A method of marking an inventory item includes providing an activatable smoke generator and a reservoir for holding a smoke fluid and adapted to provide a flow of smoke fluid to the generator. The reservoir contains a smoke fluid including a carrier nucleic acid having a uniquely identifiable sequence, and upon activation of the smoke generator, marker smoke is generated and targeted to flow over the inventory item. The method further includes activating the smoke generator to produce the marker smoke including the carrier nucleic acid so as to cause the marker smoke to flow over the inventory item and thereby to detectably mark the inventory item with carrier nucleic acid. The invention provides methods for stably binding and immobilizing deoxyribonucleic acid onto objects and substrates. The method includes exposing the deoxyribonucleic acid to alkaline conditions, and contacting the deoxyribonucleic acid to the object or substrate. The alkaline conditions are produced by mixing the deoxyribonucleic acid with an alkaline solution having a pH of about 9.0 or higher, and contacting the deoxyribonucleic acid to the substrate. The immobilized DNA can be used as a taggant and can be used in combination with other detectable taggants, such as optical reporters.