The culture supernatants were centrifuged successively at increasing speeds: 3,000 × g for 20 min, 20,000 × g for 30 min, and 120,000 × g for 2 h (Beckman Optima L-100XP, USA) to obtain SCAP-Exo. The small RNA libraries were prepared from a total of 2µg total RNA isolated from each sample using NEBN ex芒Multiplex Small RNA Library Prep Set for Illumina® (NEB, USA.) according to the manufacturer's instruction