Characteristics of highly flexible PDMS membranes for long‐term mechanostimulation of biological tissue

Abstract

Measurement of mechanical properties of soft biological tissue remains a challenging task in mechanobiology. Recently, we presented a bioreactor for simultaneous mechanostimulation and analysis of the mechanical properties of soft biological tissue samples. In this bioreactor, the sample is stretched via deflection of a flexible membrane. It was found that the use of highly compliant membranes increases accuracy of measurements. Here, we describe the production process and characteristics of thin and flexible membranes of polydimethylsiloxane (PDMS) designed to improve the signal-to-noise ratio of our bioreactor. By a spin-coating process, PDMS membranes were built by polymerization of a two component elastomer. The influence of resin components proportion, rotation duration, and speed of the spinning were related to the membrane mechanics. Membranes of 22 mm inner diameter and 33 to 36 microm thickness at homogeneous profiles were produced. Isolated rat diaphragms served as biological tissue samples. Mechanical properties of the membranes remained constant during 24 h of mechanostimulation. In contrast, time- and strain-dependent mechanical properties of the diaphragms were found.

In vivo characterization of mechanical tissue properties of internal organs using endoscopic microscopy and inverse finite element analysis

“…The membrane was produced as earlier introduced (Armbruster et al, 2009). In brief, a mix of 4% ceramic particles (ceramic beads B205, diameter of 25 7 12 mm, EW Würth, Bad Friedrichshall, Germany), 9% curing agent and 87% PDMS was created.…”

Locally measured shear moduli of pulmonary tissue and global lung mechanics in mechanically ventilated rats

“…The deformation of the surface was determined by tracking the optical size of ceramic beads (ceramic beads B205, EW Würth, Bad Friedrichshall, Germany) with an average diameter of 25 Ϯ 12 m that were placed on the tissue surface as a size reference. For this purpose, the beads were embedded in a pliant silicone (polydimethylsiloxane) membrane of ϳ22 m thickness produced by a spin-coating process (2). A strip of the membrane was glued to the tip of the endoscopic system so that it touched the lung surface during the measurement maneuvers.…”

Mechanical properties of human lung cells after mechanostimulation

“…Meanwhile pressure and volume data were recorded. Mechanostimulator: We used a previously described mechanostimulator for the mechanostimulation and measurement of mechanical properties of cell monolayers [1], [4]. The mechanostimulator consists of two cylindrical stacked chambers which are separated by a highly flexible silicone membrane on which the cells are grown.…”

“…Afterwards membranes were incubated overnight with 1mM RGD-peptide solution. The other day, membranes were washed 3 times with PBS and kept with PBS on top, until the cells were prepared for seeding [4]. Cell seeding: For cell seeding on RGD-modified PDMS membranes, membranes were placed in culture rings in a six well plate and underlaid with the corresponding medium.…”

“…The upper chamber serves as a supply chamber to provide nutrition to the cells under mechanical stimulation. Membrane production: Membranes are produced as described in Armbruster et al [4]. As membrane material we used PDMS.…”