Jérôme Dejeu

Sensor Based on Aptamer Folding to Detect Low-Molecular Weight Analytes

Aptamers have emerged as promising biorecognition elements in the development of biosensors. The present work focuses on the application of quartz crystal microbalance with dissipation monitoring (QCM-D) for the enantioselective detection of a low molecular weight target molecule (less than 200 Da) by aptamer-based sensors. While QCM-D is a powerful technique for label-free, real-time characterization and quantification of molecular interactions at interfaces, the detection of small molecules interacting with immobilized receptors still remains a challenge. In the present study, we take advantage of the aptamer conformational changes upon the target binding that induces displacement of water acoustically coupled to the sensing layer. As a consequence, this phenomenon leads to a significant enhancement of the detection signal. The methodology is exemplified with the enantioselective recognition of a low molecular weight model compound, L-tyrosinamide (L-Tym). QCM-D monitoring of L-Tym interaction with the aptamer monolayer leads to an appreciable signal that can be further exploited for analytical purposes or thermodynamics studies. Furthermore, in situ combination of QCM-D with spectroscopic ellipsometry unambiguously demonstrates that the conformational change induces a nanometric decrease of the aptamer monolayer thickness. Since QCM-D is sensitive to the whole mass of the sensing layer including water that is acoustically coupled, a decrease in thickness of the highly hydrated aptamer layer induces a sizable release of water that can be easily detected by QCM-D.

Stability of Self-Assembled Polymer Films Investigated by Optical Laser Reflectometry

We studied the influence of post-treatment rinsing after the formation of self-assembled polyelectrolyte films made with the weak base poly(allylamine hydrochloride) (PAH) and the strong acid poly(styrene sulfonate) (PSS). The stability of the film was studied using optical fixed-angle laser reflectometry to measure the release of polymeric material and AFM experiments to reveal the change of morphology and thickness. We found that the polymer films were stable upon rinsing when the pH was the same in the solution as that used in the buildup (pH 9). The films released most of the polymeric material when rinsed at higher pH values, but a layer remained that corresponded to a PAH monolayer directly bound with the silica surface. Films containing at least four bilayers were stable upon rinsing at lower pH values, but the stability of thinner films depended on the type of the last polymer deposited. They were stable in the case of PSS as an outermost deposit, but they released a large part of their material in the case of PAH. The stability results were determined using a simple model of the step-by-step assembly of the polymer film described formerly.

The nickel(II) complex of guanidinium phenyl porphyrin, a specific G-quadruplex ligand, targets telomeres and leads to POT1 mislocalization in culture cells

With the aim of finding selective and biologically active G-quadruplex ligands, modified porphyrin with bulky cationic substituents, meso-5,10,15,20-tetrakis(4-guanidinophenyl)porphyrin tetrahydrochloride, referred to as guanidinium phenyl porphyrin, was prepared. The corresponding nickel(II) and cobalt(III) metallated porphyrins were also synthesized. Interaction with quadruplexes was examined by means of fluorescence resonance energy transfer melting and surface plasmon resonance-based assays: the three compounds proved to bind to G-quadruplex DNA in a similar and highly selective way. Guanidinium phenyl porphyrin and its nickel(II) metallated derivative exhibit moderate cytotoxicity toward cells in culture. Strikingly, the nickel porphyrin derivative was able to displace hPOT1 shelterin protein from telomeres in human cells.Graphical AbstractNickel(II) guanidinium phenyl porphyrin, a cationic bulky porphyrin is a powerful specific G-quadruplex DNA ligand. It enters the cells and induces shelterin modification.

Efficient Inhibition of Telomerase by Nickel–Salophen Complexes

Four nickel(II)–salophen complexes containing alkyl‐imidazolium chains connected at the ortho or meta positions were prepared: N,N′‐bis(2‐hydroxy‐4‐methyl‐3H‐imidazol‐1‐iumbenzylideneamino)phenylenediamine (1), N,N′‐bis(2‐hydroxy‐3‐methyl‐3H‐imidazol‐1‐iumbenzylideneamino)phenylenediamine (2), N,N′‐bis(2‐hydroxy‐3‐methyl‐3H‐imidazol‐1‐iumbenzylideneamino)methyl‐3H‐imidazol‐1‐iumphenylenediamine (3), and N,N′‐bis(2‐hydroxy‐4‐methyl‐3H‐imidazol‐1‐iumbenzylideneamino)methyl‐3H‐imidazol‐1‐iumphenylenediamine (4). They protect G‐quadruplex DNA (G4‐DNA) against thermal denaturation and show KA values in the range of 7.4×105 to 4×107 m−1 for G4‐DNA models. Complex 4 exhibits an IC50 value of 70 nm for telomerase inhibition.

Redox‐Driven Host–Guest Interactions Allow the Controlled Release of Captured Cells on RGD‐Functionalized Surfaces

A quartz crystal microbalance technique with dissipation monitoring and a complementary optical microscopy technique were used for monitoring the capture and release of specific cells on a surface displaying a bifunctional molecular device, composed of a molecular scaffold endowed with the cell recognition property of an RGD ligand and a β‐CD/Fc redox‐switchable system.

Templated Formation of Discrete RNA and DNA:RNA Hybrid G-Quadruplexes and Their Interactions with Targeting Ligands.

G-rich RNA and DNA oligonucleotides derived from the human telomeric sequence were assembled onto addressable cyclopeptide platforms through oxime ligations and copper-catalyzed azide-alkyne cycloaddition (CuAAc) reactions. The resulting conjugates were able to fold into highly stable RNA and DNA:RNA hybrid G-quadruplex (G4) architectures as demonstrated by UV, circular dichroism (CD), and NMR spectroscopic analysis. Whereas rationally designed parallel RNA and DNA:RNA hybrid G4 topologies could be obtained, we could not force the formation of an antiparallel RNA G4 structure, thus supporting the idea that this topology is strongly disfavored. The binding affinities of four representative G4 ligands toward the discrete RNA and DNA:RNA hybrid G4 topologies were compared to the one obtained with the corresponding DNA G4 structure. Surface plasmon resonance (SPR) binding analysis suggests that the accessibility to G4 recognition elements is different among the three structures and supports the idea that G4 ligands might be shaped to achieve structure selectivity in a biological context.

Prefolded Synthetic G-Quartets Display Enhanced Bioinspired Properties

A water-soluble template-assembled synthetic G-quartet (TASQ) based on the use of a macrocyclodecapeptide scaffold was designed to display stable intramolecular folds alone in solution. The preformation of the guanine quartet, demonstrated by NMR and CD investigations, results in enhanced peroxidase-type biocatalytic activities and improved quadruplex-interacting properties. Comparison of its DNAzyme-boosting properties with the ones of previously published TASQ revealed that, nowadays, it is the best DNAzyme-boosting agent.

Modeling of electrostatic forces induced by chemical surface functionalisation for microrobotics applications

Non-contact microrobotics is a promising way to avoid adhesion caused by the well-known scale effects. Nowadays, several non-contact micro-robots exist. Most of them are controlled by magnetic or dielectrophoresis phenomena. To complete this, we propose a method based on electrostatic force induced by chemical functionalisation of substrates. In this study, we show a model of this force supported by experimental results. We reached long range forces measuring an interaction force of several microNewtons and an interaction distance of tens micrometers. This paper shows the relevance of using chemical electrostatic forces for microrobotics applications.

Improvement of Robotic Micromanipulations Using Chemical Functionalisations

Robotic microhandling is disturbed by the adhesion phenomenon between the micro-object and the grippers. This phenomenon is directly linked to both the object and the gripper surface chemical composition. We propose to control adhesion by using chemical self-assembly monolayer (SAM) on both surfaces. Previous distance-force measurements done with AFM have shown that the liquid pH can be used to modify the adhesion and created repulsive force between the gripper fingers and the micro-objet. This paper shows the correlation between the force distance distance measurements and the micromanipulation tasks using chemically functionalized grippers.

Robotic submerged microhandling controlled by pH swithching

Robotic microhandling is a promising way to assemble microcomponents in order to manufacture new generation of Hybrid Micro ElectroMechanical Systems (HMEMS). However, at the scale of several micrometers, adhesion phenomenon highly perturbs the micro-objects release and the positioning. This phenomenon is directly linked to both the object and the gripper surface chemical composition. We propose to control adhesion by using chemical self-assembly monolayer (SAM) on both surfaces. Different types of chemical functionalisation have been tested and this paper only focuses on the presentation of aminosilane grafted (3 (ethoxydimethylsilyl) propyl amine (APTES) and (3 aminopropyl) triethoxysilane (APDMES)). We show that the liquid pH can be used to modify the adhesion and to switch from an attractive behaviour to a repulsive behaviour. The pH control can thus be used to increase adhesion during handling and cancel adhesion during release. Experiments have shown that the pH control is able to control the release of a micro-object. This paper shows the relevance of a new type of reliable submerged robotic microhandling principle, which is based an adjusting chemical properties of liquid.