Calf thymus DNA characterization and its adsorption on different silica surfaces Senem Yetgin * and Devrim Balkose DNA adsorption is the initial stage of gene therapy for drug delivery systems and solid phase extraction methods of DNA purification. High pore volume and high adsorption capacity are simple requirements not only for producing ‘smart’ drug delivery systems but also the development of purification kits. Silica is the most used material for this purpose. The present study aimed at elucidating the calf thymus DNA biosorption process by the characterization of calf thymus DNA and silica to increase the efficiency of the currently used silica material. Mesoporous silica has long been used for DNA adsorption and silica aerogel is the new adsorbent investigated in the present study. When DNA solution was freeze dried on a silica wafer, self-assembled super helices formed as shown by atomic microscopy (AFM). Thus DNA existed not as single molecules but as large sized agglomerates in water. Thus it could be adsorbed in the macropores and on the external surface of adsorbents. Adsorption of calf thymus DNA to a silica aerogel, a mesoporous silica gel and a silica wafer was investigated in the present study. Silica aerogel was synthesized from TEOS by a supercritical ethanol drying process. The DNA adsorption capacity of the silica aerogel was nearly two times that of the mesoporous silica gel due to its macroporous structure and its higher silanol content. Silica aerogel was found to be a very promising material for DNA adsorption. Therefore silica aerogel can be considered as a good candidate for the delivery of DNA. Introduction Nano and micro particles have many functions such as anti- bacterial, 1 detection in chemical analysis, 2 tumor cell targeting, 3 polymer composites, 4,5 stable semiconductor material 6 and DNA delivery systems. 7 Recent studies have been focused on development of DNA related nanomaterials and nanotechnol- ogies and the creation of nano-sized structures. Consequently DNA is used for gene therapy, biological sensor preparation, tumor targeting delivery host for targeted drugs, gene and functional nanoscale electronic device, programmable DNA- directed self-assembly lm and DNA-conjugated metal nano- particles. 8–15 Besides DNA chips and DNA microarrays are used in molecular biology, pharmaceutical industry and clinical research to identify presence of specic biological targets. 16 These kinds of technologies require pure DNA usage and understanding of DNA interaction with surfaces. Not only DNA purication but also DNA interactions with different surfaces are directly or indirectly based on the adsorption of DNA. In the case of DNA purication Solid Phase Extraction (SPE) is the most useful and harmless technique for DNA purication. Silica is the most commonly used material for SPE and increasing its adsorption capacity is rstly required. An inorganic material, typically in the form of amorphous mesoporous silica (SiO 2 ) is one of the preferred matrices for delivery host. On the other hand silica aerogel has been in attention recently because of its tuneable physical properties of pore size, surface area (e.g.). Nucleic acids are adsorbed on silica and glass surfaces under chaotropic solution conditions because of negatively charged structure of DNA. Its adsorption by silica was extensively investigated. 17–19 It is reported that silanol group through the surface enhance the interaction. Generally both mechanism of DNA adsorption by silica and adsorption capacity are the investigated points. DNA adsorption was controlled by the three effects (i) weak electrostatic repul- sion forces, (ii) dehydration, and (iii) hydrogen bond formation. Also the presence of a monovalent cation such as Na + neutral- izes the negative charges on the phosphate backbone of DNA, reducing the electrostatic barrier between DNA and silica. 1 Therefore DNA adsorption capacity is increased. Silica particles in microchips 16 and miniaturized set up 20 were used success- fully for solid phase extraction of DNA. There are controversial approaches to the aggregation state of DNA adsorbed on porous solids. DNA bres having 30–40 nm diameter were observed between the edges and surfaces of particles when Bacillus sub- tilis DNA was adsorbed on clay. They were not adsorbed as single molecules but as bres consisting of many molecules. 21 However b-type duplex DNA molecules bearing a straight cylindrical structure with a diameter of 2 nm were included in Department of Chemical Engineering, Izmir Institute of Technology, 35430 Gulbahce Urla, Izmir, Turkey. E-mail: devrimbalkose@iyte.edu.tr; senemyetgin@gmail.com Cite this: RSC Adv. , 2015, 5, 57950 Received 29th January 2015 Accepted 17th June 2015 DOI: 10.1039/c5ra01810b www.rsc.org/advances 57950 | RSC Adv., 2015, 5, 57950–57959 This journal is © The Royal Society of Chemistry 2015 RSC Advances PAPER Published on 17 June 2015. Downloaded by Izmir Yuksek Teknoloji on 01/06/2017 08:24:41. View Article Online View Journal | View Issue