STRATEGIES AND INNOVATIVE APPROACHES DEVELOPED FOR THE ACTIVE TARGETING OF DRUGS

The ability to selectively deliver a drug to a specific organs or tissues is called “drug targetingâ€. This approach was initially reported by Paul Erlich describing a magic bullet able to act selectively towards a specific pharmacological target. In the pharmaceutical technology field the concept described by Ehrlich defines products able to selectively deliver and release the drug in a specific site thanks to the action of three components: i) an inert and water soluble polymeric carrier; ii) a biodegradable spacer linking polymer and drug; iii) a drug covalently linked to the spacer. Moreover, it is possible to add to the system a targeting agent that improve the targeting ability towards target cells reducing the nonspecific interaction of the system with normal ones. The active targeting is obtained through functionalization with portions that confer the ability to: i) recognize and specifically bind receptors overexpressed on the target cells or tissues (i.e. monoclonal antibodies or fragments, folate, transferrin); ii) be able to respond to local stimuli present in the pathological area; iii) allow the penetration of the drug into the target cells. The active targeting approach lead to an increased binding of the nanosystems to the specific site. The targeting ability is obtained thanks to the interaction of the targeting agents with specific antigens or receptors overexpressed on the target cells or tissues. The active targeted nanocarriers are characterized by increased drug uptake and reduced side effects.