Advanced in vitro
models called “organ-on-a-chip”
can mimic the specific cellular environment found in various tissues.
Many of these models include a thin, sometimes flexible, membrane
aimed at mimicking the extracellular matrix (ECM) scaffold of in vivo
barriers. These membranes are often made of polydimethylsiloxane (PDMS),
a silicone rubber that poorly mimics the chemical and physical properties
of the basal membrane. However, the ECM and its mechanical properties
play a key role in the homeostasis of a tissue. Here, we report about
biological membranes with a composition and mechanical properties
similar to those found in vivo. Two types of collagen-elastin (CE)
membranes were produced: vitrified and nonvitrified (called “hydrogel
membrane”). Their mechanical properties were characterized
using the bulge test method. The results were compared using atomic
force microscopy (AFM), a standard technique used to evaluate the
Young’s modulus of soft materials at the nanoscale. Our results
show that CE membranes with stiffnesses ranging from several hundred
of kPa down to 1 kPa can be produced by tuning the CE ratio, the production
mode (vitrified or not), and/or certain parameters such as temperature.
The Young’s modulus can easily be determined using the bulge
test. This method is a robust and reproducible to determine membrane
stiffness, even for soft membranes, which are more difficult to assess
by AFM. Assessment of the impact of substrate stiffness on the spread
of human fibroblasts on these surfaces showed that cell spread is
lower on softer surfaces than on stiffer surfaces.