Self-Assembled Structure of Peptide Nanospheres Induces High Stability against Hydrolysis and Sterilization

Chirality-controlled polymerization-induced self-assembly

Recent studies have shown that biodegradable nanoparticles can be efficiently prepared with polymerization of N-carboxyanhydrides-induced self-assembly (NCA-PISA). However, thus far, the effect of chiral monomer ratio on such NCA-PISA formulations and the resulting nanoparticles has not yet been fully explored. Herein, we show, for the first time, that the morphology, secondary structure, and biodegradation rate of PISA nanoparticles can be controlled by altering the chiral ratio of the core-forming monomers. This chirality-controlled PISA (CC-PISA) method allowed the preparation of nanoparticles that are more adjustable and applicable for future biomedical applications. Additionally, the complex secondary peptide structure (ratio of α-helix to β-sheet) and π-π stacking affect the polymer self-assembly process. More specifically, a PEG45 macro-initiator was chain-extended with l- and d-phenylalanine (l- and d-Phe-NCA) in various molar ratios in dry THF at 15 wt%. This ring-opening polymerization (ROP) allowed the preparation of homo- and hetero-chiral Phe-peptide block copolymers that self-assembled in situ into nanoparticles. For homo-chiral formulations, polymers self-assembled into vesicles once a sufficiently high phenylalanine degree of polymerization (DP) was obtained. Hetero-chiral formulations formed larger nanoparticles with various morphologies and, much to our surprise, using an equal enantiomer ratio inhibited PISA and led to a polymer solution instead. Finally, it was shown that the enzymatic biodegradation rate of such PISA particles is greatly affected by the polymer chirality. This PISA approach could be of great value to fabricate nanoparticles that exploit chirality in disease treatment.

Creation of Superhydrophobic Poly(L-phenylalanine) Nonwovens by Electrospinning

From the viewpoint of green chemistry and environmental chemistry, an important challenge in the field of superhydrophobic materials is to create them with only bio-based molecules. We developed superhydrophobic and chemically stable poly(L-phenylalanine) (PolyPhe) nonwovens by electrospinning. PolyPhe was selected because, due to its very rigid chemical structure, it is one of the toughest and most hydrophobic polymers among polymers composed only of amino acids. The water contact angle on the nonwovens is a maximum of 160°, and the droplets are stably adhered and remain still on the nonwoven surface even if it is turned over, thereby suggesting a petal-type superhydrophobicity. The nonwovens show a good chemical stability, and their weight remains unchanged after 5 days immersion in acidic (pH 2) and basic (pH 12) conditions. In addition, the superhydrophobic property is not lost even after the alkali treatment. Such tough superhydrophobic materials are intriguing for further biomedical and environmental applications.

Peptide nanostructures in biomedical technology

Nanostructures of peptides have been investigated for biomedical applications due to their unique mechanical and electrical properties in addition to their excellent biocompatibility. Peptides may form fibrils, spheres and tubes in nanoscale depending on the formation conditions. These peptide nanostructures can be used in electrical, medical, dental, and environmental applications. Applications of these nanostructures include, but are not limited to, electronic devices, biosensing, medical imaging and diagnosis, drug delivery, tissue engineering and stem cell research. This review offers a discussion of basic synthesis methods, properties and application of these nanomaterials. The review concludes with recommendations and future directions for peptide nanostructures. WIREs Nanomed Nanobiotechnol 2016, 8:730-743. doi: 10.1002/wnan.1393 For further resources related to this article, please visit the WIREs website.