RESEARCH PAPER Anion-exchanged nanosolid support of magnetic nanoparticle in combination with PNA probes for DNA sequence analysis T. Theppaleak • M. Rutnakornpituk • U. Wichai • T. Vilaivan • B. Rutnakornpituk Received: 18 April 2013 / Accepted: 29 October 2013 / Published online: 7 November 2013 Ó Springer Science+Business Media Dordrecht 2013 Abstract Poly((2-diethylamino)ethyl methacrylate) (poly(DEAEMA))-grafted magnetite nanoparticle (MNP) with a positively charged surface was used as an anion exchanger for detection of deoxyribonucleic acid (DNA) sequences by employing peptide nucleic acid (PNA) as a probe. The cationic MNP with a size ranging between 6 and 10 nm in diameter can electrostatically adsorb DNA with a capacity of 171 nmol nucleotide/g MNP. The electrostatically neutral pyrrolidinyl PNA-bearing prolyl-2-aminocy- clopentane carboxylic acid backbone (acpcPNA) can be adsorbed by the cationic MNP only when the sequence of the PNA and DNA is complementary, and the presence of adsorbed PNA could be examined by matrix-assisted laser desorption ionization time-of- flight mass spectrometry. Two DNA sequences, the sequence stimulating Kirsten Rat Sarcoma (K-ras) gene and the sequence having 5 0 methylated CpG site, were used in this study. It was found that the particles can be used as nanosolid support to differentiate between complementary and single-base mismatched DNA sequences using both single and two acpcPNA probes. This polymer-grafted MNP might be applica- ble for use as a magnetically guidable tool for detection of real DNA samples in the future. Keywords Magnetite Á Nanoparticle Á DNA sequence Á AcpcPNA probe Á Instrumentation Á Nanomedicine Introduction Magnetite nanoparticle (MNP) has been widely stud- ied over the past decade in a variety of biomedical applications, e.g., magnetic resonance imaging (MRI) contrast enhancement, drug delivery, bioseparation, and hyperthermia (Kim et al. 2008). Due to its large surface-to-volume ratio, it tends to aggregate to one another leading to a loss in nanoscale-related proper- ties. Surface modification with suitable surfactants, in particular long chain polymers, seems to be a prom- ising strategy to obtain stable and dispersible particles in suitable media (Meerod et al. 2008). Coating MNP with polymers can be accomplished by various methods including physical absorption of polymers onto the MNP surface (Liu et al. 2006), emulsion polymerization in the presence of a MNP (Cui et al. Electronic supplementary material The online version of this article (doi:10.1007/s11051-013-2106-3) contains supple- mentary material, which is available to authorized users. T. Theppaleak Á M. Rutnakornpituk Á U. Wichai Á B. Rutnakornpituk (&) Department of Chemistry and Center of Excellence in Biomaterial, Faculty of Science, Naresuan University, Phitsanulok 65000, Thailand e-mail: boonjirab@nu.ac.th T. Vilaivan Organic Synthesis Research Unit, Department of Chemistry, Faculty of Science, Chulalongkorn University, Phayathai Road, Patumwan, Bangkok 10330, Thailand 123 J Nanopart Res (2013) 15:2106 DOI 10.1007/s11051-013-2106-3