Sensitive monitoring of enterobacterial contamination of food using self-propelled Janus microsensors

Food poisoning caused by bacteria is a major cause of disease and death worldwide. Herein we describe the use of Janus micromotors as mobile sensors for the detection of toxins released by enterobacteria as indicators of food contamination. The micromotors are prepared by a Pickering emulsion approach and rely on the simultaneous encapsulation of platinum nanoparticles for enhanced bubble-propulsion and receptor-functionalized quantum dots (QDs) for selective binding with the 3-deoxy-o-manno-oct-2-ulosonic acid target in the endotoxin molecule. Lipopolysaccharides (LPS) from Salmonella enterica were used as target endotoxins, which upon interaction with the QDs induce a rapid quenching of the native fluorescence of the micromotors in a concentration-dependent manner. The micromotor assay can readily detect concentrations as low as 0.07 ng mL(-1) of endotoxin, which is far below the level considered toxic to humans (275 mu g mL(-1)). Micromotors have been successfully applied for the detection of Salmonella toxin in food samples in 15 min compared with several hours required by the existing Gold Standard method. Such ultrafast and reliable approach holds considerable promise for food contamination screening while awaiting the results of bacterial cultures in a myriad of food safety and security defense applications.Ministerio de Economía y CompetitividadComunidad de Madri

Visible light driven Janus microvehicles in biological media

A light-driven multifunctional Janus micromotor for the removal of bacterial endotoxins and heavy metals is described. The micromotor was assembled by using the biocompatible polymer polycaprolactone for the encapsulation of CdTe or CdSe@ZnS quantum dots (QDs) as photoactive materials and an asymmetric Fe3O4 patch for propulsion. The micromotors can be activated with visible light (470-490 nm) to propel in peroxide or glucose media by a diffusiophoretic mechanism. Efficient propulsion was observed for the first time in complex samples such as human blood serum. These properties were exploited for efficient endotoxin removal using lipopolysaccharides from Escherichia coli O111:B4 as a model toxin. The micromotors were also used for mercury removal by cationic exchange with the CdSe@ZnS core-shell QDs. Cytotoxicity assays in HeLa cell lines demonstrated the high biocompatibility of the micromotors for future detoxification applications.Ministerio de Ciencia e InnovaciónEuropean CommissionComunidad de Madri

Magnetic reduced graphene oxide/nickel/platinum nanoparticles micromotors for mycotoxin analysis

Magnetic reduced graphene oxide/nickel/platinum nanoparticles (rGO/Ni/PtNPs) micromotors for mycotoxin analysis in food samples were developed for food-safety diagnosis. While the utilization of self-propelled micromotors in bioassays has led to a fundamentally new approach, mainly due to the greatly enhanced target?receptor contacts owing to their continuous movement around the sample and the associated mixing effect, herein the magnetic properties of rGO/Ni/PtNPs micromotors for mycotoxin analysis are additionally explored. The micromotor-based strategy for targeted mycotoxin biosensing focused on the accurate control of micromotor-based operations: 1) on-the-move capture of free aptamers by exploiting the adsorption (outer rGO layer) and catalytic (inner PtNPs layer) properties and 2) micromotor stopped flow in just 2 min by exploiting the magnetic properties (intermediate Ni layer). This strategy allowed fumonisin B1 determination with high sensitivity (limit of detection: 0.70 ngmL@1) and excellent accuracy (error: 0.05% in certified reference material and quantitative recoveries of 104:4% in beer) even in the presence of concurrent ochratoxin A (105?108:8% in wines). These results confirm the developed approach as an innovative and reliable analytical tool for food-safety monitoring, and confirm the role of micromotors as a new paradigm in analytical chemistry.Ministerio de Economía y CompetitividadComunidad de Madri

Smartphone-based Janus micromotors strategy for motion-based detection of glutathione

Herein, we describe a Janus micromotor smartphone platform for the motion-based detection of glutathione. The system compromises a universal three-dimensional (3D)-printed platform to hold a commercial smartphone, which is equipped with an external magnification optical lens (20-400x) directly attached to the camera, an adjustable sample holder to accommodate a glass slide, and a light-emitting diode (LED) source. The presence of glutathione in peroxide-rich sample media results in the decrease in the speed of 20 mu m graphene-wrapped/PtNPs Janus micromotors due to poisoning of the catalytic layer by a thiol bond formation. The speed can be correlated with the concentration of glutathione, achieving a limit of detection of 0.90 mu M, with percent recoveries and excellent selectivity under the presence of interfering amino acids and proteins. Naked-eye visualization of the speed decrease allows for the design of a test strip for fast glutathione detection (30 s), avoiding previous amplification strategies or sample preparation steps. The concept can be extended to other micromotor approaches relying on fluorescence or colorimetric detection for future multiplexed schemes.Ministerio de Ciencia e InnovaciónMinisterio de Economía, Industria y CompetitividadComunidad de Madri

Toward early diagnosis of late-onset sepsis in preterm neonates: Dual magnetoimmunosensor for simultaneous procalcitonin and C-reactive protein determination in diagnosed clinical samples

Early diagnosis of sepsis, combining blood cultures and inflammation biomarkers, continues to be a challenge, especially in very low birth weight (VLBW) infants because of limited availability of blood samples. Traditional diagnostic procedures are cumbersome, not fast enough, and require relatively large volumes of sample. Empiric use of antibiotics, before diagnostic confirmation, is required to decrease mortality, leading to potential antibiotic resistance and side effects in VLBW infants. To solve such a serious problem, a dual magnetoimmunosensor is proposed for simultaneous assessment of two of the most important sepsis biomarkers: procalcitonin (PCT for early phase) and Creactive protein (CRP for late phase). This ?sample-to-result? approach exhibited excellent sensitivity, selectivity, precision, and stability using low sample volumes (<30 ?L) and under 20 min of total assay. The analytical usefulness of the approach was demonstrated by analyzing clinically relevant samples of preterm neonates with suspicion of sepsis.Ministerio de Economía y CompetitividadComunidad Autónoma de MadridFundación “La Caixa

Polymer-based micromotors fluorescence immunoassay for on the move sensitive procalcitonin determination in very low birth weight infants' plasma

A new fluorescence micromotor-based immunoassay (FMIm) has been developed forvprocalcitonin (PCT) determination as an early sepsis diagnostic analytical tool. The micromotorsvcombine the high binding capacity of the specific antibodies onto their polymeric polypyrrole outervlayer (PPy layer), with their magnetic guidance (Ni layer) and self-propulsion by catalytic generationvof oxygen bubbles (PtNP inner layer) to actively recognize the PCT antigen. This FMIm allowed avsensitive (LOD = 0.07 ng mL?1) and direct PCT determination in clinical samples from very lowbirth-vweight infants (VLBWI) with sepsis suspicion, using small volumes of sample (25 ?L) in a clinically relevant range of concentrations (0.5?150 ng mL?1). The good agreement between PCTvlevels obtained by our micromotor-based method and routine immunofluorescence hospitalvdetermination demonstrates the feasibility for the analysis in VLBWI samples and its potential as avpoint-of-care diagnostic tool for sepsis.Ministerio de Economía, Industria y Competitividad); Comunidad de Madrid; La Caix

2D Nanomaterials wrapped Janus micromotors with built-in multiengines for bubble, magnetic, and light driven propulsion

Graphene oxide, graphdyine oxide, and blackphosphorus coated micromotors integrating "three engines" for motion control using different stimuli such as chemical fuel, light, and magnetic fields are described. Micromotors can be massproduced by wrapping gold-sputtered polystyrene microspheres with the 2D nanomaterials, followed by simultaneous assembly of Pt or MnO2 nanoparticles (NPs) as bubble (catalytic)-engines, Fe2O3 NPs as magnetic engines, and quantum dots (QDs) as light engines. The design and composition of micromotors are key to get the desired propulsion performance. In bubble-magnetic and bubble-light mode, a built-in acceleration system allows micromotor speed to be increased up to 3.0 and 1.5 times after application of the magnetic field or light irradiation, respectively. In the bubble-magnetic-light mode, such speed increase can be combined in a single unit for on-demand braking and accelerating systems. Fluid dynamics simulations illustrate that such adaptative behavior and improved propulsion efficiency is produced by a better distribution of the fuel and thus energy propelling the micromotor by activation of the magnetic and/or light engines. The new micromotors described here, which combine multiple engines with functional nanomaterials, hold considerable promise to develop novel nanovehicles with adaptative behavior to perform complex tasks in lab-on-a-chips or dynamic micropatterning applications.Ministerio de Ciencia e InnovaciónComunidad de MadridEuropean Commissio

Prussian Blue/Chitosan Micromotors with Intrinsic Enzyme-like Activity for (bio)-Sensing Assays

Prussian Blue (PB)/chitosan enzyme mimetic tubular micromotors are used here for on-the-fly (bio)-sensing assays. The micromotors are easily prepared by direct deposition of chitosan into the pores of a membrane template and in situ PB synthesis during hydrogel deposition. Under judicious pH control, PB micromotors display enzyme mimetic capabilities with three key functions on board: the autonomous oxygen bubble propulsion (with PB acting as a catalase mimic for hydrogen peroxide decomposition), 3,3',5,5'-tetramethylbenzidine (TMB) oxidation (with PB acting as a peroxidase mimic for analyte detection), and as a magnetic material (to simplify the (bio)-sensing steps). In connection with chitosan capabilities, these unique enzyme mimetic micromotors are further functionalized with acetylthiocholinesterase enzyme (ATChE) to be explored in fast inhibition assays (20 min) for the colorimetric determination of the nerve agent neostigmine, with excellent analytical performance in terms of quantification limit (0.30 mu M) and concentration linear range (up to 500 mu M), without compromising efficient micromotor propulsion. The new concept illustrated holds considerable potential for a myriad of (bio)-sensing applications, including forensics, where this conceptual approach remains to be explored. Micromotor-based tests to be used in crime scenes are also envisioned due to the reliable neostigmine determination in unpretreated samples.Ministerio de Economía, Industria y CompetitividadComunidad de MadridEuropean Commissio

OFF-ON on-the-fly aptassay for rapid and accurate determination of procalcitonin in very low birth weight infants with sepsis suspicion

A fast and reliable OFF-ON micromotors (MM)-based aptassay for rapid, sensitive, and accurate determination of procalcitonin (PCT) as one of the leading neonatal sepsis biomarkers in very low birth weight infants? serum samples is proposed. MM were composed of three specific functional layers: graphene oxide (GO) as sensing layer, Ni for magnetic guidance and platinum nanoparticles (PtNPs) as catalytic layer for self-propulsion (MMGO/ Ni/PtNPs). The OFF-ON strategy relies on the binding of the aptamer tagged with alexa-405 as fluorescent label (AptPCT, ?em=447 nm) onto the GO outer layer of the MM (GOMM) to induce its fluorescence quenching (GOMMAptPCT, OFF state); which is next recovered due to selectively binding of the aptamer to the PCT and their separation from the GOMM surface (PCT-AptPCT, ON state). The fast OFF-ON on-the-fly aptassay allowed in just 5 min a highly selective and sensitive (LOD = 0.01 ng mL? 1) PCT determination in clinical samples from very low birth weight infants with sepsis suspicion, using only 25 ?L of sample in a clinically relevant range of concentrations (0.03?1280 ng mL? 1). The high concordance between the PCT levels obtained by our MMGO/Ni/PtNPsbased aptassay and those obtained by the Hospital, demonstrated the analytical potency of our approach for the analysis of neonatal samples as well as its potential to be used as a pre-diagnostic tool for sepsis.Ministerio de Ciencia e InnovaciónComunidad de MadridEuropean Commissio

Magnetic Janus micromotors for fluorescence biosensing of tacrolimus in oral fluids

Tacrolimus (FK506) is a macrolide lactone immunosuppressive drug that is commonly used in transplanted patients to avoid organ rejection. FK506 exhibits high inter-and intra-patient pharmacokinetic variability, making monitoring necessary for organ graft survival. This work describes the development of a novel bioassay for monitoring FK506. The bioassay is based on using polycaprolactone-based (PCL) magnetic Janus micro motors and a recombinant chimera receptor that incorporates the immunophilin tacrolimus binding protein 1A (FKBP1A) tagged with Emerald Green Fluorescent Protein (EmGFP). The approach relies on a fluorescence competitive bioassay between the drug and the micromotors decorated with a carboxylated FK506 toward the specific site of the fluorescent immunophilin. The proposed homogeneous assay could be performed in a single step without washing steps to separate the unbound receptor. The proposed approach fits the therapeutic requirements, showing a limit of detection of 0.8 ng/mL and a wide dynamic range of up to 90 ng/mL. Assay selectivity was evaluated by measuring the competitive inhibition curves with other immunosuppressive drugs usually co-administered with FK506. The magnetic propulsion mechanism allows for efficient operation in raw samples without damaging the biological binding receptor (FKBP1A-EmGFP). The enhanced target recognition and micromixing strategies hold considerable potential for FK506 monitoring in practical clinical use.Ministerio de Ciencia e InnovaciónComunidad de Madri