Evaluation of temoporfin affinity to β-cyclodextrins assuming self-aggregation

Abstract The interaction between the potent photosensitizer meta -tetrakis(3-hydroxyphenyl)chlorin (temoporfin, mTHPC) and a series of β-cyclodextrins (β-CDs) was investigated using spectroscopic analysis and molecular dynamics simulations. The possibility of improving its poor aqueous solubility with β-CDs was estimated by measuring both equilibrium solubility and association constants. Parameters of binding isotherms revealed that mTHPC strongly interacts with β-CD derivatives, forming 1:2 inclusion complexes in aqueous solution. We demonstrated that apparent binding constants strongly depend on mTHPC concentration due to the porphyrin self-aggregation. The estimated “correct” binding constants demonstrated that completely methylated β-CD exhibits the highest affinity (K = 1.1 × 10 7  M −1 ) as compared to randomly methylated β-CD (K = 7.1 × 10 5  M −1 ) and 2-hydroxypropyl substituted β-CD (K = 1.7 × 10 5  M −1 ). In fine , our results indicate that TM-β-CD should be considered as a potent vector for mTHPC targeted delivery.