Cellulose nanocrystal-based molecular machines – Cellmach

The project will be organized in five work packages (WP) according to the following plan:
WP1. Design and preparation of “motor” moieties with the suitable functional group to be anchored on nanocelluloses: We will select different nanocelluloses to be modified by the introduction of specific functional groups. We will study different stimuli-responsive systems to be coupled to nanocelluloses: pH-responsive functional groups, thermoresponsive polymers and light-responsive molecules.
WP2. Coupling between the “arms” and the “motor” and characterization of the assemblies: We will introduce the motor at the nanocellulose structure. We will use different strategies for the coupling between the nanocellulose and the motor: (i) introducing the functionality at the reducing end of the nanocellulose; and (ii) modifying the whole surface of nanocelluloses.
WP3. Evaluation of nanocellulose motion: Due to the innovative character of the project, there are not presently available routine methods for determining nanocellulose motion. We will develop novel approaches for this purpose. We will evaluate the performance of nanocellulose-based nanomachines: type of movement, reversibility, and stability of molecular machines under different conditions (temperature, solvents, ionic force, etc.).
WP4. Applications: bioinspired artificial muscles: For the development of bioinspired artificial muscles, we will evaluate expansion/contraction cycles. We will prepare thin films of motor-modified nanocelluloses, and we will evaluate the changes in porosity and thickness upon the expansion/contraction cycle.
WP5. Coordination and dissemination: Periodic internal meetings and workshops will be organized for planning the different tasks as well as for analyzing and discussing the obtained results to enforce research activities of the different WPs. The main results from this project will be first protected by patents, and published in specialized internationally recognized scientific journals.

During the first 18 months of the project Cellmach, we have selected the nanocelluloses and the motor functionalities. We started by the two different strategies: functionalities for favoring the supramolecular assembly and introduction of pH responsive groups. We focused in biotin molecules, and amine and carboxylate groups. We have functionalized tunicate cellulose nanocrystals (t-CNC) at reducing ends and cellulose nanofibers (CNF) on the surface. Modified nanocelluloses have been characterized by different techniques. In the case of t-CNC functionalized by biotin, we have succeeded in assembling several nanocrystals by the addition of streptavidin, which is a protein that can specifically bind up to 4 biotin molecules. Among the results obtained for the cellulose nanofibers, we have started to test different approaches for evaluating the motion. We have succeeded in preparing films that bend in response to pH changes.
Results obtained up to present are promising, we have demonstrated that the instruction of a chemical modification (motor) at the surface of nanocellulose has an impact on their properties and allows both the supramolecular assembly and the motion. For the next months, we will continue designing and developing new methods for the characterization of motion with the aim of using nanocelluloses for specific applications.

Cellmach is a 36-month project presently at its 18th month. For the next months, we plan to continue developing methods for evaluating motion of nanocellulose-based systems. We will test different assemblies of nanocellulose and also their response to different stimuli. In that line, we will investigate other modifications on the nanocellulose surface, such as the introduction of positive charges, or specific functional groups. Another important perspective of Cellmach it to develop new routes of nanocellulose modification, with two main objectives: (i) reduce the environmental negative impact of chemical reactions and (ii) to create novel properties (transparence, mechanical properties, response to pH or temperature, etc.).
For the next months, we also plan to develop methods for modeling the behavior of nanocelluloses in terms of their assembly and interactions with other components, in an attempt to get more insight for the fabrication of nanodevices. In fact, interactions play a key role in the architecture of nanodevices as well as in their response to external stimuli. Therefore, we will develop semi empirical equations to describe, for example, the adsorption of nanocellulose onto different kinds of surfaces. The objective is to predict the behavior of nanocelluloses for the design of smart nanodevices.
The final goal of Cellmach is the use of cellulose-based nanomolecular machines for specific applications, for example, for nanosystems performing switchable extension/contraction events for the fabrication of artificial muscles.

1. Villares, A.*; Moreau, C.; Cathala, B. «Star-like supramolecular complexes of reducing-end-functionalized cellulose nanocrystals«. ACS Omega, 2018, 3, 16203-16211 (https://pubs.acs.org/doi/abs/10.1021/acsomega.8b02559?src=recsys)

In this project we aim at fabricating molecular machines with nanocelluloses as the “arms” that will experience motion. Molecular machines are nanometer-sized systems that convert energy from external stimuli (heat, ionic force, radiation, electric field) to linear or rotary motion. Despite their outstanding potential properties, one of the main issues in the design of molecular machines is translating motion to the macroscopic scale. In this project we propose for the first time the transference of energy from the “motor” moiety at molecular level (0.2 nm) to the “arms” at the nanometric level (100-500 nm). The goal of Cellmach is the fabrication of molecular machines containing nanocelluloses as the “arms” that will move under motor motion. We will therefore use the energy released by the “motor” to move nanocelluloses.
There are two main types of nanocelluloses: cellulose nanocrystals (CNC), which are obtained by acid hydrolysis from cellulose fibers, and cellulose nanofibers (CNF), produced by the delamination of the fibers. In Cellmach, we will focus on cellulose nanocrystals from cotton, which are rigid, rod-like crystallites with two differentiated ends (reducing and non-reducing end). We will use two main strategies for fabricating cellulose-based nanomachines: in a first approach, we will take advantage of the anisotropy of cellulose nanocrystals to introduce the motor at the reducing end to create monofunctional nanomachines. In a second approach, we will create multifunctional nanocelluloses by the introduction of the motor at several sites along the nanocrystal structure. For this purpose we will take advantage of the high affinity of hemicelluloses (xyloglucan) to coat cellulose nanocrystals and for subsequently introduce the motor functionality on the hemicellulose structure.
We will investigate different types of molecular motors, including thermoresponsive polymers and light-responsive molecules. The project involves the introduction of the “motor” functionality on the surface of nanocelluloses, their characterization, and the evaluation of motion experienced by the “arms” (nanocelluloses). These assemblies will be tested for the construction of synthetic nanomachines capable of developing functions such as controlling motion, force, and mechanical properties. Cellmach will develop new cellulose-based intelligent materials that will replace synthetic polymers to be applied as different kinds of nanotweezers for applications in surgery or as bioinspired artificial muscles. Nanocelluloses can be viewed as a new generation of biosourced and renewable synthons for the development of high added value smart materials.