Here we report the use of natural, chemically-unmodified, microfibrillated cellulose (MFC) as a matrix for hepatocyte culture. We developed an original cell-culture design composed of a thin 3D-microstructured fibrous substrate consisting of a MFC sheet coating a highly O(2)-permeable polydimethylsiloxane (PDMS) membrane. The MFC-coated PDMS membranes were obtained according to a simple process where cellulose fibres were deposited from an aqueous suspension on the PDMS surfaces and the films were dried under mild conditions. To enable oxygen diffusion through the membranes, they were assembled on bottomless frames ('O(2)+' condition). Rat hepatocytes primary-cultured on such MFC-PDMS membranes quickly organized themselves into large hemispherical 3D aggregates which were tightly anchored to the MFC sheets. In contrast, hepatocytes cultured on smooth PDMS membranes in the O(2)+ system (O(2)+, PDMS) organized into unstable 2D monolayers which easily detached from the surfaces. Hepatocyte 3D cultures obtained on MFC-PDMS membranes exhibited higher liver-specific functions over a 2-week culture period, as assessed by both the higher albumin secretion and urea synthesis rate. The MFC-PDMS membranes appear suitable for obtaining stably-attached and functional hepatocyte 3D cultures and appear interesting for drug/chemical screenings in a microplate format, but also for microfluidic applications.
This paper covers innovative results on the development of an electrostatically actuated mechanical switch device made of a microfibrillated cellulose sheet coated with a thin polyimide layer. For microelectronic applications, biodegradable and biocompatible nanomaterials such as microfibrillated cellulose (MFC) have attracted attention. The studied MFC sheets reveal a fibrous-like morphology composed of cellulose nanofibres leading to a high surface roughness. Moreover, the porous microstructure and the hydrophilic nature of the MFC sheet induce poor dielectric properties. These shortcomings make MFC sheets relatively unsuitable for electronic applications. In order to overcome these drawbacks, both sides of the MFC sheet are coated with a thin polyimide layer, which greatly improves the dielectric properties, moisture sensitivity and sheet surface roughness. This new sheet is then patterned in order to be used as a substrate for the fabrication of a micromechanical switch. Gold electrodes are added onto the sheet for electrostatic actuation and switch detection. The pull-down voltage of this switch, defined as the actuation voltage needed to establish a contact between the free end of the cantilever beam and the substrate, is measured to be about 55 V.
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