Self-assembly of the mixed systems based on cationic surfactants and different types of polyanions: The influence of structural and concentration factors

Role of Polyanions and Surfactant Head Group in the Formation of Polymer-Colloid Nanocontainers

OBJECTIVES

This study was aimed at the investigation of the supramolecular systems based on cationic surfactants bearing cyclic head groups (imidazolium and pyrrolidinium) and polyanions (polyacrylic acid (PAA) and human serum albumin (HSA)), and factors governing their structural behavior to create functional nanosystems with controlled properties. Research hypothesis. Mixed PE-surfactant complexes based on oppositely charged species are characterized by multifactor behavior strongly affected by the nature of both components. It was expected that the transition from a single surfactant solution to an admixture with PE might provide synergetic effects on structural characteristics and functional activity. To test this assumption, the concentration thresholds of aggregation, dimensional and charge characteristics, and solubilization capacity of amphiphiles in the presence of PEs have been determined by tensiometry, fluorescence and UV-visible spectroscopy, and dynamic and electrophoretic light scattering.

RESULTS

The formation of mixed surfactant-PAA aggregates with a hydrodynamic diameter of 100-180 nm has been shown. Polyanion additives led to a decrease in the critical micelle concentration of surfactants by two orders of magnitude (from 1 mM to 0.01 mM). A gradual increase in the zeta potential of HAS-surfactant systems from negative to positive value indicates that the electrostatic mechanism contributes to the binding of components. Additionally, 3D and conventional fluorescence spectroscopy showed that imidazolium surfactant had little effect on HSA conformation, and component binding occurs due to hydrogen bonding and Van der Waals interactions through the tryptophan amino acid residue of the protein. Surfactant-polyanion nanostructures improve the solubility of lipophilic medicines such as Warfarin, Amphotericin B, and Meloxicam.

PERSPECTIVES

Surfactant-PE composition demonstrated beneficial solubilization activity and can be recommended for the construction of nanocontainers for hydrophobic drugs, with their efficacy tuned by the variation in surfactant head group and the nature of polyanions.

Polymer-Colloid Complexes Based on Cationic Imidazolium Amphiphile, Polyacrylic Acid and DNA Decamer

The solution behavior and physicochemical characteristics of polymer-colloid complexes based on cationic imidazolium amphiphile with a dodecyl tail (IA-12) and polyacrylic acid (PAA) or DNA decamer (oligonucleotide) were evaluated using tensiometry, conductometry, dynamic and electrophoretic light scattering and fluorescent spectroscopy and microscopy. It has been established that PAA addition to the surfactant system resulted in a ca. 200-fold decrease in the aggregation threshold of IA-12, with the hydrodynamic diameter of complexes ranging within 100-150 nm. Electrostatic forces are assumed to be the main driving force in the formation of IA-12/PAA complexes. Factors influencing the efficacy of the complexation of IA-12 with oligonucleotide were determined. The nonconventional mode of binding with the involvement of hydrophobic interactions and the intercalation mechanism is probably responsible for the IA-12/oligonucleotide complexation, and a minor contribution of electrostatic forces occurred. The latter was supported by zeta potential measurements and the gel electrophoresis technique, which demonstrated the low degree of charge neutralization of the complexes. Importantly, cellular uptake of the IA-12/oligonucleotide complex was confirmed by fluorescence microscopy and flow cytometry data on the example of M-HeLa cells. While single IA-12 samples exhibit roughly similar cytotoxicity, IA-12-oligonucleotide complexes show a selective effect toward M-HeLa cells (IC50 1.1 µM) compared to Chang liver cells (IC50 23.1 µM).

Mitochondria-targeted cationic liposomes modified with alkyltriphenylphosphonium bromides loaded with hydrophilic drugs: preparation, cytotoxicity and colocalization assay

The purpose of this work was to obtain cationic liposomes based on 1,2-dipalmitoyl-sn-glycero-3-phosphocholine noncovalently modified using alkyltriphenylphosphonium bromides (TPPB-n) with different lengths of hydrocarbon tail for targeted delivery to mitochondria. The hydrodynamic diameter and electrokinetic potential of hybrid liposomes depending on the lipid/surfactant ratio were monitored in time with the aim to optimize the composition with sufficient stability and positive charge for mitochondria-targeted delivery. It was found that increasing the alkyl tail length of the surfactant (up to TPPB-14) leads to an increase in the positive charge of the liposomes. The most optimal results of stability were obtained for hybrid liposomes based on 1,2-dipalmitoyl-sn-glycero-3-phosphocholine and TPPB-12, TPPB-14. The obtained modified liposomes were loaded with hydrophilic substrates (a model probe Rhodamine B and medicines metronidazole and doxorubicin). This is one of the first examples of fabrication of liposomes noncovalently modified using an amphiphilic TPP cation, with the alkyl tail length of surfactant and TPP/lipid ratio optimized in terms of stability of the liposomes and the binding/release behavior of hydrophilic probes. Using the confocal microscopy method, it was shown that modification of liposomes with a triphenylphosphonium cation results in targeted delivery of encapsulated compounds to mitochondria.

Self-assembled systems based on novel hydroxyethylated imidazolium-containing amphiphiles: Interaction with DNA decamer, protein and lipid

The study on aggregation capacity of novel imidazolium-containing amphiphiles of 1-(2-hydroxyethyl)alkylimidazolium bromide series and their interaction with bio-objects (DNA decamer, bovine serum albumin, phospholipid) was performed. It was revealed that introduction of hydroxyethyl moiety into the surfactant molecule resulted in 1.5-2-fold decrease of critical micelle concentration. These modified amphiphiles quantitatively bind DNA decamer due to intercalation and hydrophobic interactions with lipoplex formation. The evaluation of membranotropic properties of these surfactants exhibited that initiation of disordering and compression of the model cell wall consisting of dipalmitoyl phosphocholine (regulation of permeability for various compounds) could be achieved by variation of the length of hydrophobic tail of imidazolium-containing amphiphiles. Transition from individual surfactants solutions to their mixtures with protein (bovine serum albumin) is accompanied by 8-fold decrease of aggregation thresholds and characterized by the presence of two critical points. The binding of components of surfactant/BSA binary systems took place through tryptophan amino acid residue of peptide macromolecule.