One-dimensional Diffraction Sensors With High Sensitivity for On-site Rapid Label-free Plague Diagnosis With A Reflective Laser Detection System

Abstract For preventing widespread transmission of communicable diseases, we developed a simple method for detecting the presence of pathogens in human blood specimens quickly at the point of care, using Yersinia pestis, the bacteria for plague, as our first target. We addressed the disadvantage of the currently prevalent detection methods, which required the specimens to be transported to labs for microbial culture and analysis. Our system was highly sensitive, achieving 100 CFU/mL limit of detection with a linearity range between 102–107 CFU/mL. It was based on adding the specimens onto our in-house one-dimensional diffraction grating (ODG) chips, pointing laser beams at them at 45-degree incident angle, and measuring the intensity of the reflective diffraction, which would be reduced at the pathogen’s presence. The ODGs featured poly(methacrylic acid) (PMAA) brushes with the antibody at the tips to specifically capture the target pathogen but not other cells or pathogens. The laser beam entered the chips, which were oriented such that its trenches were parallel to the beam’s projection onto the chip plane as we found the system more sensitive in such configuration. The two- and three-dimensional reflective diffraction was characteristic in that the diffraction orders’ angles and amplitudes exhibited symmetric and asymmetric properties depending on the orientation of the chips. Their intensity was an indicator for the presence of specific pathogen. The instruments were portable, and the entire process could be completed at the point of care within minutes.