One approach to developing targeted therapies is to co-opt existing biological structures, such as cells and bacteria: "Scientists have developed bacteria that serve as mobile pharmaceutical factories, both producing disease-fighting substances and delivering the potentially life-saving cargo to diseased areas of the body. ... [Researchers] chose the term 'bacterial dirigibles' because the modified bacteria actually have the fat-cigar look of blimps and zeppelins, those famous airships of yesteryear. ... We're building a platform that could allow bacterial dirigibles to be the next-generation disease fighters. ... traditional genetic engineering reprograms bacteria so that they produce antibiotics, insulin, and other medicines and materials. The bacteria grow in nutrient solutions in enormous stainless steel vats in factories. They release antibiotics or insulin into vats, and technicians harvest the medicine for processing and eventual use in people. The bacterial dirigible approach takes bioengineering a step further. Scientists genetically modify bacteria to produce a medicine or another disease-fighting substance. Then, however, they give the bacteria a biochemical delivery address, which is the locale of the disease. Swallowed or injected into the body, the bacteria travel to the diseased tissue and start producing substances to fight the disease. ... We have created a genetic circuit that endows E. coli with targeting, sensing and switching capabilities. ... The 'targeting' molecule is attached to the outer surface of the bacteria. It gives the bacteria an ability to 'hone in' on specific cells and attach to them - in this instance, the intestinal cells where other strains of E. coli cause food poisoning symptoms. Inside the bacteria is a gene segment that acts as 'nanofactory.' It uses the bacteria's natural cellular machinery to make drugs, such as those that can fight bacterial infections, viruses, and cancer. The nanofactory also could produce signaling molecules that enable the dirigible to communicate with natural bacteria at the site of an infection. Some bacteria engage in a biochemical chit-chat, termed 'quorum sensing,' in which they coordinate the activities needed to establish an infection. Bacteria dirigibles could produce their own signaling molecules that disrupt quorum sensing."