Cellulose nanocrystals (CNCs) are emerging nanomaterials with a large range of potential applications. CNCs are typically produced through acid hydrolysis with sulfuric acid; however, phosphoric acid has the advantage of generating CNCs with higher thermal stability. This paper presents a design of experiments approach to optimize the hydrolysis of CNCs from cotton with phosphoric acid. Hydrolysis time, temperature and acid concentration were varied across nine experiments and a linear least-squares regression analysis was applied to understand the effects of these parameters on CNC properties. In all but one case, rod-shaped nanoparticles with a high degree of crystallinity and thermal stability were produced. A statistical model was generated to predict CNC length, and trends in phosphate content and zeta potential were elucidated. The CNC length could be tuned over a relatively large range (238-475 nm) and the polydispersity could be narrowed most effectively by increasing the hydrolysis temperature and acid concentration. The CNC phosphate content was most affected by hydrolysis temperature and time; however, the charge density and colloidal stability were considered low compared with sulfuric acid hydrolysed CNCs. This study provides insight into weak acid hydrolysis and proposes 'design rules' for CNCs with improved size uniformity and charge density.This article is part of a discussion meeting issue 'New horizons for cellulose nanotechnology'.
In this work, we report the development of a general strategy for enhancing the efficiency of target capture in immunoassays, using a bifunctional fusion protein construct which incorporates a substrate-anchoring moiety for the high-abundance immobilization of an antigen-binding domain. This approach was informed by the development of a pseudo first-order rate constant model, and tested in a paper-based assay format using a fusion construct consisting of an rcSso7d binding module and a cellulose-binding domain. These rcSso7d-CBD fusion proteins were solubly expressed and purified from bacteria in high molar yields, and enable oriented, high-density adsorption of the rcSso7d binding species to unmodified cellulose within a 30-second incubation period. These findings were validated using two distinct, antigen-specific rcSso7d variants, which were isolated from a yeast surface display library via flow cytometry. Up to 1.6 micromoles of rcSso7d-CBD was found to adsorb per gram of cellulose, yielding a volume-averaged binder concentration of up to 760μM within the resulting active material. At this molar abundance, the target antigen is captured from solution with nearly 100% efficiency, maximizing the attainable sensitivity for any given diagnostic system.
Cellulose nanocrystals (CNCs) are rigid rodlike nanoparticles that are derived from natural cellulose. Their high surface area, mechanical strength, and noncytotoxicity have elicited interest in their use for various applications, including composite and construction materials, cosmetic, food, and biomedical products. However, few methods exist to control the morphology and dimensions of assembled CNC structures in the micrometer range. Here, we use water-in-oil droplet microfluidics to template uniform spherical CNC droplets in a nontoxic and sustainable manner. Subsequent evaporation of the water within the droplets promotes the chemical crosslinking of surface-modified CNCs, resulting in ultraporous and flexible micrometer-sized particles. Changing the size of the microfluidic channel or the concentration of the CNC suspension results in microparticles with tunable sizes. The microparticles swell in polar solvents, with larger swelling observed for microparticles fabricated from less-concentrated CNC suspensions. While swelling is pH-independent, it is impacted by ionic strength for microparticles with low cross-link densities. Scanning electron microscopy reveals that the microparticles have macropores and mesopores, supporting a large specific surface area. These porous microparticles have potential for a range of applications, such as drug delivery or sorption agents, or as biodegradable beads for use in cosmetic and food applications.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.