Abstract
Mechano-sensitive materials convert a mechanical signal into a physical or chemical signal. These materials are ubiquitous in nature, where they regulate cell spreading and are involved in senses such as hearing and touch. Inspired by these materials, we developed DNA-based hydrogels that convert converting a mechanical signal in fluorescence response. The hydrogels were assembled from sequence controlled DNA strands produced by enzymatic synthesis. The mechanism of mechano-fluorescence relies on the functionalization of a DNA hairpin with a FRET pair (a fluorophore and a quencher that interact via Froster Resonance Energy Transfert, FRET), which becomes fluorescent only when the hairpin opens. We recently developed a new set-up, which consist of a transparent shear cell coupled to a fluorescence imager, to quantifying in stresss the mechano-fluorescence response of the hydrogels. The fluorescence of the gel increase with the stress as more and more probes open. Our quantitative measure shows the existence of a threshold in stress and strain before the fluorescence start increasing. We also observe strong correlation between non-linear mechanics, such as strain stiffening and hysteresis, and the fluorescence signal. In conclusion this work present the first quantitative stress-fluorescence measurements on mechano-fluorescent DNA-based hydrogels and proposes an interpretation of their molecular origin.