Interactions Involving Neutral Surfactants and Double-Stranded DNA: The Case of Polysorbate 80 (Tween 80)

We investigate the interaction of the neutral surfactant polysorbate 80 (Tween 80) with double-stranded DNA under nearly physiological conditions. Single-molecule force spectroscopy assays performed with optical tweezers were used to determine the binding mechanisms below and above the critical micelle concentration (CMC). Below the CMC, individual surfactant molecules bind cooperatively along the double helix, presenting a high equilibrium association constant on the order of 1 × 10⁶ M^-1. Above the CMC, on the other hand, micelles can compact DNA at high concentrations (≳140 μM), opening perspectives for novel applications. The present study advances in characterizing DNA interactions with surfactants at the single molecule level.