Photodynamic-based therapeutic modalities to fight against cancer - A review from synergistic viewpoint

Cancer has become one among the leading death causes in the world. To overcome this life frightening issue, therapeutic modalities such as chemotherapy, radiotherapy, surgery, immune therapy, photothermal therapy, and photodynamic therapy have been developed and employed to fight against cancer. However, none of the above mentioned therapeutic modalities alone has been found efficient enough to eradicate cancerous tumor completely and to control recurrence of the tumor. This insufficient efficiency of any therapeutic modality, in a solo manner, can be enhanced using a combination of different modalities. For instance, a synergistic approach involving a combination of photodynamic therapy with other therapeutic modalities has the potential to kill cancerous cells completely or prevent recurrence. Therefore, herein, we focused on the synergistic approach involving different therapeutic modalities such as photodynamic therapy, photothermal therapy, chemotherapy, radiotherapy and radiothermal therapy. A combination of two or more therapeutic modalities could help to overcome shortcomings that an individual therapy failed to demonstrate on its own, especially in hypoxia (a low oxygen condition in the tumor environment). This review also focuses on different photosensitizers and different photothermal agents such as porphyrin, human serum albumin -indocyanine green nanoparticles, graphene oxide, copper sulfide nanocrystals, phthalocyanine, silicon naphthalocyanin, gold nanoparticles, and multi-branched nano echinus that have been exploited for synergetic photothermal/photodynamic therapy. A part of the review also discussed a unique combination of photosensitizers, along with different drugs (such as doxorubicin, pentoxifylline, tirapazamine) and drug delivery carriers including PEGylated graphene oxide, double silica-shelled upconversion nanoparticles.