Stability of antibacterial self-assembled monolayers on hydroxyapatite

Area of Science:

• Biomaterials Science
• Nanotechnology
• Orthopedic Surgery

Background:

• Open fractures are prone to infection, necessitating advanced bone graft substitutes.
• Hydroxyapatite (HA) is a common bone graft material but lacks inherent antibacterial properties.
• Bacterial infections pose a significant challenge in treating open fractures.

Purpose of the Study:

• To incorporate antibacterial properties into HA using silver (Ag)-carrying self-assembled monolayers (SAMs).
• To evaluate the stability of these Ag-carrying SAMs on HA under various sterilization and physiological conditions.

Main Methods:

• Deposition of phosphonic acid SAMs (shorter and longer chains) onto HA.
• Chemical attachment of silver (Ag) to create antibacterial SAMs (ASAMs).
• Characterization using X-ray photoelectron spectroscopy, atomic force microscopy, and contact angle goniometry.
• Assessment of bacterial adhesion (Staphylococcus aureus) and stability under different conditions (sterilization, physiological).

Main Results:

• ASAMs significantly reduced Staphylococcus aureus adhesion on HA.
• Most ASAMs degraded under gas plasma, dry heat, and autoclave sterilization.
• UV and ethylene oxide treatments showed variable effects on shorter and longer chain ASAMs.
• Significant desorption of ASAMs from HA occurred under physiological conditions, with longer chains showing better stability.

Conclusions:

• ASAMs show potential for imparting antibacterial properties to HA bone grafts.
• There is a critical need to improve the stability of SAMs on HA for effective clinical application.
• Further research is required to develop robust methods for stabilizing these antibacterial coatings.