Optothermally Reversible Carbon Nanotube–DNA Supramolecular Hybrid Hydrogels

Supramolecular hydrogels (SMHs) are three-dimensional constructs wherein the majority of the volume is occupied by water. Since the bonding forces between the components of SMHs are noncovalent, SMH properties are often tunable, stimuli responsive, and reversible, which enables a range of applications including triggered drug release, sensing, and tissue engineering. Meanwhile, single-walled carbon nanotubes (SWCNTs) possess high aspect ratios, superlative electrical and thermal conductivities, high mechanical strength and resilience, and strong optical absorption at near-infrared wavelengths that have the potential to add unique functionality to SMHs. However, SWCNT-based SMHs have thus far not fully realized this potential, particularly not yet utilizing the optical properties of SWCNTs to enable reversible response to near-infrared irradiation. Here, we present a novel SMH architecture comprised solely of DNA and SWCNTs, wherein noncovalent interactions between DNA and SWCNTs provide structural integrity to the SMH without compromising the intrinsic properties of SWCNTs. The mechanical properties of these SWCNT-DNA SMHs are readily tuned by varying the relative concentrations of DNA and SWNCNTs, which varies the density of cross-linking as shown by molecular dynamics simulations. Moreover, the SWCNT-DNA SMH gelation transition is fully reversible and can be triggered by a change in temperature or near-infrared irradiation. This work explores a new regime for SWCNT-DNA SMHs with potential utility for a range of applications including sensors, actuators, responsive substrates, and 3D printing.