Determination of light dose effect in LED-based photodynamic treatment as in vitro for colorectal cancer cells

Photodynamic therapy (PDT) is currently used as an alternative therapy for the control of malignant diseases.A photosensitizer (PS) called light-sensitive agent is a treatment procedure that reacts with oxygen after being stimulated with light at a certain wavelength, causing reactive oxygen species (ROS) in target tissues, leading to cell death. It is clinically approved by the American Food and Drug Administration (FDA). The light used in PDT comes from certain types of laser or light emitting diodes (LEDs). The type of light used depends on the type of cancer and where it is found in the body. PDT is usually done as an outpatient treatment (meaning you will not have to stay in the hospital), but it is sometimes combined with surgery, chemotherapy or other anti-cancer drugs or radiation therapy. In this study, 5-Aminolevulinic acid (5-ALA) was used as the photosensitive agent. 5-ALA incubation time, optimal 5-ALA concentration, LED energy density and wavelength parameters were investigated for the most appropriate 5-ALA-guided photodynamic therapy application on the HT-29 colon cancer cell line, which was found most frequently in the clinic. WI-38 normal lung cell line was used as a control. 5-ALA is a water soluble second generation photosensitizer. It shows maximum absorption in the wavelength range of 650-800 nm. The IX (PpIX) accumulation of protoporphyrin in 5-ALA in HT-29 colon cancer cells was measured and the incubation time that was found when the most PpIX accumulated in the cell was determined as 5 hours. The concentration-dependent effect of 5-ALA on HT-29 colon cancer cells was investigated and the concentration of 5-ALA to be used during therapy was optimized. The 5-ALA concentration is fixed at 0.5 mM and 1 mM. It was determined that these selected concentrations did not inhibit and proliferate cell viability alone. As a result of the optimization study, 5-hour 5-ALA incubation and 5 J/cm2 laser energy density were determined as the best result parameter. With these parameters, the main study was started and photodynamic therapy was applied with 3 different types of wavelengths (405, 635 and 405 + 635 nm) LEDs. As a result, 5-ALA-guided Photodynamic therapy has been shown to decrease to 17% at 405 nm, 35% at 635 nm and 15% at 405 + 635 nm, where two wavelengths are combined, within the specified parameters.