Towards the development of biotin carboxylase driven robotic nanoswimmers

The objective of this research is to take the first step towards demonstrating the use of the enzyme biotin carboxylase (BC) as a biomolecular motor. BC is a homodimeric protein involved in fatty biosynthesis in all organisms. The conjecture is that BC can convert chemical energy into useful mechanical work via its conformation change, which acts as a fin or flexible oar producing nonreciprocal motion. To this end, we fabricate a proof-of-concept biomolecular machine driven by BC molecules, viz., a robotic nanoswimmer. This machine consists of a Janus-type nanosize silica particle, where one hemisphere is coated with an intermediate layer of chromium and then an outer layer of nickel. Since BC has been engineered to attach to nickel surfaces, this produces an asymmetry on the nanoparticle, which could potentially lead to non- Brownian motion in a low Reynolds number environment. The nanoswimmers have potential applications in drug delivery and transporting cargo in nano and microscale fluidic environments. The proposed nanoswimmer is fabricated using a 500 nm diameter silica particle. The chromium and nickel coatings on the nanoparticle are created using electron beam evaporation. The presence and activity of the BC molecules on the nickel coating are verified using a Bradford protein assay and a PK/LDH coupled assay. A theoretical analysis of the drag force on the nanoswimmer, velocity, and mechanical power that the BC molecules can produce is performed based on Stokes law. The analysis shows that as the particle size increases, its expected velocity increases. Further, it shows that BC should be able to produce enough power to overcome the drag force on the nanoswimmer and propel it at velocities in the micrometer per second range