,43 (d) particle separation by integrating an array of V-cup barriers on a disc, (e) size- difference-based CTC isolation on a disc.46
(a) (b) (c)
(e) (d)
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used in the simultaneous determination of nitrite, ammonium, nitrate, orthophosphate, and silicate in real seawater samples.36 This water analysis platform requires only 100 µL of sample and 10-30 µL of reagents for colorimetric detection. In addition, the full automation of the whole assay, the parallelization of assays for different nutrients, and efficient mixing on a disc allowed the reduction of the total analysis time to less than 8 min with high accuracy. Czugala et al. reported a portable lab-disc device for water quality monitoring by using a wireless paired emitter detector diode device (PEDD) as an optical sensor.41 It could be applied to on-site water testing for quantitative pH and qualitative turbidity monitoring.
Lab-on-a-disc platforms have been utilized not only for water quality checks, but also for the detection of pesticide residues from soil and vegetables. Duford et al. developed a centrifugal microfluidic device that can quantify such residues in both vegetable and soil samples by an enzyme inhibition technique.43 Liquid-solid extraction, filtration, sedimentation, and detection were integrated on a single device, which showed similar performance to the conventional benchtop method with a limit of detection of 0.1 ppm for carbofuran.
For the particle separation as well as cell isolation, a lab-disc was used to integrate the separation modules of microfluidics. Burger et al. presented the array-based capture of particles (i.e.
beads) on a disc platform for applications in bead-based assays such as multiplexed immunoassay using colored beads.46 An array of geometrical V-cup barriers was combined into the microfluidic chambers to trap particles using stopped-flow sedimentations. The particle capture efficiency was achieved nearly 100%, and this platform was used to perform the on-disc immunoassay to detect goat anti-human IgG.
Lee et al. demonstrated the size-selective isolation of circulating tumor cells (CTCs) on a disc for liquid biopsy applications.97 A track-etched PC (TEPC) membrane with 8 µm-sized pores was integrated on a disc to capture CTCs, which are usually larger than 8 µm in diameter. This system is quite simple to operate, and it achieved a capture efficiency of 61% and a 20-fold decrease in the contamination of white blood cells (WBCs) compared to those obtained using a commercialized size-based CTC isolation device. In the same group, Kim et al. improved their previous technique by equipping fluid-assisted separation technology (FAST) into their system.98 This provides clog-free, highly sensitive (95.9%), selective (>2/5 log depletion of WBCs), rapid (>3 mL/min), and label-free isolation of viable CTs from whole blood.
Overall, this section reviewed the general physics, the microfluidic functions, and the applications of lab-on-a-disc systems, and described the significance of lab-disc systems for biomedical applications, as well as various industrial and research applications.
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