Modern agricultural and food industries rely on chemical protection technologies such as bactericides, fungicides, and insecticides to maintain high productivity. Without these treatments, global agricultural output could decrease by approximately 45%, leading to food shortages. [1] However, excessive chemical use poses environmental and health risks, prompting efforts to develop eco-friendly alternatives. One promising approach is antimicrobial photodynamic inactivation (API), which utilizes light and photosensitizers (PS) to selectively inactivate pathogens while minimizing ecological harm.
This study investigates the development and application of an LED-based irradiation prototype for API experiments, designed to enable controlled photodynamic studies on PS solutions, microbial cultures, and PS-treated samples. The prototype was developed during a professional internship at the Institute of Photonics and Nanotechnology, Vilnius University. [2] The project aimed to design a reliable prototype for API research. The initial prototype was equipped with near-UV (402 nm), blue (440 nm), and white LEDs, where near-UV corresponds to the first absorption maximum (Soret band) of magnesium (Mg-Chl) and copper (Cu-Chl) chlorophyllins.
During this project, the prototype was optimized by replacing white LEDs with red LEDs (650 nm) to match the absorption maximum (Q band) of Mg-Chl and Cu-Chl. Additionally, heat dissipation improvements were implemented to enhance system stability. Furthermore, an STM32 microcontroller was programmed to allow precise control of LED intensity, and calibration procedures were refined to ensure accurate and reproducible light exposure.
Challenges encountered during development included thermal damage during LED replacement and compatibility issues with the control software, which were successfully resolved through hardware modifications and software adjustments. The optimized prototype was used to investigate the photophysical properties of Mg-Chl and Cu-Chl under near-UV (402 nm) (Soret band) and red (650 nm) (Q band) light. The experiments helped evaluate the dependence of both photosensitizers’ excitation efficiency on sample positioning and applied irradiation intensity, which, in turn, could contribute to enhancing API effectiveness. Additional details on the project and preliminary results will be presented during the poster session.
Keywords: antimicrobial photodynamic inactivation, photosensitizer, chlorophyllin, irradiation prototype, LED calibration, microcontroller programming.