Nanoparticle-based antibiotic delivery for targeting intracellular bacteria

Intracellular bacterial infections, such as Burkholderia spp, are notoriously difficult to treat, in part due to poor membrane permeability and intracellular bioavailability of antibiotics. Current treatment options involve high doses of antibiotics for sustained periods of time, therefore contributing to the issues of antibiotic resistance, and potentially causing off-target effects in the patient. In the absence of novel antibiotic compounds, intracellular targeting polymersome (PM)- encapsulated antibiotics may increase the efficacy of existing antibiotics by promoting targeted, infection-specific intracellular uptake in otherwise poorly bioavailable antibiotics. In this study it was hypothesised that PMs composed of widely available polyethylene oxide-polycaprolactone (PEO-PCL) block co-polymers could stably encapsulate antibiotics and release them intracellularly to reduce macrophage infection. PMs were generated via the nanoprecipitation method. Antibiotics doxycycline and rifampicin were retained stably for 14 days within PMs under dialysis. PM-antibiotic preparations did not inhibit the growth of free-living B. thailandensis, highlighting their ability to sequester their payloads until at the target intracellular niche. On uptake by murine macrophages, PMs co-localised with intracellular B. thailandensis and significantly reduced bacterial burden (by factors of 100 and 10 for doxycycline and rifampicin-loaded preparations respectively). It was concluded that PMs present a viable approach for the targeted treatment of persistent intracellular B. thailandensis infection

Dataset supporting the University of Southampton Doctoral Thesis "Label Free Imaging for Drug Delivery Across Biophysical Barriers".

Data underpinning thesis chapters 5 and 6 Chapter 5 data contains MATLAB Raman spectroscopic data of NISV samples Chapter 6 contains CARS cellular images of NISVs</span

Antibiotic-loaded polymersomes for clearance of intracellular burkholderia thailandensis

Melioidosis caused by the facultative intracellular pathogen Burkholderia pseudomallei is difficult to treat due to poor intracellular bioavailability of antibiotics and antibiotic resistance. In the absence of novel compounds, polymersome (PM) encapsulation may increase the efficacy of existing antibiotics and reduce antibiotic resistance by promoting targeted, infection-specific intracellular uptake. In this study, we developed PMs composed of widely available poly(ethylene oxide)-polycaprolactone block copolymers and demonstrated their delivery to intracellular B. thailandensis infection using multispectral imaging flow cytometry (IFC) and coherent anti-Stokes Raman scattering microscopy. Antibiotics were tightly sequestered in PMs and did not inhibit the growth of free-living B. thailandensis. However, on uptake of antibiotic-loaded PMs by infected macrophages, IFC demonstrated PM colocalization with intracellular B. thailandensis and a significant inhibition of their growth. We conclude that PMs are a viable approach for the targeted antibiotic treatment of persistent intracellular Burkholderia infection.</p