**2. Methods**

#### **2.1 Cell culture**

The HEp-2 cell line (human laryngeal carcinoma) and MCF7 cell line (human mammary carcinoma) were obtained from the Bank of Cells of Rio de Janeiro (BCRJ). Cells were cultured in 25 cm2 culture flask (Greiner), routinely maintained in Dulbecco's Modified Eagles Medium (DMEM) supplemented with 10% fetal bovine serum (FBS), 1% antibiotic-antimycotic (Gibco-Life-Technology), at 37°C, an atmosphere containing 5% CO2 (Forma Scientific CO2, MODEL 3110).

#### **2.2 Photosensitizer**

Aluminum phthalocyanine tetrasulfonate (AlPcS4-Frontier Scientific) at a 5 μM/mL concentration is diluted in phosphate-buffered saline (PBS).

Experimental groups HEp-2 cells were divided into four groups: control, a photosensitizer (cells incubated with AlPcS4), laser (irradiated cells only), and photodynamic therapy (PDT) (cells incubated with AlPcS4 and irradiated).
