Killing Bacteria by Faradaic Processes through Nano-Hydroxyapatite/MoO Platforms

Area of Science:

• Biomaterials Science
• Materials Chemistry
• Infectious Disease Research

Background:

• Bone regeneration aims to restore lost bone tissue, with bone grafts often enhanced by antibiotics and regenerative capabilities.
• Developing effective strategies against orthopedic infections is crucial, especially with increasing antibiotic resistance.
• Biocompatible materials with inherent antimicrobial properties are highly sought after for bone repair applications.

Purpose of the Study:

• To investigate the antimicrobial mechanism of biocompatible nano-hydroxyapatite/molybdenum oxide (nano-HA/MoO) platforms based on their electroactive behavior.
• To understand the electron transference capacity of nano-HA and nano-HA/MoO electrodes against pathogenic bacteria.
• To explore a drug-independent physical approach for combating local orthopedic infections.

Main Methods:

• Cyclic voltammetry and chronoamperometry were used to measure electron transference capacity.
• Electrodes made of nano-hydroxyapatite (nano-HA) and nano-HA/molybdenum oxide (nano-HA/MoO) were tested.
• Bacterial ultrastructure was analyzed using microscopy after material contact.

Main Results:

• Faradaic processes were confirmed, linked to MoO₄^2-/PO₄^3- group switching and OH vacancies in the nano-HA lattice.
• Direct contact with nano-HA/MoO materials disrupted the cytoplasmic membrane of *Pseudomonas aeruginosa* and *Staphylococcus aureus*.
• Eukaryotic cells showed no such disruptive effects, indicating material selectivity.
• Evidence supports an extracellular electron transfer (EET) mechanism that accelerates bacterial death.

Conclusions:

• Nano-HA/MoO platforms demonstrate a drug-independent biocidal mechanism based on EET.
• This physical approach targets bacterial cytoplasmic membrane function, leading to cell death.
• Phosphate ceramics exhibiting EET offer a promising strategy for treating orthopedic infections associated with implants.