Role of Molecular Interactions in Supramolecular Polypeptide-Polyphenol Networks for Engineering Functional Materials

Supramolecular assembly affords the development of a wide range of polypeptide-based biomaterials for drug delivery and nanomedicine. However, there remains a need to develop a platform for the rapid synthesis and study of diverse polypeptide-based materials without the need for employing complex chemistries. Herein, we develop a versatile strategy for creating polypeptide-based materials using polyphenols that display multiple synergistic cross-linking interactions with different polypeptide side groups. We evaluated the diverse interactions operating within these polypeptide-polyphenol networks via binding affinity, thermodynamics, and molecular docking studies and found that positively charged polypeptides (K_a of ∼2 × 10⁴ M^-1) and polyproline (K_a of ∼2 × 10⁶ M^-1) exhibited stronger interactions with polyphenols than other amino acids (K_a of ∼2 × 10³ M^-1). Free-standing particles (capsules) were obtained from different homopolypeptides using a template-mediated strategy. The properties of the capsules varied with the homopolypeptide used, for example, positively charged polypeptides produced thicker shell walls (120 nm) with reduced permeability and involved multiple interactions (i.e., electrostatic and hydrogen), whereas uncharged polypeptides generated thinner (10 nm) and more permeable shell walls due to the dominant hydrophobic interactions. Polyarginine imparted cell penetration and endosomal escape properties to the polyarginine-tannic acid capsules, enabling enhanced delivery of the drug doxorubicin (2.5 times higher intracellular fluorescence after 24 h) and a corresponding higher cell death in vitro when compared with polyproline-tannic acid capsules. The ability to readily complex polyphenols with different types of polypeptides highlights that a wide range of functional materials can be generated for various applications.