Reducing end thiol-modified nanocellulose: Bottom-up enzymatic synthesis and use for templated assembly of silver nanoparticles into biocidal composite material

Nanoparticle-polymer composites are important functional materials but structural control of their assembly is challenging. Owing to its crystalline internal structure and tunable nanoscale morphology, cellulose is promising polymer scaffold for templating such composite materials. Here, we show bottom-up synthesis of reducing end thiol-modified cellulose chains by iterative bi-enzymatic beta-1,4-glycosylation of 1-thio-beta-D-glucose (10 mM), to a degree of polymerization of similar to 8 and in a yield of similar to 41% on the donor substrate (alpha-D-glucose 1-phosphate, 100 mM). Synthetic cellulose oligomers self-assemble into highly ordered crystalline (cellulose allomorph II) material showing long (micrometers) and thin nanosheet-like morphologies, with thickness of 5-7 nm. Silver nanoparticles were attached selectively and well dispersed on the surface of the thiol-modified cellulose, in excellent yield (>= 95%) and high loading efficiency (similar to 2.2 g silver/g thiol-cellulose). Examined against Escherichia coli and Staphylococcus aureus, surface-patterned nanoparticles show excellent biocidal activity. Bottom-up approach by chemical design to a functional cellulose nanocomposite is presented. Synthetic thiol-containing nanocellulose can expand the scope of top-down produced cellulose materials.

Automated summary

This research demonstrated the bottom-up synthesis of reducing end thiol-modified cellulose chains for the preparation of highly ordered cellulose-silver nanocomposite materials with excellent antibacterial activity. The synthetic thiol-containing nanocellulose can expand the scope of cellulose materials produced through top-down approaches.