Nanofilamentous Virus-Based Dynamic Hydrogels with Tunable Internal Structures, Injectability, Self-Healing, and Sugar Responsiveness at Physiological pH

With expanding applications of hydrogels in diverse fields ranging from biomaterials to sensors, actuators, and soft robotics, there is an urgent need to endow one single gel with multiple physicochemical properties, such as stimuli-responsiveness, injectability, self-healing, and tunable internal structures. However, it is challenging to simultaneously incorporate these highly sought-after properties into one single gel. Herein, a conceptual hydrogel system with all of these properties is presented via combining bioconjugate chemistry, filamentous viruses, and dynamic covalent bonds. Nanofilamentous bioconjugates with diol affinity were prepared by coupling a tailor-synthesized low-pKa phenylboronic acid (PBA) derivative to a well-defined green nanofiber the M13 virus with a high aspect ratio (PBA-M13). Dynamic hydrogels with tunable mechanical strength were prepared by using multiple diol-containing agents such as poly­(vinyl alcohol) to cross-link such PBA-M13 via the classic boronic–diol dynamic bonds. The as-prepared hydrogels exhibit excellent injectability and self-healing behaviors as well as easy chemical accessibility of the PBA moieties on the virus backbone inside the gel matrix. Ordered internal structures were imparted into virus-based hydrogels by simple shear-induced alignment of the virus nanofibers. Furthermore, unique hydrogels with chiral internal structures were fabricated through in situ gelation induced by diffusion of diol-containing molecules to fix the chiral liquid crystal phase of the PBA-M13 virus. Sugar responsiveness of this gel leads to a glucose-regulated release behavior of payloads such as insulin. All of these properties have been implemented at physiological pH, which will facilitate future applications of these hydrogels as biomaterials