Ultrafast and Sensitive Screening of Pathogens by Functionalized Janus Microbeads-Enabled Rotational Diffusometry in...

Polymerase chain reaction (PCR) is widely considered the gold standard in molecular diagnostics because of its high accuracy. However, conventional PCR is very time-consuming (turnaround time 4-6 h), labor-intensive, and high-tech instruments dependent. Therefore, developing an ultrafast and sensitive nucleic amplification-based detection method is still in high demand. Herein, a rapid screening of Escherichia coli using an advanced and sensitive biosensing method known as rotational diffusometry in combination with loop-mediated isothermal amplification (LAMP) is reported. Given that the solution viscosity is increased with nucleic acid amplification, the viscosity change can be measured by the functionalized Janus microbeads-enabled rotational diffusometry. The rotational diffusivity derived from capturing images of microbeads is expressed in terms of blinking signals. Under such conditions, this method can achieve a limit of detection of 42.8 fg μL^-1 in 10 min for E. coli with sample volume as low as 2 μL. Additionally, detection of E. coli whole cells extracted from artificially contaminated milk, juice, and water is performed by the developed method and validated with real-time PCR. Through this biosensing technique, a rapid, reliable, and low sample volume screening tool can be established, improving the shortcomings of the current time-consuming and labor-intensive methods.