Abstract
D.Tech. (Biomedical Technology)
Photodynamic therapy (PDT) is an alternative treatment modality for
malignant tumours based on the photodamage to tumour cells through a
photochemical reaction (Ahn et al., 2013). PDT utilizes a light sensitive
photosensitizer (PS) that selectively localizes in tumour cells and is excited
by light of a specific wavelength in the presence of molecular oxygen. The
excited PS leads to the generation of singlet oxygen or other reactive
oxygen species(ROS) which induces cytotoxic damage to cellular
organelles and eventually cell death. Singlet oxygen has a very short life
and its generation is controlled by the presence of the PS and the laser
light (Senge and Radomski, 2013).The subcellular localization site of the
PS plays a vital role in determining the effectiveness and the extent of
cellular damage as well as the mechanism involved in cell death.
Lung cancer is the leading cause of cancer death worldwide in both males
and females, with an estimated 1.4 million deaths each year (American
Cancer Society, 2011). Therapeutic modalities used in the treatment of
lung cancer such as chemotherapy, radiotherapy and immunotherapy
have rarely yielded a good prognosis and effective treatment remains a
challenging problem to date. An alternative treatment modality with
minimal complications such as PDT needs to be explored. Most in vitro
PDT experiments are conducted on monolayer cultures and the cellular
environment of these cultures does not correspond to that of in vivo
studies. Multicellular tumour spheroids (MCTSs) serves as an important
model in cancer research for the evaluation of therapeutic interventions
since they mimic different aspects of the human tumour tissue
environment.