Rigidity is important for cells. The rigidity of the substrates in the conventional tissue cultures (hard plastics or glass with the Young’s moduli > 1 GPa) is much higher than the rigidity of soft tissues, where the Young’s moduli vary from 0.1 to 50 kPa. When cells are cultured on substrates with mechanical properties emulating those of live tissues, both gene expression and cellular physiology significantly change between substrates with the Young’s moduli <4 kPa (soft), 10 – 20 kPa (medium rigidity), and >30 kPa (hard).

Silicone gel substrates vs. hydrogel (PAA) substrates.Soft substrates for cell cultures have been often made out of hydrogels, such as polyacrylamide (PAA) gels. Nevertheless, hydrogel substrates may change their mechanical properties over time due to swelling, drying, and hydrolysis. In addition, commonly used hydrogels usually have pores with a size in a ~1 µm range that tends to change with the gel rigidity. Softsubstrates™ plates are made with silicone gels with the Young’s moduli spanning the range of 0.1 to 64 kPa and with the pore size in 10 nm range for all Young’s moduli. The Softsubstrates™ silicone gels have superior optical properties and low background fluorescence and are not susceptible to swelling, drying, or hydrolysis. Mechanical properties of the Softsubstrates™ gels remain practically unchanged even after extended time on the shelf. The Softsubstrates™ gel surfaces are functionalized with amine-reactive groups for catalyst-free ECM protein binding and the Young’s moduli of the gels are carefully measured and certified for each batch.