סמינר לפיזיקה של מערכות ביולוגיות וחומרים רכים: Peptide-based hydrogels for encapsulation and utilization of enzymes

Abstarct:

Enzyme encapsulation has been extensively employed to stabilize enzymes under various conditions and environments, playing a significant role in therapy, catalysis, biosensors and enzyme-mediated electrochemistry. Both organic and inorganic materials, as well as biomaterials, have been employed for this purpose. Among these, the self-assembly of peptides stands out as a practical and efficient strategy for fabricating supramolecular functional materials for encapsulation. Some peptides can self-assemble into 3D nanofiber networks, which form hydrogels that are soft, biocompatible, and environmentally friendly. A notable example is the ultra-short peptide hydrogelator Fluorenylmethyloxycarbonyl-diphenylalanine (FmocFF), due to its remarkable mechanical rigidity and hydrogel stability. This hydrogel was also demonstrated to stably retain proteins larger than 5kDa while allowing smaller molecules to diffuse more freely, which highlights its potential for enzyme encapsulation, where allowing mass transport of small reactants and products is crucial.

In this work, the O2-hypersensitive enzyme [FeFe]-hydrogenase was encapsulated in FmocFF hydrogels, which granted this enzyme unprecedented protection against O2, while its H2 production activity was maintained. The FmocFF hydrogel was shown to interact with O2, and significantly limit its diffusion and penetration. The interaction between the hydrogel and O2 is not mediated by metals but rather depends on a binding mechanism involving an organic supramolecular structure, formed by self-assembly of the peptide, which has not been described prior to this work. Molecular dynamics simulations suggest that the O2 binding mechanism is governed by hydrophobic interactions in pockets formed between the aromatic rings in the supramolecular structure of the gel.

The facile process of protein encapsulation in the FmocFF hydrogel was also employed to immobilize [FeFe]-hydrogenase on 3D carbon felt electrodes and harness it for enzyme-mediated electrochemical H2 production. Thus, several known requirements of enzyme electrochemistry were met, such as a simple and mild immobilization process, prolonged stability, and resistance to enzyme leakage. Peptide self-assembly avoids the need for tedious and potentially harmful chemistry and allows rapid loading of enzymes in a 3D electrode at high enzyme loads, efficient production of H2, and prolonged resistance against electrophoresis. Further, the enzyme retention was shown to arise from its interaction with the peptide nano-fibrils. Finally, this method is successfully employed to retain other redox enzymes, paving the way for a variety of enzyme-mediated electrochemical applications.