The macroscale delivery system has been one of the practical platforms for a controlled delivery system by acting as a local depot close to the target tissue. In this study, we fabricated a macroporous alginate crygel incorporated with gold nanorods (GNRs) for the on-demand release of a chemotherapeutic drug from macroscale materials placed beside the target tumor. The macroporous crygel was prepared by the ice-crystal templating of a covalently crosslinked alginate hydrogel incorporated with GNRs. Mitoxantrone (MX), one of the potent anticancer drugs with a positive charge, was strongly adsorbed on the negative alginate chains of the cryogels. This system enabled a high loading of MX and a successful on-demand release of strongly bound MX from the GNR-loaded macroporous cryogels by near-infrared (NIR) irradiation by the dissociation of the interaction between the alginate backbone and MX. Cell viability after the NIR irradiation of the MX-loaded macroporous cryogel was significantly lower compared to that under no stimuli conditions. The in vivo test showed that repetitive NIR irradiations on the MX-loaded cryogel implanted near the tumor suppressed the tumor volume six times more than that of the control group. This simple approach to fabricate a macroporous cryogel capable of the on-demand release of bioactive cargos could be beneficial in various applications including cell, gene, and the other small molecule delivery systems.
Synthetic tough hydrogels have received attention because they could mimic the mechanical properties of natural hydrogels, such as muscle, ligament, tendon, and cartilage. Many recent studies suggest various approaches to enhance the mechanical properties of tough hydrogels. However, directly comparing each hydrogel property in different reports is challenging because various testing specimen shapes/sizes were employed, affecting the experimental mechanical property values. This study demonstrates how the specimen geometry—the lengths and width of the reduced section—of a tough double-network hydrogel causes differences in experimental tensile mechanical values. In particular, the elastic modulus was systemically compared using eleven specimens of different shapes and sizes that were tensile tested, including a rectangle, ASTM D412-C and D412-D, JIS K6251-7, and seven customized dumbbell shapes with various lengths and widths of the reduced section. Unlike the rectangular specimen, which showed an inconsistent measurement of mechanical properties due to a local load concentration near the grip, dumbbell-shaped specimens exhibited a stable fracture at the reduced section. The dumbbell-shaped specimen with a shorter gauge length resulted in a smaller elastic modulus. Moreover, a relationship between the specimen dimension and measured elastic modulus value was derived, which allowed for the prediction of the experimental elastic modulus of dumbbell-shaped tough hydrogels with different dimensions. This study conveys a message that reminds the apparent experimental dependence of specimen geometry on the stress-strain measurement and the need to standardize the measurement of of numerous tough hydrogels for a fair comparison.
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