Self-Assembling Monomeric Nucleoside Molecular Nanoparticles Loaded with 5-FU Enhancing Therapeutic Efficacy against Oral Cancer

Conventional oligonucleotide based drug delivery systems suffer from lengthy synthetic protocols, high cost, and poor chemical or enzymatic stability under certain circumstances. Canonical free individual nucleosides cannot form stable nanostructures in aqueous solution as drug vehicles. Here, we report the development of a monomeric self-assembled nucleoside nanoparticle (SNNP) into an efficient drug delivery system which has currently no parallel in such field. This was achieved using a l-configurational pyrimido[4,5-d]pyrimidine nucleoside building block that can form robust discrete nanoparticles in just one step with water as the sole solvent. Its high biocompatibility and low toxicity was demonstrated in vitro and in vivo. In mouse xenograft model of oral squamous cell carcinoma (OSCC), SNNP loaded with 5-fluoro-uracile (5-FU-SNNP) remarkably retarded the tumor growth compared with free 5-FU, albeit SNNP alone showed no antitumor effect. The stability in blood circulation and the effective concentration of 5-FU in tumor tissue were increased upon the loading with SNNP. TUNEL and immunohistochemistry analyses further indicated that the superior in vivo antitumor efficacy of 5-FU-SNNP compared to free 5-FU was associated with an enhanced degree of inhibition of cell proliferation and stimulation of cell apoptosis. Furthermore, SNNP alleviated the toxic side effects of 5-FU. These findings suggested that when loaded with SNNP, 5-FU has better antitumor efficacy and lower side effects, indicating that SNNP can efficiently act as a readily accessible, robust, biocompatible and low-toxic nanobiomaterial which may find wide therapeutic applications clinically in the future.