Self-defensive nano-assemblies from camptothecin-based antitumor drugs

Camptothecin ( CPT)-based drugs always undergo the reversible, pH-dependent lactone ring-opening reaction, yielding the inactive but toxic carboxylate form. Self-assembly strategy provides an effective route for preserving their bio-stability. In this article, nano-sized self-assemblies from CPTbased antitumor drugs were simply built up by directly diluting the stock dimethylsulfoxide solutions of ( S)-(+)-CPT, ( S)-10-hydroxyl camptothecin and carboxylic CPT with water/phosphatebuffered saline solution. Because of their different molecular structures in A-ring or modification on the 20-OH group, CPT self-assembled into helical nano-ribbons, whereas 10-hydroxycamptothecin and carboxylic CPT self-aggregated into flat nano-ribbons and cylindric nano-rods, respectively. Attractively, the self-assembly of CPT-based drugs could occur within 1 min at a low concentration of 1 x 10(-5) M. Adopting the J-type self-aggregation, self-assemblies were stable in aqueous solution and could effectively protect the CPT-based drugs from hydrolysis, which thereby kept their bioactivity for tumor therapy.