# Photodynamic Inactivation of Bacteria in Boar Semen with Blue LED Light

## TL;DR

This study shows that blue LED light with a lower concentration of a chemical can safely kill bacteria in pig semen without harming the sperm.

## Contribution

The novel approach uses blue LED light and reduced chemical concentration to enable safer and more practical bacterial inactivation in pig semen.

## Key findings

- Blue LED light with 0.5 µM TMPyP effectively inactivates bacteria in boar semen.
- Lower chemical concentrations combined with blue light do not harm sperm cells.
- The method allows handling semen under normal lab lighting without unintended effects.

## Abstract

The photodynamic inactivation (PDI) of bacteria is a promising alternative to antibiotics in boar semen extenders. It was recently established using the illumination of semen samples containing 2 µM of the photosensitizer 5,10,15,20-tetrakis(N-methyl-4-pyridyl)-21H,23H-porphine (TMPyP) with white LED light. High concentrations of TMPyP require strict sample handling in the dark to avoid uncontrolled photodynamic effects caused by ambient light. This study was designed to examine whether lower concentrations of PS could be utilized along with a narrow band blue LED light source, which aligns with TMPyP’s Soret band, thereby minimizing light-induced disruption. A dose-response study with blue LED light exposure of sperm revealed no light toxicity. Importantly, substituting the established white light PDI with blue light illumination and 0.5 µM TMPyP resulted in robust antimicrobial efficiency and sperm compatibility in long-term stored semen samples. This modification led to the confirmation of the hypothesis that a diminished TMPyP concentration in concert with blue LED light facilitates semen handling in normal laboratory light while avoiding unintended light effects. In conclusion, this study plays a pivotal role in augmenting the practicality of the innovative PDI technology by establishing a method that is less susceptible to unanticipated effects of ambient light during sample management.