Sol-gel derived gold nanoparticles biosensing platform for Escherichia coli detection

A three dimensional polymeric network obtained by the sol-gel process was applied to develop disposable, sensitive, selective and stable electrochemical biosensors for detection and quantification of Escherichia coli. This biosensor is based on the integration of a thiolated capture probe sequence from E. coli and gold nanoparticles (AuNPs) into a sol-gel 3D polymeric network derived from (3-mercaptopropyl)-trimethoxysilane (MPTS), formed onto a screen-printed gold electrode surface. MPTS presents the advantage of forming a 3D polymeric network containing a large number of thiol tail groups distributed throughout its structure that enable both its anchoring onto gold surfaces and the AuNPs incorporation. Moreover, this matrix allows the incorporation of a high amount of capture probe and provides a biocompatible environment that preserves its original recognition capability after its immobilization, which is expected to improve the sensitivity of the final biosensing device. The hybridization event is detected using the ruthenium complex [Ru(NH3)5L] 2+, where L is the ligand [3-(2-phenanthren-9-yl-vinyl)-pyridine], as redox indicator, which interacts preferentially with ds-DNA. With the use of this approach, complementary target sequences of E. coli can be quantified over the range of 21-400 pmol with a detection limit of 6.3 pmol and good reproducibility (RSD = 4.3%, n = 4, C = 10 μM). In addition, this approach is very selective allowing the detection, without the need of a hybridization suppressor, of a single mismatch. It is also quite stable under storage conditions, giving response at least for 25 days. © 2013 Elsevier B.V.This work has been supported by Comunidad Autónoma de Madrid (project No. S2009/PPQ-1642, AVANSENS), Ministerio de Ciencia e Innovación (project No. CTQ2011-28157) and Ministerio de Economía y Competitividad (FIS2012-38866-C05-05).Peer Reviewe

Lactate biosensor based on a bionanocomposite composed of titanium oxide nanoparticles, photocatalytically reduced graphene, and lactate oxidase

El pdf del artículo es la versión post-print.-- et al.We have developed a lactate biosensor based on a bionanocomposite (BNC) composed of titanium dioxide nanoparticles (TiO2-NPs), photocatalytically reduced graphene, and lactate oxidase. Graphene oxide was photochemically reduced (without using any chemical reagents) in the presence of TiO2-NPs to give graphene nanosheets that were characterized by atomic force microscopy, Raman and X-ray photoelectron spectroscopy. The results show the nanosheets to possess few oxygen functionalities only and to be decorated with TiO2-NPs. These nanosheets typically are at least 1 μm long and have a thickness of 4.2 nm. A BNC was obtained by mixing lactate oxidase with the nanosheets and immobilized on the surface of a glassy carbon electrode. The resulting biosensor was applied to the determination of lactate. Compared to a sensor without TiO2-NPs, the sensor exhibits higher sensitivity (6.0 μA mM-1), a better detection limit (0.6 μM), a wider linear response (2.0 μM to 0.40 mM), and better reproducibility (3.2 %). [Figure not available: see fulltext.] © 2013 Springer-Verlag Wien.This work has been supported by Comunidad Autónoma de Madrid (project No. S2009/PPQ-1642, AVANSENS), Ministerio de Ciencia e Innovación (project No. CTQ2011-28157) and Ministerio de Economía y Competitividad (project No. FIS2012-38866-C05-05).Peer Reviewe

Electrocatalytic processes promoted by diamond nanoparticles in enzymatic biosensing devices

We have developed a biosensing platform for lactate determination based on gold electrodes modified with diamond nanoparticles of 4 nm of nominal diameter, employing the enzyme lactate oxidase and (hydroxymethyl)ferrocene (HMF) as redox mediator in solution. This system displays a response towards lactate that is completely different to those typically observed for lactate biosensors based on other nanomaterials, such as graphene, carbon nanotubes, gold nanoparticles or even diamond nanoparticles of greater size. We have observed by cyclic voltammetry that, under certain experimental conditions, an irreversible wave (E = +0.15 V) appears concomitantly with the typical Fe/Fe peaks (E = +0.30 V) of HMF. In this case, the biosensor response to lactate shows simultaneous electrocatalytic peaks at +0.15 V and +0.30 V, indicating the concurrence of different feedback mechanisms. The achievement of a biosensor response to lactate at +0.15 V is very convenient in order to avoid potential interferences. The developed biosensor presents a linear concentration range from 0.02 mM to 1.2 mM, a sensitivity of 6.1 μA mM, a detection limit of 5.3 μM and excellent stability. These analytical properties compare well with those obtained for other lactate-based biosensors that also include nanomaterials and employ HMF as redox mediator.This work has been supported by Ministerio de Economía y Competitividad (Project nos. CTQ2014-53334-C2-1-R, FIS2012-38866-C05-05 and CTQ2015-71955-REDT) and Comunidad Autónoma de Madrid (Project NANOAVANSENS S2013/MIT-3029)

Diamond nanoparticles based biosensors for efficient glucose and lactate determination

In this work, we report the modification of a gold electrode with undoped diamond nanoparticles (DNPs) and its applicability to the fabrication of electrochemical biosensing platforms. DNPs were immobilized onto a gold electrode by direct adsorption and the electrochemical behavior of the resulting DNPs/Au platform was studied. Four well-defined peaks were observed corresponding to the DNPs oxidation/reduction at the underlying gold electrode, which demonstrate that, although undoped DNPs have an insulating character, they show electrochemical activity as a consequence of the presence of different functionalities with unsaturated bonding on their surface. In order to develop a DNPs-based biosensing platform, we have selected glucose oxidase (GOx), as a model enzyme. We have performed an exhaustive study of the different steps involved in the biosensing platform preparation (DNPs/Au and GOx/DNPs/Au systems) by atomic force microscopy (AFM), field emission scanning electron microscopy (FE-SEM) and cyclic voltammetry (CV). The glucose biosensor shows a good electrocatalytic response in the presence of (hydroxymethyl)ferrocene as redox mediator. Once the suitability of the prototype system to determine glucose was verified, in a second step, we prepared a similar biosensor, but employing the enzyme lactate oxidase (LOx/DNPs/Au). As far as we know, this is the first electrochemical biosensor for lactate determination that includes DNPs as nanomaterial. A linear concentration range from 0.05mM to 0.7mM, a sensitivity of 4.0μAmM-1 and a detection limit of 15μM were obtained.This work has been supported by Ministerio de Ciencia e Innovacion (Project no. CTQ2011-28157), Ministerio de Economía y Competitividad (Project no. FIS2012-38866-C05-05) and Comunidad Autónoma de Madrid (Project NANOAVANSENS S2013/MIT-3029)