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Programmable NanoRobotics for Controlled Manipulation of Molecular Cargoes

Periodic Reporting for period 1 - ProgNanoRobot (Programmable NanoRobotics for Controlled Manipulation of Molecular Cargoes)

Reporting period: 2019-04-01 to 2021-03-31

ProgNanoRobot project proposed the development of artificial robotic systems that could be programmed to transport molecular cargoes in a programmable fashion.
The project intended to take the design of first generation of molecular robots to the next level of sophistication by studying key methodologies needed to manipulate molecular fragments through small-molecule programmable robotics. Four objectives were initially established:
1.Explore and develop a toolbox of robotic machine components
2.Use a chemical fuel to operate the molecular robotic systems
3.Develop a programmable molecular machine for transport of molecular cargoes over long distances
4.Produce a molecular robot capable of selectively pick-up and reposition cargoes using an extendable robotic arm
Several types of light-switchable robotic arms were studied to understand their rules of operation, allowing to control the robotic systems with good efficiencies using light as stimulus.
Progress towards the synthesis of a ‘bucket-brigade’ molecular device, in which a substrate can be passed directionally from one robotic arm to the next, was described. Several molecular models that constitute functional parts of the full molecular machine were produced separately and their operation conditions were tested.
A molecular machine capable of orthogonally switching both the reach and the orientation of its robotic arm was developed. The position of the arm with respect to different stations in a molecular platform can be controlled using light. Functional ‘half-machine’ models were synthesized and progress towards selective transport of a molecular cargo between different stations was carried out.
Time allocation required to carry out the synthetic work of this project was higher than initially expected. The complex behavior of these systems forced the iterative redesign and synthesis of model compounds, gradually introducing alterations and testing its efficiency in order to improve operation. The COVID-19 pandemic also affected the development of the project due to the total shutdown of activities in the University of Manchester from March to July 2020 and the restriction of activities from August 2020 to the end of the action. This unforeseen circumstance occurred in a critical stage of the project, heavily affecting general development and progress.
WP1/2:
First, focus was on the preparation of a core rotary switch unit that could be operated with light. A series of novel hydrazone photoswitches diversely functionalized were synthesized. Light-induced isomerization model studies confirmed it was possible to switch between both isomers of the hydrazone systems with light of selected wavelength. The best switching efficiencies were obtained for the original system, achieving almost full conversion between E and Z isomers with no sign of fatigue. As the operation of this rotary photoswitch had the added benefit of not generating waste products, main effort was in the application of this switching process to the proposed molecular transporters, at the expense of the second objective of this project (use of a chemical fuel).
WP3:
A molecular structure for a ‘bucket-brigade’ device was designed that allowed to directly exchange the molecular cargo between two robotic arms without the need of an intermediate station. This machine had two different arms to ensure the cargo is transported only from left to right in an irreversible transfer step.
The synthesis of each module was carried out. The development of each half-machine model consisted in the sequential formation of the track fragment bearing an aldehyde station, connection to the rotary hydrazone switch core, installing of the corresponding thiol-based arm and loading of the cargo in the left-half machine or attachment to the central linker for the right half-machine. The preparation of each half-machine entailed 15-20 synthetic steps, and an overall 40 steps for the final machine. A strategy based on late formation of the hydrazone switch was successfully optimized that allowed to obtain the left and right half-machine models separately. At the conclusion of the project, focus is on the synthesis of an operative full machine by connecting the two half parts.
In terms of operation, cargo transfer conditions based on the use of acidic media were established that will be implemented for the operation of the full machine.
WP4:
A molecular model for the construction of a robotic transporter with an extendable arm was designed based on the incorporation of a second light-switchable unit, an azobenzene. The synthesis of molecular models corresponding to the left and the right half parts of the full machine were synthesized via a synthetic route consisting of 20 steps each. A full machine model was also obtained through a 28-step procedure.
Model studies on the orthogonal switching of azobenzene and hydrazone compounds using light allowed to select the best irradiation wavelengths for both processes and confirmed that the presence of one compound in the solution does not affect the switching efficiency of the other. Switching conditions were applied to the cargo transport and realease of the half-machine compounds. At the conclusion of the project, tests for the exchange of the molecular cargo under operating conditions are being carried out.

During the period of remote working, the Researcher elaborated two reviews about the use of switchable and programmable molecular machines in catalysis and the active template synthesis of mechanically interlocked molecules.
The results obtained were presented by the Researcher at the Symposium on the Synthesis and Characterization of Functional Molecules and Molecular Machines in Brussels, Belgium, in 2019. The Researcher also participated in the event hosted by Manchester Museum during the European Researchers’ Night celebrated in September 2019, where he represented the Leigh Group and the ProgNanoRobot Project, introducing the field of molecular machines to a general audience with hands-on displays and demonstrations. Other dissemination and outreach activities envisioned during the project were cancelled due to the COVID-19 pandemic global situation.
The controlled manipulation of molecular-level structures through programmable small-molecule robotics is very much at the birth of a prospective research field and constitutes an enormous challenge that could lead us towards the dawn of an era of useful molecular nanotechnology.
The use of light as a clean and waste-free source of energy to power the operation of the robot goes significantly beyond the state-of-the-art. The successful operation of the ‘nanobots’ unite a series of innovative strategies to open up new possibilities for what artificial molecular machines can do. The novel systems capable of selectively choosing and relocating molecular substrates between multiple active sites could be directly applied to the development of a new generation of programmable molecular machines for molecular manufacturing. The results of this work will be a potentially game-changing approach to functional molecule and materials synthesis.
The successful completion of this project driven by the results obtained by the Researcher during his stay in the research group will soon result in at least two publications in top-end scientific journals. The main results will be disseminated in open-access publications to guarantee they are available to everyone.
Work Packages of the ProgNanoRobot project