Formulation of pH responsive peptides as inhalable dry powders for pulmonary delivery of nucleic acids

Abstract

Nucleic acids have the potential to be used as therapies or vaccines for many different types of disease but delivery remains the most significant challenge to their clinical adoption. pH responsive peptides containing either histidine or derivatives of 2,3-diaminopropionic acid (Dap) can mediate effective DNA transfection in lung epithelial cells with the latter remaining effective even in the presence of lung surfactant containing bronchoalveolar fluid (BALF), making this class of peptides attractive candidates for delivering nucleic acids to lung tissues. To further assess the suitability of pH responsive peptides for pulmonary delivery by inhalation, dry powder formulations of pH responsive peptides and plasmid DNA, with mannitol as carrier, were produced by either spray drying (SD) or spray freeze drying (SFD). The properties of the two types of powders were characterised and compared using scanning electron microscopy (SEM), next generation impaction (NGI), gel retardation and in vitro transfection via a twin-stage impinger (TSI) following aerosolisation by a dry powder inhaler (Osmohaler™). Although the aerodynamic performance and transfection efficacy of both powders were good, the overall performance revealed SD powders to have a number of advantages over SFD powders and are the more effective formulation with potential for efficient nucleic acid delivery through inhalation.

Spray-Drying of Biopharmaceuticals

“…Another challenge for both spray-dried and spray-freeze-dried inhaled formulations is the high excipient content. For example, of the studies referenced above, several have stabilizer concentrations in excess of 95 % of the formulation [46,78,84]. Special attention must be paid to the pulmonary safety of the excipients.…”

“…Additionally, the spray-freeze-dried formulations had significantly better dispersibility of particles less than 3 μm (53 vs. 15 % for rhDNase and 20 vs. 11 % for anti-IgE antibody) [83]. Even with a tenfold difference in geometric particle diameters, spraydried (1-2 μm) and spray-freeze-dried (approximately 10 μm) DNA/peptide/mannitol particles had similar FPFs (about 50 %); however, the spray-dried particles had a significantly higher cell transfection efficiency [46]. Comparing the two methods, spray-freeze drying is more appropriate for temperature-sensitive biopharmaceuticals but is less easily scaled to the industrial level and is more expensive.…”

“…The most important difference in particle properties for spray-drying versus spray-freeze-drying is the size and porosity. Sprayfreeze-drying results in large, highly porous, fragile particles [46]. The temperature at which the droplets are dried can also change the morphology of the particles.…”

Incorporation of a Nuclear Localization Signal in pH Responsive LAH4-L1 Peptide Enhances Transfection and Nuclear Uptake of Plasmid DNA

“…22,23 Previously, our group and others have reported the use of LAH4-L1 peptide for DNA and siRNA delivery. [24][25][26][27][28] LAH4-L1 is a histidine-rich, cationic amphipathic peptide with pH responsive properties. At pH 7, the LAH4-L1 binds with and condenses DNA to form nano-sized complexes which enter cells through endocytosis.…”

Sharpening nature's tools for efficient tuberculosis control: A review of the potential role and development of host-directed therapies and strategies for targeted respiratory delivery

“…Spray drying and spray freeze drying have both been employed for the production of peptide-based pH responsive powders for the delivery of therapeutic nucleic acids to the lungs. Due to their pH responsive nature after phagocytosis they can escape the phagolysosomal maturation before degradation takes place and they release their payload [234]. Collapsed sphere microparticles with a diameter of 2.88 ± 0.8 µm and a MMAD of 1 µm containing the HDT rapamycin were examined by Gupta et al These particles were taken up by macrophages within 3 hours and were more effective in clearing intracellular mycobacteria compared to rapamycin in solution [96].…”