Pluronic F‐127: An Efficient Delivery Vehicle for 3‐(1’‐hexyloxy)ethyl‐3‐devinylpyropheophorbide‐a (HPPH or Photochlor)

: To determine the impact of delivery vehicles in photosensitizing efficacy of HPPH, a hydrophobic photosensitizer was dissolved in various formulations: 1% Tween 80/5% dextrose, Pluronic P-123 and Pluronic F-127 in 0.5, 1 and 2% phosphate buffer solutions (PBS). HPPH was also conjugated to Pluronic F-127 and the resulting conjugate (PL-20) was formulated in PBS. Among the different delivery vehicles, only Pluronic P-123 displayed significant vehicle cytotoxicity whereas Pluronic F127 was non-toxic. Compared to PL-20, HPPH formulated in Tween80 and Pluronic F-127 showed higher cell-uptake, but lower long term retention in Colon26 cell compared to PL-20. The higher retention of PL-20 was similarly observed during in vivo uptake with BALB/c mice baring Ct26 tumors. In contrast to the in vitro uptake experiments, PL-20 showed slightly higher uptake compared to HPPH formulated in Tween or Pluronic-F127. A significant difference in pharmacokinetic profile was also observed between the HPPHPluronic formulation and PL-20. Under similar in vivo treatment parameters (drug dose 0.47 µmol/kg, light dose: 135 J/cm2 at 24 h post-injection of PS), HPPH formulated either in Tween or Pluronic F-127 formulation showed similar in vivo PDT efficacy (20-30% tumor cure on day 60), whereas PL-20 showed 40% tumor cure (day 60).