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.
Emulsion waveguides: a new modular sensing approach in which complex emulsions serve as efficient transducers in optical evanescent field-based waveguide sensors is reported.
Despite the recent emergence of microcavity resonators as label-free biological and chemical sensors, practical applications still require simple and robust methods to impart chemical selectivity and reduce cost of fabrication. We introduce the use of hydrocarbon-in-fluorocarbon-inwater (HC/FC/W) double emulsions as a liquid top cladding that expands the versatility of optical resonators as chemical sensors. The all-liquid complex emulsions are tunable droplets that undergo dynamic and reversible morphological transformations in response to a change in the chemical environment (e.g., exposure to targeted analytes). This chemical-morphological coupling drastically modifies the effective refractive index, allowing the complex emulsions to act as a chemical transducer and signal amplifier. We detect this large change in refractive index by tracking the shift of the enveloped resonant spectrum of a silicon nitride (Si 3 N 4 ) racetrack resonator-based sensor, which correlates well with a change in the morphology of the complex droplets. This combination of soft materials (dynamic complex emulsions) and hard materials (onchip resonators) provides a unique platform for liquid-phase, real-time, and continuous detection of chemicals and biomolecules, for miniaturized and remote, environmental, medical, and wearable sensing applications.
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