Characterization of DNA degradation using direct current conductivity and dynamic dielectric relaxation techniques

Abstract

The purpose of this study was to evaluate DNA degradation upon thermal heating using dielectric relaxation and direct current (DC) conductivity methods. Herring sperm DNA, human growth hormone (HgH) plasmid DNA, and secreted alkaline phosphatase (SEAP) plasmid DNA were used as the examples. DNA was heated at 80°C for 1 hour. The dielectric relaxation spectra as a function of the applied field frequency were measured for HgH DNA at 0.5 hours and at 1 hour. The frequency range covered was from 10 kHz to 100 kHz. The DC conductivity measurements were made for all 3 kinds of DNA at 4 time points: 0 hours, 0.5 hours, 0.75 hours, and 1 hour. At each time point the DC conductivity was measured for each sample as a function of concentration via water dilution. The results show that the dielectric relaxation method is less sensitive in characterizing heat-driven DNA degradation. Conversely, DC conductivity is very sensitive. The semiquantitative dependence of the conductivity upon heating suggests that DNA degradation involves more than plasmid DNA nicking. Double strand and single strand breaks may also occur. In addition, herring sperm DNA, HgH DNA, and SEAP DNA, though similar in their DC conductivity functional forms upon dilution, exhibit significant differences in their responses to sustained heating.

Effect of Ionic Ordering in Conductivity Experiments of DNA Aqueous Solutions

“…As known the electric current in DNA water solutions is caused by the motion of counterions and DNA macromolecules [17][18][19][20][21][22][23]. In case of DNA solutions without added salt (salt free solution) the conductivity increases as the concentration of DNA increases because of counterion dynamics in the ion-hydrate shell of macromolecule [17,18].…”

“…Effects of dynamical ordering of counterions around DNA double helix may become apparent in conductivity experiments due to the interaction of charged particles of the solution with the electric field. As known the electric current in DNA water solutions is caused by the motion of counterions and DNA macromolecules [17][18][19][20][21][22][23]. In case of DNA solutions without added salt (salt free solution) the conductivity increases as the concentration of DNA increases because of counterion dynamics in the ion-hydrate shell of macromolecule [17,18].…”

Tunable Hydrophobicity in DNA Micelles: Design, Synthesis, and Characterization of a New Family of DNA Amphiphiles

“…[8] Among those hybrids, DNA-based materials are especially appealing because of the sequence programmability, self-recognition, and mechanical properties of DNA, as well as its only moderate resistance to degradation. [9] A model amphiphilic DNA-based system, the DNA block copolymer, has shown great potential for drug delivery. [10] Such micellar structures allow both facile functionalization through DNA hybridization and internalization of hydrophobic payloads.…”

Evaluation of Ketorolac Tromethamine Microspheres by Chitosan/Gelatin B Complex Coacervation

“…The physical mixture of drug and blank microspheres showed the same thermal behavior 168.76°C as the individual component, indicating that there was no interaction between the drug and the polymer in the solid state. The absence of endothermic peak of the drug at 168.88°C in the DSC of the drug loaded microspheres suggests that the drug existed in an amorphous or disordered crystalline phase as a molecular dispersion in polymeric matrix [ 28 – 29 ].…”