Plasmonic microneedle arrays for rapid extraction, SERS detection, and inactivation of bacteria

Microbial contamination of food is a critical public health issue worldwide, making the rapid, efficient, and safe sensing strategies for foodborne microbes in urgent need. In this work, a plasmonic microneedle (MN) array patch was developed for rapid extraction and surface-enhanced Raman spectroscopy (SERS) detection of a model bacteria, Escherichia coli (E. coli). A hydrophilic MN matrix was firstly prepared by crosslinking [2-(methacryloyloxy)ethyl]trimethylammonium chloride (TMA), 2-carboxyethyl acrylate (CAA), and 2-hydroxyethyl methacrylate (HEMA) in a micro-mold. Then the obtained MN patch was treated with ozone and coated with SERS-active gold nanopopcorns (GNpops) that were modified with the specific aptamer towards E. coli. The resultant plasmonic MN patch could extract E. coli from agarose simulant in 3 min and was capable of on-MN SERS analysis with a detection limit of 143 CFU/g. The proposed detection method exhibited great specificity to E. coli and was feasible for evaluating the E. coli contamination of commercial mutton samples. Moreover, the extracted bacteria could be effectively inactivated through photothermal sterilization. The work opened a new avenue for simplifying the detection procedures for microorganisms and provided a potential approach for rapid and on-site microbial monitoring through the SERS-active MN patch.