Stimuli-Responsive Hydrogels Based on the Genetically Engineered Proteins: Actuation, Drug Delivery and Mechanical Characterization

Abstract

ABSTRACTHerein, we describe a biomimetic approach aimed at the development of synthetic biohybrid materials inspired by nature's sensing and actuating mechanism of action. The biomaterials are based on the incorporation of the hinge-motion binding protein calmodulin (CaM) and its low affinity ligand phenothiazine (TAPP) within the bulk of an acrylamide hydrogel network, which is accomplished through covalent binding. At the initial state and in the presence of Ca2+ ions, CaM interacts with TAPP creating chemical (non-covalent) cross-links within the bulk of the hydrogel, forcing the material to assume a constrictive configuration. Upon the removal of Ca2+, CaM releases TAPP, breaking the non-covalent cross-links within the bulk of the hydrogel and letting the material relax into a swollen state. The same type of effect is observed when a higher affinity ligand for CaM, like chlorpromazine (CPZ), is employed. In the presence of CPZ, the protein releases TAPP and binds CPZ, allowing the biomaterial to swell into a relaxed state. This swelling response of the biomaterial is reversible, and is directly related to the levels of CPZ used. The sensing and subsequent actuating mechanism of the CaM-based stimuli-sensitive hydrogels makes them suitable for a variety of applications, including sensing, mechanical actuation, high-throughput screening, and drug delivery. Additionally, it is shown that the CaM-based stimuli-sensitive hydrogels developed present unique mechanical properties, suitable for integration within microfluidics and MEMS structures. It is envisioned that these biomaterials will find a number of applications in a variety of fields, including drug delivery.