ct-DNA compaction by nanoparticles formed by silica and gemini surfactants having hydroxyl group substituted spacers: In vitro, in vivo, and ex vivo gene uptake to cancer cells

Hybrid nanoparticles formed by Silica (SiO₂) coated with cationic gemini surfactants with variable hydroxyl group substituted spacers, 12-4(OH)-12,2Br⁻ and 12-4(OH)₂-12,2Br⁻ have shown a great extent of compaction of calf thymus DNA (ct-DNA) compared to conventional counterpart cationic surfactant, dodecyl trimethylammonium bromide (DTAB). Study shows not only the hydrophobicity of the spacer but also the hydrogen bonding interactions between the hydroxyl group substituted spacer and DNA have a great role in DNA compaction. 12-4(OH)₂-12,2Br⁻ is more efficient in compacting ct-DNA compared to 12-4(OH)-12,2Br⁻ due to the stronger binding of the former with ct-DNA than the latter. While 12-4(OH)-12,2Br⁻ makes 50 % ct-DNA compaction at its 0.63 μM concentration in the presence of SiO₂ nanoparticles, the same % of compaction can be achieved at a concentration as low as 0.25 μM of 12-4(OH)₂-12,2Br⁻. However, DTAB makes 50 % ct-DNA compaction at a concentration as high as 7.00 μM under the same condition. Therefore, the present systems address the very common challenge, i.e., cytotoxicity due to cationic surfactants. The system of 12-4(OH)₂-12,2Br⁻ coated SiO₂ nanoparticles displays the maximum cell viability (≥90 %), causing the least cell death in the mouse fibroblast cells (NIH3T3) cell lines compared to the cell viability of ≤80 % for DTAB. 12-4(OH)₂-12,2Br⁻ coated SiO₂ nanoparticles system has presented excellent in vitro cellular uptake of genes on mouse mammary gland adenocarcinoma (4T1) cells after incubating for 3 h and 6 h. In vivo study shows that 12-4(OH)₂-12,2Br⁻ coated SiO₂ nanoparticles system takes the highest amount of ct-DNA in cells and tumors in a time-dependent manner. The ex vivo studies using different organs of the mice demonstrate that the tumor sites in the breast of the mice are most affected by these formulations. Cytotoxicity assays and cellular uptake studies suggest that the present systems can be used for potential applications for gene delivery and oncological therapies.