A fluorescence probe study of gemini surfactants in aqueous solution: a comparison between n-2-n and n-6-n series of the alkanediyl-a,w-bis (dimethylalkylammonium bromides)

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.

Antimicrobial Activity of Gemini Surfactants with Ether Group in the Spacer Part

Due to their large possibility of the structure modification, alkylammonium gemini surfactants are a rapidly growing class of compounds. They exhibit significant surface, aggregation and antimicrobial properties. Due to the fact that, in order to achieve the desired utility effect, the minimal concentration of compounds are used, they are in line with the principle of greenolution (green evolution) in chemistry. In this study, we present innovative synthesis of the homologous series of gemini surfactants modified at the spacer by the ether group, i.e., 3-oxa-1,5-pentane-bis(N-alkyl-N,N-dimethylammonium bromides). The critical micelle concentrations were determined. The minimal inhibitory concentrations of the synthesized compounds were determined against bacteria Escherichia coli ATCC 10536 and Staphylococcus aureus ATCC 6538; yeast Candida albicans ATCC 10231; and molds Aspergillus niger ATCC 16401 and Penicillium chrysogenum ATCC 60739. We also investigated the relationship between antimicrobial activity and alkyl chain length or the nature of the spacer. The obtained results indicate that the synthesized compounds are effective microbicides with a broad spectrum of biocidal activity.

Profound implication of histological alterations, haematological responses and biocidal assessment of cationic amphiphiles unified with their molecular architecture

The interfacial properties depicting the micellization behaviour of the cationic amphiphiles (surfactants) belonging to the class of quaternary ammonium salts varying in degree of hydrophobicity were evaluated using tensiometry, conductivity and fluorescence spectrophotometric methods at 303.15 K. The impact of the amphiphilic nature of these amphiphiles as a function of their concentration is accounted against the selective microbial strains using the well-diffusion approach. Also, its influence on the histological (shrinkage/curling of lamellae, necrosis, haemorrhage, hyperplasia of villi in gills and intestine) alterations and haematological (blood parameters) changes in fingerling of Cirrhinus mrigala (C. mrigala) offers an insight into the stern damages reported as aquatic toxicity. The lesions exhibited moderate to severe alterations that are further correlated with the semi-quantitative mean alteration value (MAV). The in vitro and in vivo findings are explained significantly in terms of amphiphilic hydrophobicity which followed the order: C₁₆TAB > C₁₂TAB. All the observed outcomes are rationalized by the structural assessment of the selected amphiphiles as specified by the computational simulation approach using density functional theory (DFT) with B3LYP method and 3-21G basis source set. This work also portrays the biodegradability of these cationic amphiphiles and their fate on the environment. Graphical abstract Molecular architecture of cationic amphiphiles integrated with their in vitro and in vivo rejoinders.

On the hydrophobic chains effect on critical micelle concentration of cationic gemini surfactants using molecular connectivity indices

The influence of the structure of hydrophobic tail chains on the critical micelle concentration of cationic gemini surfactants, using only the molecular connectivity indices, has been investigated in this work. The best model obtained shows that the relationship between the logarithm of critical micelle concentration and the alkyl chains length is parabolic. The formula has been derived for compounds with the same head groups and the same, medium length, spacer but with various hydrocarbon tail chains. Good-quality QSPR model obtained can be used to predict the critical micelle concentration value of structurally similar gemini surfactants as well as to design the structure of the hydrophobic tail chains to obtain new molecules more active in micelle formation.

Graphic abstract

A comprehensive insight on H-type aggregation in Congo red-surfactant systems revealed through spectroscopic and electrochemical study unified with a simulation framework

Schematic illustration depicting the aggregation phenomenon and shifts in the cationic surfactants-Congo red (CR) dye system investigated through spectral, scattering, voltammetry techniques along with the computational simulation approach.

Interactions of ionic liquids with hydration layer of poly(N-isopropylacrylamide): comprehensive analysis of biophysical techniques results

Here, we report comprehensive analysis of biophysical technique results for the influence of ionic liquids (ILs) containing the same cation, 1-butyl-3-methylimidazolium (Bmim(+)), and commonly used anions such as SCN(-), BF4(-), I(-), Br(-), Cl(-), CH3COO(-) and HSO4(-) on the phase transition temperature of poly(N-isopropylacrylamide) (PNIPAM) aqueous solution. Further, the effect of these ILs on bovine serum albumin (BSA) has also been studied. The modulations in UV-visible (UV-vis) absorption spectra, fluorescence intensity spectra, viscosity (η), hydrodynamic diameter (dH), Fourier transform infrared (FTIR) spectra and scanning electron microscopy (SEM) micrographs clearly reflect the change in the hydration state of PNIPAM in the presence of ILs. The observed single phase transition of PNIPAM aqueous solution at higher concentration of IL is the result of weak ion-ion pair interactions in IL.

Modelling of the Critical Micelle Concentration of Cationic Gemini Surfactants Using Molecular Connectivity Indices

Modelling of the critical micelle concentrations (cmc) using the molecular connectivity indices was performed for a set of 21 cationic gemini surfactants with medium-length spacers. The obtained model contains only the second-order Kier and Hall molecular connectivity index. It is suggested that the index ²χ includes some information about flexibility. The obtained model was used to predict log₁₀ cmc of other cationic gemini surfactants. The agreement between calculated and experimental values of log₁₀ cmc for the gemini surfactants that were not used in the correlation is very good.