{'fraction_non_alphanumeric': 0.04916732751784298, 'fraction_numerical': 0.004758128469468675, 'mean_word_length': 6.011111111111111, 'pattern_counts': {'":': 0, '<': 0, '<?xml version=': 0, '>': 0, 'https://': 0, 'lorem ipsum': 0, 'www.': 0, 'xml': 0}, 'pii_count': 0, 'substrings_counts': 0, 'word_list_counts': {'cursed_substrings.json': 0, 'profanity_word_list.json': 0, 'sexual_word_list.json': 0, 'zh_pornsignals.json': 0}}
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.