Cellular Flocculation Driven by Concentrated Polymer Brush-Modified Cellulose Nanofibers with Different Surface Charges.

This study examined the effect of the surface charge of concentrated polymer brush (CPB)-grafted cellulose nanofibers (CNFs) on HepG2 cell flocculation. Four polyelectrolytes, poly(p-styrenesulfonic acid sodium salt) (PSSNa), poly(acrylic acid) (PAA), poly(2-(dimethylamino)ethyl methacrylate) (PDMAEMA), and poly([(2-methacryloyloxy)ethyl]trimethylammonium chloride) (PMTAC), were grafted onto the CNF surface via surface-initiated atom transfer radical polymerization to form CNF-CPBs. The floc size of HepG2 cells depended on the surface charge of CNF-CPBs, where the anionic CNF-PSSNa formed larger flocs than CNF-PAA; due to the electrostatic repulsive forces, CNF-CPBs with a lower ζ-potential yielded smaller floc sizes. Contrastingly, the cytotoxic cationic CNF-PDMAEMA and CNF-PMTAC limited the floc size growth. Thus, appropriate electrostatic interactions are essential for floc formation and improved cell function in three-dimensional (3D) cell culture systems. Interestingly, while developing a novel 3D cell culture system, we reveal that colloidal flocculation theory is the driving mechanism behind this unique phenomenon.

Cellular Flocculation Using Concentrated Polymer Brush-Modified Cellulose Nanofibers with Different Fiber Lengths.

In this study, concentrated polymer brush-modified cellulose nanofibers (CNFs) with different fiber lengths were used for the flocculation of cells for systematically studying the mechanism of this unique cellular flocculation based on colloidal flocculation theory. Concentrated poly(p-styrenesulfonic acid sodium salt) brush-grafted CNF (CNF-PSSNa) with different fiber lengths were cultured with three different cell types to examine their influence on floc (cell clusters formed by cellular flocculation) characteristics. The floc size and survival rate could be controlled by modifying the CNF-PSSNa fiber lengths. The three cell types showed the same flocculation tendency after culture, indicating the applicability of the method in different cell lines. After 2 weeks of culture, CNF-PSSNa increased the specific expression of hepatocytes compared to the two-dimensional cell culture. Thus, owing to its wide applicability, high cell viability, and ability to control cell size and improve cell function, this technology could be used as a new three-dimensional cell culture method.

Controlling the degradation of cellulose scaffolds with Malaprade oxidation for tissue engineering.

This study was conducted to develop biodegradable cellulose scaffolds by oxidising porous cellulose sponges for tissue engineering applications. Cellulose powder was dissolved in ionic liquid using a salt leaching method, and porous cellulose scaffolds of various pore sizes were prepared. The scaffolds were oxidised with periodate to introduce aldehyde at a rate controlled by the periodate concentration. Oxidised scaffolds exhibited weight loss in cell culture medium, but not in phosphate buffer. Therefore, we confirmed that Schiff base formation between the aldehyde and amino groups through a Maillard reaction triggered cellulose molecular degradation. The degradation rate was controlled by the oxidation degree, whereas the aldehyde content controlled protein adsorption and cell proliferation. Additionally, in vivo implantation tests revealed that optimising the oxidation ratio not only improved biodegradability but also reduced inflammation. In conclusion, our results suggest that simple oxidised cellulose is useful as a low-toxicity biodegradable scaffold.