New antimicrobial surface treatment

Preventing bacterial colonization in artificial joints

The technology

Infections around artificial joints are uncommon, but they are the most serious complication following prosthetic implantation – and the mortality rate and the cost associated with single episodes is high.

These infections involve the formation of a bacterial biofilm – a matrix of bacterial cells and adhesive slime, which inhibits the penetration of antimicrobial agents, meaning the infection is both persistent and resistant to treatment.

The most widely proposed strategy for preventing biofilm formation is coating prostheses with anti-infective metals. Silver is the most prevalent metal used in biomedical applications, but the main obstacle preventing broader usage is the concern about cytotoxicity.

Researchers at the University of Birmingham have been investigating called defensins, which are immune cell derived antimicrobial peptides.

Defensins are known to stimulate antimicrobial activity through direct pathways (leading to cell lysis) and indirect pathways (stimulating the production of anti-inflammatory cytokines).

The researchers have developed a synthetic peptide with a similar structure biological defensins, and improved antimicrobial function. These synthetic peptides are known as defensomes.

The team has developed a novel method of modifying the surface at the material–tissue interface with an antimicrobial peptide (AMP) coating which allows cell attachment while inhibiting bacterial colonization.

This means that defensomes can be chemically attached to the surfaces of prostheses, to form an antimicrobial layer beneath the biofilm-protected bacteria.

In vivo studies have shown that defensomes strongly inhibit biofilm formation.