Claire Dalmay

Label free biosensors for human cell characterization using radio and microwave frequencies

A novel micro biosensor concept functioning at microwave frequencies has been developed in order to study the intrinsic electrical parameters of human cells. This sensor is based on a resonant structure allowing a sensitive detection which associated to its microscopic size permits to work at the scale of one cell. The proposed bio-sensing method presents the advantage to be a label free method and allows potentially cell identification and discrimination. Hence, using a specific experimental protocol, tests performed have demonstrated the biosensor ability to differentiate at least two particular cell types.

Microwave biosensors for identifying cancer cell aggressiveness grade

This paper illustrates the potential of microwave frequencies for biological analysis. Once penetrating inside biological cells, microwaves can interact with their intracellular content and inform on their safe or malignant state. This work demonstrates that their cancer grade (i.e. aggressiveness level) can also be identified by this way. Hence, based on permittivity measurements on three colon cancer cell lines loading RF resonators, the presented results show significant differences of electromagnetic signature in the cancer grade of analyzed cells. This sensing method appears very promising to develop new powerful tools for early cancer diagnostic.

Tunable frequency resonant biosensors dedicated to dielectric permittivity analysis of biological cell cytoplasm

This paper presents an improved design of resonant biosensor, dedicated to dielectric analysis on biological cells at microwave frequencies. Such sensor uses the capability of microwaves to penetrate inside biological cells in order to interact with their intracellular content. Hence, individual dielectric properties of the cell cytoplasm can be known and then used as a signature of the cell pathological state (living or dead, malignant or safe...). In this paper is introduced a continuously tunable frequency sensor prototype, able to perform an accurate dielectric analysis over at least a 1GHz bandwidth while keeping enough sensitivity to detect and analyze a single cell. As a proof of concept, permittivity measurements have been led on calibrated size polystyrene beads: achieved results show good agreement with expected permittivity values. Finally experiments on Glioblastoma cells will be presented.

Electric pulses: a flexible tool to manipulate cytosolic calcium concentrations and generate spontaneous-like calcium oscillations in mesenchymal stem cells.

Human adipose mesenchymal stem cells (haMSCs) are multipotent adult stem cells of great interest in regenerative medicine or oncology. They present spontaneous calcium oscillations related to cell cycle progression or differentiation but the correlation between these events is still unclear. Indeed, it is difficult to mimic haMSCs spontaneous calcium oscillations with chemical means. Pulsed electric fields (PEFs) can permeabilise plasma and/or organelles membranes depending on the applied pulses and therefore generate cytosolic calcium peaks by recruiting calcium from the external medium or from internal stores. We show that it is possible to mimic haMSCs spontaneous calcium oscillations (same amplitude, duration and shape) using 100 μs PEFs or 10 ns PEFs. We propose a model that explains the experimental situations reported. PEFs can therefore be a flexible tool to manipulate cytosolic calcium concentrations. This tool, that can be switched on and off instantaneously, contrary to chemicals agents, can be very useful to investigate the role of calcium oscillations in cell physiology and/or to manipulate cell fate.

Microwave sensors for stem cell identification and discrimination

An original label free bio detection method has been developed in order to discriminate biological samples at the cell scale. In this objective, highly sensitive resonant microwave biosensors have been designed in order to achieve analysis on very limited cells concentration. This paper demonstrates the potential of microwave frequencies for biological analysis using their ability to penetrate inside biological cells and probe their intracellular content without denaturation. Based on permittivity measurement in the 10 to 35 GHz range, the presented results illustrate that it is possible to use microwaves to discriminate biological cells in an non-invasive way as function of their differentiation degree. Application of this technique for stem cells identification appears as a very promising application and opens new areas in research for improving cancer treatments.

High frequency microfluidic biosensors for intracellular dielectric spectroscopy

This paper deals with the development and characterization of a high frequency (HF) label-free microfluidic biosensor for the non-invasive analysis of cell intracellular properties. The presented microfluidic biosensor is based on a band pass filter architecture made of thick gold electrodes designed to ensure a high sensitivity to cells flowing in the microfluidic channel. In a first step, to prove the feasibility of the proposed approach, HF measurements have been successfully achieved on polystyrene beads. Then, combining HF measurements with dielectrophoresis forces, to trap cells in the sensitive area, it has been possible to characterize cell dielectric properties without any denaturation. We demonstrate here the proof of concept of using high frequency impedance spectroscopy to analyze single cells in a microfluidic environment.

Surface-Micromachined Rectangular Micro-Coaxial Lines for Sub-Millimeter-Wave Applications

This letter describes the design, fabrication and characterization of surface micro-machined micro-coaxial transmission lines. The fabrication process relies on successive deposition of sacrificial polymer layers and metal electroplating. Transmission lines with a cross-section of 88 μm × 42 μm have been fabricated on a fused silica substrate, with various shapes. These lines are very well suited for applications above 50 GHz, where propagation in air minimizes both loss and dispersion. The measured lines have good performances with measured insertion losses of -0.33 dB/mm @ 127 GHz and return loss better than -15 dB.

Improved sedimentation field-flow fractionation separation channel for concentrated cellular elution

SdFFF is now commonly used for cell sorting. Nevertheless, as with many other separation methods, SdFFF Hyperlayer elution leads (1) to sample dilution resulting in cell loss which could restrict further use; and (2) to a high output flow rate impacting detector sensitivity and selectivity. In order to limit these problems, we proposed modifications of the SdFFF separation channel consisting both in downscaling and the insertion of an outlet stream splitter. This last system corresponded to a strip which divides the flow rate output into two parts, one containing concentrated cells in a reduced volume and flow rate, the other containing the excess mobile phase useless for further cell manipulation, detection and characterization. For the first time we have shown that splitter implementation and downscaling respected channel flowing and resulted in Hyperlayer elution of around 95% of cells in less than 50% of input flow rate. Improved cell sorting was demonstrated by enrichment (∼10 times) of cancer stem cells from WiDr cells with two times less quantity of injected cells.

On-Chip Biosensors Based on Microwave Detection for Cell Scale Investigations

This paper presents original label free bio sensors allowing the study of electrical properties of human cells and so potentially cell identification and discrimination. Proposed biosensors are based on planar devices operating at microwave frequencies and fabricated using a standard microelectronic process. Actually, their microscopic sensitive areas allow an improved detection at the cell scale which represents a significant progress in the study of many biological phenomenon. In this paper, biosensor detection capabilities are demonstrated on only few biological cells analysis up to one single cell interacting with the sensor. Fabricated micro-sensors can be used to determine cell intrinsic electrical impedance at microwave frequencies allowing a label free approach to accurately discriminate biological cells.

3D micro-fabricated high-Q 140 GHz filter

This paper introduces a new fabrication process for the realization of cavity resonators and band pass filters, using additive micro fabrication. 3D air-filled structures with a 195 μm thickness are obtained by using successive electroplating. Thanks to this fabrication process, a 140 GHz cavity resonator with an unloaded quality factor of 511 has been fabricated. A four-pole band pass filter at 140 GHz is presented, with a 3.1% bandwidth at −3 dB, and measured 3.7 dB in-band loss. Measurements are in good agreement with HFSS simulations without any post-processing tuning.