Magnetorheological elastomer and smartphone enable microfluidic biosensing of foodborne pathogen

Rapid detection of foodborne pathogens is crucial to prevent the outbreaks of foodborne diseases.In this work,we proposed a novel microfluidic biosensor based on magnetorheological elastomer(MRE)and smartphone.First,micropump and microvalves were constructed by deforming the MRE under magnetic actuation and integrated into the microfluidic biosensor for fluidic control.Then,the micropump was used to deliver immune porous gold@platinum nanocatalysts(Au@PtNCs),bacterial sample,and immunomagnetic nanoparticles(MNPs)into a micromixer,where they were mixed,incubated and magnetically separated to obtain the Au@PtNC-bacteria-MNP complexes.After 3,3',5,5'-tetramethylbenzidine and hydrogen peroxide were injected and catalyzed by the Au@PtNCs,smartphone was used to measure the color of the catalysate for quantitative analysis of target bacteria.Under optimal conditions,this biosensor could detect Salmonella typhimurium quantitatively and automatically in 1 h with a linear detection range of 8.0×10^(1) CFU/mL to 8.0×10^(4) CFU/mL and a detection limit of 62 CFU/mL.The microfluidic biosensor was compact in size,simple to use,and efficient for detection,and might be used for in-field screening of foodborne pathogens to prevent food poisoning.

Magnetic Bead Manipulation in Microfluidic Chips for Biological Application

Magnetic beads manipulation in microfluidic chips is a promising research field for biological application,especially in the detection of biological targets.In this review,we intend to present a thorough and indepth overview of recent magnetic beads manipulation in microfluidic chips and its biological application.First,we introduce the mechanism of magnetic manipulation in microfluidic chip,including force analysis,particle properties,and surface modification.Then,we compare some existing methods of magnetic manipulation in microfluidic chip and list their biological application.Besides,the suggestions and outlook for future developments in the magnetic manipulation system are also discussed and summarized.

A microfluidic biosensor for rapid detection of Salmonella typhimurium based on magnetic separation,enzymatic catalysis and electrochemical impedance analysis

Rapid screening of foodborne pathogens is of great significance to ensure food safety.A microfluidic biosensor based on immunomagnetic separation,enzyme catalysis and electrochemical impedance analysis was developed for rapid and sensitive detection of S.typhimurium.First,the bacterial sample,the magnetic nanoparticles(MNPs)modified with capture antibodies,and the enzymatic probes modified with detection antibodies and glucose oxidase(GOx)were simultaneously injected into the microfluidic chip,followed by mixing and incubation to form MNP-bacteria-probe sandwich complexes.Then,glucose with high impedance was injected into the chip and catalyzed by the GOx on the complexes into hydrogen peroxide with high impedance and gluconic acid with low impedance,which was finally measured using the low-cost interdigitated microelectrode and the electrochemical impedance analyzer to determine the target bacteria.Under the optimal conditions,this biosensor could quantitatively detect S.typhimurium at the concentrations from 1.6×10^(2) CFU/m L to 1.6×10^(6) CFU/m L in 1 h with the low detection limit of 73 CFU/m L.Besides,this biosensor was demonstrated with good feasibility for practical applications by detecting the S.typhimurium spiked chicken meat samples.

Development of automatic and efficient immuno-separator of foodborne pathogenic bacteria using magnetophoresis and magnetic mixing

In recent years,the outbreaks of foodborne diseases caused by pathogenic bacteria have made considerable economic losses and shown a threat to public health.The key to prevent and control these diseases is fast screening of pathogenic bacteria,which is usually performed with three procedures:sample collection,bacteria separation and bacteria detection.For sample collection,the national standard methods are often employed.For bacteria detection,currently available methods such as Polymerase Chain Reaction and Enzyme Linked Immuno-Sorbent Assay are often used.For bacteria separation,traditional methods such as filtration and centrifugation are not capable to specifically separate the target bacteria.However,food samples are very complicated and require efficient pretreatment for bacteria separation and concentration to achieve accurate and reliable results.The conventional immune magnetic separation method can be used to specifically separate the bacteria,but it still cannot meet the requirements for food sample pretreatment due to very low concentration of target bacteria in food.Therefore,this study developed an automatic and efficient immuno-separator of foodborne bacteria based on magnetophoresis and magnetic mixing,and E.coli O157:H7 was used as research model.A magnetic mixer was applied to facilitate the immunoreaction between the immune magnetic nanoparticles and the target bacteria cells,and a magnetophoretic separation tubing was utilized for magnetophoretic separation of the magnetic bacteria.Under the optimal mixing time of 20 min and the optimal flow rate of 50μL/min,the separation efficiency of E.coli O157:H7 could be more than 90%,showing that the developed immuno-separator is promising to be applied for efficient separation of foodborne bacteria and can be easily extended for separation of other biological targets by using their specific antibodies.