Development of novel antibacterial drug delivery systems as wound scaffolds using electrospinning technology

Abstract

Tõusvate kulude ning aina keerulisemate ravijuhtude tõttu on halvasti paranevad kroonilised haavandid muutunud kaasaegses ühiskonnas väga suureks probleemiks. Haavadega kaasneb alati infektsioonioht, seetõttu näeb kaasaegne haavaravi ette, et taastatakse haava homeöstaas ning hoitakse kontrolli all bakterite arvukus. Kõige probleemsemaks osutuvad kaasuvate haigustega patsientidid (näiteks diabeedihaiged), kelle häirunud immuunvastus võib takistada ravi efektiivsust ning pikendada ravi kestvust. Infektsioosse haavandi raviskeemis on antibiootikumide manustamine väga olulisel kohal. Lokaalne antibakteriaalne haavaravi (kasutades enamlevinud traditsioonilisi ravimvorme) on väga levinud, kuid selle efektiivsus on siiani küsitav ravimi lühikese toimeaja ja pideva manustamise tõttu. Seetõttu on kaasaegne ravimvormide teadustöö keskendunud just kohaspetsiifiliste lokaalsete antibakteriaalsete ravimkandursüsteemide väljatöötamisele, mis omaksid veel täiendavat funktsionaalsust (haava paranemise toetamine). Elektrospinnimine (ES) on lihtne ja laialtlevinud meetod polümeersete fiibermaatriksite tootmiseks, millele iseloomulikeks omadusteks on: kontrollitav morfoloogia, suur eripind ning poorsus. Lisaks on maatriksitesse võimalik lihtsa vaevaga inkorporeerida erinevaid raviaineid, mis võimaldab neid kasutada ravimkandursüsteemidena. ES fiibermaatriksid sobivad ideaalselt haavakateteks: omades nahale omase rakuvälise maatriksiga sarnast struktuuri, mis annab neile hea haavaeksüdaadi absorbeerimise võime ning tagab gaasi – ja ainevahetuse haavas. Maatriksite mehaanilised omadused on muudetavad vastavalt vajadusele – lihtsustamaks kasutust ning tagamaks soodsat keskkonda rakkudele, mis vastutavad haavade paranemise eest. Antibakteriaalsete haavakatete väljatöötamisel on oluline uurida nende mõju bakterirakkudele. Haavakate peaks inhibeerima bakterite arvukuse tõusu haavas ning kaitsma haava kontaminatsiooni eest. Käesolevas töös valmistati ES teel antibakteriaalsete omadustega fiibermaatrikseid, mida saaks kasutada lokaalseks haavaraviks. Leiti, et poorseid fiibreid sisaldavate maatriksite valmistamiseks oli oluline sobivate lahustite ning keskkonnaparameetrite valik. Maisivalgul baseeruvate fiibermaatriksite valmistamiseks osutus sobivaimaks koaksiaalse ES ning abiainete kasutamine. Kasutatud lahustid ja abiained mõjutasid fiibermaatriksite morfoloogiat, struktuuri, mehhaanilisi omadusi ning raviaine vabanemise kiirust. Maatriksite ehitus mõjutas oluliselt elusrakkude (bakteri- ning eükarüootsete rakkude) käitumist maatriksitel. Leiti, et poorseid fiibreid sisaldav maatriks soodustas fibroblastide kinnitumist ning kasvu, ja omas ka kõige suuremat E. coli biokile vastast toimet. Maisivalgul baseeruvatel fiibermaatriksitel oli fibroblastide kasv ning kinnitumine väiksem võrreldes polükaprolaktooni sisaldava fiibermaatriksiga.

Wound treatment is a worldwide problem with annually increasing costs and insufficient treatment options. There is always contamination related to wounds which increases the risk for the development of infection. Therefore the main treatment strategy has been to restore the homeostasis at the wound site as well as control the bacterial load. The problem arises when the patient's medical condition (for example diabetes) inhibits the native immune response causing failed and long-lasting treatment. The administration of antibacterial drugs is a vital part of chronic wound and infection treatment strategy. Topical treatment with antibiotics (conventional drug formulations such as gels, creams) is frequently used but its efficiency is still uncertain. Therefore novel drug delivery research is focused on finding the site-specific drug delivery systems (DDS) with enhanced antibacterial properties. Electrospinning (ES) is a straightforward method for the production of polymeric fibers with specific features: controlled surface morphology, large specific surface area, tunable porosity and relatively simple incorporation of drugs giving them potential to be used as DDS. ES scaffolds have potential in wound healing due to having structure similar to the extracellular matrix, which offers superior absorption of the wound exudate as well as enhanced gas exchange properties. Furthermore, the scaffolds have suitable mechanical properties which can be designed to ease application and offer suitable surface for cell growth in charge of native wound healing. When developing antibacterial scaffold for wound infection treatment the bacterial/scaffold interactions have to be addressed. Ideally the scaffold should inhibit the bacterial growth at the wound site and protect the wound from further contamination. In the present thesis ES was used to prepare antibacterial fiber scaffolds for wound healing applications. It was seen that the combination of suitable solvent systems, and environmental parameters were vital in order to produce antibacterial drug containing polymer based fibers with surface porosity. The solvent systems had an effect on the morphology, structure, mechanical and drug release properties of the scaffolds. The structural differences also affected the behaviour of cells (bacterial and eukaryotic) on scaffolds . Fibers with surface porosity supported fibroblast attachment and growth as well as provided the best antibiofilm activity against E. coli. Another part of the thesis was to develop zein based antibacterial fiber scaffolds. Coaxial ES method together with plasticisers were used in order to develop zein-based core-shell structured scaffolds. The scaffolds were also characterised and differences were seen compared to the polycaprolactone-based scaffolds.