On-chip coupling magnetic Hyperthermia and Electrochemistry

Principle Investigators:  Isabelle Le Potier (Paris Saclay University), Jean Gamby (CNRS).

Participants (recents): Postdoc : Djamila Kechkeche (CNRS); Engineers : Pedro Gonzalez Losada (CNRS), Jihed Khemir (CNRS); Ph.D students : Claire Poujouly (Paris Saclay University), Martina Freisa (Paris Saclay University).

Funding : LabEx MiChem (2014), Labex Nanosaclay Program Valorisation (2018), CNRS Prematuration (2018), ANR DIMELEC (2020).

Collaborations: PHENIX, Paris (Jean-Michel Siaugue, Vincent Dupuis), IRBA, Clamart (Sébastien Banzet), LISE (Alain Pailleret), ENS Département de Chimie (Laurent Thouin).

The heating of a biologic solution is a crucial part in an amplification process such as the catalytic detection of a biological target. However, in many situations, heating must be limited in microfluidic devices, as high temperatures can cause the denaturation of the chip components. Local heating through magnetic hyperthermia on magnetic nanoobjects has opened the doors to numerous improvements. In Biosys team, in collaboration with PHENIX Laboratory (Sorbonne University), we designed and implemented a new strategy combining to existing methods as modules in microfluidics. It takes advantage of the extreme efficiency of DNA-modified superparamagnetic core-shell nanoparticles to capture complementary sequences (microRNA-target), uses magnetic hyperthermia to locally release these targets (Horny et. al., Nanomaterials 2021), and detects them through electrochemical techniques using ultra-sensitive channel DNA-modified ultramicroelectrodes (Horny et. al., Sensor 2021). As illustrated in Figure 1, the combination of magnetic hyperthermia and microfluidics coupled with on-chip electrochemistry opens the way to a drastic reduction in the time devoted to the steps of extraction, amplification and nucleic acids detection. The originality of the patented device (Horny et al., US Patent 2020) comes from the design and microfabrication of the microfluidic chip suitable to its insertion in the millimetric gap of a toric inductance with a ferrite core.

The first axis of our researches is the improvement of the microRNA release with on-chip magnetic hyperthermia at room temperature. Hyperthermia in microfluidics allows a fine and dynamic tuning of a confined environment (concentrations, flow rates, time of residency of particles), while keeping the volume of reaction under the microliter, especially relevant for the use of expensive biological samples. The second axis of researches is dedicated to microelectrode integration on the on-chip magnetic hyperthermia device to combine microRNA release and electrochemical detection in a one-step microfluidic protocol (Horny et al., L’actualité Chimique 2021).


Figure. (A) Picture of the final PDMS/glass microfluidic setup for magnetic hyperthermia and electrochemical detection coupling. For convenient the microfluidic channel is highlighted in blue. (B) Microchip insertion for the localized magnetic hyperthermia through the ferrite gap. (C) On-chip hyperthermia protocol to release micro-RNA targets from magnetic nanoparticles coupled with electrochemical detection. (D) Electrochemical impedance responses of the electrochemical on-chip detection of hybridization (following hyperthermia on-chip step) between 100 kHz to 0.2 Hz with 10 mV AC signal perturbation on the microchannel electrode sensor filled with of 3mM [Fe(III)(CN)6]3− /[Fe(II)(CN)6]4− + 10-8 M Methylene Blue in 0.5 M NaCl. Nyquist plot of probe immobilized on carbon nitride microelectrode after circulating of 100 µg mL-1 DNA probe sequence diluted in 0.5 M NaCl for a 0.5 µL s-1 working flow (O blue). Target hybridization of miR-122 released for a working flow of 0.056 µL s-1 (O red).

Integrated multiplexed electrochemical sensing system and instrumentation

Scientific Leader:  Jean Gamby (CNRS)

Participants (recents): Engineers : Pedro Gonzalez Losada (CNRS), Jérémy Le Gall (CNRS), Jihed Khemir (CNRS); Ph.D students : Claire Poujouly (Paris Saclay University) and Martina Freisa (Paris Saclay University)

Funding : Labex Nanosaclay Program Valorisation (2018), CNRS Prematuration (2020).

Collaborations: PHENIX, Paris (Jean-Michel Siaugue, Vincent Dupuis), IRBA, Clamart (Sébastien Banzet).

In the context of new strategies and instrumentation developments to perform easy, accurate and rapid detection of nucleic acids in microfluidics. Our Biosys proposes three strategies: i) microfluidic chip configurations, designs and fabrications to perform multiplexed electrochemical measurements; ii) custom made electronic systems dedicated for several 2-electrodes cell instead of conventional 3-electrodes; iii) validation protocols of the readout and multiplexing for DNA/ RNA biosensors. One of the great advantage consists to concomitantly reduce microfabrication complexity and integration of individual electronics readout related to the need of several reference electrodes for multiplexing in microfluidics.

To this goal, new architectures of microfluidic device fabrication and its dedicated electronic system are designed to perform the multiplexed electrochemical measurements. Recently wehighlighted that parallelization of eight microchannels bearing 2-electrodes cell and its dedicated electronics is as robust as conventional 3-electrodes cell and commercially available potentiostats. The great advantage that we found is a concomitantly reduction of microfabrication steps and decrease of integration of individual electronic readout for several reference electrodes in microfluidics. Our recent results demonstrate thus the validity of the fabricated chip the functionality of the readout and multiplexing showing that the system is able of detecting synthetic miRNA concentrations with a dynamic range from 10-18 mol/L to 10-6 mol/L onto self-assembled monolayer (SAM) modified gold microelectrode.

The electronic board permits the realization of a so-called cyclic voltammetry (CV) measurement. In brief, CV consists in a potential sweep applied between the WE and the CE, and the measurement of the collected current at the WE. For this purpose, the electronic circuit must drive the electrodes with a triangular shaped polarization potential, what produces the reduction and oxidation of the species of interest on the surface of the WE. Thus, the current generated at the WE is proportional to the DNA/RNA strands hybridization occurred after the functionalization of the electrodes with the single strand DNA (ssDNA) complementary to the RNA under investigation. Therefore, measuring the WE current during the CV experiment it is possible to quantify the RNA species under investigation in the analyzed sample, obtaining, thus, a direct transduction from the hybridization phenomena to an electric current.