The existence of contaminants in food poses a serious threat to human health. In recent years, aptamer sensors (aptasensors) have been developed rapidly for the detection of food contaminants because of their high specificity, design flexibility, and high efficiency. However, the development of high-throughput, highly sensitive, on-site, and cost-effective methods for simultaneous detection of food contaminants is still restricted due to multiple signal overlap or mutual interference and cross-reaction between different analytes with similar molecular structures. To overcome these problems, this Review summarizes some effective strategies from the articles published in recent years about multiplexed aptasensors for the simultaneous detection of food contaminants. This work focuses on the application of multiplexed aptasensors to simultaneously detect antibiotics, pathogens, and mycotoxins in food. These aptasensors mainly contain fluorescent aptasensors, electrochemical aptasensors, surface-enhanced Raman scattering-based aptasensors, microfluidic chip aptasensors, and paper-based multiplexed aptasensors. In addition, this Review also covers the application of nucleic acid cycle amplification and nanomaterial amplification strategies to improve the detection sensitivity. Finally, the limitations and challenges in the design of multiplexed aptasensor are also taken into account.

Application of Multiplexed Aptasensors in Food Contaminants Detection.

Recent advances in nanotechnology for simultaneous detection of multiple pathogenic bacteria

Ratiometric fluorescent signals-driven smartphone-based portable sensors for onsite visual detection of food contaminants

Reliable on-site monitoring of antibiotic residue is critical to establish the efficient pollution early-warning mechanism for ensuring food safety and environmental health. Herein, we reported the engineering of liposome-encapsulated aggregation-induced emission fluorogen into the portable smartphone for achieving the visual on-site detection of residual tetracycline (TC). Through nanoprecipitation, the aggregation-induced emission fluorogen (AIEgen) tetraphenylethene (TPE) was encapsulated into an amphiphilic phospholipid polymer, affording a scaffold to assemble Eu3+ for forming Eu3+-functionalized liposome-based AIEgen (Eu3+@AIEgen) with bright blue fluorescence at ~456 nm. Upon assistance of citrate, TC was capable of triggering the remarkable fluorescence color change from bright blue (~456 nm) to pink owing to the new red fluorescence emission appeared at ~611 nm, thereby emerging a significant dual-emission for ratiometric response. As expected, an ingenious citrate-assisted Eu3+@AIEgen liposome-based smartphone was proposed to precisely on-site report the residual levels of TC in real sample among the linear range of 0.0961–10.0 μM. Furthermore, this portable sensor exhibited a high sensitivity attributable to the low detection limit of 28.83 nM together with a fast response kinetics of 2.0 min for TC, agreeing well with the demands of on-site assay. This study showed the promising potential for utilizing AIEgen liposome to develop a new category of portable sensors for the point-of-care detection of antibiotic residue in complicated food and environment-related matrixes, which might open a novel way to establish efficient pollution early-warning mechanism for safeguarding public health. 

Liposome-encapsulated aggregation-induced emission fluorogen assisted with portable smartphone for dynamically on-site imaging of residual tetracycline

Engineering efficient artificial nanozyme based on chitosan grafted Fe-doped-carbon dots for bacteria biofilm eradication.

Rapid, accurate, reliable, and risk-free tracking of pathogenic microorganisms at the single-cell level is critical to achieve efficient source control and prevent outbreaks of microbial infectious diseases. For the first time, we report a promising approach for integrating the concepts of a remarkably large Stokes shift and dual-recognition into a single matrix to develop a pathogenic microorganism stimuli-responsive ratiometric fluorescent nanoprobe with speed, cost efficiency, stability, ultrahigh specificity, and sensitivity. As a proof-of-concept, we selected the Gram-positive bacterium Staphylococcus aureus (S. aureus) as the target analyte model, which easily bound to its recognition aptamer and the broad-spectrum glycopeptide antibiotic vancomycin (Van). To improve the specificity and short sample-to-answer time, we employed classic noncovalent π-π stacking interactions as a driving force to trigger the binding of Van and aptamer dual-functionalized near-infrared (NIR) fluorescent Apt-Van-QDs to the surface of an unreported blue fluorescent π-rich electronic carbon nanoparticles (CNPs), achieving S. aureus stimuli-responsive ratiometric nanoprobe Apt-Van-QDs@CNPs. In the assembly of Apt-Van-QDs@CNPs, the blue CNPs (energy donor) and NIR Apt-Van-QDs (energy acceptor) became close to allow the fluorescence resonance energy transfer (FRET) process, leading to a remarkable blue fluorescence quenching for the CNPs at ∼465 nm and a clear NIR fluorescence enhancement for Apt-Van-QDs at ∼725 nm. In the presence of S. aureus, the FRET process from CNPs to Apt-Van-QDs was disrupted, causing the nanoprobe Apt-Van-QDs@CNPs to display a ratiometric fluorescent response to S. aureus, which exhibited a large Stokes shift of ∼260 nm and rapid sample-to-answer detection time (∼30.0 min). As expected, the nanoprobe Apt-Van-QDs@CNPs showed an ultrahigh specificity for ratiometric fluorescence detection of S. aureus with a good detection limit of 1.0 CFU/mL, allowing the assay at single-cell level. Moreover, we also carried out the precise analysis of S. aureus in actual samples with acceptable results. We believe that this work offers new insight into the rational design of efficient ratiometric nanoprobes for rapid on-site accurate screening of pathogenic microorganisms at the single-cell level in the early stages, especially during the worldwide spread of COVID-19 today.

Engineering of a Dual-Recognition Ratiometric Fluorescent Nanosensor with a Remarkably Large Stokes Shift for Accurate Tracking of Pathogenic Bacteria at the Single-Cell Level.

Na Ling

Papers

Engineering of a Dual-Recognition Ratiometric Fluorescent Nanosensor with a Remarkably Large Stokes Shift for Accurate Tracking of Pathogenic Bacteria at the Single-Cell Level.