Daniel Brassard

Assessment of multidrug resistance on cell coculture patterns using scanning electrochemical microscopy

The emergence of resistance to multiple unrelated chemotherapeutic drugs impedes the treatment of several cancers. Although the involvement of ATP-binding cassette transporters has long been known, there is no in situ method capable of tracking this transporter-related resistance at the single-cell level without interfering with the cell’s environment or metabolism. Here, we demonstrate that scanning electrochemical microscopy (SECM) can quantitatively and noninvasively track multidrug resistance-related protein 1–dependent multidrug resistance in patterned adenocarcinoma cervical cancer cells. Nonresistant human cancer cells and their multidrug resistant variants are arranged in a side-by-side format using a stencil-based patterning scheme, allowing for precise positioning of target cells underneath the SECM sensor. SECM measurements of the patterned cells, performed with ferrocenemethanol and [Ru(NH3)6]3+ serving as electrochemical indicators, are used to establish a kinetic “map” of constant-height SECM scans, free of topography contributions. The concept underlying the work described herein may help evaluate the effectiveness of treatment administration strategies targeting reduced drug efflux.

3D thermoplastic elastomer microfluidic devices for biological probe immobilization

Microfluidics has emerged as a valuable tool for the high-resolution patterning of biological probes on solid supports. Yet, its widespread adoption as a universal biological immobilization tool is still limited by several technical challenges, particularly for the patterning of isolated spots using three-dimensional (3D) channel networks. A key limitation arises from the difficulties to adapt the techniques and materials typically used in prototyping to low-cost mass-production. In this paper, we present the fabrication of thin thermoplastic elastomer membranes with microscopic through-holes using a hot-embossing process that is compatible with high-throughput manufacturing. The membranes provide the basis for the fabrication of highly integrated 3D microfluidic devices with a footprint of only 1 × 1 cm(2). When placed on a solid support, the device allows for the immobilization of up to 96 different probes in the form of a 10 × 10 array comprising isolated spots of 50 × 50 μm(2). The design of the channel network is optimized using 3D simulations based on the Lattice-Boltzmann method to promote capillary action as the sole force distributing the liquid in the device. Finally, we demonstrate the patterning of DNA and protein arrays on hard thermoplastic substrates yielding spots of excellent definition that prove to be highly specific in subsequent hybridization experiments.

Advanced EWOD-based digital microfluidic system for multiplexed analysis of biomolecular interactions

This paper presents a low-cost technique for the fabrication of complex electrowetting-on-dielectric (EWOD) digital microfluidic devices. Using this original technology, we have developed devices in which 560 electrodes are used to mix and split nl-size liquid droplets and transport them to 100 analysis spots patterned on a disposable plastic top plate. We demonstrate the multiplexing capability of the developed devices by creating on-chip arrays of droplets with various concentration gradients. Finally, automated biomolecular immobilization and hybridization assays are performed in nl-size droplets under numerous conditions simultaneously with only a limited number of stock solutions.

Fabrication of Microfluidic Devices in Thermoplastic Elastomeric Materials for DNA Detection on Thermal Plastic Substrate

Thermoplastic elastomer (TPE) based microfluidic devices integrated with a microfluidic pumping manifold which consists of 4 electromagnetic valves (EMV) were fabricated. The back and forth shuttling flow and its application in the DNA hybridization process were validated on a thermal plastic Zeonor 1060R substrate. The flow rate can be as fast as 23μl/min when the channel width and the channel height are in 100μm, and 25μm, respectively. The DNA hybridization process is detected by using a fluorescence microscopy. Remarkable DNA hybridization is achieved with the continuous flow of the target DNA at a concentration of 10 nM within the first 1 min by using this device.