Staphylococcus aureus and Escherichia coli inactivation through mercaptophenylboronic acid-functionalized fluorinated porphyrin

Photodynamic inactivation (PDI) represents an effective strategy to combat resistant pathogens, emerging as a potential approach against Gram-positive and Gram-negative bacteria. Here, we report for the first time the synthesis, characterization, and photophysical properties of novel free-base fluorinated porphyrin tetra-substituted with 4-mercaptophenylboronic acid units (H 2 Por 1 ). The PDI of H 2 Por 1 was assessed against methicillin resistant Staphylococcus aureus (MRSA) and Escherichia coli using two photosensitizer (PS) concentrations (5.0 and 10.0 μM) under white light irradiation at 100 mW cm −2 , with exposure times of up to 60 min (total light dose of 360 J cm −2 ). For MRSA, H 2 Por 1 alone at 5–10 μM promoted bacterial inactivation in 45–60 min (270–360 J cm −2 ) of irradiation, highlighting the PS concentration and irradiation time dependence. When combined with KI, H 2 Por 1 exhibited pronounced synergistic effects, leading to a viability reduction >8 Log CFU/mL in MRSA in ≤5 min (30 J cm −2 ). For E. coli , H 2 Por 1 alone, even at 10 μM, did not inactivate the bacterium under the tested conditions. The addition of KI enabled effective inactivation of E. coli within ≤5 min of irradiation, demonstrating a strong combined effect between the PS and KI > 8 Log CFU/mL. These findings reinforce the potential of H 2 Por 1 as a versatile antimicrobial agent, particularly when combined with KI, for the photodynamic treatment of infections caused by Gram-positive and Gram-negative bacteria. The H 2 Por 1 effective performance even with low PS concentrations and low irradiation levels represents a significant advantage for future clinical applications in antimicrobial photodynamic therapy. • Photoinactivation (PDI) of S. aureus and E. coli bacteria using a porphyrin dye (H 2 Por 1 ). • H 2 Por 1 generates singlet oxygen under white light irradiation. • Potassium iodide (KI) enhances PDI efficiency, reducing time for bacterial inactivation. • H 2 Por 1 achieved a bacterial viability reduction >8 Log CFU/mL in ≤5 min.