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ISSN 1998-9539

Supramolecular Nanocontainers Based on Hydrophobized Calix[4]resorcinol: Modification by Gemini Surfactants and Polyelectrolyte

E. A. Vasilieva,a,b@ F. G. Valeeva,a O. E. Yeliseeva,b S. S. Lukashenko,a M. N. Saifutdinova,b V. M. Zakharov,b E. L. Gavrilova,b and L. Ya. Zakharovaa,b
aA.E. Arbuzov Institute of Organic and Physical Chemistry, Kazan Scientific Center, Russian Academy of Sciences, 420088 Kazan, Russia
bKazan National Research Technological University, 420015 Kazan, Russia
DOI: 10.6060/mhc170509v
Macroheterocycles2017 10(2) 182-189
Supramolecular systems based on amphiphilic compounds can be used as hosts (nanocontainers) for practically useful synthetic or natural substrates. The use of the calixarene platform makes it possible to significantly expand the host-guest interactions due to the participation of the hydrophobic cavity and the directed functionalization of the upper or lower rim. The low water solubility of such systems significantly restricts their use in biotechnology. This problem can be solved by non-covalent modification of the calixarene platform with micelle-forming surfactants and polyelectrolytes.
New amphiphilic calix[4]resorcinol (CR), functionalized with alanine residues on the upper rim was used as a macrocyclic matrix. CR solubilization is carried out in aqueous micellar solutions of gemini (dicationic) surfactants of different hydrophobicity 16-12-16 (OH) and 12-6-12 (OH). In the case of a less hydrophobic surfactant, 12-6-12 (OH), ternary CR-12-6-12 (OH)-polyacrylic acid (PAA) system was used. The mechanism of interaction of components in surfactant-CR binary system might be different depending on the nature of calixarene. The value of the critical micelle concentration (CMC) found by fluorescence spectroscopy decreases in the presence of CR in the case of a more hydrophobic surfactant 16-12-16 (OH) from 0.06 mM to 0.01 mM and increases in the case of 12-6-12 (OH). The reason of different effects may be caused by different localization of the CR molecule or different mechanism of interaction of the components of the binary system: solubilization by surfactant micelles or the formation of mixed type aggregates.
Supramolecular systems 12-6-12 (OH)-CR were investigated as nanocontainers for the spectral probe Sudan I and a drug curcumin. Calculation of solubilization capacity showed that individual micelles 12-6-12(OH) effectively bind molecules of both guests, Sudan I and curcumin. Binary surfactant-CR systems are less effective nanocontainers: the solubilization capacity decreases twice compared with individual surfactant. Probably this may be caused by competition between guest molecules and the CR. Structural changes occurring upon the transition from an individual to a binary system are confirmed by dynamic light scattering. The particle size increases sharply in binary systems. The hydrodynamic diameter of the individual surfactant micelles Dh is 6-8 nm and 12-6-12 (OH)-CR mixed aggregate is Dh≥100 nm, which is in accordance with the assumption of morphological rearrangements micelle-vesicle and with literature data.
The addition of the polyelectrolyte component allows increasing the colloidal stability of the systems and further reducing the aggregation threshold. Mixed systems PAA-12-6-12 (OH) at different concentrations of surfactants and a fixed concentration of polyelectrolyte (1, 3, and 5 mM) were studied. A decrease of the value of the CAC1 binary systems is observed for all systems compared with the CMC of an individual solution of 12-6-12 (OH). An increase of the concentration of PAA from 1 to 5 mM has a negligible effect on the value of the CAC. The solubilization activity of the binary system 12-6-12 (OH)-PAA depends significantly on the nature of the guest. In the case of Sudan I, the solubilization properties increase in passing from an individual surfactant solution to mixed systems, and the solubilization of curcumin becomes less effective after addition of polyelectrolyte. The most probable reason is the different localization of guest molecules in mixed aggregates. A solubilization of curcumin was studied only in the ternary system 12-6-12 (OH)-CR-PAA: the maximum solubilization capacity is observed for individual micellar solutions and decreases in the presence of both components.

Thus, mixed supramolecular systems with improved properties can be used as nanocontainers for practically significant diagnostic probes and drugs.


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