Adenosine triphosphate (ATP) is the most abundant and primary carrier of the required energy for various functions in cells. Prolonged ischemia, reperfusion, anaerobic metabolism and lactate accumulation can lead to a dramatic decrease of ATP, cell swelling, cell rupture, and finally cell death by necrotic, necroptotic, apoptotic, and autophagic mechanisms. Due to drastic hydrolysis of ATP in vivo by ectoenzymes and poor cellular penetration, the direct delivery of ATP to the ischemic tissues is difficult.

To increase delivery of ATP to the tissues and protect from enzymatic degradation, encapsulation in liposomes has been proposed and demonstrated in various models of ischemia [1,2]. Studies on myocardial [1,3,4], liver [5-8], retina [9] and wound healing [10-12] ischemia have shown the ability of liposomal encapsulated ATP to prevent cell death and tissue dysfunction following ischemic events.

The encapsulation of ATP in liposomes markedly promotes its effectiveness by preventing the hydrolysis by extracellular enzymes, increasing ATP circulation time and enhancing its intracellular penetration. Depending on the type of the cell line and the target organ various types of liposomes with different surface charges such as anionic, cationic and neutral has been studied by various groups. Moreover, ATP encapsulated liposomes has been demonstrated to improve energy state and function of the cold-stored liver [6,7,13].