Asymmetric water transport in dense leaf cuticles and cuticle-inspired compositionally graded membranes

Abstract

Most of the aerial organs of vascular plants are covered by a protective layer known as the cuticle, the main purpose of which is to limit transpirational water loss. Cuticles consist of an amphiphilic polyester matrix, polar polysaccharides that extend from the underlying epidermal cell wall and become less prominent towards the exterior, and hydrophobic waxes that dominate the surface. Here we report that the polarity gradient caused by this architecture renders the transport of water through astomatous olive and ivy leaf cuticles directional and that the permeation is regulated by the hydration level of the cutin-rich outer cuticular layer. We further report artificial nanocomposite membranes that are inspired by the cuticles’ compositionally graded architecture and consist of hydrophilic cellulose nanocrystals and a hydrophobic polymer. The structure and composition of these cuticle-inspired membranes can easily be varied and this enables a systematic investigation of the water transport mechanism.

Asymmetric Mass Transport through Dense Heterogeneous Polymer Membranes: Fundamental Principles, Lessons from Nature, and Artificial Systems

“…Adapted under the terms of the CC-BY license. [19] Copyright 2021, The Authors, published by Springer Nature. e) Preparation of bi-and multi-layer dense membranes using preformed layers and thermal and/or mechanical treatment methods (e.g., overmolding, calendaring, roll-to-roll processes, lamination, compression molding).…”

“…[37,38] In addition to these methods, our group demonstrated recently that compositionally graded nanocomposite membrane architectures can be prepared by using a simple solvent casting-evaporation process, which exploits the colloidal instability of cellulose nanocrystals (CNCs) in the utilized casting solvent (see schematic Figure 3d). [19,20,74] More specifically, mixtures of poly(styrene)block-poly(butadiene)-block-poly(styrene) (SBS) and CNCs were cast from tetrahydrofuran resulting in transversal compositional gradients of the CNC filler in the SBS matrix. [19,20,74] This method allowed us to tune the distribution of CNCs along the transversal direction of the membranes and regulate directionally the transport of water (Figure 6), but also ethanol.…”

“…[25,27,28] According to membrane theory, compositional and/or structural gradients in the transversal direction of the membrane may result in asymmetric permeation properties. [11][12][13][14][15][16]29,30] Such gradients of inhomogeneity may be structural and/or compositional and are commonly found in many living organisms, [17][18][19][31][32][33][34][35] including plants and insects. [17][18][19]35] Asymmetric mass transport, also known as "valve effect", [12,36] "anisotropic flow", [37,38] "vectorized flow", [37,39,40] "flow reversal" effect, [11,16,41] and "directional transport", [11,42] means that the permeation rate of chemical species diffusing under the same conditions (driving force, temperature, etc.)…”

“…Efforts to develop a better understanding of the principles that govern the often quite complex transport characteristics of biological membranes, and attempts to utilize this knowledge to create artificial counterparts have seen a recent surge. [2,19,20] This thrive is in part related to the burgeoning interest in developing bio-inspired materials, and in part driven by the realization that asymmetric membranes remain underexploited. While efforts to develop porous "Janus-like" membranes have been recently reviewed, [21][22][23][24] the state of the art as it pertains to biological and artificial dense membranes with asymmetric structure has yet to be summarized.…”

Mechanical Performances of Isolated Cuticles Along Tomato Fruit Growth and Ripening

“…In the literature, there is a limited number of DMA studies on this topic. Some of them were performed with apple cortex tissues (Videcoq et al, 2017) and tomato fruit peels (Wang et al, 2014;Vidyarthi et al, 2020), others with isolated cuticles of persimmon fruits and olive and ivy leaves (Tsubaki et al, 2013;Kamtsikakis et al, 2021). However, to our knowledge, no results using isolated tomato cuticles have been published yet.…”