Rapid and Sensitive Escherichia coli Detection: Integration of SERS and Acoustofluidics in a Lysis-Free Microfluidic Platform

Bacterial infections, such as sepsis, require prompt and precise identification of the causative bacteria for appropriate antibiotics treatment. Traditional methods such as culturing take 2-5 days, while newer techniques such as reverse transcription-polymerase chain reaction and mass spectrometry are hindered by blood impurities. Consequently, this study developed a surface-enhanced Raman scattering (SERS)-based acoustofluidic technique for rapid bacterial detection without culturing or lysing. Target bacteria are first tagged with SERS nanotags in a microtube. The solution with tagged bacteria and unbound SERS nanotags is passed through a silicon microfluidic channel. A piezoelectric transducer generates acoustic waves within the channel, concentrating larger tagged bacteria in the center and pushing smaller unbound nanotags toward the channel walls. A laser beam is focused at the center of the channel, and the Raman signals of bacteria passing through the focal volume are measured for quantitative analysis. As a proof of concept, this study detected various concentrations of Escherichia coli at a limit of detection of 1.75 × 105 CFU/mL within 1 h. This method offers significant clinical potential, enabling rapid and accurate bacterial identification without genetic material extraction, cultivation, or lysis.