A Study on the Photobleaching Effect of 5-ALA Conjugated Gold Nanoparticles in a CT26 Tumor Model During Photodynamic Therapy

Document Type : Original Paper


1 Department and Research Center of Medical Physics, Mashhad University of Medical Sciences, Mashhad, Iran

2 Medicinal Chemistry Department, Faculty of Pharmacy, Mashhad University of Medical Sciences, Mashhad, Iran

3 Electrical Engineering Department, Faculty of Engineering, Ferdowsi University of Mashhad, Mashhad, Iran


During the process photodynamic therapy (PDT), bleaching of photosensitizer induced by irradiation and generation of reactive oxygen species (ROS) can provide some information concerning the efficiency of treatment. Since gold nanoparticles (GNPs) have been highlighted as efficient drug delivery systems, in this study, by utilizing GNPs conjugated with 5 aminolevulinic acid (5-ALA-GNPs), the photobleaching of ALA-induced protoporphyrin IX (PpIX) was estimated on a colon carcinoma tumor model.
Materials and Methods
CT26 tumor models were prepared by subcutaneous injection of 5×105 cells into the right flank of Balb/c inbred mice. To estimate the time required to reach maximum concentration of PpIX in the tumors, the fluorescence signal of PpIX was monitored and PDT was performed by intratumoral injection of 5-ALA-GNPs, GNPs, and 5-ALA in separated groups for 15 min with a cycle of 5 min irradiation and 1 min darkness. The photobleaching rate was calculated from recorded fluorescence signals at the darkness intervals.
The maximum fluorescence of PpIX was recorded 3 and 5 hr after injection of 5-ALA and 5-ALA-GNPs, respectively. Despite the low PpIX accumulation in tumors receiving conjugate, the photobleaching rate of PpIX was determined to be higher than 5-ALA. The reduction of the fluorescence signal due to 5-ALA-GNPs clearance was higher than that of 5-ALA.
Administration of 5-ALA-GNPs, intensification of ROS generating and the subsequent elevation of photobleaching results in higher treatment efficiency. Also, more rapid clearance of PpIX has an important implication in clinical application of 5-ALA-GNPs that decreases the undesirable effects on healthy tissues.


Main Subjects

  1. Dolmans DE, Fukumura D, Jain RK. Photodynamic therapy for cancer. Nat Rev Cancer. 2003 May; 3(5):380-387.
  2. Marcus SL. Photodynamic therapy of human cancer. Proceedings of the IEEE. 1992; 80(6):869-89.
  3. Cai W, Gao T, Hong H, Sun J. Applications of gold nanoparticles in cancer nanotechnology. Nanotechnol Sci Appl. 2008;1(1):17-32.
  4. Bonnett R, Martı́nez G. Photobleaching of sensitisers used in photodynamic therapy. Tetrahedron. 2001; 57(47):9513-47.
  5. Ghahremani FH, Sazgarnia A, Bahreyni-Toosi MH, Rajabi O, Aledavood A. Efficacy of microwave hyperthermia and chemotherapy in the presence of gold nanoparticles: an in vitro study on osteosarcoma. Int J Hyperthermia. 2011; 27(6):625-36.
  6. Amelink A, van der Ploeg van den Heuvel A, de Wolf WJ, Robinson DJ, Sterenborg HJ. Monitoring PDT by means of superficial reflectance spectroscopy. J Photochem Photobiol B. 2005 Jun 1; 79(3):243-51.
  7. Atif M. , Stringer M.R. , Cruse-Sawyer J.E. ,  Dyer P.E., Brown S.B.  The influence of intracellular mTHPC concentration upon photobleaching dynamics. 2005. Photodiagnosis and Photodynamic Therapy, Volume 2, Issue 3, Pages 235-238.
  8. Imaging PpIX fluorescence photobleaching during ALA-PDT of basal cell carcinoma. 2003. Available from http://www.biop.dk/biophot03/Posters/poster_ven2003_kruijt.pdf. Accessed Oct 10, 2012.
  9. Haj-Hosseini N, Richtera J, Andersson-Engels S, Wårdell K. Photobleaching behavior of protoporphyrin IX during 5-aminolevulinic acid marked glioblastoma detection. Proc SPIE.2009; 7161(1).
  10. Oo MK, Yang X, Du H, Wang H. 5-aminolevulinic acid-conjugated gold nanoparticles for photodynamic therapy of cancer. Nanomedicine (Lond). 2008 Dec; 3(6):777-86.
  11. Naghavi N, Miranbaygi MH, Sazgarnia A. Simulation of fractionated and continuous irradiation in photodynamic therapy: study the differences between photobleaching and singlet oxygen dose deposition. Australas Phys Eng Sci Med. 2011 Jun; 34(2):203-11.
  12. Johansson A. Spectroscopic Techniques for Photodynamic Therapy Dosimetry: Lund University; 2007.
  13. Cottrell WJ, Paquette AD, Keymel KR, Foster TH, Oseroff AR. Irradiance-dependent photobleaching and pain in delta-aminolevulinic acid-photodynamic therapy of superficial basal cell carcinomas. Clin Cancer Res. 2008 Jul 15; 14(14):4475-83.



Volume 9, Issue 3 - Serial Number 3
September and October 2012
Pages 217-224
  • Receive Date: 03 April 2012
  • Revise Date: 23 January 2013
  • Accept Date: 11 July 2012
  • First Publish Date: 01 September 2012