Flow cytometry: Interesting tool for studying binding behavior of DNA on inorganic layered double hydroxide (LDH)

Background: A new method was established to characterize the binding kinetics of DNA toward layered double hydroxides (LDHs). The setup consisted of a newly developed sampling tube that allows the injection of analyte during the flow cytometric measurement. Methods: Layered double hydroxides consist of cationic metal hydroxide layers and exchangeable interlayer anions. This negatively charged structure permits biomolecules such as DNA to adsorb, and a so-called DNA-LDH hybrid is formed. The hydroxide layers can be removed in acidic media and the DNA will be released. CERATOFIX(R) (a registered trademark of SudChemie AG NA that belongs to the family of LDHs, produced by Sud-Chemie AG). The chemical structure can be summarized as [Mg2Al(OH)(6)](CO3)(0.5). The binding capacity and kinetic characteristics of different types of CERATOFIX(R)NA for a model DNA was determined by flow cytometry. Results: The static binding capacities of the different LDHs were determined after 1- and 16-h incubation with DNA solution, showing different binding patterns between the LDH materials. The binding kinetics were revealed by flow cytometric measurements in short-term and long-term kinetic experiments, showing that the majority of DNA adsorbs within the first 60 s. Conclusions: DNA removal from cell culture supernatants is one of the major concerns in downstream processing. Due to the anion exchange capabilities of LDHs it seemed a very interesting approach to use these materials for binding of DNA for elimination purposes. (C) 2004 Wiley-Liss, Inc.