Abstract
Doxorubicin is a broad-spectrum antibiotic and anticancer drug used to treat a variety of human malignancies like
breast cancer and leukaemia. Unfortunately, a dose-dependent side effect of this drug is common, representing a major
obstacle to its use despite its therapeutic efficacy. Photodynamic therapy is an emerging non-invasive potential adjuvant
for conventional cancer treatment. In an attempt to circumvent the dose-limiting effect of doxorubicin, this study aimed
to investigate cellular anticancer activity of doxorubicin and sulfonated zinc phthalocyanine–mediated photodynamic
therapy on MCF-7 cells alone and in combination. Furthermore, we investigated the cell death pathway resulting from
the combination treatment. MCF-7 cells were incubated with 0.5 μM concentration of doxorubicin for 20 h, afterwards,
various concentrations of sulfonated zinc phthalocyanine were added and incubated for 4 h. Cells were irradiated using
a 681.5 nm diode laser at 4.53 mW/cm2 for 18 min 24 s (5 J/cm2). Cell viability and proliferation were measured using
trypan blue assay and homogeneous adenosine triphosphate quantitation assay, respectively, while qualitative changes
in cellular morphology were observed under inverted light microscopy. Cellular DNA damage was assessed under
fluorescent microscopy and Annexin V/propidium iodide stain was used to investigate the cell death pathway. Findings
from this study shown that combined treatment with doxorubicin and photodynamic therapy was more effective in
inhibiting the proliferation and growth of MCF-7 cells. Overall, the results indicate that combination of smaller dose of
doxorubicin with photodynamic therapy is a promising combined treatment strategy for breast carcinoma. However,
this combination warrants further investigation.