Development of dicyanomethylene-4H-pyran-based activatable fluorescent probes and photosensitizers

Cancer is used to express the abnormal growth of the cells and World Health Organization (WHO) reported that almost 16% of the worldwide deaths are caused by cancer. Chemotherapy and radiotherapy have surpassed surgery as the most effective cancer treatments. These treatments have proven effective in slowing tumour growth. Early detection of cancer is crucial in the development of new cancer treatments. Molecular biomarkers provide a molecular imaging pathway for early cancer detection. Several imaging agents are developed to image specific locations in living cells. In the first part of this thesis, a dicyanomethylene-4H-pyran (DCM) based fluorescent probe for the detection of Cu+ in cancer cell lines were developed. Activity-based theranostic photosensitizers (aPSs) are highly attractive in the scope of photodynamic therapy as they offer enhanced therapeutic outcome on cancer cells with a live cell imaging opportunity at the same time. In the second part of this study, we modified the long known fluorescent DCM core with a heavy iodine atom to get a PS that can be further converted to aPS after simple modifications. DCMO-I was tested in cell culture studies and proved to be a promising phototheranostic scaffold. Later, a cysteine (Cys) activatable PS based on the DCM core was developed, which exhibited remarkable 1O2 generation capacity and a turn-on fluorescence response after reacting with Cys. In the third part, sulfur was introduced into the DCM scaffold and singlet oxygen generation capacities along with photophysical properties of sulfur-DCM analogues were investigated.