Lectin-Rose Bengal Conjugates for Targeted Photodynamic Inactivation of Pathogenic Bacteria

Area of Science:

• Biochemistry
• Microbiology
• Materials Science

Background:

• Antibiotic resistance is a growing global health threat.
• Development of alternative antimicrobial strategies is crucial.
• Photodynamic inactivation (PDI) offers a promising approach.

Purpose of the Study:

• To design and evaluate novel photodynamic agents based on Rose Bengal (RB) conjugated to Pisum sativum agglutinin (PSA) and Laburnum anagyroides agglutinin (LABA).
• To assess the targeted photodynamic inactivation of Gram-positive and Gram-negative bacteria using these conjugates.
• To investigate the synergistic effects of a binary mixture of conjugates.

Main Methods:

• Conjugation of Rose Bengal (RB) to PSA and LABA lectins.
• Assessment of singlet oxygen quantum yields.
• Evaluation of antibacterial efficacy against Staphylococcus aureus (MSSA and MRSA), Escherichia coli, Pseudomonas aeruginosa, and Salmonella paratyphi B under white LED illumination.
• Uptake studies of conjugates in bacteria.

Main Results:

• Both PSA-RB and LABA-RB conjugates exhibited high singlet oxygen quantum yields.
• PSA-RB showed superior broad-spectrum bactericidal activity, while LABA-RB was effective against specific strains, particularly Gram-negative bacteria.
• A binary mixture of PSA-RB and LABA-RB demonstrated synergistic inactivation of MSSA and MRSA.
• Complete killing of E. coli and S. paratyphi B was achieved at lower RB concentrations with the mixture.
• Lectin-conjugated RB showed significantly enhanced bacterial uptake compared to free RB, with synergistic uptake for the mixture.

Conclusions:

• Lectin-based RB conjugates are effective antibacterial agents for photodynamic therapy.
• The dual-targeting strategy using a conjugate mixture enhances synergistic bacterial inactivation.
• These novel agents represent a promising alternative to conventional antibiotics for combating resistant bacterial infections.