We created an automated bioassay system based on inkjet printing. Compared to conventional manual bacterial culture systems our printing approach improves the quality as well as the processing speed. A hydrophobic/hydrophilic pattern as a container supporting a culture medium was built on filter paper using a toluene solution of polystyrene for hydrophobization, followed by toluene printing to create several hydrophilic areas. As culture media we used a novel poly(vinyl alcohol) based hydrogel and a standard calcium alginate hydrogel. The poly(vinyl alcohol) hydrogel was formed by physical crosslinking poly(vinyl alcohol) with adipic acid dihydrazide solutions. The conditions of poly(vinyl alcohol) gelation were optimized for inkjet printability and the optimum mixture ratio was determined. The calcium alginate hydrogel was formed by chemical reaction between sodium alginate and CaCl2solutions. Together with nutrients both hydrogel solutions were successfully printed on paper by means of the modified inkjet printer. The amount of each solution was demanded simply by outputting CMYK values. In the last step bacterial cells were printed on both hydrogel media. For both media we achieved a stable bacteria growth which was confirmed by microscopical imaging of the developed bacterial colonies.
Generally, bacterial culture is performed manually and is subject to error. Here, we created a novel, wellordered and reliable system for dispensing bacteria microscopically by using paper and an ink-jet printer for controlled patterning. For paper to accommodate a culture medium, hydrophobic/hydrophilic patterns were incorporated onto the paper by immersing paper in a toluene solution of polystyrene and drying for complete hydrophobization, followed by etching discrete, small areas of hydrophilicity by ink-jet printing with toluene. Agar was hydrolyzed with sulfuric acid for appropriate viscosity and dispensed with an ink-jet printer. In a separate experiment, bacterial cells were sequentially printed on a medium and colonies were observed microscopically. The results of this experiment ensured the successful dispensing of bacteria using ink-jet printing. An almost constant number of particles per droplet were ejected using a polystyrene latex as a model of bacterial dispersion. Consequently, we expect this technology to be adapted for the development of a paper-based bioassay system.
We demonstrate the detection of an increase in refractive index and/or thickness by specific adsorption of proteins on a plasmonic surface on a paper substrate in the Otto configuration. Propagating surface plasmon resonance is observed on a gold surface deposited onto polymer-coated papers through angular scans of reflectivity in the Otto configuration under attenuated total reflection conditions. According to a surface analysis with atomic force microscope, the gold surface roughness on a polyvinyl chloride (PVC)-coated paper is comparable to that of a Si wafer, leading to the achievement of protein detection. On the other hand, the propagating length of the surface plasmons is shorter than that on the Si wafer. According to an observation of the gold surface with scanning electron microscope, the gold grain size on the PVC-coated paper is smaller than that on the Si wafer. Thus, many boundaries cause a reduction in the propagating length on the PVC-coated paper.
In this work, we evaluated the feasibility of a paper-based bacterial detection system. The paper served as a substrate for the measurement electrodes and the culture medium. Using a printing technique, we patterned gold electrodes onto the paper substrate and applied Luria broth (LB) agar gel as a culture medium on top of the electrodes. As the first step towards the development of a bacterial detection system, we determined changes in the surface potential during bacterial growth and monitored these changes over 24 h. This allowed us to correlate changes in the surface potential with the different growth phases of the bacteria.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.