Hydrophobins (Hyd), small amphipathic proteins secreted by fungi, are among the most surface-active molecules known1. These cysteine-rich proteins with molecular masses of about 10 kDa, have the ability to convert hydrophobic surfaces to hydrophilic ones and vice versa by self-assembly into an amphipathic protein membrane2.
Due to their amphiphilic nature and self-assembly properties, hydrophobins have been suggested to serve as surfactants, emulsifiers and encapsulating agents for drugs3, but their application in nanoencapsulation of nutraceuticals for food enrichment has apparently not yet been explored.
Using pyrene as a fluorescent probe for hydrophobic domain formation, we found the critical micellization concentration (CMC) of a commercially available Hyd, to be 0.041±0.006 mg/ml. Using quenching of the intrinsic protein fluorescence we showed that both vitamin D3 (VD3) and Nile Red (NR- a model for a nutraceutical) bind to Hyd, with high association constants: Hyd- NR Ka=(8.2±0.5) x105M-1; Hyd- VD3 Ka=(0.65±0.04)x105M-1. Using dynamic light scattering we showed that while VD3 particles have a mean diameter of 235nm, Hyd- VD3 complexes are nanosized (two subpopulations of particles were formed: 79% of the particles have a mean diameter of 30nm, and 21% have a mean diameter of 100nm). VD3 in phosphate buffer showed low shelf-stability, with ~70% loss in 21 days of storage at room temperature. The VD3 – Hyd nano-particle system was very stable, without any loss of VD3 during that time. Hydrophobins show promise as nanovehicles of hydrophobic nutraceuticals for food and particularly clear beverages enrichment.
Principal investigator: Prof. Yoav D. Livney Livney@technion.ac.il
References:
1. Linder, M. B., 2009, Current Opinion in Colloid & Interface Science, 14, (5), 356-363.
2. Wessels, J. G. H. , 1997, Adv Microb Physiol, 38, 1-45.
3. Valo, H. K.; Laaksonen, P. i. H.; Peltonen, L. J.; Linder, M. B.; Hirvonen, J. T.; Laaksonen, T. J., 2010, American Chemical Society Nano, 4, (3), 1750- 1758.
