S. Assavapanumat, T. Yutthalekha, P. Garrigue, B. Goudeau, V. Lapeyre, A. Perro, N. Sojic, C. Wattanakit, A. Kuhn
see also CNRS press release
Concepts leading to single enantiomers of chiral molecules are of crucial importance for many applications, including pharmacology and biotechnology. Recently, mesoporous metal phases encoded with chiral information have been developed. We propose here to fine-tune the enantioaffinity of such structures by imposing an electric potential, which can influence the electrostatic interactions between the chiral metal and the target enantiomer. This allows increasing the binding affinity and thus the discrimination between two enantiomers. The concept is illustrated by generating chiral encoded metals in a microfluidic channel via the reduction of a platinum salt in the presence of a liquid crystal and L-tryptophan as a chiral model template. After removal of the template molecules, the modified microchannel retains a pronounced chiral character. Its chiral recognition efficiency can be fine-tuned by applying a suitable potential to the metal phase. This enables the separation of both components of a racemate flowing through the channel. The approach constitutes a promising and complementary strategy in the frame of chiral discrimination technologies.
Herein is reported a surface-confined microscopy based on electrochemiluminescence (ECL) that allows to image the plasma membrane of single cells at the interface with an electrode. By analyzing photoluminescence (PL), ECL and AFM images of mammalian CHO cells, we demonstrate that, in contrast to the wide-field fluorescence, ECL emission is confined to the immediate vicinity of the electrode surface and only the basal membrane of the cell becomes luminescent. The resulting ECL microscopy reveals details that are not resolved by classic fluorescence microscopy, without any light irradiation and specific setup. The thickness of the ECL-emitting regions is ∼500 nm due to the unique ECL mechanism that involves short-lifetime electrogenerated radicals. In addition, the reported ECL microscopy is a dynamic technique that reflects the transport properties through the cell membranes and not only the specific labeling of the membranes. Finally, disposable transparent carbon nanotube (CNT)-based electrodes inkjet-printed on classic microscope glass coverslips were used to image cells in both reflection and transmission configurations. Therefore, our approach opens new avenues for ECL as a surface-confined microscopy to develop single cell assays and to image the dynamics of biological entities in cells or in membranes.
Les mesures sélectives et sensibles dans des échantillons complexes tels que l’urine ou le sang sont devenues des outils indispensables dans le domaine du diagnostic. Le développement de nouvelles méthodes d’analyse, plus sensibles, dynamiques, à haut débit représente un défi d’une grande importance sociétale. L’électrochimiluminescence (ECL) constitue une méthode largement commercialisée pour l’immunodosage. Cet article présente des travaux qui portent, d’une part sur la compréhension fine des mécanismes de l’ECL mis en jeu et, d’autre part, sur le développement de l’ECL pour la bioanalyse, avec un accent particulier sur le couplage entre l’électrochimie bipolaire et l’ECL.
Hanan Al-Kutubi, Silvia Voci, Liza Rassaei, Neso Sojic, Klaus Mathwig
Microfabricated nanofluidic electrochemical devices offer a highly controlled nanochannel geometry; they confine the volume of chemical reactions to the nanoscale and enable greatly amplified electrochemical detection. Here, the generation of stable light emission by electrochemiluminescence (ECL) in transparent nanofluidic devices is demonstrated for the first time by exploiting nanogap amplification. Through continuous oxidation and reduction of [Ru(bpy)3]2+ luminophores at electrodes positioned at opposite walls of a 100-nm nanochannel, we compare classic redox cycling and ECL annihilation. Enhanced ECL light emission of attomole luminophore quantities is evidenced under ambient conditions due to the spatial confinement in a 10-femtoliter volume, resulting in a short diffusion timescale and highly efficient ECL reaction pathways at the nanoscale.
H. Labie, A. Perro, V. Lapeyre, B. Goudeau, B. Catargi, R. Auzély, V. Ravaine
A simple route to deliver on demand hydrosoluble molecules such as peptides, packaged in biocompatible and biodegradable microgels, is presented. Hyaluronic acid hydrogel particles with a controlledstructure are prepared using a microfluidic approach. Their porosity and their rigidity can be tuned bychanging the crosslinking density. These negatively-charged polyelectrolytes interact strongly withpositively-charged linear peptides such as poly-L-lysine (PLL). Their interactions induce microgel deswellingand inhibit microgel enzymatic degradability by hyaluronidase. While small PLL penetrate the wholevolume of the microgel, PLL larger than the mesh size of the network remain confined at its periphery.They make a complexed layer with reduced pore size, which insulates the microgel inner core fromthe outer medium. Consequently, enzymatic degradation of the matrix is fully inhibited and nonaffinityhydrophilic species can be trapped in the core. Indeed, negatively-charged or small neutral peptides,without interactions with the network, usually diffuse freely across the network. By simple additionof large PLL, they are packaged in the core and can be released on demand, upon introduction ofan enzyme that degrades selectively the capping agent. Single polyelectrolyte layer appears as a simplegeneric method to coat hydrogel-based materials of various scales for encapsulation and controlled delivery ofhydrosoluble molecules.