Céline Vivien

Covalent attachment of trypsin on plasma polymerized allylamine

This paper focuses on the immobilization of a proteolytic enzyme, trypsin, on plasma polymerized allylamine (ppAA) films. The later have been deposited onto silicon substrate by means of radiofrequency glow discharge. The covalent attachment of the enzyme was achieved in three steps: (i) activation of the polymer surface with glutaraldehyde (GA) as a linker, (ii) immobilization of trypsin and (iii) imino groups reduction treatment. The effects and efficiency of each step were investigated by X-ray photoelectron spectroscopy (XPS) and atomic force microscopy (AFM). Fluorescent spectroscopy was used to evaluate the change of the biological activity following the immobilization steps. The results showed that enzyme immobilization on GA-modified substrate increases the enzyme activity by 50% comparing to adsorbed enzymes, while the imino reduction treatment improves the enzyme retention by about 30% comparing to untreated samples. In agreement with XPS and AFM data, UV-vis absorption spectroscopy, used to quantify the amount of immobilized enzyme, showed that allylamine plasma polymer presents a high adsorption yield of trypsin. Although the adsorbed enzymes exhibit a lower activity than that measured for enzymes grafted through GA linkers, the highest catalytic activity obtained was for the enzymes that underwent the three steps of the immobilization process.

Design of silicon-PPTMDS bio-MEMS by cold RPECVD

An important activity is developed today in the field of biosensors and biochips. These sensors are used essentially in the detection and/or characterization of biological or chemical entities in complex media. The aim of this paper is the development of a new type of biosensors combining microfluidic components and millimeter or sub-millimeter wave (or THz or FIR) spectroscopy tools. Today, many different microsystems in the field of biology are realized in all polymers or in silicon with a bounding of silicon or glass. We have selected to deposit a Plasma Polymerized TetraMethylDiSiloxane (PPTMDS) on a silicon wafer. A new technological process based on cold remote nitrogen plasma allows us to obtain 50-80μm thick layers with a rigid texture and a very good link with silicon. This technological process is now well defined and is compatible with a classical microelectronic process for the deposition of the metallic planar waveguides. For the first time, measurements using an-in-house vectorial network analyzer (VNA) 140-220GHz are reported. Fairly good results have been obtained from impedance and propagation characteristics. These measurements allow us to determine the PPTMDS permittivity in this bandwidth. Thanks to this knowledge, we have designed a matched coplanar waveguide where a water droplet is deposited. An inversion model has been developed to retrieve the water permittivity and will be broadened to biological entities.

ppTMDS as a new polymer technology for a high throughput bio-MEMS design

The development of more complex biochips in terms of functionality requires some technological evolutions. A high frequency biological micro-electro-mechanical-system dedicated to biological analysis is a typical case of this requirement for providing compatibility between high frequency propagation and microfluidic circulation. Mixed fabrication technologies using silicon and polymers appear to be a good alternative. We have developed a promising deposition process of an organosilicon polymer by remote afterglow plasma technology, also called plasma polymerized tetramethyldisiloxane (ppTMDS). This technique allows us to obtain high deposition rate values in the range of 160 A s−1 and a thick layer up to 140 µm without any crack. Moreover, this process is compatible with high throughput microelectronic designs and it is done near room temperature. This last point is very interesting for further development of surface bio-functionalization, for example. We have characterized this siloxane polymer by physico-chemical analysis. The roughness has been optimized, thus allowing the realization of high frequency waveguides. The ppTMDS permittivity presents a low dispersive characteristic and constitutes one of the best low-loss polymers up to 1 THz.

Plasma polymer process for microfluidic devices fabrication

Plasma polymerization, so called Remote Plasma Enhanced Chemical Vapour Deposition (RPECVD) has been increasingly used in microsystems field. Plasma polymers served primarily as supports for electronic sensors or carriers for biomolecules and cell attachment1. This work describes the first use of plasma thin film deposition for the easy, fast and reduced cost fabrication of microfluidic channels. A new method named “plasma polymerization on a micropatterned surface” (PPMS) is presented. First, micropatterns representing the desired channels were designed on a silicon wafer, either by lithography of a sacrificial photoresist or by plasma etching of the Si substrate. Then, the patterned substrate was introduced into the reaction chamber of a home-made microwave (2.45 GHz) plasma reactor1. The organosilicon monomer 1,1,3,3,TetraMethylDiSiloxane was used as the precursor to synthetize and deposit a polymer organosilicon film by a remote afterglow PECVD2. The deposited polymer is used as the structural material of the microfluidic network.