Hydrophobins, a class of amphiphilic fungal proteins, form highly ordered interfacial films with remarkable mechanical properties, making them promising candidates for bio-based functional materials. Here, we explore the potential of HFBI, a class II hydrophobin, as a building block for bioengineered membranes. HFBI self-assembles into a crystalline, hexagonally ordered monolayer at the air-water interface, exhibiting strong lateral interactions that confer high cohesion and intrinsic two-dimensional elasticity. Using atomic force microscopy in force spectroscopy mode, we determined a Young’s modulus in the GPa range for free-standing HFBI monolayers, exceeding that of lipid membranes by two orders of magnitude.

The layer’s high stability and amphiphilicity enable the formation of bilayers that structurally resemble lipid membranes, with a hydrophobic core and hydrophilic exterior. Capacitance and interfacial tension measurements confirm the formation of true bilayers, held together by van der Waals interactions [1], yet exhibiting extremely low ion and water permeability [2]—the latter can, however, be tuned by disrupting the layer structure. Extending this concept, we developed hydrophobin vesicles via microfluidic jetting, yielding stable proteinosomes. Preliminary experiments demonstrate the successful incorporation of functional channels into these protein membranes, highlighting their potential for selective transport applications. Future challenges include characterizing the mechanical properties of these vesicles, e.g., via force spectroscopy, and further functionalizing them with specialized transport channels. These vesicles offer exciting opportunities for nanoreactors, targeted drug delivery, and artificial cell models, leveraging the intrinsic biocompatibility and mechanical robustness of hydrophobin-based materials.

[1] Hähl et al. Advanced Materials 29, 1602888 (2017). DOI: 10.1002/adma.201602888

[2] Nolle et al., Langmuir 39, 13790 (2023). DOI: 10.1021/acs.langmuir.3c01006