Abstract
Stimuli-responsive materials that exhibit a mechanical response to specific biological conditions are of considerable interest for responsive, implantable medical devices. Herein, we report the synthesis, processing and characterization of oxidation-responsive liquid crystal elastomers that demonstrate programmable shape changes in response to reactive oxygen species. Direct ink writing (DIW) is used to fabricate Liquid Crystal Elastomers (LCEs) with programmed molecular orientation and anisotropic mechanical properties. LCE structures were immersed in different media (oxidative, basic and saline) at body temperature to measure in vitro degradation. Oxidation-sensitive hydrophobic thioether linkages transition to hydrophilic sulfoxide and sulfone groups. The introduction of these polar moieties brings about anisotropic swelling of the polymer network in an aqueous environment, inducing complex shape changes. 3D-printed uniaxial strips exhibit 8% contraction along the nematic director and 16% orthogonal expansion in oxidative media, while printed LCEs azimuthally deform into cones 19 times their original thickness. Ultimately, these LCEs degrade completely. In contrast, LCEs subjected to basic and saline solutions showed no apparent response. These oxidation-responsive LCEs with programmable shape changes may enable a wide range of applications in target specific drug delivery systems and other diagnostic and therapeutic tools.
Highlights
Stimuli-responsive materials demonstrating sensitivity to physical or chemical stimuli have been investigated extensively in the field of biomedical sciences
An oxidative environment, Phosphate-buffered saline (PBS) was used as a negative control, and 0.1M NaOH was (TATATO))
Direct ink writing (DIW) enabled the spatial control of the nematic director in the direction of the print path
Summary
Stimuli-responsive materials demonstrating sensitivity to physical or chemical stimuli have been investigated extensively in the field of biomedical sciences. These materials are characterized by dramatic physical changes demonstrating either reversible or irreversible transformations in shape [1], color [2], elastic modulus [3], or solubility [4], in response to small or moderate environmental variations. ROS are generated by all living organisms as a response to mitochondrial metabolism or by activated macrophages during foreign pathogen invasion [14] They include chemically reactive radical and non-radical oxygen species such as the superoxide anion (O2− ), hydroxyl radical (HO )
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