Introduction: Real-time force measurement and mapping present significant challenges in biomechanical research. Traditional methods, such as Atomic Force Microscopy (AFM) and Fluorescence Resonance Energy Transfer (FRET), are facing challenges, including complex sample preparation and laboratory setups, alongside difficulties in accurately calibrating forces. We propose a mechanochemical approach to enhance direct cellular and sub-cellular biomechanical mapping. Over the past two decades, mechanochemistry has emerged as a powerful tool for real-time force measurement and sensing in soft materials. Mechanophores, molecular force sensors, undergo chemical transformations when subjected to mechanical forces, resulting in color changes, luminescence, or chemical reactions. We have developed a highly sensitive mechanophore embedded in hydrogels to facilitate dynamic force sensing, simulating biomechanical processes. This innovation paves the way for versatile, mechanochemistry-based tools for real-time and accurate cellular biomechanical mapping.
Materials and
Methods: We designed and synthesized a sensitive and dynamic mechanophore, DPAC, which was incorporated into hydrogels and polymer films through crosslinking and covalent linkage. The fluorescence of DPAC changes in response to varying mechanical forces. Force measurement was conducted based on fluorescence wavelength readings. Comprehensive DFT simulations and AFM-based characterization confirmed its force sensitivity within the range of 0.5-2 nN. Additionally, we utilized hydrogel swelling to simulate a dynamic force environment and further test the sensitivity of the DPAC-based molecular force sensor.
Results, Conclusions, and Discussions: DPAC-based molecular force sensors demonstrate sensitive force sensing and measurement capabilities in both hydrogels and polymer films. We have designed a series of DPAC derivatives to fine-tune the force sensitivity range. DFT simulation results are consistent with experimental results. Incorporating mechanochemical tools into biomechanical measurement represents early-stage pioneering work. The sophisticated synthetic strategies and versatile structural variations provide a comprehensive development platform for molecular force sensors. We anticipate significant advancements in cellular biomechanical mapping and precise force measurement using mechanochemical molecular sensors in the near future.
Acknowledgements (Optional): This work was supported by the National Science Foundation (Grant Nos. 1925596 and 2347621) and a startup fund from Clarkson University. Many students and postdocs in the Lu Research Group contributed to this work, particularly Dr. Nnamdi Ofodum, Dr. Qingkai Qi, Dr. Richard Chandradat, Theodore Warfle, and Robert Davis.
