In Vitro Fabrication of Microscale Secretory Granules

Abstract

AbstractAdvanced medical treatments involving drug delivery require fully biocompatible materials with the ability to release functional drugs in a time‐prolonged way. Ideally, the delivered molecules should be self‐contained as chemically homogenous entities to prevent the use of potentially toxic scaffolds or hold matrices. In nature, peptidic hormones are self‐stored in protein‐only secretory granules formed by the reversible coordination of Zn2+ and histidine residues. Inspired by this concept, an in vitro transversal procedure is developed, analyzed, and comparatively applied for the fabrication of protein‐only secretory granules at the microscale. These materials can be produced from any polyhistidine‐tagged protein using physiological concentrations of Zn2+ as a potent and versatile glue‐like agent. The screening of granules formed by 12 engineered and nonengineered proteins at different Zn2+ concentrations revealed optimal fabrication conditions and the consequent release profiles. Moreover, the functional and structural properties of the delivered protein are fully validated using a drug‐targeting protein platform in a mouse model of human colorectal cancer. In summary, short histidine tags allow the packaging of structurally and functionally dissimilar polypeptides, which supports the proposed fabrication method as a powerful protocol extensible to diverse clinical scenarios in which slow protein drug delivery is required.