Development of an antimicrobial wound dressing by co-electrospinning bacteriocins of lactic acid bacteria into polymeric nanofibers

Heunis, Tiaan de Jager (2012-12)

Thesis (PhD)--Stellenbosch University, 2012.

Thesis

ENGLISH ABSTRACT: Skin is the largest organ in the human body and serves as a barrier that protects the underlying tissue of the host from infection. Injury, however, destroys this protective barrier and provides a perfect opportunity for microorganisms to invade the host and cause infection, thereby affecting the normal wound healing processes. Furthermore, the ability of microbial pathogens to rapidly develop resistance towards a variety of antimicrobial compounds hampers the effective treatment and control of infections. Antimicrobial-resistant pathogens are increasingly being isolated from patients, placing a huge burden on the health care sector. The search for new and novel antimicrobial agents and treatments is thus of utmost importance and will continue to play an integral role in medical research. Antimicrobial peptides (AMPs) may serve as possible alternatives to antibiotics, or may be used in combination with antibiotics to reduce the risk of antimicrobial resistance. AMPs play a role in innate defence and are produced by a variety of mammals, plants, reptiles, amphibians, birds, fish and insects. The AMPs of bacteria (bacteriocins), especially those of lactic acid bacteria (LAB), are receiving increased attention as antimicrobial agents to treat bacterial infections. 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. The ability to incorporate of a variety of biologically active compounds into nanofibers increases their potential as wound dressings. A novel approach would be to incorporate bacteriocins from LAB into nanofiber scaffolds to generate antimicrobial wound dressings. In this study, the feasibility of co-electrospinning bacteriocins from LAB into nanofibers was investigated. Plantaricin 423, produced by Lactobacillus plantarum 423, was successfully co-electrospun into poly(ethylene oxide) (PEO) nanofibers. Plantaricin 423 retained activity after the electrospinning process and continued to inhibit the growth of Lactobacillus sakei DSM 20017T and Enterococcus faecium HKLHS. Viable cells of L. plantarum 423 were also successfully co-electrospun into PEO nanofibers, albeit with a slight reduction in viability. A nanofiber drug delivery system was developed for plantaricin 423 and bacteriocin ST4SA, produced by Enterococcus mundtii ST4SA, by blending PEO and poly(D,L-lactide) (PDLLA) in a suitable solvent before electrospinning. Nanofibers were produced that released the bacteriocins over an extended time period. The PEO:PDLLA (50:50) nanofiber scaffold retained its structure the best upon incubation at 37 °C and released active plantaricin 423 and bacteriocin ST4SA. Nisin A was also successfully co-electrospun into a PEO:PDLLA (50:50) nanofiber scaffold and nisin A, released from the nanofibers, inhibited the growth of Staphylococcus aureus in vitro. Nisin A-containing nanofiber scaffolds significantly reduced viable S. aureus cells in infected skin wounds and promoted wound healing in non-infected wounds. As far as we could determine we are the first to show that bacteriocin-eluting nanofiber scaffolds can be used to treat skin infections and influence wound healing.

AFRIKAANSE OPSOMMING: Vel is die grootse orgaan in die menslike liggaam en dien as buitelaag wat die gasheer se onderliggende weefsel teen infeksie beskerm. Beskadigde vel verloor egter hierdie beskermende eienskap en gee mikroörganismes die geleentheid om die liggaam binne te dring, infeksie te veroorsaak en die normale prosesse geassosieer met wondgenesing te beïnvloed. Die suksesvolle behandeling en beheer van infeksies word gedemp deur die vermoë van mikroörganismes om vinnig weerstand teen antimikrobiese middels te ontwikkel. Mikroörganismes met antimikrobiese weerstand word geredelik van pasiënte geïsoleer en dit plaas enorme druk op die gesondheidssektor. Die soeke na nuwe antimikrobiese middels en behandelings is dus van uiterste belang en sal altyd ‘n integrale rol in geneeskunde navorsing speel. Antimikrobiese peptiede (AMPe) kan moontlik as alternatief tot antibiotika dien, of kan in kombinasie daarmee gebruik word om die ontwikkeling van antimikrobiese- weerstandbiedenheid te verhoed. AMPe speel ‘n rol in ingebore beskerming en word deur soogdiere, plante, reptiele, voëls, visse en insekte geproduseer. AMPe van bakterieë (bakteriosiene), veral die van melksuurbakterieë (MSB), wek toenemende belangstelling as antimikrobiese middels vir die behandeling van bakteriële infeksies. Nanovesels, wat deur middel van ‘n elektrospin proses geproduseer word, het eienskappe wat hul aanloklik maak as wondbedekking, naamlik hoë suurstof deurlaatbaarheid, verskeie porie grottes, ‘n hoë oppervlakte tot volume verhouding, sowel as ‘n morfologiese struktuur wat die ekstrasellulêre matriks naboots. Die vermoë om ‘n verskeidenheid biologies aktiewe komponente in nanovesels te inkorporeer verhoog hul potensiaal as wondbedekkingsmateriaal. ‘n Unieke benadering is die inkorporasie van bakteriosiene van MSB in nanovesels om ‘n antimikrobiese wondbedekking te ontwikkel. In hierdie studie is die vermoë om bakteriosiene van MSB in nanovesels te inkorporeer, deur middel van ‘n mede-elektrospin proses, ondersoek. Plantarisien 423, geproduseer deur Lactobacillus plantarum 423, was suksesvol deur die mede-elektrospin proses in poliëtileen oksied (PEO) nanovesels geinkorporeer. Plantarisien 423 het na die elektrospin proses steeds sy antimikrobiese aktiwiteit behou en het die groei van Lactobacillus sakei DSM 20017T en Enterococcus faecium HKLHS geïnhibeer. Lewende selle van L. plantarum 423 was ook suksesvol deur die mede-elektrospin proses in PEO nanovesels geinkorporeer, alhoewel die lewensvatbaarheid van die selle effens afgeneem het. ‘n Nanovesel matriks is ontwikkel om die vrystelling van plantarisien 423 en bakteriosien ST4SA, geproduseer deur Enterococcus mundtii ST4SA, te beheer deur PEO en poli(D,L-melksuur) (PDLMS) in ‘n geskikte oplosmiddel te vermeng voor die elektrospin proses. Nanovesels is geproduseer wat die bakteriosiene oor ‘n verlengde tydperk kon vrystel. ‘n PEO:PDLMS (50:50) nanovesel matriks het sy stuktuur die beste behou tydens inkubasie by 37 °C en het aktiewe plantarisien 423 en bakteriosien ST4SA vrygestel. Nisien A was met dieselfde tegniek in PEO:PDLMS (50:50) geinkorporeer en nisien A, wat deur die nanovesels vrygestel was, het die groei van Staphylococcus aureus in vitro geïnhibeer. Die nisien A-bevattende nanovesel matriks het die aantal lewende selle van S. aureus noemenswaardig verminder in geïnfekteerde wonde en kon die genesing van wonde, wat nie geïnfekteer was, stimuleer. Sover ons kon vastel is hierdie die eerste gepubliseerde navorsing wat toon dat bakteriosiene, geinkorporeer in nanovesels, gebruik kan word om vel infeksies te beheer en wondgenesing te stimuleer.

Please refer to this item in SUNScholar by using the following persistent URL: http://hdl.handle.net/10019.1/71616
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