Synthetic Strategies for the Fabrication of Cationic Surface-Modified Cellulose Nanocrystals

Abstract

Cellulose nanocrystals (CNCs) are renewable nanosized materials with exceptional physicochemical properties that continue to garner a high level of attention in both industry and academia for their potential high-end material applications. These rod-shaped CNCs are appealing due to their non-toxic, carbohydrate-based chemical structure, large surface area, and the presence of ample surface hydroxyl groups for chemical surface modifications. CNCs, generally prepared from sulfuric acid-mediated hydrolysis of native cellulose, display an anionic surface that has been exploited for a number of applications. However, several recent studies showed the importance of CNCs' surface charge reversal towards the design of functional cationic CNCs. Cationization of CNCs could further open up other innovative applications, in particular, bioapplications such as gene and drug delivery, vaccine adjuvants, and tissue engineering. This mini-review focuses mainly on the recent covalent synthetic methods for the design and fabrication of cationic CNCs as well as their potential bioapplications.

Highly Charged Cellulose Nanocrystals Applied as A Water Treatment Flocculant

“…CNC etherification was achieved via alkaline hydrolysis. A basic medium was required for the activation of the hydroxyl groups as well as for cleavage of the sulfate half-ester groups in order to ensure the pure cationic nature, at the same time CHPTAC formed the reactive epoxy functional group EPTMAC [22]. As a result, a nucleophilic reaction between the alkali group (-OH) of the CNCs and the EPTMAC epoxy group occurred, yielding CNC-EPTMAC (Figure 1).…”

Synthesis and Cytotoxicity Studies of Wood-Based Cationic Cellulose Nanocrystals as Potential Immunomodulators

“…The emerging interest in CNCs for biomedical purposes led us to synthesize a novel functionalized series of wood-based CNCs possessing surface positive charges with potential immunomodulatory activities that could hopefully be further developed in newly engineered vaccine nanoadjuvants. For applications that required a positively charged CNCs surface, synthetic routes for cationization of CNCs were developed such as nucleophilic ring-opening of epoxide, esterification, copper(I)-catalyzed 1,3-cycloaddition and surface initiated-atom transfer radical polymerization [17][18][19][20][21][22]. In this work, we reported the design, synthesis, characterization and cytotoxicity of wood-based cationic CNCs as potential immunomodulators.…”

Emerging development of nanocellulose as an antimicrobial material: an overview

“…There are several other compounds, such as small organic molecules, polymers, dendrimers and porphyrin, that can be functionalized with nanocellulose to make it positively or negatively-charged. 53 However, not all of these examples have been tested as a filter against viruses.…”