PEG and mPEG–Anthracene Induce DNA Condensation and Particle Formation

Abstract

In this study, we investigated the binding of DNA with poly(ethylene glycol) (PEG) of different sizes and compositions such as PEG 3350, PEG 6000, and mPEG-anthracene in aqueous solution at physiological conditions. The effects of size and composition on DNA aggregation and condensation as well as conformation were determined using Fourier transform infrared (FTIR), UV-visible, CD, fluorescence spectroscopic methods and atomic force microscopy (AFM). Structural analysis showed moderate complex formation for PEG 3350 and PEG 6000 and weaker interaction for mPE-anthracene-DNA adducts with both hydrophilic and hydrophobic contacts. The order of ± stability of the complexes formed is K(PEG 6000) = 1.5 (±0.4) × 10(4) M(-1) > K(PEG 3350) = 7.9 (±1) × 10(3) M(-1) > K(m(PEG-anthracene))= 3.6 (±0.8) × 10(3) M(-1) with nearly 1 bound PEG molecule per DNA. No B-DNA conformational changes were observed, while DNA condensation and particle formation occurred at high PEG concentration.

Effect of Synthetic Polymers on tRNA Nanoparticle Formation

“…The major intensity increases were associated with the guanine at 1698 (guanine N7), uracil at 1660 (uracil O 2 and adenine at 1609 cm -1 (adenine N7) in the difference spectra of PEG-3350, PEG-6000, mPEG-anthracene, mPEG-PAMAM-G3, mPEG-PAMAM-G4 and PAMAM-G4 complexes of tRNA ( Figure 2-panels A and B, diff., 1 mM). The observed intensity changes were attributed to polymer interactions with tRNA guanine N7, uracil O 2 and adenine N7 sites [25,27]. Similarly, increase in the intensity of the backbone PO 2 groups at 1241 (asymmetric PO 2 ) and 1085 cm -1 (symmetric PO 2 vibrations) were observed due to synthetic polymer-PO 2 interaction (Figure 2-panels A and B, diff., 1 mM).…”

“…Similarly, the shifting of the NH stretching vibration at 3280 cm -1 in the spectra of the free dendrimer and pegylated dendrimers was due to the hydrophilic contacts between dendrimers terminal NH 2 groups and the tRNA polar groups [25,27]. However, hydrophobic interactions between tRNA and synthetic polymer were characterized by the shifting of the polymer antisymmetric and symmetric CH 2 stretching vibrations, in the region of 3000-2800 cm ; for free mPEG-PAMAM-G4 at 2942, 2876 and 2856 cm -1 and free PAMAM-G4 at 2969, 2940 and 2834 cm -1 shifted to higher frequencies in the spectra of dendrimertRNA complexes.…”

“…FTIR spectroscopy is widely used to characterize the binding of ligand to DNA and RNA [25][26][27][28][29]. Synthetic polymer complexes with DNA and tRNA via hydrophilic, hydrophobic contacts, groove binding and phosphate interaction [25][26][27][28][29].…”

“…Synthetic polymer complexes with DNA and tRNA via hydrophilic, hydrophobic contacts, groove binding and phosphate interaction [25][26][27][28][29]. The infrared spectra and difference spectra of the free tRNA showed major alterations of tRNA in-plane vibrations and the backbone phosphate asymmetric and symmetric stretching bands [30][31][32][33][34][35], upon polymer complexation ( Figure 2-panels A and B).…”

“…PEGylation of synthetic polymers such as dendrimers is shown to reduce toxicity and increase biocompatibility and DNA Transfection [6,7,9]. It is well demonstrated that synthetic polymers induce DNA and RNA aggregation and particle formation [25][26][27][28][29]. However, not much of investigation on the effect of synthetic polymers on tRNA structure and dynamic has been reported.…”