Biguanide Iridium(III) Complexes with Potent Antimicrobial Activity.

Area of Science:

• Organometallic Chemistry
• Antimicrobial Drug Discovery
• Medicinal Chemistry

Background:

• Biguanides, like metformin, are known for their therapeutic properties.
• Development of novel antimicrobial agents is crucial to combat rising drug resistance.
• Organometallic complexes offer unique mechanisms for drug delivery and action.

Purpose of the Study:

• To synthesize and characterize novel organoiridium(III) antimicrobial complexes.
• To evaluate the antimicrobial and antifungal potency of these complexes.
• To assess the selectivity, stability, and resistance potential of the new compounds.

Main Methods:

• Synthesis of organoiridium(III) complexes featuring chelated biguanides.
• Characterization using NMR, ESI-MS, elemental analysis, and X-ray crystallography.
• Evaluation of antimicrobial activity against Gram-negative and Gram-positive bacteria, including MRSA, and fungi (C. albicans, C. neoformans).
• Cytotoxicity assays on mammalian cells.
• Biofilm eradication assays.
• Studies on coadministration with vancomycin against VRE.
• Investigation of reactions with biomolecules.

Main Results:

• Novel 16- and 18-electron organoiridium(III) complexes were successfully synthesized and characterized.
• Several complexes demonstrated potent activity against a broad spectrum of bacteria and fungi, with minimum inhibitory concentrations (MICs) in the nanomolar range.
• High selectivity was observed, with low cytotoxicity toward mammalian cells.
• The complexes exhibited excellent stability in broth medium and a low tendency to induce resistance mutations.
• Co-administration restored vancomycin activity against vancomycin-resistant Enterococci (VRE).
• The complexes effectively disrupted and eradicated mature bacterial biofilms.
• Evidence suggests these complexes deliver active biguanides into microorganisms, which are otherwise inactive alone.

Conclusions:

• Novel organoiridium(III) biguanide complexes represent a promising new class of antimicrobial agents.
• These compounds exhibit potent, selective, and stable antimicrobial activity, addressing key challenges in drug resistance.
• Their ability to restore antibiotic efficacy and eradicate biofilms highlights their therapeutic potential.
• The mechanism involves targeted delivery of active biguanides, offering a novel approach to antimicrobial therapy.