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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., Ministerio de Ciencia e Innovación (España), Comunidad de Madrid, 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

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

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

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