Engineers developed a mussel‑inspired bioadhesive patch designed to localize to glioblastoma margins and deliver cytotoxic payloads that eliminate invasive tumor cells in preclinical models. The adhesive leverages mussel‑derived chemistries for robust wet‑tissue attachment and controlled drug release, enabling focal treatment of residual disease after resection. The platform aims to address glioblastoma’s infiltrative nature by providing local, sustained therapy with reduced systemic exposure. If translated, the approach could become an adjunct to surgery and radiation for a cancer with few durable treatment options.