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Research Article

Aggregation Behavior and Thermodynamics of Binding between Poly(ethylene oxide)-block-Poly(2-(diethylamino)ethyl methacrylate) and Plasmid DNA

J. F. Tan,^† H. P. Too,^†^‡ T. A. Hatton,*^†^§ and K. C. Tam*^†

Department of Biochemistry, National University of Singapore, Singapore 117576, Department of Chemical Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, and School of Mechanical & Aerospace Engineering, Nanyang Technological University, 50 Nanyang Avenue, Singapore 639798

Langmuir, 2006, 22 (8), pp 3744–3750

DOI: 10.1021/la052591i

Publication Date (Web): March 17, 2006

†

Singapore−MIT Alliance.

‡

National University of Singapore.

Corresponding authors. E-mails: mkctam@ntu.edu.sg (K.C.T.); tahatton@mit.edu (T.A.H.).

Massachusetts Institute of Technology.

Nanyang Technological University.

Abstract

The aggregation behavior and the thermodynamics of binding between poly(ethylene oxide)-block-poly(2-(diethylamino)ethyl methacrylate) (PEO-b-PDEAEMA) block copolymers and plasmid DNA were examined. Binding between the polymer and DNA were confirmed by gel electrophoresis. The high affinity between the polymer and DNA was demonstrated through the ethidium bromide (EtBr) displacement assay, and the binding was found to be related to the stoichiometric balance between the amine group of the polymer and the DNA nucleotide molar ratio (N/P molar ratio). The light scattering and TEM results showed that, at low polymer concentration, the hydrodynamic radii (R_h) of the polymer/DNA complexes was around 90 nm; however, at sufficiently high polymer concentration, the complexes condensed to around 35 nm induced by a structural rearrangement of the amphiphilic nature of the block copolymer. The isothermal titration calorimetric results showed that the binding between the polymer and DNA is driven by a large favorable enthalpy.

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