Intracellular chemiluminescence activates targeted photodynamic destruction of leukaemic cells

Abstract

Photodynamic therapy (PDT) involves a two-stage process. A light-absorbing photosensitiser (Ps) is endocytosed and then stimulated by light, inducing transfer of energy to a cytoplasmic acceptor molecule and the generation of reactive oxygen species that initiate damage to cellular membrane components and cytolysis. The expanded use of PDT in the clinic is hindered by the lack of Ps targetcell specificity and the limited tissue penetration by external light radiation. This study demonstrates that bioconjugates composed of transferrin and haematoporphyrin (Tf -Hp), significantly improve the specificity and efficiency of PDT for erythroleukemic cells by a factor of almost seven-fold. Fluorescence microscopy showed that the conjugates accumulate in intracellular vesicles whereas free Hp was mostly membrane bound. Experiments with cells deliberately exposed to Tf -Hp at oLD 100 doses showed that surviving cells did not develop resistance to subsequent treatments with the conjugate. Furthermore, we show that the compound luminol induces intracellular chemiluminescence. This strategy was then used to obviate the use of external radiation for Ps activation by incubating the cells with luminol either before or together with Tf -Hp. This novel chemical means of PDT activation induced cytotoxicity in 95% of cells. These combined approaches provide an opportunity to develop broader and more effective applications of PDT.

Characterizing low fluence thresholds for in vitro photodynamic therapy

“…Although positive results have been seen in vivo [16], they will ultimately still be limited by the penetration depth of the near infrared light. Chemiluminescence utilizes chemical reactions to produce light and has been demonstrated to activate PDT in vitro [17]. However, finding chemicals that can be used in the in vivo setting still remains a significant challenge.…”

An insight on the role of photosensitizer nanocarriers for Photodynamic Therapy

“…Despite the aforementioned advantages, PDT possesses also some drawbacks: (i) the PS often used in the treatment are water-insoluble molecules, and consequently their injection into the body is not easy; (ii) patients who are treated with the available PS may get sensitive to light for a while, thus light exposure precautions must be taken after the treatment; (iii) lack of PS targetcell specificity; and (iv) limited light penetration in the tissues if the conventional light (600-700 nm) is used because it cannot penetrate deeper than 10 mm into the skin to reach the tumor site, thus limiting PDT to treat only superficial tumors such as skin cancer, nasopharyngeal cancer and oral cancer (Hu et al 2011, Huang et al 2013, Iranifam 2014, Laptev et al 2006, Theodossiou et al 2003. Nevertheless, PDT has been used to treat other types of cancer such as digestive tumors, prostate cancer and brain tumors (Agostinis et al 2011).…”

Specific Targeting to Murine Myeloma Cells of Cyt1Aa Toxin from Bacillus thuringiensis Subspecies israelensis

“…Most of the cytotoxic components currently used are designed to interfere with intracellular biochemical processes (7)(8)(9)(10). For instance, we recently demonstrated that delivery of the ribosome-inactivating protein Ricin-A efficiently destroys murine myeloma cells (11) and that targeted, chemiluminescent activation of the photodynamic process results in endomembrane destruction (12). The activity of these types of cytotoxic systems requires endocytosis, and this process often induces intracellular activation of resistance mechanisms (2).…”