The disposable plastic syringes are best sterilised by:

Ethylene oxide: Ethylene oxide is a colorless liquid used for gaseous sterilization. It is active against all kinds of bacteria, spores, and viruses. It kills all types of microorganisms by inhibiting proteins and nucleic acids. It is both microbicidal and sporicidal. It is a highly effective sterilizing agent because it rapidly penetrates packing materials, including plastic wraps. It is used to sterilize disposable plastic Petri dishes, sutures, syringes, heart-lung machine, respirators, and dental equipments. Ethylene oxide is highly inflammable and carcinogenic. Extensive aeration of the sterilized materials is necessary to remove residual ethylene oxide gas, which is toxic. Parija SC. Textbook of Microbiology & Immunology. Elsevier Health Sciences; 2014. Page: 32