Template-mediated synthesis and bio-functionalization of flexible lignin-based nanotubes and nanowires

Abstract

Limitations of cylindrical carbon nanotubes based on the buckminsterfullerene structure as delivery vehicles for therapeutic agents include their chemical inertness, sharp edges and toxicological concerns. As an alternative, we have developed lignin-based nanotubes synthesized in a sacrificial template of commercially available alumina membranes. Lignin is a complex phenolic plant cell wall polymer that is generated as a waste product from paper mills and biorefineries that process lignocellulosic biomass into fuels and chemicals. We covalently linked isolated lignin to the inner walls of activated alumina membranes and then added layers of dehydrogenation polymer onto this base layer via a peroxidase-catalyzed reaction. By using phenolic monomers displaying different reactivities, we were able to change the thickness of the polymer layer deposited within the pores, resulting in the synthesis of nanotubes with a wall thickness of approximately 15 nm or nanowires with a nominal diameter of 200 nm. These novel nanotubes are flexible and can be bio-functionalized easily and specifically, as shown by in vitro assays with biotin and Concanavalin A. Together with their intrinsic optical properties, which can also be varied as a function of their chemical composition, these lignin-based nanotubes are expected to enable a variety of new applications including as delivery systems that can be easily localized and imaged after uptake by living cells.

Recent Advances in Nanomaterials for Gene Delivery—A Review

“…Since lignin can be formed from different monolignols, there is considerable variation in lignin structure across plant species and among tissues and developmental stages within a given species. Caicedo et al [122] developed a method to synthesize lignin-based nanotubes (LNTs) and nanowires using an alumina membrane as a sacrificial template. After showing the ability of DNA to adsorb onto LNTs, Ten et al [123] demonstrated the potential of LNTs to be used as a gene delivery vector.…”

“…Western analysis showed that the pDNA encoding GFP that was carried by the LNTs was expressed. The combined results suggest that various properties of LNTs can be fine-tuned by selecting the source of the lignin and synthesis conditions [122,123]. …”

Lignin from Micro- to Nanosize: Production Methods

“…Caicedo et al [100] and Ten et al . [101] used sacrificial alumina membranes with a nominal pore diameter of 200 nm as a template for the synthesis of lignin-based nanotubes and nanowires.…”

Functionalized Polymers from Lignocellulosic Biomass: State of the Art

“…One of the challenges associated with these types of nanotubes, however, is their chemical inertness and sharp, needle-like shape that can mimic asbestos [233,234]. The production of nanotubes derived from lignin, as described by Caicedo et al [235], may overcome some of these challenges (Figure 10). A template-mediated synthesis protocol was developed in which a lignin base layer was cross-linked to an alumina membrane, followed by peroxidase-mediated addition of dehydrogenation polymer ("synthetic lignin").…”