Stimulus-responsive, biocompatible materials can be used to design platforms to remotely study and manipulate cellular processes for applications in bioengineering and soft robotics. We have developed an azobenzene-based photoswitchable scaffold that can exert nanoscale oscillatory forces on cells by means of rapid cis-trans isomerization of a push-pull azobenzene upon irradiation with visible light. Previously, it was shown that rapid photomechanical stimulation for as low as 5 minutes upregulated the expression of cell adhesion-associated genes such as talin, vinculin, paxillin and zyxin in fibroblasts. 

The process of stem cell differentiation is regulated by mechanotransductive pathways, and therefore, we hypothesized that stem cell differentiation can be directed by our photoresponsive azobenzene scaffolds. It was observed that stimulation of human mesenchymal stem cells cultured on our azobenzene-functionalized surface increased YAP translocation into the nucleus and upregulated the expression of osteogenic and adipogenic master regulators, RUNX2 and PPARγ, respectively. This indicates that azobenzene-mediated photomechanical stimulation can regulate stem cell differentiation.

We have also developed a novel method to study azobenzene isomerization in solution by using Brillouin spectroscopy. This method detects changes in the solution elastic modulus upon a conformational change induced by azobenzene photoisomerization, which is seen as a change in the Brillouin frequency shift. As such, Brillouin spectroscopy can be used as a biocompatible, non-invasive method to investigate conformational changes of molecules.