Development And Application Of Visual Analysis Methods Based On Paper-Based Microfluidics Technology

Since the introduction of microfluidic technology,unprecedented breakthroughs have been made in various fields such as biology,chemistry and medical science.As a powerful tool for analysis and detection,the microfluidic chip is high throughput,integrated and automated.Therein the paper-based microfluidic chip has the characteristics of low cost,strong operability,easy modification,natural harmlessness,and one-time use.It can be used for sample detection and analysis by visual colorimetry.Besides,it also has a wide application value in point-of-care testing.In this study,we put forward two novel paper-based micro fluidic devices for visual bioanalytical detection.Firstly,based on capillarity of filter paper,we developed a wick-like paper-based microfluidic device with a novel folded paper strip as wick structure,which used for medium self-driven perfusion during the three-dimensional(3D)cell culture.The proposed device with patterns of hydrophilic channel,culture areas,and hydrophobic barrier could be easily fabricated through wax-printing.After printing,the hydrophilic paper strip at the periphery of the lower layer was folded at 90 degrees and extended into the medium container for continuous automatic supply of medium to the cell culture area.MCF-7 and HepG2 cells were taken as model cells for verifying the cell culture and further anticancer drug screening by using the proposed paper microfluidic device.Based on the principle of CCK-8 staining live cells,visualized cell viability and chemical sensitivity testing can be achieved by colorimetry combined with simple smartphone monitoring,effectively reducing precision instrument dependence.The wick paper-based microfluidic device for cell culture endows our method the advantages of lower cost,ease-of-operation,miniaturization and shows a great potential for large-scale cell culture,antibody drug production and efficient screening.In addition,based on paper with adsorption characteristics and fidget spinner,we also designed a centrifugal paper-based microfluidic device,combining the loop-mediated isothermal amplification(LAMP)technology and fuchsin-based colorimetric analysis method for rapid detection of pathogens.The paper chip was composed of sample zone,reaction zone,and detection zone,which fully integrated DNA purification,amplification and detection processes for detecting multiple foodborne pathogens.After adding sample solution to polydopamine-coated paper,we utilized a fidget-spinner to provide continuous centrifugal force with simple flick of a finger for DNA purification and separation from the mixture.Then the DNA template solution was transferred to the reaction chambers without any pump instrument and performed isothermal amplification on a hot plate.Subsequently,the detection zone was folded so that the fuchsin-stained areas were completely soaked into the amplified product of the reaction zone.Finally,according the color change of fuchsin to determine whether there are single or multiple targets in the tested sample.Genomic DNAs of pathogenic bacteria can be directly identified by naked eyes based on coloration results of detection zone within 1 hour.In conclusion,using this paper-based microfluidic device,the detection limit of Salmonella in milk samples was as low as 102 CFU/mL.Such an integrated,portable,easy-touse,low-cost,high-sensitivity,results visible gyro-centrifugal paper-based microfluidic device offers a promising solution for the sensitive,simple,and effective detection of pathogenic bacteria in resource-limited environment,providing new possibilities for on-site genetic diagnostics and other biological monitoring areas.