Frédéric Lemaître

Ecole Normale Supérieure de Paris | ENS · Département de Chimie

Photosynthesis is a fundamental process used by Nature to convert solar energy into chemical energy. For the last twenty years, many solutions have been explored to provide electrical power from the photosynthetic chain. In this context, the coupling between microalgae and exogenous quinones is an encouraging strategy because of the capability of q...

The permeabilization of liposomes by melittin, an antimicrobial peptide (AMP), has been studied by an electrochemiluminescence (ECL) imaging strategy. The methodology consisted first of encapsulating ECL reagents in sealed giant asymmetrical liposomes (100 μm in diameter) made of DOPG/DOPC phospholipids (i.e., 1,2-dioleoyl-sn-glycerol-3-phospho-(1′...

Prostaglandin D2 (PGD2) is one of the most potent endogenous sleep-promoting molecules. However, the cellular and molecular mechanisms of the PGD2-induced activation of sleep-promoting neurons in the ventrolateral preoptic nucleus (VLPO), the major nonrapid eye movement (NREM)-sleep center, still remains unclear. We here show that PGD2 receptors (D...

Optical fibers have opened avenues for remote imaging, bioanalyses and recently optogenetics. Besides, miniaturized electrochemical sensors have offered new opportunities in sensing directly redox neurotransmitters. The combination of both optical and electrochemical approaches was usually performed on the platform of microscopes or within microsys...

In this work, four different new Fluorescent False Neurotransmitters probes were synthesized to contribute to the rationale of the FFN design. Their electroactive and spectroscopic properties were investigated. Hence, the optimal excitation and emission wavelengths (from 344 to 393 nm and 423 to 474 nm respectively) make these probes adapted to flu...

Among all the chemical and biotechnological strategies implemented to extract energy from oxygenic photosynthesis, several concern the use of intact photosynthetic organisms (algae, cyanobacteria…). This means rerouting (fully or partially) the electron flow from the photosynthetic chain to an outer collecting electrode generating thus a photocurre...

Amperometry with ultramicroelectrodes is nowadays a routine technique to investigate neurotransmitter secretion by vesicular exocytosis at the single-cell level. This electroanalytical tool allows one to understand many aspects of the vesicular release in terms of mechanisms. However, the electrochemical detection relies on the oxidation of release...

In this article, we have summarized the recent important results related to the electrochemical detection of vesicular exocytosis by amperometry with microelectrodes over the past three years. In this fascinating scientific field that began 40 years ago, the historical carbon fiber amperometry method still continues to be used to address biological...

This short review is aimed at emphasizing the most prominent recent works devoted to the fluorescence modulation of organic fluorescent or fluorogenic molecules by electrochemistry. This still expanding research field not only addresses the smart uses of known molecules or the design of new ones, but also investigates the development of instrumenta...

Solar cells using living micro-organisms often require the help of a redox mediator, a small molecule which carries the electrons from inside the organisms to the electrode. Ideally the mediator is able to cross biological membranes to access the source of electrons, without causing damage. The diffusion rate across membranes, reduction rate inside...

Secretion of neurotransmitters and hormones via vesicular exocytosis is a fundamental biological field where physicochemical machinery is still source of controversy. Over the last decades, real-time techniques have been developed at the single cell level including electrochemistry (amperometry) and fluorescence (total internal reflection fluoresce...

Microbial solar cells that mainly rely on the use of photosynthesic organisms are a promising alternative to photovoltaics for solar electricity production. In that way, we propose a new approach involving electrochemistry and fluorescence techniques. The coupled set-up Electro-Pulse-Amplitude-Modulation (“e-PAM”) enables the simultaneous recording...

Microbial solar cells that mainly rely on the use of photosynthesic organisms are a promising alternative to photovoltaics for solar electricity production. In that way, we propose a new approach involving electrochemistry and fluorescence techniques. The coupled set-up Electro-Pulse-Amplitude-Modulation ("e-PAM") enables the simultaneous recording...

In this work, a new dual electrofluorescent probe (FFN42) belonging to Fluorescent False Neurotransmitter family was rationally designed for investigating cell secretion. This coumarin including one amino and two hydroxy groups is very promising due to its electroactive and fluorescent properties. The optimal excitation and emission wavelengths (38...

In the last years, many strategies have been developed to benefit from oxygenic photosynthesis in the present context of renewable energies. To achieve this, bioelectricity may be produced by using photosynthetic components involved in anodic or cathodic compartments. In this respect, harvesting photosynthetic electrons from living biological syste...

An original redox-responsive fluorescent probe combining a rhodamine derivative and a ferrocenyl moiety used as the fluorescence modulator was designed, synthesized and characterized. The fluorescence of this new dyad could be tuned from the redox state of ferrocene, a feature observed both electrochemically and on cancer cells incubated with this...

Plants, algae, and some bacteria convert solar energy into chemical energy by using photosynthesis. In light of the current energy environment, many research strategies try to take benefits from photosynthesis in order to generate usable photobioelectricity. Among all the developed strategies for transferring electrons from the photosynthetic chain...

An innovative microfluidic platform was designed to monitor electrochemically four primary reactive oxygen (ROS) and reactive nitrogen species (RNS) released by aerobic cells. Taking advantage of the space confinement and electrode performances under flow conditions, only few experiments were sufficient to directly provide significant statistical d...

Applications of the Fluorescent False Neurotransmitter FFN102, an analog of biogenic neurotransmitters and a suitable probe for coupled amperometry and TIRFM (total internal reflexion fluorescence microscopy) investigations of exocytotic secretion, were considered here. The electroactivity of FFN102 was shown to very likely arise from the oxidation...

The Inside Cover picture displays a preparative scale electrocatalytic mechanism with a chemical step involving Michaelis–Menten kinetics. Such a model may be tested to experimental data related to photosynthetic electrons harvesting from algae suspensions. This notably paves the way for analyzing the transient and steady-state corresponding photoc...

In the past years, many strategies were implemented to take benefits from oxygenic photosynthesis to harvest photosynthetic electrons and produce a significant photocurrent. Therefore, electrochemical tools were considered and globally relied on the electron transfer(s) between the photosynthetic chain and a collecting electrode. In this context, w...

Strategies to harness photosynthesis from living organisms to generate electrical power has long been considered, yet efficiency remains low. Here, we aimed to reroute photosynthetic electron flow in photosynthetic organisms without compromising their phototrophic properties. We show that 2,6-dimethyl-p-benzoquinone (DMBQ) can be used as an electro...

Supplementary Figures and Supplementary Tables

Oxygenic photosynthesis is the process used by plants, cyanobacteria or algae to convert the solar energy into a chemical one from the carbon dioxide reduction and water oxidation. In the past years, many strategies were implemented to take benefits from the overall low yield of this process to extract photosynthetic electrons and thus produce a su...

In this work, Fluorescent False Neurotransmitter 102 (FFN102), a synthesized analogue of biogenic neurotransmitters, was demonstrated to show both pH-dependent fluorescence and electroactivity. To study secretory behaviors at the single-vesicle level, FFN102 was employed as a new fluorescent/electroactive dual probe in a coupled technique (amperome...

In this work, Fluorescent False Neurotransmitter 102 (FFN102), a synthesized analogue of biogenic neurotransmitters, was demonstrated to show both pH-dependent fluorescence and electroactivity. To study secretory behaviors at the single-vesicle level, FFN102 was employed as a new fluorescent/electroactive dual probe in a coupled technique (amperome...

The design, fabrication and test of an indium tin oxide (ITO) microdevice to investigate exocytotic behaviors of migratory dendritic cells (DCs) in confined three-dimensional environment were reported in this work. Indeed, immature DCs were able to migrate into micro-fabricated biocompatible polydimethylsiloxane (PDMS) channels that mimic their nat...

Plants or algae take many benefits from oxygenic photosynthesis by converting solar energy into chemical energy through the synthesis of carbohydrates from carbon dioxide and water. However, the overall yield of this process is rather low (about 4% of the total energy available from sunlight is converted into chemical energy). This is the principal...

Electrochemical quantification of four reactive oxygen and nitrogen species (e.g., H2O2, ONOO⁻, NO and NO2⁻) emitted from macrophages populations was completed using a four-chambers microchip. This microchip was fabricated from a glass substrate equipped with four sets of microband electrodes. Each set consisted of a platinum-black coated working e...

Sleep has been hypothesised to maintain a close relationship with metabolism. Here we focus on the brain structure that triggers slow-wave sleep, the ventrolateral preoptic nucleus (VLPO), to explore the cellular and molecular signalling pathways recruited by an increase in glucose concentration. We used infrared videomicroscopy on ex vivo brain sl...

Vesicular exocytosis is an essential biological mechanism used by cellular organisms to release bioactive molecules (hormones, neurotransmitters…) in their environment. For instance, this is the pathway by which chromaffin cells deliver catecholamines (adrenaline, nor-adrenaline, dopamine…) in blood. During this process, secretory vesicles that ini...

In the two last decades, electrochemical techniques have been shown to be an efficient tool to investigate oxidative stress and the production of reactive oxygen and nitrogen species. Among them, the "artificial synapse" configuration involving platinized carbon fiber UMEs is of particular interest because it allows one to quantify in real time the...

Among all the analytical techniques able to monitor exocytosis in real time at the single cell level, electrochemistry (particularly amperometry at constant potential) using ultramicroelectrodes has been demonstrated to be an important and convenient tool for more than two decades. Indeed, because the electrochemical sensor is located in the close...

Both fluorescence and electrochemistry techniques aim at converting a chemical signal into an optical or an electrical one respectively. Particularly, they correspond to appropriate techniques for investigating biological phenomena due to the electroactivity of many biomolecules while cells or proteins can be labeled with fluorophores. Therefore, t...

Ferrocifens are an original class of ferrocifen-type breast cancer drugs. They possess anti-proliferative effects due to the association of the ferrocene moiety and the tamoxifen skeleton. In this work, fluorescence measurements indicated the production of reactive oxygen species (ROS) if hormone-dependent or -independent breast cancer cells were i...

Transport of active molecules across biological membranes is a central issue for the success of many pharmaceutical strategies. Herein, we combine the patch-clamp principle with amperometric detection for monitoring fluxes of redox-tagged molecular species across a suspended membrane patched from a macrophage. Solvent- and protein-free lipid bilaye...

Amperometric currents displaying a pre-spike feature (PSF) may be treated so as to lead to precise information about initial fusion pores, viz., about the crucial event initiating neurotransmitter vesicular release in neurons and medullary glands. However, amperometric data alone are not self-sufficient, so their full exploitation requires external...

The electrochemical detection of hydrogen peroxide and nitrite, as important representatives of cytotoxic reactive oxygen/nitrogen (ROS, RNS) species released during cellular oxidative bursts, is reported in microfluidic devices. Platinum-black coated platinum (Pt/Pt-black) electrodes were microfabricated and optimized to achieve optimal detection...

Reactive oxygen and nitrogen species (ROS and RNS) produced by macrophages are essential for protecting a human body against bacteria and viruses. Micrometer-sized electrodes coated with Pt black have previously been used for selective and sensitive detection of ROS and RNS in biological systems. To determine ROS and RNS inside macrophages, one nee...

SOD-mimics are small complexes that reproduce the activity of superoxide dismutases, natural proteins that catalytically dismutate the superoxide anion. Activated macrophages, which produce ROS and RNS fluxes, constitute a relevant model to challenge antioxidant activity in a cellular context and were used to test a Mn-complex which was shown to ef...

The microfabrication and successful testing of a series of three ITO (Indium Tin Oxide) microsystems for amperometric detection of cells exocytosis are reported. These microdevices have been optimized in order to simultaneously (i) enhance signal-to-noise ratios, as required electrochemical monitoring, by defining appropriate electrodes geometry an...

Transport, reactivity and interactions of anti-tumor ferrocene-based compounds within lipid environments have been investigated electrochemically at a glassy carbon electrode (GCE) modified with a lipid bilayer film. Cyclic voltammetry performed in the presence of an adsorbed bilipid film in a H2O/EtOH (8/2) mixture, clearly showed that the affinit...

More transparency in bioanalysis: A microdevice based on transparent indium tin oxide (ITO) electrodes allows simultaneous total internal reflection fluorescence microscopy and amperometric measurements. Use of the device in the coupled optical and electrochemical detection of single exocytotic events is demonstrated with enterochromaffin BON cells...

Exocytosis is a key mechanism by which a cellular organism releases molecular messengers into the extracellular medium. C. Amatore et al. report in their Communication on page 5081 ff. the elaboration of an ITO microdevice that combines two powerful techniques—amperometry at microelectrodes and total internal reflection fluorescence microscopy—whic...

Free radical production in aerobic living beings is generally perceived only through a negative viewpoint since one focuses mostly on their deleterious effects. Yet, oxidative stress is an essential mechanism underlying many important functions in aerobic organisms including non specific immunedefenses or many regulations. This is mostly true for t...

Electrochemical monitoring of the exocytosis process is generally performed through amperometric oxidation of the electroactive messengers released by single living cells. Herein, we consider the vesicular release of catecholamines by chromaffin cells. Each exocytotic event is thus detected as a current spike whose morphology (intensity, duration,...

[Figure Presented] macrophage Removing cytotoxics: A MnII- pentaazamacrocycle removes NO; Cy2- and their ONOO - product as shown by real-time amperometry at single cells (see picture). This is the first compound able to completely abolish the cytotoxic effects of reactive oxygen (ROS) and reactive nitrogen species (RNS) in inflammation.

Etched carbon fiber microelectrodes of different radii have been used for amperometric measurements of single exocytotic events occurring at adrenal chromaffin cells. Frequency, kinetic, and quantitative information on exocytosis provided by amperometric spikes were analyzed as a function of the surface area of the microelectrodes. Interestingly, t...

Several important contributions of electroanalytical techniques over the past 20 years for investigating three major biological processes at the single cell level: vesicular exocytosis, oxidative stress, and nitric oxide metabolism in brain have been reported. It is evident that molecular electrochemistry at microelectrodes enhances the understandi...

Amperometry is a simple and powerful technique to study exocytosis at the single cell level. By positioning and polarizing (at an appropriate potential at which the molecules released by the cell can be oxidized) a carbon fiber microelectrode at the top of the cell, each exocytotic event is detected as an amperometric spike. More particularly, a po...

Exocytosis is an important biological process used by cells to deliver messengers or effectors to target cells with high spatial, quantitative, and kinetic precision. This process occurs by interaction and fusion of vesicles containing the (bio)chemical information with the cell membrane to release their contents into the surrounding medium. Becaus...