International Journal of Biological Macromolecules 46 (2010) 153–158 Contents lists available at ScienceDirect International Journal of Biological Macromolecules journal homepage: www.elsevier.com/locate/ijbiomac Release of DNA from surfactant complexes induced by 2-hydroxypropyl--cyclodextrin Jonas Carlstedt a,∗ , Alfredo González-Pérez a,b,∗∗ , Manuel Alatorre-Meda c , Rita S. Dias d , Björn Lindman a,d a Physical Chemistry, Center for Chemistry and Chemical Engineering, Lund University, P.O. Box 124, 22100 Lund, Sweden b MEMPHYS – Center for Biomembrane Physics, Department of Physics and Chemistry, University of Southern Denmark, Campusvej.55, DK-5230 Odense M, Denmark c Grupo de Nanomateriales y Materia Blanda, Departamento de Física de la Materia Condensada, Universidad de Santiago de Compostela, Campus Sur s/n, 15782, Santiago de Compostela, Spain d Department of Chemistry, University of Coimbra, Rua Larga, 3004-535 Coimbra, Portugal article info Article history: Received 14 August 2009 Received in revised form 30 November 2009 Accepted 9 December 2009 Available online 16 December 2009 Keywords: Compaction/Decompaction CTAB Non-equilibrium abstract Decompaction of DNA–CTA self-assembled complexes by 2-hydroxypropyl--cyclodextrin (2-HP--CD) was studied and the results were compared with -CD. Different degrees of 2-HP substitution (0.6, 0.8 and 1.0, respectively) were used and the decompaction was successful with all degrees of substitution. Fluo- rescence microscopy, steady state fluorescence spectroscopy, density and sound velocity measurements, thermal melting and circular dichroism were used. Compared to previous work using - and -CD, the fluorescence spectroscopy results showed that the 2-HP-substituted CDs more efficiently released DNA into solution. Furthermore, dissociation of macroscopically phase separated DNA–CTA complexes was achieved upon addition of 2-HP--CD and the results gave strong indications on the non-equilibrium nature of the system. The globule-to-coil transition was not found to proceed through a coexistence region, which seems to be a general phenomenon in DNA decompaction using CDs. © 2009 Elsevier B.V. All rights reserved. 1. Introduction Important cellular processes involving DNA, such as transcrip- tion and replication, can be strongly affected by the extent of condensation of the chromatin fiber. The degree of condensation affects the access of regulatory factors [1]. In synthetic gene deliv- ery systems, the use of cationic lipids can protect and compact the large DNA molecule. Once the DNA-compacting agent complex reaches the target inside the cell, the DNA should be decompacted to be accessible to the cell machinery responsible for translating the enclosed information. Obviously, it is desirable to achieve a reversible DNA condensation process in order to be able to control the transfection efficiency. Many chemical agents have been suc- cessfully used in vitro in order to compact DNA, thus mimicking the natural process occurring in the cell. In the last few years, the fun- damental understanding of the compaction process using different chemical agents has improved. DNA condensation was previously reviewed by Bloomfield [2], while the behavior of DNA and surfac- ∗ Corresponding author. Tel.: +46 46 222 81 88; fax: +46 46 222 44 13. ∗∗ Corresponding author at: MEMPHYS – Center for Biomembrane Physics, Depart- ment of Physics and Chemistry, University of Southern Denmark, Campusvej 55, DK-5230 Odense M, Denmark. Tel.: +45 6550 3474; fax: +45 6550 4048 . E-mail addresses: jonas.carlstedt@fkem1.lu.se (J. Carlstedt), alfredo@memphys.sdu.dk (A. González-Pérez). tants in bulk and at interfaces was summarized by Dias et al. [3], covering both surfactant induced compaction and decompaction of DNA. More recent reviews addressing the condensation of DNA [4] and compaction and decompaction strategies [5] were newly published. DNA decompaction is a process substantially dependent on the compacting agent. The decompacting agent has to compete with the DNA for the binding of the compacting agents. However, the process is dependent not only on the decompacting agent, but also on the solution conditions. An example of the latter is the decom- paction of DNA-poly(allylamine hydrochloride) complexes using the polyanion poly(sodium styrenesulfonate). At relatively large ionic strength (1 M), a coexistence between coils and globules was found, whereas with salt concentrations in the order of 10 mM, a coexistence between globules and intrasegregated DNA chains was observed [6]. We have previously investigated DNA compaction induced by cationic surfactants [3,4]. The compaction is achieved through the formation of micelles in the vicinity of the DNA (sometimes referred to as surface micelles), that, being highly charged structures, induce ion correlation effects leading to the attraction of different parts of the DNA molecule [7]. The possibility of controlling the DNA morphology using self-assembled structures like surface micelles is very interesting and, in fact, it has already been used to improve the efficiency of other condensing agents, such as polyamines [8,9] and peptides [10,11]. DNA-cationic surfactant complexes can be 0141-8130/$ – see front matter © 2009 Elsevier B.V. All rights reserved. doi:10.1016/j.ijbiomac.2009.12.002