Deliver anti-biotic only when it’s needed – smart band aids

Bacteria like MRSA, Staphylococcus are becoming increasing anti-biotic resistance because of the misuse and over-exposure to the antibiotics.
In a study, a team of chemists from the University of Bath, UK, have taken steps to engineer a “smart” wound dressing system that releases an encapsulated antimicrobial agent only in the presence of pathogenic bacteria, allowing the body’s normal microflora to continue providing a natural defense against infection.

The prototype wound dressing is made of a non woven polypropylene fabric. Attached to the fabric are vesicles containing an antibacterial agent. One of the virulence factors of many pathogenic bacteria (but not non pathogenic bacteria) is that they secrete toxins or enzymes that damage vesicle membranes by lysing (bursting) them. When the pathogenic bacteria lyse the membranes of the vesicles attached to the smart fabric, the vesicles rupture, releasing the antibacterial agent and destroying the bacteria. In this way, the vesicle system can be thought of as a “Trojan horse,” inciting pathogenic bacteria to act as agents of their own destruction.

In their experiments, the researchers took samples of a viable bacterial population of two species (Staphylococcus aureus and Pseudomonas aeruginosa) every 20 minutes for four hours following exposure to the smart fabric. They observed significant decreases in the concentrations of both species, and eventually nearly complete inhibition. The researchers also found that concentrations of P. aeruginosa declined at a faster rate than S. aureus due to P. aeruginosa’s greater sensitivity to the encapsulated antimicrobial agent

Further, the researchers observed that, in uninfected samples that contained only non-pathogenic Escherichia coli, concentrations of the E. coli were only slightly reduced, which likely resulted from minor leakage of the vesicles. By ensuring that the antibacterial agent is released only in the presence of pathogenic bacteria, the strategy minimizes evolutionary pressure for the selection of antibiotic-resistant bacteria, prolonging the effectiveness of the antibacterial agent.

When toxins secreted from pathogenic bacteria lyse a vesicle containing an antibacterial agent, the agent destroys the bacteria. Image credit: Zhou, et al. ©2010 American Chemical Society.

These fluorescence images show vesicles containing an antibacterial agent in the presence of three bacteria species. The two pathogenic bacteria species (top two rows) lyse the vesicle membrane, causing it to lose its encapsulated dye, while nonpathological E. coli does not damage the vesicle membrane. Image credit: Zhou, et al. ©2010 American Chemical Society.

Between this discovery and the one where dressing itself can detect the presence of pathogens, these are a step in the right direction in the fight against these dangerous and killer bacteria. But the war goes on…

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