Patterned Cellulose Nanocrystal Aerogel Films with Tunable Dimensions and Morphologies as Ultra-Porous Scaffolds for Cell Culture

Abstract

Aerogel films are interesting as coatings due to their unique properties including high surface area, sorption capacity and insulating properties. To date, silica-based aerogel films have been most widely explored due to their ultrahigh surface areas and well-known chemistry. However, the fragile nature of silica aerogels coupled with the limited control over film thickness and dimensions when using traditional deposition techniques limits their use in applications requiring films with good mechanical stability (e.g., in flexible devices). To address these challenges, we present a pressure-aided freeze casting method to pattern, on a variety of substrates (e.g., glass or flexible polyethylene terephthalate), mechanically robust aerogel films composed of covalently cross-linked cellulose nanocrystals (CNCs) with controlled dimensions and internal morphology. To accomplish this, a film of the desired aerogel thickness was deposited on the substrate and a mold with the specific shape for the aerogel was fabricated by xurography (>1 mm lateral dimensions, 7–85 μm thickness) or photolithography (2–500 μm lateral dimensions, 3 μm thickness). An aqueous gel of reactive CNCs or CNCs with poly­(oligoethylene-glycol-methacrylate) was drop cast onto the substrate, and pressure was applied so that the gel adopted the mold shape. The gel was subsequently frozen and lyophilized, and the mold was lifted off the substrate, leaving behind patterned porous aerogel films, which were first explored as cell culture scaffolds. Human prostate cancer cells strongly adhered to the aerogels, where individual cells could be isolated on small aerogel arrays while cell clusters were obtained on larger arrays. This system has potential applications in studying single-cell phenotype and developing miniaturized cell-based assays. The simplicity of this freeze casting and lift-off patterning technique makes it attractive for the fabrication of cellulose-nanocrystal-based aerogels with a variety of compositions for applications requiring materials with high surface area, low density, and good mechanical stability.

Cellulose Nanocrystal Aerogels as Electrolyte Scaffolds for Glass and Plastic Dye-Sensitized Solar Cells

“…Aerogel films (1 wt % sol–gel concentration, 1:1 aCNC:hPOEGMA weight ratio) were patterned onto the counter electrodes by using a recently developed pressure-aided freeze casting technique. 40 Briefly, FTO-coated glass was cleaned with piranha solution (5:1 H 2 SO 4 :H 2 O 2 v/v) for 15 min at 110 °C while ITO-coated PET was cleaned by using UV-ozone (Novascane, Boone, IA) for 2 h to remove organic residue. A 20 nm thick catalytic Pt layer was sputtered onto the counter electrodes by using a Torr Compact Research Coater CRC-600 manual planar magnetron sputtering system (Torr International, New Window, NY).…”

Mechanically tunable elastomer and cellulose nanocrystal composites as scaffolds for in vitro cell studies

“…44,46,47 Cellulose and its derivatives', specifically CNCs, mechanical properties improve stiffness and strength of polymer composites promoting the creation of novel polymer nanocomposites and lubricants 48,49 or improving shape memory effects of polymer matrices. 50 In addition to synthetic polymers, chemically modified cellulose derivatives such as cellulose acetate, hydroxypropyl cellulose, and carboxymethyl cellulose have been used as additives for functional biomaterials to create films, membranes, electrospun into nanofibers 51 as well as formed into aerogel films, 52 hydrogels, 53 and three-dimensional porous foams. 54,55,56,57 Fernandes et al presented several studies that showed cellulose and its derivatives are biocompatible and have tunable biodegradable properties.…”

Synthesis of Nanocellulose Aerogels and Cu-BTC/Nanocellulose Aerogel Composites for Adsorption of Organic Dyes and Heavy Metal Ions

“…Aerogels are ultra-low-density [33], dry, and very porous monolithic materials [34] taken from a gel composed of nanoparticles or polymers that chemically or physically cross-linked to a three-dimensional network [35]. Typically there are two stages for the synthesis of these materials, which are, rst, the formation of wet-gels through the process of sol-gel [36], and then drying the obtained gels using a method that keeps the internal porous morphology as possible [35] [37]. The aerogel, rst synthesized in the late 1930s by Kistler [38], can be inorganic [39], organic [40], and hybrid [41] aerogels according to their composition [42].…”