Corrigendum: Fibronectin-bound α5β1 integrins sense load and signal to reinforce adhesion in less than a second

Building a microfluidic cell culture platform with stiffness control using Loctite 3525 glue

The study of mechanotransduction signals and cell response to mechanical properties requires designing culture substrates that possess some, or ideally all, of the following characteristics: (1) biological compatibility and adhesive properties, (2) stiffness control or tunability in a dynamic mode, (3) patternability on the microscale and (4) integrability in microfluidic chips. The most common materials used to address cell mechanotransduction are hydrogels, due to their softness. However, they may be impractical when complex scaffolds are sought and they lack viscous dissipative properties that are very important in mechanobiology. In this work, we show that an off-the-shelf, biocompatible photosensitive glue, Loctite 3525, may be used readily in mechanobiology assays without any special treatment prior to fabrication of cell culture platforms. Despite a high (MPa) stiffness easily tunable by UV exposure time at a fixed dose, 3T3 fibroblasts showed a response to the mechanics of the material similar to that obtained on much softer (kPa) hydrogels. Loctite's viscous dissipation properties indeed seemed to be responsible for such cell mechanical response, as suggested by recent works where more complex two-phase hydrogels were employed. More interestingly, it was possible to stiffen soft Loctite substrates by post-exposing them during cell culture, to observe changes in cell spreading caused by a dynamic stiffness modification. Thanks to Loctite 3525's patternability, micropillars were also fabricated to demonstrate the compatibility with traction force microscopy studies. Finally, the glue was used as an excellent adhesion layer for hydrogels on glass or PDMS, without the need for additional treatment, enabling the easy fabrication of microfluidic chips integrating hydrogels.

Integrin Clustering Matters: A Review of Biomaterials Functionalized with Multivalent Integrin-Binding Ligands to Improve Cell Adhesion, Migration, Differentiation, Angiogenesis, and Biomedical Device Integration

Material systems that exhibit tailored interactions with cells are a cornerstone of biomaterial and tissue engineering technologies. One method of achieving these tailored interactions is to biofunctionalize materials with peptide ligands that bind integrin receptors present on the cell surface. However, cell biology research has illustrated that both integrin binding and integrin clustering are required to achieve a full adhesion response. This biophysical knowledge has motivated researchers to develop material systems biofunctionalized with nanoscale clusters of ligands that promote both integrin occupancy and clustering of the receptors. These materials have improved a wide variety of biological interactions in vitro including cell adhesion, proliferation, migration speed, gene expression, and stem cell differentiation; and improved in vivo outcomes including increased angiogenesis, tissue healing, and biomedical device integration. This review first introduces the techniques that enable the fabrication of these nanopatterned materials, describes the improved biological effects that have been achieved, and lastly discusses the current limitations of the technology and where future advances may occur. Although this technology is still in its nascency, it will undoubtedly play an important role in the future development of biomaterials and tissue engineering scaffolds for both in vitro and in vivo applications.