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

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

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

Biosensing Strategy for Simultaneous and Accurate Quantitative Analysis of Mycotoxins in Food Samples Using Unmodified Graphene Micromotors

A high-performance graphene-based micromotor strategy for simultaneous, fast, and reliable assessment of two highly concerning mycotoxins (fumonisin B1 (FB1) and ocratoxin A (OTA)) has successfully been developed. The assay principle is based on the selective recognition from aptamers to the target mycotoxins and further "on-the-move" fluorescence quenching of the free aptamer in the outer layer of unmodified reduced graphene (rGO; sensing layer) micromotors. Template-prepared rGO/platinum nanoparticles (PtNPs) tubular micromotors were synthesized rapidly and inexpensively by the direct electrodeposition within the conical pores of a polycarbonate template membrane. The new wash-free approach offers using just 1 μL of sample, a simultaneous and rapid "on-the-fly" detection (2 min) with high sensitivity (limits of detection of 7 and 0.4 ng/mL for OTA and FB1, respectively), and high selectivity. Remarkable accuracy (Er < 5%) during the mycotoxin determination in certified reference material as well as excellent quantitative recoveries (96-98%) during the analysis of food samples were also obtained. The excellent results obtained allow envisioning an exciting future for the development of novel applications of catalytic micromotors in unexplored fields such as food safety diagnosis.Depto. de Química en Ciencias FarmacéuticasCAI Ciencias de la Tierra y ArqueometríaTRUEpu

An on-chip microfluidic-based electrochemical magneto-immunoassay for procalcitonin determination in plasma from sepsis diagnosed preterm neonates

A novel on-chip electrochemical magneto-immunoassay for Procalcitonin (PCT) determination is proposed. The strategy implies the on-line performing of the biorecognition event and the detection onto thin film microfluidic gold electrodes chamber operating at E= ?0.20 V (vs Au). The complete assay was performed in less than 15 minutes using only 25 ?L of sample, covering the entire spectrum of relevant clinically PCT concentrations in sepsis diagnosis and with a limit of detection and quantification of 0.02 ng/mL and 0.05 ng/mL, respectively (sepsis diagnosis threshold: 0.5 ng/mL). The onchip electrochemical magneto-immunoassay provided excellent results in the analysis of very unique samples coming from preterm neonates with sepsis suspicion, in which sample volume is hardly available. These characteristics fulfill the POCT requirements for PCT determination in the whole relevant clinical concentrations. Because of the high clinical relevance and the important role of PCT in sepsis, this approach opens new perspectives for the sepsis diagnosis and therapy guidance using low volume samples.La CaixaMinisterio de Economía, Industria y CompetitividadComunidad de Madri

An array-based electrochemical magneto-immunosensor for early neonatal sepsis diagnostic: Fast and accurate determination of C-reactive protein in whole blood and plasma samples

An array-based electrochemical magneto-immunosensor (a-EMI) constituted by eight screen-printed carbon electrodes is proposed for the determination of C-reactive protein (CRP). Remarkably, the analytical usefulness of the approach was demonstrated not only by analyzing whole blood samples, but plasma ones from newborns with suspicion of sepsis, which sample volume is hardly available. The a-EIM enabled the accurate determination of CRP in these unique samples (Er < 3%) with excellent intra (CV<4%, n=8) and inter-assays (CV<9%, n=8) precision, using only 5 µL of clinical sample, covering the sepsis diagnostic range and employing only 15 min for total assay. The electrode array enabled to work with up to 8 tailored dilutions simultaneously accordingly to the CRP clinical diagnostic range. It constitutes by itself a valuable advantage for speed and reliability improvements in the sample analysis and further sepsis diagnosis. These results non-only highly met the clinical needs for sepsis newborns diagnosis, but they opened new perspectives in low volumes-based diagnostics.Depto. de Química en Ciencias FarmacéuticasCAI Ciencias de la Tierra y ArqueometríaTRUEpu

Magnetic Bead-Based Electrochemical Immunoassays On-Drop and On-Chip for Procalcitonin Determination: Disposable Tools for Clinical Sepsis Diagnosis

Procalcitonin (PCT) is a known protein biomarker clinically used for the early stages of sepsis diagnosis and therapy guidance. For its reliable determination, sandwich format magnetic bead-based immunoassays with two different electrochemical detection approaches are described: (i) disposable screen-printed carbon electrodes (SPE-C, on-drop detection); (ii) electro-kinetically driven microfluidic chips with integrated Au electrodes (EMC-Au, on-chip detection). Both approaches exhibited enough sensitivity (limit of detection (LOD) of 0.1 and 0.04 ng mL−1 for SPE-C and EMC-Au, respectively; cutoff 0.5 ng mL−1), an adequate working range for the clinically relevant concentrations (0.5–1000 and 0.1–20 ng mL−1 for SPE-C and EMC-Au, respectively), and good precision (RSD < 9%), using low sample volumes (25 µL) with total assay times less than 20 min. The suitability of both approaches was successfully demonstrated by the analysis of human serum and plasma samples, for which good recoveries were obtained (89–120%). Furthermore, the EMC-Au approach enabled the easy automation of the process, constituting a reliable alternative diagnostic tool for on-site/bed-site clinical analysis

Polymer-Based Micromotor 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 for procalcitonin (PCT) determination as an early sepsis diagnostic analytical tool. The micromotors combine the high binding capacity of the specific antibodies onto their polymeric polypyrrole outer layer (PPy layer), with their magnetic guidance (Ni layer) and self-propulsion by catalytic generation of oxygen bubbles (PtNP inner layer) to actively recognize the PCT antigen. This FMIm allowed a sensitive (LOD = 0.07 ng mL-1) and direct PCT determination in clinical samples from very low-birth-weight infants (VLBWI) with sepsis suspicion, using small volumes of sample (25 μL) in a clinically relevant range of concentrations (0.5-150 ng mL-1). The good agreement between PCT levels obtained by our micromotor-based method and routine immunofluorescence hospital determination demonstrates the feasibility for the analysis in VLBWI samples and its potential as a point-of-care diagnostic tool for sepsis.Ministerio de Economía, Industria y Competitividad (España)TRANSNANOAVANSENS programComunidad de MadridLa CaixaDepto. de Química en Ciencias FarmacéuticasFac. de FarmaciaTRUEpu