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20 p.-9 fig.-2 tab., Colorectal cancer (CRC) is the second leading cause of cancer-related death worldwide. The 5-year survival rate of CRC patients depends on the stage at diagnosis, being higher than 80% when CRC is diagnosed in the early stages but lower than 10% when CRC is diagnosed in advanced stages. Autoantibodies against specific CRC autoantigens (tumor-associated antigens (TAAs)) in the sera of patients have been widely demonstrated to aid in early diagnosis. Thus, we herein aim to identify autoantigens target of autoantibodies specific to CRC that possess a significant ability to discriminate between CRC patients and healthy individuals by means of liquid biopsy. To that end, we examined the protein content of the exosomes released by five CRC cell lines and tissue samples from CRC patients by means of immunoprecipitation coupled with mass spectrometry analysis. A total of 103 proteins were identified as potential autoantigens specific to CRC. After bioinformatics and meta-analysis, we selected 15 proteins that are more likely to be actual CRC autoantigens in order to evaluate their role in CRC prognosis by Western blot (WB) and immunohistochemistry (IHC). We found dysregulation at the protein level for 11 of these proteins in both tissue and plasma exosome samples from patients, along with an association of nine of these proteins with CRC prognosis. After validation, all but one showed a statistically significant high diagnostic ability to distinguish CRC patients and individuals with premalignant lesions from healthy individuals, either by luminescence Halotag-based beads, or by a multiplexed biosensing platform involving the use of magnetic microcarriers as solid support modified with covalently immobilized Halotag fusion proteins constructed for CRC detection. Taken together, our results highlight the usefulness of the approach defined here to identify the TAAs specific to chronic diseases; they also demonstrate that the measurement of autoantibody levels in plasma against the TAAs identified here could be integrated into a point-of-care (POC) device for CRC detection with high diagnostic ability., This work was supported by the financial support of the PI17CIII/00045 and PI20CIII/00019 grants from the AES-ISCIII program to R.B. The financial support of the PID2019-103899RB-I00 (Ministerio de Ciencia e Innovación) Research Project and the TRANSNANOAVANSENS-CM Program from the Comunidad de Madrid (S2018/NMT-4349) to S.C. are gratefully acknowledged. G.D. acknowledges the financial support of PI15/00246 grant of the FIS and Cátedra UAM-Roche en Medicina de Innovación. The FPU predoctoral contract to A.M-C. is supported by the Spanish Ministerio de Educación, Cultura y Deporte. G.S-F. is recipient of a predoctoral contract (1193818N) supported by The Flanders Research Foundation (FWO). M.A-N. was supported by a contract of the Programa Operativo de Empleo Juvenily la Iniciativa de Empleo Juvenil (YEI) with the participation of the Consejería de Educación, Juventud y Deporte de la Comunidad de Madrid y del Fondo Social Europeo. The predoctoral contract from the Spanish Ministerio de Economía y Competitividad (BES-2016-076606, E.P.) and Talento-Contract from Comunidad de Madrid (2019-T2/IND-15965, R.M.T-R.) are also gratefully acknowledged.

Early diagnosis in primary care settings can increase access to therapies and their efficiency as well as reduce health care costs. In this context, we report in this paper the development of a disposable immunoplatform for the rapid and simultaneous determination of two protein biomarkers recently reported to be involved in the pathological process of neurodegenerative disorders (NDD), tau protein (tau), and TAR DNA-binding protein 43 (TDP-43). The methodology involves implementation of a sandwich-type immunoassay on the surface of dual screen-printed carbon electrodes (dSPCEs) electrochemically grafted with p-aminobenzoic acid (p-ABA), which allows the covalent immobilization of a gold nanoparticle-poly(amidoamine) (PAMAM) dendrimer nanocomposite (3D-Au-PAMAM). This scaffold was employed for the immobilization of the capture antibodies (CAbs). Detector antibodies labeled with horseradish peroxidase (HRP) and amperometric detection at − 0.20 V (vs. Ag pseudo-reference electrode) using the H2O2/hydroquinone (HQ) system were used. The developed methodology exhibits high sensitivity and selectivity for determining the target proteins, with detection limits of 2.3 and 12.8 pg mL−1 for tau and TDP-43, respectively. The simultaneous determination of tau and TDP-43 was accomplished in raw plasma samples and brain tissue extracts from healthy individuals and NDD-diagnosed patients. The analysis can be performed in just 1 h using a simple one-step assay protocol and small sample amounts (5 μL plasma and 2.5 μg brain tissue extracts).

This paper reports a simple electrochemical strategy for the determination of microRNAs (miRNAs) using a commercial His-Tag-Zinc finger protein (His-Tag-ZFP) that binds preferably (but non-sequence specifically) RNA hybrids over ssRNAs, ssDNAs, and dsDNAs. The strategy involves the use of magnetic beads (His-Tag-Isolation-MBs) as solid support to capture the conjugate formed in homogenous solution between His-Tag-ZFP and the dsRNA homohybrid formed between the target miRNA (miR-21 selected as a model) and a biotinylated synthetic complementary RNA detector probe (b-RNA-Dp) further conjugated with a streptavidin-horseradish peroxidase (Strep-HRP) conjugate. The electrochemical detection is carried out by amperometry at disposable screen-printed carbon electrodes (SPCEs) (- 0.20 V vs Ag pseudo-reference electrode) upon magnetic capture of the resultant magnetic bioconjugates and H2O2 addition in the presence of hydroquinone (HQ). The as-prepared biosensor exhibits a dynamic concentration range from 3.0 to 100 nM and a detection limit (LOD) of 0.91 nM for miR-21 in just ~ 2 h. An acceptable discrimination was achieved between the target miRNA and other non-target nucleic acids (ssDNA, dsDNA, ssRNA, DNA-RNA, miR-122, miR-205, and single central- or terminal-base mismatched sequences). The biosensor was applied to the analysis of miR-21 from total RNA (RNAt) extracted from epithelial non-tumorigenic and adenocarcinoma breast cells without target amplification, pre-concentration, or reverse transcription steps. The versatility of the methodology due to the ZFP's non-sequence-specific binding behavior makes it easily extendable to determine any target RNA only by modifying the biotinylated detector probe.

The evolution of human diseases involves a highly dynamic and interactive system of multiple layers of molecular markers. Therefore, it is now fully accepted that simultaneous analysis of molecular markers from the same or different omics layers leads to novel strategies for their realistic early detection and monitoring, thus improving disease prevention, treatment, and outcomes. In this regard, features such as versatility for profiling multiple and/or multi-omics biomarkers, simplicity, affordable cost, markedly shorter analysis time and smaller sample amount required for analyses compared to conventional or state-of-the-art methodologies, make electrochemical bioplatforms suitable alternatives for routine determinations in clinical and basic research settings. The great advances demonstrated by electrochemical biosensors in recent years have gone hand in hand with the development of new electrochemical substrates, attractive surface chemistries, bioassay formats and amplification strategies, but also with the production and application of new bioreceptors, such as those provided by HaloTag and Phage Display technologies, which has allowed these devices to incur and demonstrate pioneering applications. With all this in mind, this communication will discuss bioelectroanalytical tools recently developed by us and our partners potentially transferable to the clinic due to their simplicity, cost, testing time and decentralized character, which have shown pioneering applications to decisively aid in personalized diagnostics by targeting methylation events in nucleic acids both globally and regionally and deregulated autoantibody expression. These biotools have shown to be able to determine simultaneously and with monobasic sensitivity the most common methylated bases in nucleic acids: 5-methylcytosine 5-mC), 5-hydroxymethylcytosine (5-hmC) and N6-methyladenine (6mA) in DNA and N6-methyladenosine (m6A) in RNA, both globally and regionally and without adopting other amplification strategies than conventional enzymatic labeling [1,2]. A multiplexed platform was proposed with application to the global determination of m6A in total RNA extracted from colorectal cancer cells with different metastatic potential, and to the determination of global methylations of 5-mC, 5-hmC and 6mA in genomic DNA extracted from matched tumor and healthy tissues of CRC patients. The obtained results demonstrated the clinical potential of the developed multiplexed bioplatform to discriminate the aggressiveness of tumor cells as well as tumor versus healthy tissues (accuracy, sensitivity, and specificity of 87.5, 100 and 75 %, respectively, using Ward's clustering method) in only 45 min from small amounts (no more than 100 ng) of denatured genomic DNA and crude total RNA without fragmentation and amplification. As for the electroanalytical bioplatforms developed for autoantibodies determination, they have shown ability to identify and confirm the clinical potential of previously undescribed specific autoantibody signatures against i) tumor-associated antigens, identified in the circulation or in tumor exosomes, for early and differential diagnosis of a given neoplasm [3,4]; ii) phage-derived and aberrant HaloTagged peptides to diagnose Alzheimer's disease (AD) [5]; and iii) SARS-CoV-2 serum-specific immunoglobulins to identify vulnerable population or with natural or acquired immunizations, allowing early detection of exaggerated immune system responses or epidemiological studies on the strain responsible for the infection and the efficacy of available vaccines against the different variants of the virus. It is exciting and rewarding to think that we are tackling and developing highly versatile technologies with the potential to efficiently provide relevant information on key aspects of known and unexpected diseases, such as their onset, severity, and immune response, enabling their management in a fast, simple, affordable, and personalized way in diverse settings. [1] Povedano et al. Anal. Chem. 92 (2020) 5604−5612. [2] Povedano et al. Anal. Chim. Acta 1182 (2021) 338946. https://doi.org/10.1016/j.aca.2021.338946. [3] Garranzo-Asensio et al. Theranostics 10(7) (2020) 3022–3034. [4] Montero-Calle et al. Engineering (2021) in press. https://doi.org/10.1016/j.eng.2021.04.026. [5] Valverde et al. Analysis & Sensing 1 (2021) 161-165. The financial support of PID2019-103899RB-I00 (Spanish Ministerio de Ciencia e Innovación), Research Project, PI17CIII/00045 and PI20CIII/00019 grants from the AES-ISCIII program grants from the AES-ISCIII program and the TRANSNANOAVANSENS-CM Program from the Comunidad de Madrid (Grant S2018/NMT-4349) are gratefully acknowledged.

This paper describes the first biosensor reported to date for the determination of mustard seed traces. The biosensor consists of an amperometric immunosensing platform able to sensitively and selectively determine Sin a 1 content, the major allergen of yellow mustard and the most abundant protein of these seeds. The immunosensing platform exploits the coupling of magnetic microbeads (MBs) modified with sandwich-type immune complexes, comprising polyclonal and monoclonal antibodies, selective to the target protein for its capturing and detection, respectively. In addition, a HRP-conjugated secondary antibody was used for enzymatic labelling of the monoclonal antibody, and amperometric transduction was made at screen-printed carbon electrodes (SPCEs) using the hydroquinone (HQ)/H2O2 system. The electrochemical immunosensor allows the simple and fast detection (a single 1-h incubation step) of Sin a 1 with a limit of detection of 0.82 ng mL−1 (20.5 pg of protein in 25 μL of sample) with high selectivity against structurally similar non-target allergenic proteins (such as Pin p 1 from pine nut). The developed immunoplatform was successfully used for the analysis of peanut, rapeseed, cashew, pine nut and yellow mustard extracts, giving only positive response for the yellow mustard extract with a Sin a 1 content, in full agreement with that provided by conventional ELISA methodology.

Early diagnosis in primary care settings can increase access to therapies and their efficiency as well as reduce health care costs. In this context, we report in this paper the development of a disposable immunoplatform for the rapid and simultaneous determination of two protein biomarkers recently reported to be involved in the pathological process of neurodegenerative disorders (NDD), tau protein (tau), and TAR DNA-binding protein 43 (TDP-43). The methodology involves implementation of a sandwich-type immunoassay on the surface of dual screen-printed carbon electrodes (dSPCEs) electrochemically grafted with p-aminobenzoic acid (p-ABA), which allows the covalent immobilization of a gold nanoparticle-poly(amidoamine) (PAMAM) dendrimer nanocomposite (3D-Au-PAMAM). This scaffold was employed for the immobilization of the capture antibodies (CAbs). Detector antibodies labeled with horseradish peroxidase (HRP) and amperometric detection at - 0.20 V (vs. Ag pseudo-reference electrode) using the H

This work describes the first electrochemical immunosensor reported for the determination of IL-13 receptor Rα2 (IL-13Rα2), an emerging relevant biomarker in metastatic colon cancer. The approach involves the formation of sandwich immunocomplexes using specific capture (CAb) and biotinylated detector antibodies (BDAb) further labeled with an streptavidin-horseradish peroxidase (Strep-HRP) polymer, onto carboxylic acid-modified magnetic microbeads (HOOC-MBs). Amperometric detection at disposable carbon screen-printed electrodes (SPCEs) using the (H2O2)/hydroquinone (HQ) system was employed to monitor the affinity reactions. The developed immunosensor exhibits a linear calibration plot over the 3.9–100 ng mL−1 concentration range, a LOD of 1.2 ng mL−1 and excellent selectivity against other non-target proteins. The amperometric immunosensor was applied successfully to quantify for the first time the IL-13Rα2 expression in raw lysates of colon cancer cells and to discriminate the metastatic potential of intact cells through recognition of this target extracellular receptor. In comparison with the commercial Enzyme-Linked ImmunoSorbent Assay (ELISA) kit involving the same immunoreagents, the immunosensor provides a similar LOD in a half-time for the assay.

We report a rapid and sensitive electrochemical strategy for the detection of gene-specific 5-methylcytosine DNA methylation. Magnetic beads (MBs) modified with an antibody for 5-methylcytosines (5-mC) are used for the capture of any 5-mC methylated single-stranded (ss)DNA sequence. A flanking region next to the 5-mCs of the captured methylated ssDNA is recognized by hybridization with a synthetic biotinylated DNA sequence. Amperometric transduction at disposable screen-printed carbon electrodes (SPCEs) is employed. The developed biosensor has a dynamic range from 3.9 to 500 pm and a limit of detection of 1.2 pm for the methylated synthetic sequence of the tumor suppressor gene O-6-methylguanine-DNA methyltransferase (MGMT) promoter region. The method is applied in the 45-min analysis of specific methylation in the MGMT promoter region directly in raw spiked human serum samples and in genomic DNA extracted from U-87 glioblastoma cells and paraffin-embedded brain tumor tissues without any amplification and pretreatment step.

This paper describes the first immunosensor reported so far for the highly sensitive determination of the egg white allergen, ovomucoid (OM). The approach involves the selective capture of sandwich immunocomplexes formed by capture antibody-target protein allergen-HRP-labeled detector antibody onto carboxylic acid-functionalized magnetic beads (HOOC-MBs). The resulting magnetic bioconjugates were captured on the surface of disposable screen-printed carbon electrodes (SPCE) to perform amperometric detection at −0.20 V vs. the Ag pseudo-reference electrode in the presence of hydroquinone (HQ) and H2O2. The as prepared electrochemical immunoplatform showed a wide range of linearity (0.3–25 ng mL−1), a LOD of 0.1 ng mL−1, which is much lower than those claimed for commercial ELISA kits, and a great selectivity against other white egg allergenic proteins. The developed immunosensor was successfully employed for the simple and accurate determination of trace amounts of OM in unprocessed (eggs and wheat flour) and baked (bread) food samples.

This paper describes two different electrochemical affinity biosensing approaches for the simple, fast and bisulfite and PCR-free quantification of 5-methylated cytosines (5-mC) in DNA using the anti-5-mC antibody as biorecognition element. One of the biosensing approaches used the anti-5-mC as capture bioreceptor and a sandwich type immunoassay, while the other one involved the use of a specific DNA probe and the anti-5-mC as a detector bioreceptor of the captured methylated DNA. Both strategies, named for simplicity in the text as immunosensor and DNA sensor, respectively, were implemented on the surface of magnetic microparticles and the transduction was accomplished by amperometry at screen-printed carbon electrodes by means of the hydrogen peroxide/hydroquinone system. The resulting amperometric biosensors demonstrated reproducibility throughout the entire protocol, sensitive determination with no need for using amplification strategies, and competitiveness with the conventional enzyme-linked immunosorbent assay methodology and the few electrochemical biosensors reported so far in terms of simplicity, sensitivity and assay time. The DNA sensor exhibited higher sensitivity and allowed the detection of the gene-specific methylations conversely to the immunosensor, which detected global DNA methylation. In addition, the DNA sensor demonstrated successful applicability for 1 h-analysis of specific methylation in two relevant tumor suppressor genes in spiked biological fluids and in genomic DNA extracted from human glioblastoma cells. The financial support of the Spanish Ministerio de Economía y Competitividad CTQ2015-64402-C2-1-R and SAF2014-53209-R Research Projects, the PI17CIII/00045 research project from AESI and the NANOAVANSENS Program from the Comunidad de Madrid (S2013/MT-3029) and predoctoral contracts from the Spanish Ministerio de Economía y Competitividad (R.M. Torrente-Rodríguez and E. Povedano) and Universidad Complutense de Madrid (V. Ruiz-Valdepeñas Montiel) are also gratefully acknowledged. Sí

Currently, electrochemical nucleic acid-based biosensing methodologies involving hybridization assays, specific recognition of RNA/DNA and RNA/RNA duplexes, and amplification systems provide an attractive alternative to conventional quantification strategies for the routine determination of relevant nucleic acids at different settings. A particularly relevant objective in the development of such nucleic acid biosensors is the design of as many as possible affordable, quick, and simple methods while keeping the required sensitivity. With this aim in mind, this work reports, for the first time, a thorough comparison between 11 methodologies that involve different assay formats and labeling strategies for targeting the same DNA. The assayed approaches use conventional sandwich and competitive hybridization assays, direct hybridization coupled to bioreceptors with affinity for RNA/DNA duplexes, multienzyme labeling bioreagents, and DNA concatamers. All of them have been implemented on the surface of magnetic beads (MBs) and involve amperometric transduction at screen-printed carbon electrodes (SPCEs). The influence of the formed duplex length and of the labeling strategy have also been evaluated. Results demonstrate that these strategies can provide very sensitive methods without the need for using nanomaterials or polymerase chain reaction (PCR). In addition, the sensitivity can be tailored within several orders of magnitude simply by varying the bioassay format, hybrid length or labeling strategy. This comparative study allowed us to conclude that the use of strategies involving longer hybrids, the use of antibodies with specificity for RNA/DNA heteroduplexes and labeling with bacterial antibody binding proteins conjugated with multiple enzyme molecules, provides the best sensitivity.

Made available in DSpace on 2018-11-26T15:37:44Z (GMT). No. of bitstreams: 0 Previous issue date: 2017-03-15 Spanish Ministry of Economy and Competitiveness Comunidad de Madrid, Programme NANOAVANSENS A novel nanocomposite material consisting of reduced graphene oxide/Rh nanoparticles was prepared by a one-pot reaction process. The strategy involved the simultaneous reduction of RhCl3 and graphene oxide with NaBH4 and the in situ deposition of the metal nanoparticles on the 2D carbon nanomaterial planar sheets. Glassy carbon electrode coated with this nanocomposite was employed as nanostructured support for the cross-linking of the enzyme laccase with glutaraldehyde to construct a voltammperometric biosensor for 17 beta-estradiol in the 0.9-11 pM range. The biosensor showed excellent analytical performance with high sensitivity of 25.7 A mu M-1 cm(-1), a very low detection limit of 0.54 pM and high selectivity. The biosensor was applied to the rapid and successful determination of the hormone in spiked synthetic and real human urine samples. (C) 2016 Elsevier B.V. All rights reserved. Univ Complutense Madrid, Fac Chem, Dept Analyt Chem, E-28040 Madrid, Spain State Univ Sao Paulo, Inst Chem, POB 780, BR-13560970 Sao Carlos, SP, Brazil Mackenzie Presbiterian Univ, Engn Sch, BR-01302907 Sao Paulo, SP, Brazil State Univ Sao Paulo, Inst Chem, POB 780, BR-13560970 Sao Carlos, SP, Brazil Spanish Ministry of Economy and Competitiveness: CTQ2014-58989-P Spanish Ministry of Economy and Competitiveness: CTQ2011-24355 Spanish Ministry of Economy and Competitiveness: CTQ2015-71936-REDT Spanish Ministry of Economy and Competitiveness: CTQ2012-34238 Comunidad de Madrid, Programme NANOAVANSENS: S2013/MIT-3029

This work reports the first bioplatform able to determine electrochemically 5-hydroxymethylcytosine (5-hmC) methylation events at localized sites and single-base sensitivity. The described bioplatform relies on a specific antibody (anti-5-hmC), further conjugated with commercial bioreagents loaded with multiple horseradish peroxidase (HRP) molecules, recognizing the epimark in a target DNA, captured through hybridization onto streptavidin-magnetic microbeads (Strep-MBs) modified with a complementary DNA capture probe. The electrochemical detection is performed by amperometry (-0.20 V vs Ag pseudoreference electrode) at disposable screen-printed carbon electrodes (SPCEs) in the presence of H2O2/hydroquinone (HQ) upon magnetic capture of the modified MBs onto the SPCE. The use of the commercial bioreagents ProtA-polyHRP80 and Histostar, very scarcely explored so far in electrochemical biosensors, provides high sensitivities for a synthetic target DNA sequence with a unique 5-hmC in the promoter region of MG...

[Background and Purpose]: The humoral immune response in cancer patients can be used for early detection of the disease. Autoantibodies raised against tumor-associated antigens (TAAs) are promising clinical biomarkers for reliable cancer diagnosis, prognosis, and therapy monitoring. In this study, an electrochemical disposable multiplexed immunosensing platform able to integrate difficult- and easy-to-express colorectal cancer (CRC) TAAs is reported for the sensitive determination of eight CRC-specific autoantibodies., [Methods]: The electrochemical immunosensing approach involves the use of magnetic microcarriers (MBs) as solid supports modified with covalently immobilized HaloTag fusion proteins for the selective capture of specific autoantibodies. After magnetic capture of the modified MBs onto screen-printed carbon working electrodes, the amperometric responses measured using the hydroquinone (HQ)/H2O2 system were related to the levels of autoantibodies in plasma., [Results]: The biosensing platform was applied to the analysis of autoantibodies against 8 TAAs described for the first time in this work in plasma samples from healthy asymptomatic individuals (n=3), and patients with high-risk of developing CRC (n=3), and from patients already diagnosed with colorectal (n=3), lung (n=2) or breast (n=2) cancer. The developed bioplatform demonstrated an improved discrimination between CRC patients and controls (asymptomatic healthy individuals and breast and lung cancer patients) compared to an ELISA-like luminescence test., [Conclusions]: The proposed methodology uses a just-in-time produced protein in a simpler protocol, with low sample volume, and involves cost-effective instrumentation, which could be used in a high-throughput manner for reliable population screening to facilitate the detection of early CRC patients at affordable cost., This work was supported by the financial support of the PI17CIII/00045 grant from the AES-ISCIII program to R.B., cofounded by FEDER funds. The financial support of the CTQ2015-64402-C2-1-R (Spanish Ministerio de Economía y Competitividad) and RTI2018-096135-B-I00 (Ministerio de Ciencia, Innovación y Universidades) Research Projects and the TRANSNANOAVANSENS-CM Program from the Comunidad de Madrid (Grant S2018/NMT-4349) to P.Y-S., S.C. and JM.P are gratefully acknowledged. G.D. acknowledges the financial support of PI15/00246 grant of the FIS and Cátedra UAM-Roche en Medicina de Innovación. M.G-A. was supported by a contract of the Programa Operativo de Empleo Juvenil y la Iniciativa de Empleo Juvenil (YEI) with the participation of the Consejería de Educación, Juventud y Deporte de la Comunidad de Madrid y del Fondo Social Europeo. A.M-C. is a recipient of a FPU fellowship from the Ministerio de Educación, Cultura y Deporte. G.S-F. is recipient of a predoctoral contract (grant number 1193818N) supported by The Flanders Research Foundation (FWO). Predoctoral contracts from the Spanish Ministerio de Economía y Competitividad (E.P.) and Universidad Complutense de Madrid (V.R.V-M.) are also gratefully acknowledged.

This work describes the preparation of an immunoplatform for the sensitive and selective determination of N6-methyladenosine (m6A). The simple and fast protocol involves for the first time the use of micromagnetic immunoconjugates to establish a direct competitive assay between the m6A target and a biotinylated RNA oligomer bearing a single m6A enzymatically labelled with a commercial conjugate of streptavidin-peroxidase (Strep-HRP) as tracer. The cathodic current change measured in the presence of H2O2/hydroquinone (HQ) at screen-printed carbon electrodes (SPCEs) upon surface capturing the magnetic bioconjugates is inversely proportional to the m6A target concentration. After evaluating the effect of key variables, the analytical characteristics were established for the determination of three different targets: the N6-methyladenosine-5′-triphosphate (m6ATP) ribonucleotide, a short synthetic RNA oligomer bearing a single m6A and the positive control provided in a commercial colorimetric kit for m6A-RNA quantification. The obtained results show that this immunoplatform is competitive with other methods reported to date, achieving an improved sensitivity (limit of detection of 0.9 pM for the short synthetic oligomer) using a much simpler and faster protocol (~1 h) and disposable electrodes for the transduction. Furthermore, the applicability for discriminating the metastatic potential of cancer cells by directly analyzing a small amount of raw total RNA without enriching or fragmenting was also preliminary assessed.

Here we describe the development of a dual electrochemical immunosensor microchip for simultaneous detection of insulin (I) and cortisol (C) biomarkers that can enhance the ability to improve glucose regulation using automated insulin delivery. The successful realization of the simultaneous I and C measurements has been realized by integrating different enzymatically-tagged competitive and sandwich immunoassay formats on a single chip platform. The insulin detection is based on a peroxidase (HRP)-labeled sandwich assay whereas the cortisol detection relies on an alkaline phosphatase (ALP)-labeled competitive immunoassay. The attractive analytical performance of the dual marker immunosensor, with no apparent cross-talk, was achieved through systematic optimization of the incubation and amperometric detection of the different captured enzyme tags. Evaluation of dual biosensor chip in untreated serum samples indicated favorable simultaneous detection of picomolar (pM) insulin and nanomolar (nM) cortisol concentrations in a single microliter sample droplet within less than 25min. The new dual immunosensor chip offers considerable promise for frequent decentralized testing of I and C towards a tighter glycemic control and improved management of diabetes.

This paper reports the preparation of versatile electrochemical biosensing platforms for the simple, rapid, and PCR-independent detection of the most frequent DNA methylation marks (5-methylcytosine, 5-mC, and/or 5-hydroxymethylcytosine, 5-hmC) both at global and gene-specific levels. The implemented strategies, relying on the smart coupling of immuno-magnetic beads (MBs), specific DNA probes and amperometric detection at screen-printed carbon electrodes (SPCEs), provided sensitive and selective determination of the target methylated DNAs in less than 90 min with a great reproducibility and demonstrated feasibility for the simultaneous detection of the same or different cytosine epimarks both at global level and in different loci of the same gene or in different genes. The bioplatforms were applied to determine global methylation events in paraffin-embedded colorectal tissues and specific methylation at promoters of tumor suppressor genes in genomic DNA extracted from cancer cells and paraffin-embedded colorectal tissues, and in serum without previous DNA extraction from cancer patients.

This paper reports the development of an amperometric immunosensing platform for the determination of cadherin-17 (CDH-17), an atypical adhesion protein involved in the progression, metastatic potential, and survival of high prevalence gastric, hepatocellular, and colorectal tumors. The methodology developed relies on the efficient capture and enzymatic labeling of the target protein on the magnetic microparticles (MBs) surface using commercial antibodies and amperometric transduction at screen-printed carbon electrodes (SCPEs) through the HRP/H2O2/HQ system. The developed immunosensing platform allows the selective determination of the target protein at low ng mL-1 level (LOD of 1.43 ng mL-1) in 45 min and using a single incubation step. The electrochemical immunosensor was successfully used for the accurate determination of the target protein in a small amount (0.5 μg) of raw lysates of colon cancer cells with different metastatic potential as well as in extracts from paraffin embedded cancer colon tissues of different metastatic grade., The financial support of the Spanish Ministerio de Economía y Competitividad, Grants CTQ2015-70023-R and CTQ2015-64402-C2-1-R, and the NANOAVANSENS Program from the Comunidad de Madrid (Grant S2013/MT-3029), and predoctoral contracts from the Spanish Ministerio de Economia y Competitividad (E.P.) and Universidad Complutense de Madrid (V.R.-V.M.) are grate fully acknowledged. R.B. acknowledges the financial support of the PI17CIII/00045 Grant from the AES-ISCIII program. M.G.-A. was supported by a contract of the Programa Operativo de Empleo Juvenil y la Iniciativa de Empleo Juvenil (YEI) with the participation of the Consejería de Educacion, Juventud y Deporte de la Comunidad de Madrid y del Fondo Social Europeo.

This work reports an amperometric biosensor for the determination of miRNA-21, a relevant oncogene. The methodology involves a competitive DNA-target miRNA hybridization assay performed on the surface of magnetic microbeads (MBs) and amperometric transduction at screen-printed carbon electrodes (SPCEs). The target miRNA competes with a synthetic fluorescein isothiocyanate (FITC)-modified miRNA with an identical sequence for hybridization with a biotinylated and complementary DNA probe (b-Cp) immobilized on the surface of streptavidin-modified MBs (b-Cp-MBs). Upon labeling, the FITC-modified miRNA attached to the MBs with horseradish peroxidase (HRP)-conjugated anti-FITC Fab fragments and magnetic capturing of the MBs onto the working electrode surface of SPCEs. The cathodic current measured at −0.20 V (versus the Ag pseudo-reference electrode) was demonstrated to be inversely proportional to the concentration of the target miRNA. This convenient biosensing method provided a linear range between 0.7 and 10.0 nM and a limit of detection (LOD) of 0.2 nM (5 fmol in 25 μL of sample) for the synthetic target miRNA without any amplification step. An acceptable selectivity towards single-base mismatched oligonucleotides, a high storage stability of the b-Cp-MBs, and usefulness for the accurate determination of miRNA-21 in raw total RNA (RNAt) extracted from breast cancer cells (MCF-7) were demonstrated.

A novel electrochemical disposable nucleic acid biosensor for simple, rapid, and specific detection of adulterations with horsemeat is reported in this work. The biosensing platform involves immobilization of a 40-mer RNA probe specific for a characteristic fragment of the mitochondrial DNA D-loop region of horse onto the surface of magnetic microcarriers. In addition, signal amplification was accomplished by using a commercial antibody specific to RNA/ DNA duplexes and a bacterial protein conjugated with a horseradish peroxidase homopolymer (ProtA-HRP40). Amperometric detection at −0.20 V vs Ag pseudoreference electrode was carried out at disposable screen-printed carbon electrodes. The methodology achieved a limit of detection (LOD) of 0.12 pM (3.0 attomoles) for the synthetic target and showed ability to discriminate between raw beef and horsemeat using just 50 ng of total extracted mitochondrial DNA (∼16 660 bp in length) without previous fragmentation. The biosensor also allowed discrimination between 100% raw beef and beef meat samples spiked with only 0.5% (w/w) horse meat (levels established by the European Commission) using raw mitochondrial lysates without DNA extraction or polymerase chain reaction (PCR) amplification in just 75 min. These interesting features made the developed methodology an extremely interesting tool for beef meat screening, and it can be easily adapted to the determination of other meat adulterations by selection of the appropriate specific fragments of the mitochondrial DNA region and capture probes.

Gold nanoparticles-decorated silver-bipyridine coordination polymers with intrinsic peroxidase-like activity are reported. Both morphology and mimetic enzyme activity can be tuned by rational manipulation of the nanohybrid composition. The nanomaterial was used for the electrochemical determination of H2O2 and glucose.