Adhesive Vesicles through Adaptive Response of a Biobased Surfactant

Abstract

Adaptive response in functional systems of nature is best exemplified by the homeostasis (homeoviscous alterations) or the tropism observed in flora and fauna. The term "homeoviscous alteration" describes the process whereby the fluidity of the membrane is adjusted in response to a perturbation such as temperature, pressure, etc. [1,2] Most of the natural lipids utilize their characteristic unsaturations as a tool to execute such elegant processes. The biophysical properties of the membranes thus depend on the subtle adjustments in the structure and composition of the alkyl chains that are attached to glycerol backbones. [3] Chilling sensitivity in plants is the direct repercussion of the membrane dynamics in plants that involves conformational changes and variations in unsaturation component of the lipid membranes.[4] Deciphering the stimuli-responsive character in such biological systems not only sheds light on the underlying mechanism in the race for survival of the fittest, but also provides clues to generate unique functional materials in the laboratory. Amphiphilic molecules rich in unsaturations in their side chain are expected to display such interesting phenomena and provide vistas for new soft materials.[5] Taking cue from this, we designed an amphiphile from a naturally available raw material-cardanol-that possesses structural features akin to natural lipidic systems.Cardanol is a biobased non-isoprene lipid obtained from cashew nut shell liquid (CNSL). It consists of a rich mixture of phenolic lipids: 5 % of 3-(pentadecyl)phenol, 49 % of 3-(8Z-pentadecenyl)phenol, 17 % of 3-(8Z,11Z-pentadecadienyl)-phenol and 29 % of 3-(8Z,11Z,14-pentadecatrienyl)phenol. [6] The unique feature of cardanol is that it contains 1) lipid chains with varying degree of allylic cis double bonds, 2) alkyl chains with odd numbers of carbon atoms, 3) a reactive phenolic group in the meta position for further functionalization, and 4) saturated/unsaturated versions of hydrocarbon chains. Hence one can envision an amphiphilic building block from cardanol, which show a stimuli-responsive behavior that could be utilized to reconfigure them into functional architectures. Herein, we report vesicle formation and vesicular adhesion from a biobased surfactant, N-cardanyl tauramide (NCT), obtained by the judicious combination of cardanol as the hydrophobic part and taurine (a vital aminosulfonic acid) as the hydrophilic head group. The molecular structure of NCT is shown in Figure 1 c.NCT behaved as a surfactant in aqueous solution with a critical micelle concentration (CMC) of 1.2 mm at 25 8C. Typically, when a 5 mm micellar solution was warmed to 55 8C and annealed, the solution transformed into a viscous phase at 45 8C with a restricted flow. Upon reaching room temperature, the solution resumed back to the micellar phase. Interestingly, the viscous phase appeared elastic and could be pulled into a "wet string" (Figure 1 d). In order to understand this behavior, we performed a cryo-TEM analysis of the sample at 45 8C in the cooling ...

Functionalization of cardanol: towards biobased polymers and additives

“…157,158 The authors reported that the presence of several CH 2 groups was signicant for micelle formation. Balachandran et al 159 described the vesicle formation and vesicular adhesion from a cardanol-based surfactant, N-cardanyl tauramide (NCT) (Fig. 9, S7), obtained by the judicious combination of cardanol as the hydrophobic part and taurine (a vital aminosulfonic acid) as the hydrophilic head group.…”

Recent advances in cardanol chemistry in a nutshell: from a nut to nanomaterials

“…9). 46 An amide linker was used to facilitate hydrogen-bonded association. At room temperature, a 5 mM aqueous solution of NCT formed micellar aggregates of B8-10 nm diameter (Fig.…”

Functional self‐assembled lipidic systems derived from renewable resources

“…By introducing the aminosulfonic acid taurine into an amphiphilic cardanol system, the nature of the resultant self-assembled system changes [31]. The conditionally essential amino acid taurine facilitates a series of equilibrium processes in mammalian development and imparts similar functionality in micelle, vesicle, and bilayer assemblies of (2) cardanyl tauramide ( Fig.…”

“…Useful to the materials scientist is that the micelles possess distinctly different physical and chemical properties compared to the vesicles that form in heating the solution 30°above room temperature. To confirm the importance of the unsaturations, John et al synthesized an all trans conformation of the pentadecylphenol tauramide from which no viscous phase formed [31]. To recreate cardanol's specific lipid mixture in the lab would have been tedious and costly, and yet by using a naturally occurring mixtures, researchers were able to develop highly functional systems as capable as synthetic alternatives.…”