Bacterial cellulose nanofibrils-reinforced composite hydrogels for mechanical compression-responsive on-demand drug release.

Herein, we propose a cellulose-reinforced hybrid hydrogel system that not only increases mechanical strength, but also allows on-demand drug release. This hybrid hydrogel is specialized by its semi-interpenetrating network structure in which bacterial cellulose nanofibers (BCNFs) penetrate through a polyacrylamide (PAM) mesh. We showed that the interpenetrating BCNFs with a higher aspect ratio of 240 increased the compression strength of PAM/BCNF composite hydrogels approximately 3-fold, compared with that prepared with PAM only, stemming from the reinforcing effect of the rigid natural nanofibers between PAM meshes. We also observed that the swelling kinetics depended on the mechanical properties determined by the BCNF aspect ratio. From further studies on drug release, we demonstrated that the tailored composition of BCNFs with PAM retarded drug release by a factor of two compared to PAM only while enabling on-demand drug release in response to the applied compressive stress. These results highlight that our BCNFs-reinforced hydrogel system can be applied as a mechanical stress-responsive smart drug delivery patch.