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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 micromotors 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., UCM for a predoctoral contract, Depto. de Química Analítica, Fac. de Ciencias Químicas, TRUE, pub

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., Spanish Ministry of Education, Spanish Ministry of Science, Innovation and Universities, University of Alcala, TRANSNANOAVANSENS program, Depto. de Química en Ciencias Farmacéuticas, Fac. de Farmacia, TRUE, pub

Oxidative decontamination: An effective strategy for the oxidative neutralization of organophosphorus nerve agents that is based on self-propelled micromotors has been developed. The movement of multiple motors across a peroxide-activated contaminated solution enhances the decontamination efficiency compared with common neutralization processes for chemical warfare agents., Defense Threat Reduction Agency–Joint Science and Technology Office for Chemical and Biological Defense, Ministerio de Economía y Competitividad, Depto. de Química Analítica, Fac. de Ciencias Químicas, TRUE, pub

Magnetocatalytic hybrid Janus micromotors encapsulating phenylboronic acid (PABA) modified graphene quantum dots (GQDs) are described herein as ultrafast sensors for the detection of deadly bacteria endotoxins. A bottom-up approach was adopted to synthesize an oil-in-water emulsion containing the GQDs along with a high loading of platinum and iron oxide nanoparticles on one side of the Janus micromotor body. The two different “active regions” enable highly efficient propulsion in the presence of hydrogen peroxide or magnetic actuation without the addition of a chemical fuel. Fluorescence quenching was observed upon the interaction of GQDs with the target endotoxin (LPS), whereby the PABA tags acted as highly specific recognition receptors of the LPS core polysaccharide region. Such adaptive hybrid operation and highly specific detection hold considerable promise for diverse clinical, agrofood, and biological applications and integration in future lab-on-chip technology., Depto. de Química en Ciencias Farmacéuticas, Fac. de Farmacia, TRUE, pub

Novel single-walled carbon nanotube press-transfer electrodes (SW-PTEs) for microfluidic sensing are proposed. In this approach, carbon nanotubes are press-transferred on poly- (methyl methacrylate) (PMMA) substrates and are easily coupled to microfluidic chips and act as the exclusive transducer in electrochemical sensing. The detector design consisted of a presstransferred SW film (7 mm × 1 mm) positioned and centered on the PMMA substrate (33 mm × 9 mm). The analytical performance of the SW-PTEs was deeply evaluated using two commercial SWs sources and employing a mixture of dopamine and catechol as model analytes. Analyte detection was influenced by the volume of commercial SW dispersion used in the fabrication of SW-PTEs, with 5 mL taken from a dispersion of 0.5 mg/100 mL being the most favorable volume. In addition, excellent repeatability (relative standard deviation (RSD) of ≤7%, n = 5), interelectrodes reproducibility (RSD ≤ 9%, n = 5), and an extreme resistance to fouling were obtained even after 1 h of microchip analysis with RSD values of ≤4% and ≤9% (n = 15) for migration times and peak heights, respectively. Good sensitivity, remarkable signal-to-noise characteristics, and a well-defined linear concentration dependence (r ≥ 0.990) was also obtained, which allowed these novel detectors to be considered as valuable tools for quantitative analysis. Analytical characterization of the SW-PTEs by field-emission scanning electron microscopy (FESEM) revealed individual bundles of SWs that were highly ordered over the PMMA at the background where the SW bundles were embedded on the PMMA substrate, giving the electrode a high stability. Furthermore, the laboratory-fabricated SW-PTEs can be afforded in any laboratory since they do not require clean-room facilities and are highly compatible with microfluidic scale, mass production, and disposability. In addition, the proposed approach draws new and exciting horizons for electrochemical microfluidic sensing, such a, Ministerio de Economía y Competitividad, Comunidad de Madrid, Junta de Castilla y León, Caja de Burgos, Depto. de Química Analítica, Fac. de Ciencias Químicas, TRUE, pub

WS2/Pt and MoS2/Pt bubble propelled micromotors are used as “on-the-fly” sensing platforms in bioassays, using a highly selective affinity peptide probe for “OFF-ON” detection of Escherichia coli as a model endotoxin. The different outer micromotor surface characteristics play an important role in the sensing performance. The relatively high outer surface of WS2/Pt micromotors results in a 3.5-fold increase in sensitivity compared to MoS2/Pt micromotors due to enhanced peptide probe loading and release. The peptide-modified WS2 micromotors are used as a low-cost and high-throughput approach for the determination of E. coli endotoxin after only 60 s, with a limit of detection of 1.9 ng mL–1 and high selectivity. The method has been validated using spiked samples (tap water, blood serum, and saliva) and bacteria media (blank broth, Staphylococcus aureus, and E. coli). The concept can be extended to the analysis of other (bio)-analytes and easily incorporated into portable instrumentation, holding great promise in a myriad of clinical, environmental, or food-safety applications., Depto. de Química en Ciencias Farmacéuticas, Fac. de Farmacia, TRUE, pub

WS2/Pt and MoS2/Pt bubble propelled micromotors are used as “on-the-fly” sensing platforms in bioassays, using a highly selective affinity peptide probe for “OFF-ON” detection of Escherichia coli as a model endotoxin. The different outer micromotor surface characteristics play an important role in the sensing performance. The relatively high outer surface of WS2/Pt micromotors results in a 3.5-fold increase in sensitivity compared to MoS2/Pt micromotors due to enhanced peptide probe loading and release. The peptide-modified WS2 micromotors are used as a low-cost and high-throughput approach for the determination of E. coli endotoxin after only 60 s, with a limit of detection of 1.9 ng mL–1 and high selectivity. The method has been validated using spiked samples (tap water, blood serum, and saliva) and bacteria media (blank broth, Staphylococcus aureus, and E. coli). The concept can be extended to the analysis of other (bio)-analytes and easily incorporated into portable instrumentation, holding great promise in a myriad of clinical, environmental, or food-safety applications., Spanish Ministry of Science, Innovation and Universities, Spanish Ministry of Economy, Industry and Competitiveness, Community of Madrid-UAH, Spanish Ministry of Economy, Industry and Competitiveness, Depto. de Química en Ciencias Farmacéuticas, CAI Ciencias de la Tierra y Arqueometría, TRUE, pub

In this work it was demonstrated that sample endogenous polyphenols are selectively driving the gold-nanoparticle (AuNPs)-formation process when representative food samples were used as natural sources of reducing compounds. The process of AuNPs formation was characterized by UV–visible spectroscopy and was described by a sigmoidal curve (R 2 ≥ 0.990) which gave information about the polyphenol concentration at which the localized surface plasmon resonance (LSPR) absorption reached its half-value, X50c, and about AuNPs production per polyphenol concentration unit, K AuNPs. The behavior of phenolic acids was different, with lower X 50c and higher K AuNPs values than flavonoids. For the food samples tea, apple, pear, wine, and honey X50c values were 0.22, 7.3, 11.5, 20.4, 30.3, and 53.5 (mg mL−1) and K AuNPs values were 28.7, 0.70, 0.60, 0.20, 0.14, and 0.10 (mg−1 mL), respectively. Excellent correlation between K AuNPs and total phenolics (TP) was obtained (r = 0.98, p-value < 0.05), implying K AuNPs is a novel marker for evaluation of food sample antioxidant capacity in vitro. The K AuNPs values of samples indicated their antioxidant capacity was in the order: tea > apple > pear > wine > honey. The reproducibility of the AuNPs formation approach was excellent, not only for polyphenol standards (RSD < 6 % for X50c and RSD < 11 % for K AuNPs) but also for food samples (RSD < 9 % for X50c and RSD < 15 % for K AuNPs). Transmission electronic microscopy (TEM) enabled confirmation of the formation of stabilized Au-nanospheres from endogenous polyphenols with very well-defined sizes under 20 nm diameter for all the food samples investigated., Ministerio de Ciencia e Innovación, Comunidad de Madrid, Ministerio de Economía y Competitividad, Depto. de Química Analítica, Fac. de Ciencias Químicas, TRUE, pub

Herein we describe an “OFF-ON” Janus micromotor approach for the fast (5 min) and sensitive determination (limit of detection, 120 pM) of Escherichia coli O111:B4 lipopolysaccharide (LPS) associated with sepsis shock in microliter samples. The OFF-ON strategy relies on the loading of a specifically designed rhodamine-labeled affinity peptide into WS2–Pt–Fe2O3 polycaprolactone Janus micromotors. Specific attachment of the peptide with the WS2 via electrostatic and hydrophobic interactions results in fluorescent quenching, which is subsequently recovered by the detachment of the probe in the presence of the target LPS. Peptide loading into the micromotor structure increases the overall stability for over 2 months without any change in its properties and excellent analytical performance. No fluorescence recovery is observed in the presence of LPS with a similar structure, illustrating the high selectivity of the protocol, along with quantitative recoveries in human serum and bacteria cultures. The method was validated against the gold standard Limulus Amoebocyte lysate assay in real bacteria culture containing naturally occurring LPS, with similar recoveries in both cases. The micromotors hold great potential to carry out analytical measurements in real-time with small amounts of sample and reagents, allowing for fast detection of deadly toxins with high clinical relevance., Spanish Ministry of Economy, Industry and Competitiveness, Spanish Ministry of Education and Universities, Community of Madrid, TRANSNANOAVANSENS, Universidad de Alcalá, Depto. de Química en Ciencias Farmacéuticas, Fac. de Farmacia, TRUE, pub

Single-walled carbon nanotubes (SWCNTs) should constitute an important natural step towards the improvement of the analytical performance of microfluidic electrochemical sensing. SWCNTs inherently offer lower detection potentials, higher surfaces and better stability than the existing carbon electrodes. However, pristine SWCNTs contain some carbonaceous and metallic impurities that influence their electrochemical performance. Thus, an appropriate processing method is important for obtaining high purity SWCNTs for analytical applications. In this work, a set of 0.1 mg mL−1 SWCNT dispersions with different degrees of purity and different dispersants (SDBS; pluronic F68 and DMF) was carefully characterized by near infrared (NIR) spectroscopy giving a Purity Index (NIR-PI) ranging from 0.039 to 0.310. The highest purity was obtained when air oxidized SWCNTs were dispersed in SDBS, followed by centrifugation. The SWCNT dispersions were utilized to modify microfluidic chip electrodes for the electrochemical sensing of dopamine and catechol. In comparison with non-SWCNT-based electrodes, the sample with the highest NIR-PI (0.310) exhibited the best analytical performance in terms of improved sensitivity (3-folds higher), very good signal-to-noise ratio, high resistance-to-fouling in terms of relative standard deviation (RSD 7%; n = 15), and enhanced resolution (2-folds higher). In addition, very well-defined concentration dependence was also obtained with excellent correlation coefficients (r ≥ 0.990). Likewise, a good analytical sensitivity, suitable detection limits (LODs) and a very good precision with independence of the concentration assayed (RSDs ≤ 5%) was achieved. These valuable features indicate the suitability of this material for quantitative analysis. NIR-PI and further TEM and XRD characterization demonstrated that the analytical response was driven and controlled by the high NIR-PI of the SWCNTs used. The significance of this work is the demonstration for the, Ministerio de Ciencia e Innovación, Comunidad de Madrid, Depto. de Química Analítica, Fac. de Ciencias Químicas, TRUE, pub