Externally addressable hydrogel nanocomposites for biomedical applications

•Hydrogel nanocomposites based on carbon, gold, or iron oxide nanoparticles are reviewed.•Nanoparticles act as transducers of current, near-IR irradiation, or alternating magnetic fields.•Combining nanoparticles with ‘smart’ hydrogels creates externally addressable biomaterials.•Applications in on-demand drug delivery, hyperthermia therapy, and adhesives emphasized.

Hydrogels are widely applied in a variety of biomedical applications given their biologically-relevant mechanical, interfacial, and chemical properties. By combining (soft) hydrogels with (hard) nanoparticles, the attractive electromagnetic properties of many nanoparticles can be applied in vivo while maintaining biocompatibility. Herein, we outline recent progress in the design of hydrogel nanocomposites coupling carbon nanotubes, gold nanoparticles, and superparamagnetic iron oxide nanoparticles (SPIONs) with hydrogels, including both conventional hydrogels as well as ‘smart’, stimuli-responsive hydrogels whose properties can be remotely changed ‘on-demand’ using the nanoparticle as a transducer to convert highly penetrative near-infrared radiation or alternating magnetic fields into a physically relevant phase transition stimulus. The applications of such materials for on-demand drug delivery, hyperthermia therapies, and tissue adhesives are described.

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