A Simple Injectable Moldable Hydrogel Assembled from Natural Glycyrrhizic Acid with Inherent Antibacterial Activity

Injectable low-molecular-weight hydrogels (LMWHs) from biocompatible materials have attracted much attention in biomedical applications because they can adapt any desired sizes and cavity shapes. Searching for simple, biocompatible injectable LMWHs owning inherent antibacterial activity without complicated chemical modification remains an open question to avoid the tedious synthesis/purification process and the easy bacterial infection of hydrogels in a moist environment. In this work, glycyrrhizic acid (GL), a naturally occurring compound, was found to form a stable transparent LMWH at 37 °C in physiological phosphate buffered saline (PBS) with nanoclusters as the microstructures. Moreover, this hydrogel exhibited great injectable and moldable properties. The antibacterial study showed that the growth of Gram-positive Staphylococcus aureus (S. aureus) could be completely inhibited by GL, whereas noneffect on Gram-negative Escherichia coli (E. coli) was observed. In addition, cell viability and hemolysis assay revealed that GL had good biocompatibility and hemocompatibility to mammalian cells because of its natural origin. Our simple biocompatible injectable moldable LMWH with inherent antibacterial ability has potential in the area of biomaterials and 3D bioprinting.