Understanding and Advancing the 3-mercaptophenylboronic Acid Chemical Label for Optimal Surface-enhanced Raman Spectroscopic Analysis of Bacteria Populations.

3-mercaptophenylboronic acid (3-MPBA) was applied as a capturer and label for bacteria detection using surface-enhanced Raman spectroscopy (SERS). The objective of this study was to further understand and advance 3-MPBA as a SERS labeling chemical to study bacteria populations using SERS. We report that the coating of bacteria cells with 3-MPBA was very strong, with bacteria producing 3-MPBA SERS signals after five thorough rinse water applications. The procedure was also found to implement harm to bacterial ecology, and the trend was quantitatively different based on the initial cell population being labeled. SERS imaging by this approach measured all labeled bacteria cells, regardless of viability. Nonculturable cells are therefore detectable by this SERS approach. Nanoparticle administrations were optimal when bacteria cells were suspended in a liquid or applied to substrates which already possessed nanostructures. Circumstances in which dried bacteria cells were present upon a substrate prior to nanoparticle administrations warranted lower SERS signals in comparison. Bacteria were analyzed at the single-cell scale using this approach, and the data revealed that microscopic objective lenses and overall bacteria population influenced the SERS limit-of-detection in this respect. The information obtained from this study provides useful guidelines for advancing 3-MPBA labeling for the SERS analysis of bacteria.