4 research outputs found
Thin-film dielectric elastomer sensors to measure the contraction force of smooth muscle cells
The development of thin-film dielectric elastomer strain sensors for the characterization of smooth muscle cell (SMC) contraction is presented here. Smooth muscle disorders are an integral part of diseases such as asthma and emphysema. Analytical tools enabling the characterization of SMC function i.e. contractile force and strain, in a low-cost and highly parallelized manner are necessary for toxicology screening and for the development of new and more effective drugs. The main challenge with the design of such tools is the accurate measurement of the extremely low contractile cell forces expected as a result of SMC monolayer contraction (as low as ~ 100 ÎŒN). Our approach utilizes ultrathin (~5 ÎŒm) and soft elastomer membranes patterned with elastomer-carbon composite electrodes, onto which the SMCs are cultured. The cell contraction induces an in-plane strain in the elastomer membrane, predicted to be in the order 1 %, which can be measured via the change in the membrane capacitance. The cell force can subsequently be deduced knowing the mechanical properties of the elastomer membrane. We discuss the materials and fabrication methods selected for our system and present preliminary results indicating their biocompatibility. We fabricate functional capacitive senor prototypes with good signal stability over the several hours (~ 0.5% variation). We succeed in measuring in-plane strains of 1 % with our fabricated devices with good repeatability and signal to noise ratio
Cell metabolism monitoring using a microfluidic cartridge with enzyme-based microreactors
We present a novel microfluidic approach for on-line analysis of cell metabolism by simultaneous measurement of two important indicators (glucose and lactate) in a small volume (100 ”l) of cell-culture medium. The in-vitro study of cell metabolism is especially valuable for evaluating the effect of toxins on physiochemical state of living organism
Delineating Fibronectin Bioadhesive Micropatterns by Photochemical Immobilization of Polystyrene and Poly(vinylpyrrolidone)
Bioadhesive
micropatterns, capable of laterally confining cells to a 2D lattice,
have proven effective in simulating the in vivo tissue environment.
They reveal fundamental aspects of the role of adhesion in cell mechanics,
proliferation, and differentiation. Here we present an approach based
on photochemistry for the fabrication of synthetic polymer micropatterns.
Perfluorophenyl azide (PFPA), upon deep-UV exposure, forms a reactive
nitrene capable of covalently linking to a molecule that is in close
proximity. PFPA has been grafted onto a backbone of polyÂ(allyl amine),
which readily forms a self-assembled monolayer on silicon wafers or
glass. A film of polystyrene was applied by spin-coating, and by laterally
confining the UV exposure through a chromium-on-quartz photomask,
monolayers of polymers could be immobilized in circular microdomains.
PolyÂ(vinylpyrrolidone) (PVP) was attached to the background to form
a barrier to nonspecific protein adsorption and cell adhesion. Micropatterns
were characterized with high-lateral-resolution time-of-flight secondary
ion mass spectrometry (TOF-SIMS), which confirmed the formation of
polystyrene domains within a PVP background. Fluorescenceâmicroscopy
adsorption assays with rhodamine-labeled bovine serum albumin demonstrated
the nonfouling efficiency of PVP and, combined with TOF-SIMS, allowed
for a comprehensive characterization of the pattern geometry. The
applicability of the micropatterned platform in single-cell assays
was tested by culturing two cell types, WM 239 melanoma cells and
SaOs-2 osteoblasts, on micropatterned glass, either with or without
backfilling of the patterns with fibronectin. It was demonstrated
that the platform was efficient in confining cells to the fibronectin-backfilled
micropatterns for at least 48 h. PVP is thus proposed as a viable,
highly stable alternative to polyÂ(ethylene glycol) for nonfouling
applications. Due to the versatility of the nitrene-insertion reaction,
the platform could be extended to other polymer pairs or proteins
and the surface chemistry adapted to specific applications
HMGB1 is an endogenous immune adjuvant released by necrotic cells
Immune responses against pathogens require that microbial components promote the activation of antigen-presenting cells (APCs). Autoimmune diseases and graft rejections occur in the absence of pathogens; in these conditions, endogenous molecules, the so-called âinnate adjuvants', activate APCs. Necrotic cells contain and release innate adjuvants; necrotic cells also release high-mobility group B1 protein (HMGB1), an abundant and conserved constituent of vertebrate nuclei. Here, we show that necrotic HMGB1(â/â) cells have a reduced ability to activate APCs, and HMGB1 blockade reduces the activation induced by necrotic wild-type cell supernatants. In vivo, HMGB1 enhances the primary antibody responses to soluble antigens and transforms poorly immunogenic apoptotic lymphoma cells into efficient vaccines