Lead ions can bind to DNA via nonelectrostatic interactions and hence alter its structure, which may be related to their adverse effects. The dynamics of Pb2+–DNA interaction has not been well understood. In this study, we report the monomolecular dynamics of the Pb2+–DNA interaction using a magnetic tweezers (MT) setup. We found that lead cations could induce DNA compaction at ionic strengths above 1 μM, which was also confirmed by morphology characterization. The chelation behavior of the Pb2+–DNA and the Cd2+–DNA complex solutions after adding EDTA were compared. The results showed that EDTA chelated with the bound metal ions on DNA and consequently led to restoring the DNA to its original length but with different restoration speeds for the two solutions. The fast binding dynamics and the slower chelation dynamics of the Pb2+ scenario compared to that of Cd2+ suggested that Pb2+ was more capable to induce DNA conformational change and that the Pb2+–DNA complex was more stable than the Cd2+–DNA complex. The stronger affinities for DNA bases and the inner binding of lead cations were two possible causes of the dynamics differences. Three agents, including EDTA, sodium gluconate, and SDBS, were used to remove the bound lead ions on DNA. It was shown that EDTA was the most efficient, and sodium gluconate could not fully restore DNA from its compact state. We concluded that both EDTA and SDBS were good candidates to restore the Pb2+-bound DNA to its original state.
Bojuan Hao,Kaige Wang,Yukun Zhou,Chaofan Sui,Lei Wang,Ren Bai,Zhaojin Yang
DNA molecular compaction/decompaction is of great significance for the exploration of basic life processes, the research of biomedical and genetic engineering, and so forth. However, the detailed mechanism of DNA compaction/decompaction caused by surfactants remains an open and challenging problem that has not been fully solved so far. In this paper, a sort of novel solid substrate, nanoPAA-ZnCl2-AuLs, with good stability and high sensitivity, was prepared by a self-assembly method. Based on this substrate, the surface-enhanced Raman scattering (SERS) technology was employed to investigate characteristics of interactions between DNA molecules and surfactants at a single molecular level. SERS spectra of calf thymus DNA (ctDNA), cetyl trimethyl ammonium bromide (CTAB), and sodium dodecyl sulfate (SDS) with a concentration as low as 10–9 M, and SERS spectra of ctDNA–CTAB and ctDNA–CTAB–SDS composites were collected, respectively. The interactions between ctDNA and surfactants were analyzed by changes in SERS spectra, for example, disappearances and appearances of SERS bands and relative changes of peak intensity, in which CTAB resulted in the compaction of the DNA molecule while SDS induced the decompaction of the ctDNA–CTAB complex. Moreover, UV–visible spectrophotometry was employed to demonstrate the compaction/decompaction of ctDNA molecules caused by surfactants. The local binding modes of ctDNA molecules and surfactant molecules were expounded. This work will be helpful for understanding biological processes such as DNA compaction and recombination within nucleus or/and cells and for the development of gene therapy technologies.
Sheng-Li Wu,Yifan Zhang,Lichen Wang,Yunjun Mei,Dong Zeng,Yi Wang,Jintao Guan,Liang Liu
A critical challenge in advancing gene therapy lies in developing safe and efficient gene delivery vectors. While polyethyleneimine (PEI) demonstrates superior DNA condensation capacity as a non-viral vector, its clinical application is hindered by inherent cytotoxicity. To address these challenges, this study presents a novel gene delivery system utilizing natural polyphenol resveratrol (Res) as a cross-linker through its hydroxyl groups capable of interacting with the amino groups in PEI by chemical modification. Three resveratrol-modified PEI (Res-P600, Res-P1800 and Res-P10k) polymers were synthesized and structurally validated by FTIR and 1 H NMR. The gene delivery efficacy of Res-PEI was rigorously examined through in vitro assessments, focusing on DNA condensation capacity, DNA protection ability and cytotoxicity. Concurrently, the particle size, zeta potential, cell uptake efficiency and transfection efficiency of the Res-PEI/DNA polyplexes were quantitatively characterized. Experimental data revealed that Res-PEI/DNA polyplexes effectively shielded genetic material against enzymatic degradation while demonstrating rapid cellular uptake in 293T cells. Cytotoxicity evaluations confirmed Res-PEI's improved biosafety profile relative to conventional PEI polymers. Notably, Res-P10k demonstrated superior transfection efficiency (78.96 % at w/w = 1) in 293T cells which was closed to lipo 6000. Data from HeLa cells align with our original findings in 293T cells, demonstrating broader applicability. Collectively, these findings position Res-PEI polyplexes as a biocompatible and effective alternative for next-generation gene delivery systems.
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