Improved in-vivo airway gene transfer via magnetic-guidance, with protocol development informed by synchrotron imaging

Abstract

Gene vectors to treat cystic fibrosis lung disease should be targeted to the conducting airways, as peripheral lung transduction does not offer therapeutic benefit. Viral transduction efficiency is directly related to the vector residence time. However, delivered fluids such as gene vectors naturally spread to the alveoli during inspiration, and therapeutic particles of any form are rapidly cleared via mucociliary transit. Extending gene vector residence time within the conducting airways is important, but hard to achieve. Gene vector conjugated magnetic particles that can be guided to the conducting airway surfaces could improve regional targeting. Due to the challenges of in-vivo visualisation, the behaviour of such small magnetic particles on the airway surface in the presence of an applied magnetic field is poorly understood. The aim of this study was to use synchrotron imaging to visualise the in-vivo motion of a range of magnetic particles in the trachea of anaesthetised rats to examine the dynamics and patterns of individual and bulk particle behaviour in-vivo. We also then assessed whether lentiviral-magnetic particle delivery in the presence of a magnetic field increases transduction efficiency in the rat trachea. Synchrotron X-ray imaging revealed the behaviour of magnetic particles in stationary and moving magnetic fields, both in-vitro and in-vivo. Particles could not easily be dragged along the live airway surface with the magnet, but during delivery deposition was focussed within the field of view where the magnetic field was the strongest. Transduction efficiency was also improved six-fold when the lentiviral-magnetic particles were delivered in the presence of a magnetic field. Together these results show that lentiviral-magnetic particles and magnetic fields may be a valuable approach for improving gene vector targeting and increasing transduction levels in the conducting airways in-vivo.

Ultra-fast in vivo directional dark-field x-ray imaging for visualising magnetic control of particles for airway gene delivery

“…The ability to visualise the magnetic nanoparticles via their dark-field signal shows a significant advantage over the phase contrast imaging used by Donnelley et al (2022). The delivery image sequence shows that the magnetic particles are unexpectedly agglomerating or settling within the delivery tube for some reason, with the final 10% of the delivery period containing a substantially greater number of magnetic nanoparticles.…”

“…Their motion within pulsatile blood vessel fluid can be modelled (Heidsieck et al 2012), but the non-stop, complex motion of the reversing air (breathing) and liquid (mucociliary clearance (Gardner et al 2020)) environment within the airway surface extends the challenges further. Simply visualising the magnetic nanoparticles to develop control mechanisms is difficult, however Donnelley et al (2022) have had some success using high-resolution x-ray imaging. That study utilised propagation-based phase-contrast effects to enhance image contrast, and showed that strings of magnetic nanoparticles formed in the airways of rats when a static external magnetic field was applied, similar to the strings that iron filings form under the influence of magnet fields.…”