Synthesis of Au/lignin–tannin particles and their anticancer application

Gold (Au) nanoparticles are widely adopted as nonbiological-toxic and biocompatible biomaterials. In this study, Au nanoparticles supported on lignin–tannin (LT) micro-/nanoparticles were prepared via a green and novel method without the use of an additional reducing agent. Soluble lignin oligomers and tannin were first obtained from H2O–tetrahydrofuran (THF) solvothermal treatment of the corncob residue and bayberry bark, which are industrial and forestry wastes of biomass, respectively. With outstanding self-assembly capability, the lignin oligomers induced the co-self-assembly of tannins into LT particles considerably, which enhanced the density of ortho-phenolic hydroxyls on the hydrophilic shell. Consequently, Au3+ can be stabilized and subsequently reduced into Au0 particles that were highly dispersed on the LT particles. Upon increasing the proportion of tannins, the amount of Au species on LT particles and the Au0/Aun+ ratio increased, accompanied by the inferior thermal stability of the particles. In addition, the as-prepared Au/LT particles can be taken up by cells and can reduce the vitality of several cancer cells, indicating a potential biotherapy application.