Effect of alkyl chain functionalization of ionic liquid surfactants on the complexation and self-assembling behavior of polyampholyte gelatin in aqueous medium

Abstract

The complexation behaviour of an imidazolium based ionic liquid surfactant (ILS) 3-methyl-1-dodecylimidazolium chloride, [Cmim][Cl], and its amide and ester functionalized counterparts 3-(2-(dodecylamino)-2-oxoethyl)-1-methyl-1H-imidazol-3-ium chloride, [CAmim][Cl], and 3-methyl-1-dodecyloxycarbonylmethylimidazolium chloride, [CEmim][Cl], with a model protein gelatin (G) in aqueous solution has been investigated. Complexation of G with ILSs at the air-solution interface has been monitored by tensiometry, whereas complexation and ILS mediated self-assembly of G-ILS complexes in the bulk have been followed by dynamic light scattering (DLS), zeta-potential measurements, conductivity, and fluorescence techniques. The morphology of different self-assembled architectures has been monitored by scanning electron microscopy (SEM). Different transitions observed from various techniques in different concentration regimes of ILSs have been assigned to the varying extent of complexation and ILS mediated self-assembly of G-ILS complexes. The functionalization of the alkyl chain of the ILS [Cmim][Cl] with an amide ([CAmim][Cl]) or ester ([CEmim][Cl]) moiety owing to their additional hydrogen bonding (H-bonding) ability along with rigidity ([CAmim][Cl]) or flexibility ([CEmim][Cl]) near the imidazolium head group has been found to exert great influence on their complexation with G. This influence is fashioned as self-assembled structures of G-ILS complexes into discrete large hexagonal sheet-like or near spherical architectures, depending on the concentration and type of functionality of the alkyl chain of ILSs. The thermodynamic forces behind the complexation and self-assembly processes have been monitored by isothermal titration calorimetry (ITC) measurements and are discussed in detail. As both the nature of the ILS and protein (charge and structure) could affect their interactional behavior, the present results are expected to be very useful in deeply understanding the structure-property relationship between the nature of the ILS and proteins, which would be of great importance in the field of functional soft-materials.

Aqueous colloidal systems of bovine serum albumin and functionalized surface active ionic liquids for material transport

“…Such observations are quiet common in protein/polymer-SAIL systems. 46,48 Further information about the degree of counterion binding (b) and standard free energy of micellization ðDG mic Þ calculated using conductivity measurements (Annexure S2, ESI †) is provided in footnote of Table S3 (ESI †).…”

“…8,[46][47][48][49][50][51][52][53][54][55][56][57] Different proteins such as BSA, Gelatin and blactoglobulin (b-LG) has been investigated for their complexation with SAILs, where the length of alkyl chain and nature of head group of SAIL has been found to exert signicant inuence on complexation behavior of BSA with SAILs. 8,[46][47][48][49]56,57 It is stressed that in most of the investigations, SAILs without any functionalization of ionic head group or alkyl chain have been employed with the exception of few studies. 8,46,48 A contrasting complexation behavior of functionalized SAILs as compared to non-functionalized ones towards BSA, 8 Gelatin 48 and b-lactoglobulin (b-LG) 46 has been observed.…”

“…8,[46][47][48][49]56,57 It is stressed that in most of the investigations, SAILs without any functionalization of ionic head group or alkyl chain have been employed with the exception of few studies. 8,46,48 A contrasting complexation behavior of functionalized SAILs as compared to non-functionalized ones towards BSA, 8 Gelatin 48 and b-lactoglobulin (b-LG) 46 has been observed. Different types of SAILprotein complexes varying in morphology, internal structure and hydrophobicity etc., governed by the nature and extent of varying set of interactions has been observed.…”

“…Aer C 4(cmc) , I 1 /I 3 begin to rise in all the cases indicating a relative increase in the polarity of SAIL-BSA aggregates. It is quite probable that beyond C 4(cmc) , the forming micelles containing high surface charge8,46,48 disintegrate the respective SAIL-BSA ACs into smaller micelle bound/unbound ACs. A similarity in values of I 1 /I 3 in the absence and presence of BSA beyond C 4(cmc) supports the partition of pyrene into the micelle bound to ACs.3.2.3.…”

Correlating Lipid Membrane Permeabilities of Imidazolium Ionic Liquids with their Cytotoxicities on Yeast, Bacterial, and Mammalian Cells

“…The interactions between ILs in aqueous solution and lipid bilayer membranes have guided the development of IL-based drug formulation and drug-delivery applications [10,11,12,13,14,15,16,17,18,19,20] and opened research avenues for IL-based antibiotics and antibiotic-IL combinations. There have also been several reports highlighting both experimental and computational studies on how ILs interact with lipid bilayers [21,22].…”