Extraction, preparation and characterization of cellulose nanofibers from Coix lacryma-jobi L. straw

In China, agricultural waste such as plant straw is frequently burned or buried, generating significant pollution. Urgent reuse is required, notably for Coix lacryma-jobi L. – a medicinal-edible herb whose straw may contain valuable bioactive compounds. In this study, we employed Coix lacryma-jobi L. straw (CS) as a novel source for the preparation of cellulose nanofibers (CNFs) via chemical methods, which was further characterized using SEM, TEM, FTIR, TGA and XRD, and the biocompatibility, biosafety and bioactivity of CS-CNFs were also systematically evaluated. The average diameter of produced CS-CNFs was (7.95 ± 2.67) nm, average length was (405.30 ± 109.40) nm. Hemicellulose and lignin were gradually removed after different stages of treatment. The crystallinity index progressively increased to (68.1 ± 1.6) % following successive treatments. The CS-CNFs showed excellent biocompatibility and biosafety within the assayed concentration range (10–200 µg/mL). Their hemolysis ratio was below 3.8%, and could promote migration and proliferation of L-929 cells with a cell migration rate of (88.1 ± 3.1) % when incubated with 10 μg/mL CS-CNFs for 72 h. The colony number of CS-CNFs at concentrations of 200 μg/mL was 305 ± 13.1, compared with the control group (234 ± 14.0). In addition, 1 wt% CS-CNFs showed the potential to inhibit the growth of S. aureus, E. coli and P. aeruginosa. More importantly, CS-CNFs at a concentration of 200 µg/mL could reduce the release of inflammatory factor NO. The study paved a promising approach to reutilize the biomass agricultural wastes from CS for biomedical applications, especially in the field of wound dressings.

Graphical abstract