Green synthesis of lignin nanoparticle in aqueous hydrotropic solution toward broadening the window for its processing and application

•A green and facile method for producing lignin nanoparticles (LNPs) was initiated.•LNPs can be produced in water with wide pH range at room temperature.•LNPs can be produced from varieties of lignin species with high yields.•The process can encapsulate various drugs with high efficiency.•The resultant drug-encapsulated LNPs can realize the sustained release.