AbstractWhile the advent of antibiotics has proved to be one of the most important medical triumphs of the 20th century, antimicrobial resistance is threatening the return of a pre-antibiotic era. Wound pathogens can exhibit antibiotic resistance; significantly increasing patient morbidity and the associated financial costs of treatment and prevention of nosocomial outbreaks. Accordingly, attention is now focused towards alternative approaches to infection control. Bacteriophage therapy, well-established in Eastern Europe and the former Soviet Union (FSU), is increasingly being considered as one option. Lytic bacteriophage are viruses that infect and kill bacteria through cell lysis, releasing virion progeny to continue the bacteriolytic process.
The objective of this study was to produce and characterise virulent bacteriophage-integrated and immobilised wound dressings which demonstrate lytic activity against clinically relevant bacteria in vitro. Through judicious material design; the material structure, and bacteriophage stability, infectivity and release characteristics were characterised and modified to achieve enhanced antibacterial efficacy. Bacteriophage distribution, orientation and integrity were determined using a range of direct and indirect, techniques. Finally, the developed bacteriophage-integrated biomaterials were evaluated for cytotoxicity in preliminary studies to determine suitability for the proposed application.
The candidate wound dressing materials developed for bacteriophage integration were built upon the base material, plasticised agarose (PLAg), to which two novel modifications were made dependant on the approach to bacteriophage integration. Surface charge modification of PLAg was achieved by application of a highly charged cationic polymer, poly(vinyl amine) (PVAm), to produce a cationic interface (PVAm-PLAg) for bacteriophage adsorption. Results presented in this thesis reveal the preferential immobilisation and increased infectivity of bacteriophage adsorbed to the surface of PVAm-PLAg films when compared to unmodified PLAg. The modification of surface charge, determined by surface zeta potential measurements and elemental analysis, suggests orientated attachment of the negatively charged bacteriophage capsid to PVAm-PLAg, leaving the infective machinery available to initiate bacterial infection. Synthesis of a composite material, comprised of PVAm modified PLAg and an alginate hydrogel (Alg-PVAm-PLAg), allowed integration of bacteriophage within the porous matrix of the alginate hydrogel, protecting viral particles from harsh external conditions and demonstrating a further increase in antimicrobial efficacy.
As reports of bacteriophage efficacy in in vitro and in vivo studies amass, delivery of bacteriophage to the target site will be of utmost importance. This study demonstrates the successful integration of bacteriophage with two novel wound dressing materials; PVAm-PLAg and Alg-PVAm-PLAg. Extensive comparative characterisation of PLAg and PVAm-PLAg films allowed a compilation of physical and chemical profiles of the developed materials, also suggesting no cytotoxic effects of the base material.
|Date of Award||Nov 2019|
|Supervisor||Iain Allan (Supervisor), Cressida Bowyer (Supervisor), Stephen Denyer (Supervisor) & Irina Savina (Supervisor)|