Reliable early-stage detection of foodborne pathogens is a global public health challenge that requires new and improved sensing strategies. Here, we demonstrate that dynamically reconfigurable fluorescent double emulsions can function as highly responsive optical sensors for the rapid detection of carbohydrates fructose, glucose, mannose, and mannan, which are involved in many biological and pathogenic phenomena. The proposed detection strategy relies on reversible reactions between boronic acid surfactants and carbohydrates at the hydrocarbon/water interface leading to a dynamic reconfiguration of the droplet morphology, which alters the angular distribution of the droplet’s fluorescent light emission. We exploit this unique chemical–morphological–optical coupling to detect Salmonella enterica, a type of bacteria with a well-known binding affinity for mannose. We further demonstrate an oriented immobilization of antibodies at the droplet interface to permit higher selectivity. Our demonstrations yield a new, inexpensive, robust, and generalizable sensing strategy that can help to facilitate the early detection of foodborne pathogens.

Using 3-mercaptopropyltrimethoxysilane (MPS)-coated ${\left(\mathrm{Pb}{\mathrm{Mg}}_{1∕3}{\mathrm{Nb}}_{2∕3}{\mathrm{O}}_3\right)}_{0.63}–{\left(\mathrm{Pb}\mathrm{Ti}{\mathrm{O}}_3\right)}_{0.37}$ (PMN-PT)/tin and lead zirconate titanate/glass piezoelectric microcantilever sensors (PEMSs) with single-chain variable fragment (scFv) immobilized on the MPS surface, we have demonstrated real-time, label-free detection of human epidermal growth factor receptor 2 (Her2) in a background of $1\mathrm{mg}∕\mathrm{ml}$ bovine serum albumin. Coupled with a scFv with a $K_D$ of $3.4\times {10}^{-8}M$ , the MPS-insulated PMN-PT/tin PEMS $560\mu \mathrm{m}$ long and $720\mu \mathrm{m}$ wide exhibited a Her2 concentration sensitivity of $5\mathrm{ng}∕\mathrm{ml}$ in a background of $1\mathrm{mg}∕\mathrm{ml}$ BSA.

Amplified luminescent proximity homogenous assay-linked immunosorbent assay (AlphaLISA) is comprised of a bead-based immunoassay that is used for small molecule detection. In this study, a novel AlphaLISA was developed and optimized for the detection of Shiga-toxin 2 (Stx2). Efficacy and sensitivity trials showed the AlphaLISA could detect ≥0.5 ng/mL of purified Stx2, which was comparable to the industry-standard enzyme-linked immunosorbent assay (ELISA) tests for Stx2 detection. In addition, evaluation of Shiga toxin-producing Escherichia coli (STEC)-inoculated Romaine lettuce and ground beef samples demonstrated that both the AlphaLISA and the ELISA were able to discern uninoculated samples from 1× and 10× diluted samples containing ~10 CFU/mL of STEC enriched in modified tryptic soy broth with mitomycin C for 16 h. Overall, the increased signal-to-noise ratios indicated a more robust signal was produced by the AlphaLISA compared to the ELISA and the delineation of higher toxin concentrations without the need for sample dilution implied a greater dynamic range for the AlphaLISA. Implementation of the newly developed AlphaLISA will allow for more rapid analysis for Stx2 with less manual manipulation, thus improving assay throughput and the ability to automate sample screening while maintaining detection limits of 0.5 ng/mL.