Featured ApplicationRapid magnetic enrichment strategy can significantly improve the sensitivity of multiplex PCR analysis and shorten the pre-concentration time. The simultaneous and sensitive detection of pathogenicListeriaspp. was achieved.AbstractListeria monocytogenesandListeria ivanoviiare important pathogenicListeriaspp. that cause infections in humans and animals. Establishing a rapid and sensitive method for the simultaneous screening of pathogenicListeriaspp. is of great significance for ensuring food safety. Multiplex polymerase chain reaction (mPCR) has been extensively reported to simultaneously detect several pathogens in food with high sensitivity, but a time-consuming pre-enrichment process is necessary. In this study, we report the usage of surface-modified polyethyleneimine-coated positively charged magnetic nanoparticles (PEI-MNPs) for rapid enrichment of pathogenicListeriaspp. through electrostatic interactions. The enrichment process takes only 10 min with high capture efficiency (more than 70%) at a wide pH range and ionic strength. Combined with mPCR analysis, the PEI-MNPs-mPCR strategy can simultaneously, rapidly, and sensitively detect pathogenicListeriaspp. without a time-consuming pre-concentration process. Under the optimal conditions, the detection limits ofL. monocytogenesandL. ivanoviiin lettuce were both as low as 101CFU/mL, which was a hundred times lower than that without magnetic enrichment. In conclusion, the magnetic enrichment strategy based on charge interaction combined with mPCR analysis has great application potential in shortening the pre-concentration time of foodborne pathogens and improving the detection sensitivity.Keywords:magnetic enrichment;multiplex PCR;electrostatic interaction;bacteria detection;method sensitivity;food safety
The detection of bifenthrin is closely related to the adsorption of SERS substrates. In this study, superparamagnetic Fe3O4@Au MNPs coated with GO were used to detect the adsorption and enrichment of bifenthrin molecules with benzene rings. Firstly, the thermal solvent method synthesized Fe3O4magnetic nanoparticles (MNPs) with a particle size of ~250 nm. Next, polyethylene imide (PEI) was used as an intermediate layer to modify the surface of Fe3O4to form a positively charged ultra-thin polymer middle layer. Next, the gold shell was developed by adsorption of ~20 nm AuNPs, without affecting the magnetic properties. Then, the additional amount of colloidal gold and GO on SERS performance was systematically studied. Using crystal violet (CV) as the probe, we investigated the SERS performance of composite nanomaterials. The lowest detected concentration reached 10−8mol/L, confirming that the composite functional material had good SERS activity and magnetic properties. Finally, the substrate was used to detect bifenthrin in an acetone solution, and the lowest detection concentration was 10−8mol/L. These results showed that the prepared GO/Fe3O4@Au MNPs were efficient SERS substrates that could detect bifenthrin pesticide residue with high sensitivity.
Conventional surface plasmon resonance (SPR) sensor often fails to detect low-concentration small molecules due to insufficient refractive index changes. To address this challenge, we have developed an enhanced SPR sensor utilizing Fe 3 O 4 @Au@polydopamine (PDA) core–shell magnetic nanoparticles as signal amplification tags for the detection of tebuconazole (TBZ). These nanoparticles improve sensitivity through their high refractive indices and enable TBZ enrichment from complex matrices via their magnetic properties. The sensor surface is further modified with PDA, which acts as a reducing agent for Au nanoparticle deposition, enhancing monoclonal antibody (Ab) immobilization and boosting the SPR signal. Our optimized sensor reaches a limit of detection (LOD) at 0.61 ng/mL for TBZ, with a linear response from 1-200 ng/mL, and demonstrates high selectivity and reproducibility, ideal for pesticide monitoring in food samples.
Sophisticated surface-enhanced Raman scattering (SERS)-active nanocomposites with both self-correction and cleaning capabilities provide new perspectives for the quantitative detection and degradation of hazardous molecules. In this work, a multifunctional GO-coated Fe3O4@TiO2@AuAg SERS substrate was developed. Attributed to the magnetic core, a relatively uniform substrate was induced by an external magnetic field and a sensitive SERS-based detection of trace mixed additives in foods was facilitated by electromagnetic enhancement from the well-modified Au/Ag binary nanoparticles in conjunction with the molecular enrichment ability of the GO. Particularly, the intrinsic Raman signal at 149 cm–1 of TiO2 was fully exploited to act as an intrinsic internal standard for the improvement of the quantitative level of such detection. Additionally, the efficient green elimination of these target molecules within 60 min was enabled by the multifunctional TiO2 layer. It is expected that this novel SERS substrate with both quantitative analytical and photocatalytic capability may extend to a broad application for detecting analytes in complex systems.
危险品化学品经营许可证（带存储）