Sunday, 21 April 2013 19:16

Novel antimicrobial wound dressing by encapsulation of bacteriocins in nanofibers

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Antibiotic resistance in bacterial pathogens is a major cause of concern for modern medicine, as this renders these “miracle drugs” ineffective. The accidental discovery of penicillin in 1928 by Alexander Fleming and the countless lives saved by this antibiotic in the 1940’s pioneered modern medicine. However, injudicious use of penicillin and various other antibiotics has caused a major problem in the treatment of “once easily treatable” bacterial infections. A marked increase in antibiotic-resistant pathogens has been reported over the last few decades, including the well-known methicillin-resistant Staphylococcus aureus (MRSA). The emergence of multi-drug resistant bacteria has amplified this problem. Antibiotic resistance is causing a regression back to a “pre-antibiotic era” where a minor scrape or cut can lead to a battle between life and death. Skin is our first line of defence against the onslaught of various pathogens causing infection; it plays a role in thermoregulation and maintaining of homeostasis in addition to having immunological, neurosensory and metabolic functions. Severe skin damage, however, exposes underlying tissue to microbial invasion which can easily progress into severe life threatening infections if not treated successfully.

Electrospun PEO:PDLLA nanofibers (generated in this study) versus human hair. Copyright T. Heunis 2013Scientists at the Department of Microbiology (University of Stellenbosch) have developed an antimicrobial wound dressing to treat bacterial skin infections caused by Gram-positive bacteria, such as S. aureus. S. aureus is a major pathogen implicated in superficial and invasive skin and soft-tissue infections and antibiotic-resistant strains are wreaking havoc in intensive care units, as well as in community settings. Bacteriocins (antimicrobial peptides) of lactic acid bacteria were incorporated into nanofibers to produce an antimicrobial nanofiber scaffold. Electrospun nanofibers have characteristics that make them suitable as wound dressings, i.e. high oxygen permeability, variable pore size, high surface area to volume ratio and nanofibers are morphologically similar to the extracellular matrix. Firstly, the feasibility of electrospinning bacteriocins into nanofibers was investigated by using plantaricin 423 as model peptide. Plantaricin 423 was successfully electrospun into poly(ethylene oxide) (PEO) nanofibers and this peptide retained antimicrobial activity, as determined against Lactobacillus sakei DSM 20017T and Enterococcus faecium HKLHS. Viable cells of L. plantarum 423 were also successfully electrospun into PEO nanofibers, albeit with a slight reduction in viability. A nanofiber delivery system was then developed for plantaricin 423 by using PEO and poly(D,L-lactide) (PDLLA). Different scaffolds were generated and evaluated in vitro to determine the most suitable potential wound dressing material for further in vivo trials.

Nisin A was successfully electrospun into PEO:PDLLA nanofibers and evaluated as wound dressing. Active nisin diffused from the nanofiber wound dressings for at least 4 days
in vitro, as shown with consecutive transfers onto plates seeded with MRSA strains. The nisin-containing nanofiber wound dressing significantly reduced the S. aureus numbers in experimental excisional wounds from 2.2 x 107 CFU/wound to 4.3 x 102 CFU/wound, as compared to control wounds (treated with nanofiber wound dressings without nisin). Furthermore, the wound dressings stimulated wound closure of excisional, non-infected wounds and no adverse effects could be observed by histological analysis. Nisin-containing nanofiber wound dressings thus have the potential to treat S. aureus-skin infections and potentially accelerate wound healing of excisional wounds.

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The above story is reprinted from materials provided by University of Stellenbosch.

Journal References:

  1. Heunis, T. D. J., M. Botes, and L. M. T. Dicks. "Encapsulation of Lactobacillus plantarum 423 and its bacteriocin in nanofibers." Probiotics and Antimicrobial Proteins 2, no. 1 (2010): 46-51.
  2. Heunis, Tiaan, Osama Bshena, Bert Klumperman, and Leon Dicks. "Release of bacteriocins from nanofibers prepared with combinations of poly (D, L-lactide)(PDLLA) and poly (ethylene oxide)(PEO)." International Journal of Molecular Sciences 12, no. 4 (2011): 2158-2173.
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