RESUMO
This work proposes an approach for Cu2+ sensing in water which combines the selectivity of the Gly-Gly-His (GGH) peptide probe with the sensitivity of the electrolyte-gated organic field-effect transistor (EGOFET). The oligopeptide probe was immobilized onto the gate electrode of the transistor by electrooxidation of the primary amine of the glycine moiety. Cu2+ complexation by the grafted GGH was at first electrochemically evidenced, using cyclic and square wave voltammetries, then it was demonstrated that GGH-functionalized EGOFETs can transduce Cu2+ complexation through a significant threshold voltage shift and therefore a change in drain current. The limit of detection is ca. 10-12 M and the sensitivity in the linear range (10-12 - 10-8 M) is 1â¯mAâ¯dec-1 (drain current variations).
Assuntos
Técnicas Biossensoriais , Cobre/isolamento & purificação , Peptídeos/química , Cobre/química , Eletrólitos/química , Limite de Detecção , Oligopeptídeos/química , Transistores Eletrônicos , Água/químicaRESUMO
We investigated an Electrolyte-Gated Organic Field-Effect transistor based on poly(N-alkyldiketopyrrolo-pyrrole dithienylthieno[3,2-b]thiophene) as organic semiconductor whose gate electrode was functionalized by electrografting a functional diazonium salt capable to bind an antibody specific to 2,4-dichlorophenoxyacetic acid (2,4-D), an herbicide well-known to be a soil and water pollutant. Molecular docking computations were performed to design the functional diazonium salt to rationalize the antibody capture on the gate surface. Sensing of 2,4-D was performed through a displacement immunoassay. The limit of detection was estimated at around 2.5 fM.
Assuntos
Ácido 2,4-Diclorofenoxiacético/análise , Técnicas Biossensoriais/instrumentação , Compostos de Diazônio/química , Herbicidas/análise , Transistores Eletrônicos , Poluentes Químicos da Água/análise , Anticorpos Imobilizados/química , Técnicas Biossensoriais/métodos , Eletrólitos/química , Desenho de Equipamento , Imunoensaio/instrumentação , Imunoensaio/métodos , Limite de Detecção , Modelos Moleculares , Água/análiseRESUMO
We describe an electrochemical immunosensor based on functionalization of a working electrode by electrografting two functional diazonium salts. The first one is a molecular probe, diclofenac, coupled with an arylamine onto which a specific antibody is immobilized by affinity interactions; the second is a redox probe (a quinone) also coupled with an arylamine, able to transduce the hapten-antibody association into a change in electroactivity. The steric hindrance induced by the antibody leads to a current decrease upon binding of the antibody on the grafted molecular probe; conversely, when diclofenac is present in solution, a displacement equilibrium occurs between the target diffusing into the solution and the grafted probe. This leads to dissociation of the antibody from the electrode surface, event which is transduced into a current increase ("signal-on" detection). The detection limit is ca. 20 fM, corresponding to 6pgL-1 diclofenac, which is competitive compared to other label-free immunosensors. We demonstrate that the sensor is selective and is able to quantify diclofenac in tap water.
Assuntos
Anticorpos Imobilizados/química , Diclofenaco/análise , Água Potável/análise , Técnicas Eletroquímicas/métodos , Poluentes Químicos da Água/análise , Benzoquinonas/química , Técnicas Biossensoriais/métodos , Compostos de Diazônio/química , Eletrodos , Imunoensaio/métodos , Limite de Detecção , OxirreduçãoRESUMO
Variable drug responses among malignant cells within individual tumors may represent a barrier to their eradication using chemotherapy. Carcinoma cells expressing mesenchymal markers resist conventional and epidermal growth factor receptor (EGFR)-targeted chemotherapy. In this study, we evaluated whether mesenchymal-like sub-populations within human squamous cell carcinomas (SCCs) with predominantly epithelial features contribute to overall therapy resistance. We identified a mesenchymal-like subset expressing low E-cadherin (Ecad-lo) and high vimentin within the upper aerodigestive tract SCCs. This subset was both isolated from the cell lines and was identified in xenografts and primary clinical specimens. The Ecad-lo subset contained more low-turnover cells, correlating with resistance to the conventional chemotherapeutic paclitaxel in vitro. Epidermal growth factor induced less stimulation of the mitogen-activated protein kinase and phosphatidylinositol-3-kinase pathways in Ecad-lo cells, which was likely due to lower EGFR expression in this subset and correlated with in vivo resistance to the EGFR-targeted antibody, cetuximab. The Ecad-lo and high E-cadherin subsets were dynamic in phenotype, showing the capacity to repopulate each other from single-cell clones. Taken together, these results provide evidence for a low-turnover, mesenchymal-like sub-population in SCCs with diminished EGFR pathway function and intrinsic resistance to conventional and EGFR-targeted chemotherapies.