Cationic Gemini Surfactant–Plasmid Deoxyribonucleic Acid Condensates as a Single Amphiphilic Entity

Cationic gemini surfactant properties, its potential as a promising bioapplication candidate, and strategies for improving its biocompatibility: A review

Gemini surfactants consist of two cationic monomers of a surfactant linked together with a spacer. The specific structure of a cationic gemini surfactant is the reason for both its high surface activity and its ability to decrease the surface tension of water. The high surface activity and unique structure of gemini surfactants result in outstanding properties, including antibacterial and antifungal activity, anticorrosion properties, unique aggregation behaviour, the ability to form various structures reversibly in response to environmental conditions, and interactions with biomacromolecules such as DNA and proteins. These properties can be tailored by selecting the optimal structure of a gemini surfactant in terms of the nature and length of its alkyl substituents, spacer, and head group. Additionally, regarding their properties, comparison with their monomeric counterparts demonstrates that gemini surfactants have higher performance efficacy at lower concentrations. Hence, less material is needed, and the toxicity is lower. However, there are some limitations regarding their biocompatibility that have led researchers to develop amino acid-based and sugar-based gemini surfactants. Owing to their remarkable properties, cationic gemini surfactants are promising candidates for bioapplications such as drug delivery systems, gene carriers, and biomaterial surface modification.

Kelvin probe force microscopy to study electrostatic interactions of DNA with lipid-gemini surfactant monolayers for gene delivery

In novel gene therapy mechanisms utilising gemini surfactants, electrostatic interactions of the surfactant molecules with the DNA strands is a primary mechanism by which the two components of the delivery vehicle bind. In this work, we show for the first time direct evidence of electrostatic interactions of these compounds visualised with Kelvin probe force microscopy (KPFM) and correlated to their topography from atomic force microscopy (AFM). We construct monolayers of lipids and gemini surfactant to simulate interactions on a cellular level, using lipids commonly found in cell membranes, and allow DNA to bind to the monolayer as it is formed on a Langmuir-Blodgett trough. The difference in topography and electrical surface potential between monolayers with and without DNA is striking. In fact, KPFM reveals a strongly positive relative electrical surface potential in between where we identify a background lipid and the DNA strands, evidenced by the height profiles of the domains. Such identification is not possible without KPFM. We conclude that it is likely we are seeing cationic surfactant molecules surrounding DNA strands within a sea of background lipid.

In situ exfoliation and modification of graphite foil in supercapacitor devices: a facile strategy to fabricate high-performance supercapacitors

Graphite foils (GFs) are emerging as a new class of electrodes in supercapacitors (SCs) based on their light weight, and high electrical conductivity, although the surface area remains low. A novel method of, in situ electrochemical exfoliation and modification of GF in the assembled SCs, showed high energy density and power density of the SC devices.

Simple fabrication for high performance supercapacitors.

Mixing behaviour of Pluronics with gemini surfactant/plasmid DNA condensates: effect of Pluronic composition

Nanoparticles prepared from plasmid DNA (pDNA) and N,N-bis(dimethylhexadecyl)-1,3-propanediammonium bromide (16-3-16) have been mixed with various Pluronic block copolymers and investigated as binary surfactant systems in water using the previously demonstrated critical aggregation concentration of the surfactant-DNA complex. Surface tensiometry was used to determine critical micelle concentrations of mixed micelles formed within these Pluronic/16-3-16/pDNA mixtures. Use of mixed micelle theories reveals that mixed micelle composition and the interaction parameter, β, are influenced by the structure, in particular hydrophobicity, of the Pluronic component. Ethidium bromide fluorescence studies demonstrate the ability of the Pluronics to de-condense the plasmid DNA from the cationic 16-3-16 gemini surfactant complex, and show some relationship to the interaction parameter and Pluronic composition.

Lipoaminoacids Enzyme-Based Production and Application as Gene Delivery Vectors

Biosurfactant compounds have been studied in many applications, including biomedical, food, cosmetic, agriculture, and bioremediation areas, mainly due to their low toxicity, high biodegradability, and multifunctionality. Among biosurfactants, the lipoplexes of lipoaminoacids play a key role in medical and pharmaceutical fields. Lipoaminoacids (LAAs) are amino acid-based surfactants that are obtained from the condensation reaction of natural origin amino acids with fatty acids or fatty acid derivatives. LAA can be produced by biocatalysis as an alternative to chemical synthesis and thus become very attractive from both the biomedical and the environmental perspectives. Gemini LAAs, which are made of two hydrophobic chains and two amino acid head groups per molecule and linked by a spacer at the level of the amino acid residues, are promising candidates as both drug and gene delivery and protein disassembly agents. Gemini LAA usually show lower critical micelle concentration, interact more efficiently with proteins, and are better solubilising agents for hydrophobic drugs when compared to their monomeric counterparts due to their dimeric structure. A clinically relevant human gene therapy vector must overcome or avoid detect and silence foreign or misplaced DNA whilst delivering sustained levels of therapeutic gene product. Many non-viral DNA vectors trigger these defence mechanisms, being subsequently destroyed or rendered silent. The development of safe and persistently expressing DNA vectors is a crucial prerequisite for a successful clinical application, and it one of the main strategic tasks of non-viral gene therapy research.

Alkyl triphenylphosphonium surfactants as nucleic acid carriers: complexation efficacy toward DNA decamers, interaction with lipid bilayers and cytotoxicity studies

Herein, for the first time the complexation ability of a homological series of triphenylphosphonium surfactants (TPPB-n) toward DNA decamers has been explored. Formation of lipoplexes was confirmed by alternative techniques, including dynamic light scattering, indicating the occurrence of nanosized complexes (ca. 100-150 nm), and monitoring the charge neutralization of nucleotide phosphate groups and the fluorescence quenching of dye-intercalator ethidium bromide. The complexation efficacy of TPPB-surfactants toward an oligonucleotide (ONu) is compared with that of reference cationic surfactants. Strong effects of the alkyl chain length and the structure of the head group on the surfactant/ONu interaction are revealed, which probably occur via different mechanisms, with electrostatic and hydrophobic forces or intercalation imbedding involved. Phosphonium surfactants are shown to be capable of disordering lipid bilayers, which is supported by a decrease in the temperature of the main phase transition, T_m. This effect enhances with an increase in the alkyl chain length, indicating the integration of TPPB-n with lipid membranes. This markedly differs from the behavior of typical cationic surfactant cetyltrimethylammonium bromide, which induces an increase in the T_m value. It was demonstrated that the cytotoxicity of TPPB-n in terms of the MTT-test on a human cell line 293T nonmonotonically changes within the homological series, with the highest cytotoxicity exhibited by the dodecyl and tetradecyl homologs.