Role of Gemini Surfactants with Variable Spacers and SiO₂ Nanoparticles in ct-DNA Compaction and Applications toward In Vitro/In Vivo Gene Delivery

Abstract

Compaction of calf thymus DNA (ct-DNA) by two cationic gemini surfactants, 12-4-12 and 12-8-12, in the absence and presence of negatively charged SiO2 nanoparticles (NPs) (∼100 nm) has been explored using various techniques. 12-8-12 having a longer hydrophobic spacer induces a greater extent of ct-DNA compaction than 12-4-12, which becomes more efficient with SiO2 NPs. While 50% ct-DNA compaction in the presence of SiO2 NPs occurs at ∼77 nM of 12-8-12 and ∼130 nM of 12-4-12, but a conventional counterpart surfactant, DTAB, does it at its concentration as high as ∼7 μM. Time-resolved fluorescence anisotropy measurements show changes in the rotational dynamics of a fluorescent probe, DAPI, and helix segments in the condensed DNA. Fluorescence lifetime data and ethidium bromide exclusion assays reveal the binding sites of surfactants to ct-DNA. 12-8-12 with SiO2 NPs has shown the highest cell viability (≥90%) and least cell death in the human embryonic kidney (HEK) 293 cell lines in contrast to the cell viability of ≤80% for DTAB. These results show that 12-8-12 with SiO2 NPs has the highest time and dose-dependent cytotoxicity compared to 12-8-12 and 12-4-12 in the murine breast cancer 4T1 cell line. Fluorescence microscopy and flow cytometry are performed for in vitro cellular uptake of YOYO-1-labeled ct-DNA with surfactants and SiO2 NPs using 4T1 cells after 3 and 6 h incubations. The in vivo tumor accumulation studies are carried out using a real-time in vivo imaging system after intravenous injection of the samples into 4T1 tumor-bearing mice. 12-8-12 with SiO2 has delivered the highest amount of ct-DNA in cells and tumors in a time-dependent manner. Thus, the application of a gemini surfactant with a hydrophobic spacer and SiO2 NPs in compacting and delivering ct-DNA to the tumor is proven, warranting its further exploration in nucleic acid therapy for cancer treatment.

Compaction of Calf Thymus DNA by a Potential One-Head-Two-Tail Surfactant: Properties of Nanomaterials and Biological Testing for Gene Delivery

“…Stober’s process , has been pursued to synthesize the SiO 2 NPs (∼100 nm) based on the sol–gel method with ammonia as a catalyst and TEOS as the silicon source. The detailed methods are available elsewhere . They are characterized by FEI-Apreo S FE-SEM (20 kV) , and JEM-F2OO Multipurpose Microscope (JOEL) HR-TEM (200 kV).…”

“…The detailed methods are available elsewhere. 48 They are characterized by FEI-Apreo S FE-SEM (20 kV) 52,53 and JEM-F2OO Multipurpose Microscope (JOEL) HR-TEM (200 kV). The details of field emission scanning electron microscopy (FE-SEM) and high-resolution transmission electron microscopy (HR-TEM) measurements are given under Section S1 in the Supporting Information (SI).…”

“…These results are in accordance with that found from EDAX and zeta potential experiments. In our earlier study, 48 it has been observed that the 50% compaction of even for 0.5 μM ct-DNA against 5.0 μM ct-DNA in the present case has occurred at ∼0.08 and ∼0.13 μM of other two Gemini surfactants, 12-8-12,2Br − and 12-4-12,2Br − , respectively, with SiO 2 NPs. These results thus prove that DDAB is the most effective cationic surfactant as the DNA compacting agent among all five surfactants studied.…”

“…In the present work, the ability of DDAB surfactant to compact ct-DNA has been compared with that by a cationic conventional surfactant, DTAB, and a Gemini surfactant, 12-6-12 (in order to indicate bromide ions as counterions, hereafter it is presented as 12-6-12,2Br – ) with equal hydrocarbon tail length (Scheme ) in the presence of SiO 2 NPs. We have reported earlier the compaction of ct-DNA by some Gemini surfactants, 12-4-12,2Br – and 12-8-12,2Br – . In the present work, even for a higher concentration of ct-DNA (5.0 μM against 0.5 μM for the Gemini surfactants), DDAB has shown excellent ct-DNA compaction at a concentration significantly lesser than that is done by all three Gemini surfactants and of course by the DTAB surfactant.…”

“…We have reported earlier the compaction of ct-DNA by some Gemini surfactants, 12-4-12,2Br − and 12-8-12,2Br − . 48 In the present work, even for a higher concentration of ct-DNA (5.0 μM against 0.5 μM for the Gemini surfactants 48 ), DDAB has shown excellent ct-DNA compaction at a concentration significantly lesser than that is done by all three Gemini surfactants and of course by the DTAB surfactant.…”