Scientists at Basel University have designed a highly-tunable amphiphilic peptide system, inspired by the repetitive L-Trp-D-Leu sequence of the antibiotic gramicidin A. Peptides in this system reversibly self-assemble in aqueous media into nanostructures, the size and shape of which can be precisely tailored by specific modifications to the primary sequence of the peptide. Properties such as pH-dependence or labels can easily be introduced and adapted to external needs.
In the case of microspheres formed in this way, large amounts of hydrophobic and/or hydrophilic molecules can be encapsulated and concentrated within the microspheres during their formation. Experiments with dyes, hydrophilic and hydrophobic drugs, gold nanoparticles, as well as siRNA, has proved the ability to encapsulate and co-encapsulate of such payloads. Preliminary experiments with human cancer cells show uptake of the microspheres into the cells, with subsequent release of the encapsulated molecules.
Advantages include the flexibility of the system, which makes it easy to control size and shape, the ability to co-encapsulate hydrophilic and hydrophobic molecules, the protection of these molecules in solid microspheres with the capacity to withstand lyophilisation, storage and re-dispersion. And since the amino acids within the peptides are naturally occurring, it is assumed they can be biodegraded to prevent accumulation in tissue.
The scientists say the peptides will be ideal candidates for applications in the field of drug encapsulation and delivery. In addition, the tunable nanostructures could serve as scaffolds for bone replacement, with or without a payload.