delivering nitric oxide to a treatment site , such as in the area of an implanted stent , over a period of hours or days is desirable ; however , the storage and release of nitric oxide in medically - relevant situations and amounts is a challenge , in part due to the gaseous nature of nitric oxide and its instability in the presence of oxygen . the present invention provides a method of preparing compositions of matter , particularly those comprising nanotubules , containing nitric oxide or gases with nitric oxide - like biological activity , where the gas is non - covalently bound to the composition . these compositions allow for the storage of nitric oxide or a related gas , followed by controlled release of the gas . compositions disclosed in the present invention include polymers , articles , pills , capsules , and medical devices .