Formulation of probiotics and bacteriophages for respiratory delivery

Abstract

This thesis explores biological agents that confers benefits in maintaining lung health and investigates the feasibility of localised delivery to the lungs to maximise efficacy and minimise systemic adverse events. Probiotics and bacteriophages (phages) are increasingly gaining interest in their antibacterial properties to combat the rising antimicrobial resistance. The nature of phage production involves pathogenic bacteria lysis, which in the process produces bacterial debris including endotoxins. Additionally, current purification methods use organic solvents, caesium chloride or chloroform, which may not be completely removed. Hence, an effective purification method with low endotoxin levels and high phage titre without the use of the beforementioned chemicals was developed. To utilise the health-benefiting properties of probiotics and to ensure therapeutic efficiency, probiotics have been nebulised for the first time. The viability of L. rhamnosus GG (LGG) was more superior with the vibrating mesh nebuliser compared to the jet nebuliser. Also, LGG suspended in PBS had a reasonable nebulisation time, which is critical for patient compliance. A higher viability and a more superior aerosol performance compared to 0.9% NaCl was also noted. Finally, a novel approach of combining two different biological materials, probiotics and phage was adopted to test for synergy, for formulation into an inhalable power and tested for stability over 3 months at 25 °C. The synergistic effects and the viability of probiotics after spray drying and during storage were species-dependent. Stability of both probiotics and PEV1 were dependent on the sugar:leucine ratio and the type of sugar. Higher sugar content protected both probiotics and phages during the spray drying process and during storage, with lactose conferring a higher protective effect than trehalose. Spray drying and storage did not affect the antibacterial activity of L. reuteri and L. salivarius combined with PEV1.