Magneto- and photo-responsive hydrogels by co-assembly of peptides, cyclodextrins and superparamagnetic nanoparticles

Dual response to external, non invasive stimuli such as light and magnetic field is a highly desirable property in soft nanomaterials with potential applications in soft robotics, tissue engineering and life-like materials. Within this class of materials, hydrogels obtained by self assembly of low molecular weight gelators (LMWGs) are of special interest due to their ease in preparation and modification. Herein we report a modular co-assembly strategy for a magneto- and photo-responsive supramolecular hydrogel based on the arylazopyrazole (AAP) modified pentapeptide gelator Nap-GFFYS and β cyclodextrin vesicles (CDV) with superparamagnetic cobaltferrite nanoparticles embedded in their membrane. Upon application of a magnetic field a reversible increase of the storage modulus is observed during rheological measurements. Additionally, a gel rod could be manipulated with a weak permanent magnet, resulting in macroscopic bending of the rod. Furthermore, by irradiation with UV and visible light, respectively, the host guest interaction between the AAP moiety and the hydrophobic cavity of the β CD can be deactivated on demand, thus lowering the stiffness of the hydrogel reversibly.