Effect of chelation to lanthanum ions on the photodynamic properties of hypocrellin A

Hypocrellin A (HA), an efficient phototherapeutic agent, can chelate with lanthanum ion to form a 1:1 complex, which exhibits enhanced (super 1)O2 generation yield, a red-shifted absorption window greatly improved water solubility, a much lengthened triplet excited state lifetime, and an increased affinity to DNA with respect to HA. The effects in turn lead to a more potent photodamage ability on calf thymus DNA for La(super 3+)-HA in both aerobic and anaerobic conditions, indicating the potential application of La(super 3+) HA in the field of photodynamic therapy.