Stimuli-Responsive Hydrogels Based on the Genetically Engineered Proteins: Actuation, Drug Delivery and Mechanical Chara
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0952-F05-02
Stimuli-Responsive Hydrogels Based on the Genetically Engineered Proteins: Actuation, Drug Delivery and Mechanical Characterization Elizabeth A. Moschou, Nitin Chopra, Santoshkumar L. Khatwani, Jason D. Ehrick, Sapna K. Deo, Leonidas G. Bachas, and Sylvia Daunert Department of Chemistry, University of Kentucky, Lexington, KY, 40506
ABSTRACT Herein, 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 CaMbased 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. INTRODUCTION Nature is a showcase of highly complex molecules and materials that are a result of billions of years of evolution. These materials illustrate nature’s ability to fabricate sophisticated structures and molecular devices from the “bottom-up” utilizing different kinds of “raw” materials as building blocks. Naturally manufactured materials exhibit unique biological functions and exquisite mechanical properties, and they are often superior to man-made ones of the same dimensions fabricated by employing current “top-down” microfabrication technologies. Rather recently, attention has been drawn to the design of synthetic biohybrid “nanomachines”, capable of performing efficiently a series of tasks at the nanoscale by mimicking nature. A variety of biological molecules have been employed thus far in the design of such biohybrid materials. These include ATPase motors [1,2], the silaffin-mediated synthesis of silica pearls mimicking diatom cell biochemistry [3,4], the temperature-dependence phase change of ela
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