Phenylboronic acid or benzeneboronic acid, abbreviated as PhB(OH)₂ where Ph is the phenyl group C₆H₅-, is a boronic acid containing a phenyl substituent and two hydroxyl groups attached to boron. Phenylboronic acid is a white powder and is commonly used in organic synthesis

Although injectable hydrogels show promise for promoting healing of lesions and health of surrounding tissue, enabling cellular ingrowth and restoring neural tissue continue to be challenging. Hu et al. hypothesized that these challenges arise in part from the mismatch of composition, stiffness and viscoelasticity between the hydrogel and the brain parenchyma, and tested this hypothesis by developing and evaluating a self-healing hydrogel that not only mimicked the composition, but also the stiffness and viscoelasticity of native brain parenchyma. The hydrogel was crosslinked by dynamic boronate ester bonds between phenylboronic acid grafted hyaluronic acid (HA-PBA) and dopamine grafted gelatin (Gel-Dopa). This HA-PBA/Gel-Dopa hydrogel could be injected into a lesion cavity in a shear-thinning manner with rapid hemostasis, high tissue adhesion and efficient self-healing. They tested this in an in vivo mouse model of brain lesions and found the multi-functional injectable hydrogel to support neural cell infiltration, decrease astrogliosis and glial scars, and close the lesions. The results suggest a role for extracellular matrix-mimicking viscoelasticity in brain lesion healing, and motivate additional experimentation in larger animals as the technology progresses towards potential application in humans ¹⁾.