Nano- and microscale chemical traction such as that observed in the motion of myosin along actin filaments play a pivotal role in the directed motion of molecules and other larger structures within the cell. This motive force is fundamental to processes such as mitosis, cellular motion and muscle contraction. Yet, despite intense research into the mechanisms that underpin it there are currently no artificial analogues that can replicate its strength and utility at the nanometer and micrometre length scales. This fellowship sought to address this by creating nano- and microparticles that autonomously move across a surface directed by chemical gradients.
To achieve this a new system of particle traction was devised that exploits the precise and adaptive nature of disulphide bonds (i.e. covalent bonds between two sulphur atoms) between particles and surfaces. The hypothesis that drives this work is that stimuli that affected the rate and equilibrium position of the bond-forming reactions, if applied asymmetrically around the particle, would cause it to move across the surface. Disulphide bonds were chosen as the dynamic covalent bond for this system because the stimuli that affect their equilibrium include the presence of oxidants or reductants. Such stimuli can be created by electrodes, offering the possibility of electrical control of particle motion. They are also present inside and outside of cells meaning this method of particle traction can be reconfigured to work with enzymes that catalyse disulphide exchange in life-like environments. The ultimate aims of this work are to use these motile particle systems to create electrically driven artificial micro muscles and to use them to probe and map the redox environment around cells, particularly those in diseased tissues.
