EFFECT OF TRITON X-405 ON THE ADSORPTION AND DESORPTION OF SINGLE-STRANDED-DNA FRAGMENTS ONTO POSITIVELY CHARGED LATEX-PARTICLES

The influence of a nonionic surfactant (Triton X-405) on the adsorptio n behavior of single-stranded oligodeoxyribonucleotide (poly(thymidyli c acid) (dT(35))) Onto cationic aminated polystyrene latex particles h as been investigated. A preliminary study was performed on the adsorpt ion of Triton X-405 onto these cationic particles, showing a maximum a mount of similar to 0.5 mg m(-2) at the plateau. Desorption of the non ionic surfactant even after an extensive cleaning procedure was not co mpleted, indicating that probably low HLB (hydrophilic and lipophilic balance) species were still strongly adsorbed. The modification of the electrophoretic mobility of the latex particles together with the sli ght decrease in the colloidal stability suggested that the residual Tr iton X-405 molecules would adopt a flat conformation at the particles surface. Then, the adsorption behavior of dT(35) onto precoated cation ic latex was thoroughly examined under various conditions and compared with the case of bare latex particles. It was clearly evidenced that the residual adsorbed amount of nonionic surfactant significantly affe cted the surface nature, especially at basic pH. It was interesting to notice that dT(35) adsorption was strongly reduced at basic pH and th at its desorption was favored using basic pH buffer containing Triton X-405 and high ionic strength. Kinetic exchange experiments were also performed using labeled P-32-dT(35) and unlabeled dT(35), indicating t hat the exchange took place with no marked differences between coated and bare latex particles.