Photoresponsive Hydrogels with Photoswitchable Stiffness: Emerging Platforms to Study Temporal Aspects of Mesenchymal Stem Cell Responses to Extracellular Stiffness Regulation

Regulation of Mesenchymal Stem Cell Morphology Using Hydrogel Substrates with Tunable Topography and Photoswitchable Stiffness

“…Conversely, these changes in stiffness were found to have no effect on cell alignment or eccentricity (Figure 6). A reduction in matrix stiffness was also found to reduce the cell and nuclear size in a manner that was consistent with our previous study of MSCs cultured on AZO-PA, whereby softer gels gave smaller cell areas, even in the absence of surface features [19]. A clear trend was, therefore, observed, whereby the MSC shape and alignment could be regulated through changes in the topographical features of the AZO-PA gel, while the cell size could be directly altered through in situ changes in substrate stiffness.…”

“…However, the exploitation of these cell-material interactions for technological applications has, thus far, been largely limited to cell culture materials and surfaces with properties that are static (i.e., fixed at the point of production), thus, eliminating any ability to temporally regulate the extracellular environment in situ. More recently, interest in the field has shifted towards systems that can allow for more dynamic control over the cell morphology and phenotype with the temporal control of extracellular factors such as matrix stiffness [19,20] or surface topography [21], but there is still a lack of systems that allow for such a manipulation of structural and mechanical properties in parallel. More accessible platforms for controlling both stiffness and topography are, therefore, required to better understand the interplay between them, particularly whether they can be controlled in a dynamic (i.e., time-dependent) fashion.…”

“…Additionally, systems that allow for the regulation of the mechanical and structural properties of the cell culture substrate in real time are of increasing value, because they allow for the observation of dynamic cellular responses to changes in the extracellular environment. We have previously demonstrated that the stiffness of polyacrylamide hydrogels bearing photoisomerisable azobenzene crosslinks can be manipulated using irradiation with the appropriate wavelength of light, and that azobenzene-crosslinked polyacrylamide (AZO-PA) hydrogels can be manipulated in real-time to temporally control the morphology of human MSCs [19,22].…”

A Review on the Design of Hydrogels With Different Stiffness and Their Effects on Tissue Repair

“…And the optical signal, as a trigger in the photo-responsive hydrogels, can remotely control the self-structure of hydrogels and cause changes in mechanical properties ( Burdick and Murphy, 2012 ). Compared with traditional stimulation conditions, the optical signal regulation has biocompatibility and “reagent-free” irritation ( Richards et al, 2018 ). Lee et al (2018b) designed a PAAm photo-switchable hydrogel based on photo-responsive molecule azobenzene.…”