A nanopolymer-based mouthwash formulation containing a mimetic of the glycosaminoglycan (GAG) heparan sulfate, with potential anti-mucositic and protective activities. Upon rinsing with the mouthwash, GAGs bind to heparan sulfate binding sites on macromolecules within the extracellular matrix (EMC), which prevents the destruction of the ECM and protects both growth factors and cytokines from being degraded. By replacing the GAGs damaged by chemotherapy and/or radiation, this mouthwash may protect healthy tissue against the cytotoxic effects of chemotherapy and radiation and may prevent against radiotherapy- and chemotherapy-induced mucositis.