Discovered the determining factors for the propulsion of microrobots

Swallowing a pill to cure a serious disease or adding a pinch of a synthetic powder to purify water seemed like concepts from science fiction up to only a few generations ago. However, the appearance of new disciplines, such as bioengineering, is raising the level of sophistication and specialisation of new materials to unforeseen limits.

An example of this is the group of Nanobio Smart Devices led by Samuel Sánchez, ICREA investigator at the Institute for Bioengineering of Catalonia (IBEC).

After years developing devices the size of a thousandth part the thickness of a strand of hair for technological and biomedical applications, the Sanchez Group, in multidisciplinary collaboration with a computational chemistry team, has taken a new significant step in its investigations: understanding the processes on a molecular level that allow so-called micromotors to be propelled in a liquid. In the study, which was published today in the prestigious journal Nature Communications, Sánchez and his collaborators describe what was up to now a mystery for the scientific community: how was it possible that enzymes, which are catalytic machines on a nanoscopic scale, managed to propel enormous particles in relation to themsleves?

While most of the research groups focussed their efforts on equipping microrobots with propellants based on an enzyme called urease, investigators at IBEC have managed to attach and test the mobility of these microscopic objects with a completely new series of enzymes. Xavier Arqué, doctoral student at IBEC and first author of the study, states: “The secret of the mobility of these microrobots lies in the properties of the enzymes themselves”. While enzymes, such as urease and acetylcholinesterase could change their internal structure, this process being related with a greater reaction speed (known as composition in scientific terminology) and generate the propulsion of micromotors, other more rigid enzymes with a slower reaction speed were not capable of generating said mobility. In the words of Sánchez himself: “it is the first time we can predict whether an enzyme is going to be useful for us to propel microscopic objects”.

To complete their discovery, the investigators combined the most advanced simulation techniques via computer with experimental techniques, thanks to collaboration with Dr Sílvia Osuna’s group, ICREA professor at the University of Girona. This discovery opens the door to a whole new series of self-propelled microrobots with applications in medicine, water treatment and biotechnology.

Article: Xavier Arqué, Adrian Romero-Rivera, Ferran Feixas, Tania Patiño, Sílvia Osuna & Samuel Sánchez (2019) Intrinsic enzymatic properties modulate the self-propulsion of micromotors, Nature Communications 10, 2826. DOI: https://doi.org/10.1038/s41467-019-10726-8