Photoacoustic Flow Cytometry Using Functionalized Microspheres for Selective Detection of Bacteria

Abstract

Photoacoustic flow cytometry is a method to detect rare analytes in fluids. We developed photoacoustic flow cytometry to detect pathological cells in body fluids, such as circulating tumor cells or bacteria in blood. In order to induce specific optical absorption in bacteria, we use modified bacteriophage that precisely target bacterial species or subspecies for rapid identification. In order to reduce detection variability and to halt the lytic lifescycle that results in lysis of the bacteria, we attached dyed latex microspheres to the tail fibers of bacteriophage that retained the bacterial recognition binding sites. We tested these microsphere complexes using Salmonella enterica (Salmonella) and Escherichia coli (E. coli) bacteria and found robust and specific detection of targeted bacteria. In our work we used LT2, a strain of Salmonella, against K12, a strain of E. coli. Using Det7, a bacteriophage that binds to LT2 and not to K12, we detected an average of 109.3±9.0 of LT2 versus 2.0±1.7 of K12 using red microspheres and 86.7±13.2 of LT2 versus 0.3±0.6 of K12 using blue microspheres. These results confirmed our ability to selectively detect bacterial species using photoacoustic flow cytometry.

A Miniature Multi-Functional Photoacoustic Probe

“…Thirdly, optical lenses used for focusing lasers in the reported work were separated with the TUTs such that a mount must be applied to fix and adjust the lens coaxially with the TUT. Therefore, the TUT with the lens mount would give a bulky photoacoustic probe, restricting the applications especially for those requiring a compact portable setup [ 16 , 17 ], such as in vivo photoacoustic flow cytometry [ 18 , 19 , 20 , 21 ] and wearable PAM [ 22 , 23 , 24 ].…”

A Miniature Multi-Functional Photoacoustic Probe

“…Thirdly, optical lenses used for focusing laser in the reported work were separated with the TUT such that a mount must be applied to fix and adjust the lens coaxially with the TUT. Therefore, the TUT with the lens mount would give a bulky photoacoustic probe, restricting the applications especially for those requiring compact portable setup [16,17], such as in vivo photoacoustic flow cytometry [18][19][20][21] and wearable PAM [22][23][24].…”