Construction of high strength hollow fibers by self-assembly of a stiff polysaccharide with short branches in water

Abstract

The development of biological high-performance materials fabricated from natural polysaccharides has attracted great attention for a sustainable world. In this work, hollow fibers with high strength were spun from a polysaccharide aqueous solution at a concentration of 0.02 g mL⁻¹. The polysaccharide was a comb-like β-glucan with short branches isolated from Auricularia auricula-judae, coded as AF1. Atomic force microscopy (AFM) and transmission electron microscopy (TEM) confirmed directly that AF1 existed as a stiff chain conformation in water, and displayed parallel self-orientation behavior. AF1 could self-assemble into well defined hollow nanofibers with diameters less than 100 nm and lengths of tens of micrometers in dilute solution, supported by scanning electron microscopy (SEM). Moreover, AF1 in the disulfonated tetraphenylethene (TPE-SO₃Na) aqueous solution exhibited strong luminescence, indicating that the TPE-SO₃Na molecules without luminescence in water were trapped in the cavities of the hollow nanofibers through hydrophobic interactions, leading to the aggregation-induced emission (AIE). The nanofibers were composed of relatively hydrophobic inner-walls and hydrophilic shells in water. Interestingly, SEM and polarized light microscopy verified that the nanofibers fused to form an ordered architecture of lamella and then tended to curl into hollow fibers in relatively concentrated solution. The hollow fibers exhibited excellent tensile strength, biocompatibility, organic solvent resistance and birefringence. A schematic model was proposed to describe the construction of the hollow fibers via the hierarchical self-assembly process. The new materials would have potential applications such as drug release as a new class of fibrous carrier, indicators with fluorescence to detect cell growth in cell transplantation, and biomolecular recognition (e.g., DNA).