Light-Responsive Polymer Particles as Force Clamps for the Mechanical Unfolding of Target Molecules

Abstract

Single-molecule force spectroscopy techniques are powerful tools for investigating the mechanical unfolding of biomolecules. However, they are limited in throughput and require dedicated instrumentation, restricting the utility and applicability of these techniques. Motivated by these limitations, here, we report a force-generating particle that can unfold target molecules on-demand. The particle consists of a plasmonic nanorod core encapsulated with a thermo-responsive polymer shell. Optical heating of the nanorod leads to the rapid collapse of the polymer, thus transducing light into mechanical work to unfold target molecules. In this work, a commercially available galvo illuminator system was employed to generate a NIR laser spot and validate the collapse of the polymer particles. The polymer particle functions as an excellent experimental tool to harness the input photon energy to deliver piconewton (pN) mechanical force on conjugated biological systems (i.e. biomolecules) with high spatiotemporal resolution. Most importantly, the particle collapse is highly tunable in space (μm), time (msec), and force magnitude (pN), which happens to be an essential requirement of mechanobiological studies, as the delivery of a precise amount of mechanical force without thermal denaturation or alteration of the native properties of the biological sample is needed. Besides, single-molecule fluorescence imaging showed reproducible mechanical unfolding of DNA hairpins with the polymer particles. We also demonstrate the triggering of 50 different particles in <1 min, exceeding the speed of conventional atomic force microscopy. In summary, the polymer force clamp represents a novel and bottom-up approach to force manipulation of biomolecules.