title: Ultrasound-Mediated Self-Healing Hydrogels Based on Tunable Metal-Organic Bonding.
abstract: Stimulus-responsive hydrogels make up an important class of programmable materials for a wide range of biomedical applications. Ultrasound (US) is a stimulus that offers utility because of its ability to permeate tissue and rapidly induce chemical alterations in aqueous media. Here we report on the synthesis and US-mediated disintegration of stimulus-responsive telechelic Dopa-modified polyethylene glycol-based hydrogels. Fe3+-[PEG-Dopa]4hydrogels are formed through Fe3+-induced cross-linking of four-arm polyethylene glycol-dopamine precursors to produce networks. The relative amounts of H-bonds, coordination bonds, and covalent bonds can be controlled by the [Fe3+]:[Dopa] molar ratio in precursor solutions. Networks formed from precursors with high [Fe3+]:[Dopa] ratios create mechanically robust networks (G' = 6880 ± 240 Pa) that are largely impervious to US-mediated disintegration at intensities of ≤43 W/cm2. Conversely, lightly cross-linked networks formed through [Fe3+]:[Dopa] molar ratios of <0.73 are susceptible to rapid disintegration upon exposure to US. Pulsatile US exposure allows temporal control over hydrogel disintegration and programmable self-healing. Sustained US energy can also stabilize hydrogels through the formation of additional cross-links via free radical-mediated coupling of pendant catechols. Taken together, the diverse ranges of mechanical behavior, self-healing capability, and differential susceptibility to ultrasonic disintegration suggest that Fe3+-[PEG-Dopa]4hydrogels yield a class of application-specific stimulus-responsive polymers as smart materials for applications ranging from transient medical implants to matrices for smart drug delivery.
authors.affiliation: Graduate Institute of Biomedical Materials and Tissue Engineering, Taipei Medical University , 250 Wu-Xing Street, Taipei City, 30010 Taiwan.
authors.forename: Wei-Chen
authors.identifier: 0000-0002-2772-0468
authors.initials: WC
authors.lastname: Huang
authors.forename: Faisal
authors.initials: F
authors.lastname: Ali
authors.forename: Jingsi
authors.initials: J
authors.lastname: Zhao
authors.forename: Kelsey
authors.initials: K
authors.lastname: Rhee
authors.forename: Chenchen
authors.initials: C
authors.lastname: Mou
authors.forename: Christopher J
authors.initials: CJ
authors.lastname: Bettinger
mesh_terms: D004298:Dopamine / Q000737:chemistry; D016503:Drug Delivery Systems; D020100:Hydrogels / Q000737:chemistry*; D007501:Iron / Q000737:chemistry*; D011092:Polyethylene Glycols / Q000737:chemistry; D014465:Ultrasonics
chemical_list: D020100:Hydrogels; D011092:Polyethylene Glycols; D007501:Iron; D004298:Dopamine