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Engineered Conductive Proteins for Bioelectronics

Periodic Reporting for period 2 - e-Prot (Engineered Conductive Proteins for Bioelectronics)

Reporting period: 2023-03-01 to 2024-02-29

The e-Prot project vision encompasses the rational design of efficient conductive protein systems (e-Ps), and the fabrication of all-protein based conductive structures and materials, targeting a radical change in design of green electronic and energy storage devices.This groundbreaking approach surpasses current bio-inspired technologies, transforming the emerging research field of protein-based bioelectronics, currently still limited to basic research, to a new level of sophistication facilitating real-world applications. These developments will be fundamental for the emergence of biocompatible and sustainable components for the electronics industry. The European Green Deal roadmap towards a sustainable EU economy highlights the need for new green electronics and sustainable batteries for the production of efficient, low-cost, renewable, and environmentally friendly devices. In this context, e-Prot will develop a platform technology for sustainable and efficient bioinspired all-protein-based green bio-electronic systems as an alternative to the traditional technologies used in the electronics industry.
The objectives of e-Prot are: 1) Define guidelines for the fabrication of efficient conductive proteins e-Ps, 2) Optimization and prototyping of e-Ps conductive materials for applications and 3) efficient implementation of e-Ps in e-biological applications.
The main results from the work performed during the reporting period along the diferent WPs is:

(WP1) Has been focused on the synthesis and characterization of conductive CTPR sequences:
- Several approaches towards the production of self-assembled fibers have been developed.
- CTPR have been bioconjugated with conductive elements.
- Optimization of the upscale production of CTPR variants.

(WP2) Has been focused on the characterization of the local structural, electrical, and mechanical properties of ePs assemblies, specifically CTPR films. Moreover, computer models were used to understand the intramolecular electronic transport mechanism of simplified peptide systems, polyalanine and polyglycine.
- Conductivity, mechanical and assembly properties of CTPR variants from WP1 were evaluated.
- CTPR-E variants showed improved ionic conductivity, likely protonic, CTPR4-4E being the best performing mutant. (D2.1)
- Ion conductivity of the CTPR protein films was improved by two orders of magnitude by external doping with salt (NaCl).
- The introduction of aromatic amino acids was shown to enhance electron conductivity in SAH variants (D2.1) best performing configuration was identified.
- Computational simulations were performed on simplified peptide systems for evaluation of intramolecular electronic transport and their conductance, intrinsic and when integrated into molecular junctions. An attenuation of conductance decay with length was observed in the latter. Cysteine was also tested and compared as a suitable linker for molecular junction anchorage.

(WP3) Has been focused on the formulation and manufacturing of electrolyte films and inks based on protein materials and the preparation of flexible electrodes with standard and novel binders and development of structuration methods.
- Various strategies for producing ionic conductive electrolyte films using the CTPR-E series were selected.
- For the first strategy (protein encapsulation) formulations of various resins were studied.
- The processability, the compatibility and the films properties of the selected formulations were investigated.
- The fundamental of ink formulation for screen and inkjet printing was described.
- The optimal formulation for water-based flexible electrodes has been determined. Electrodes with various aqueous based binders were fabricated.
- The adhesion and the electrochemical properties of the electrodes were studied, and the best formulation selected for the structuration experiments.
- Novel waterborne binders were tested.

(WP5) Establishment of the website and Twitter account and the establishment of the intellectual property rights and exploitation strategy.

(WP4) has not started along this reporting period.
Results in WP1 indicate that CTPR proteins are a relevant platform for developing new design strategies towards enhanced ionic and electronic conductivity. Engineered CTPR protein variants maintain their structural integrity while encoding mutations that promote the conductivity.
Results in WP2, indicate that controlling film thickness, homogeneity, aggregation and residual salt doping is key to improve conductivity in ePs assemblies. Results also suggest a successful improvement of ionic conductivity in engineered protein biomaterials.
The novel binders developed in WP3 open opportunities for wearable electronics.
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