PAMAM dendrimers as solubilizers and hosts for 8-methoxypsoralene enabling transdermal diffusion of the guest

Abstract PAMAM dendrimers form host–guest complexes with 8-methoxypsoralene (8-MOP) – the photosensitizer for PUVA therapy. The stoichiometry of complexes was studied by 1 H NMR spectroscopy in solution and by differential scanning calorimetry in neat mixtures containing 8-MOP and dendrimers of generations G2.5 , G3 , G3.5 , and G4 . The dendrimers showed solubilization effect for 8-MOP resulting in increase of 8-MOP concentration in methanol up to 15 molecules of 8-MOP per G2.5 and G3 and 30 molecules of 8-MOP per G3.5 , and G4 . Isolation of oily host–guest complexes containing 3 or 7 molecules of 8-MOP per G3 and G4 , respectively corroborate well with DSC results; glass transition temperature of neat host–guest complexes increases with number of host molecules in comparison with G3 or G4 , until the capacity of host is exceeded. The oily host–guest complexes of stoichiometry 3:1 and 7:1 of 8-MOP to G3 and G4 , respectively are well soluble in water. The 3:1 host–guest complexes diffused slowly through polyvinyldifluoride and pig ear skin membranes, when released from o/w emulsion. The host–guest complex 8-MOP- G3 was proposed as convenient formulation for psoralene skin administration in PUVA therapy.