The development of new biopharmaceutical therapeutics including proteins, peptides, vaccines, antibodies and nucleic acids is steadily increasing presenting new opportunities for the treatment and prevention of disease. However, it is challenging to effectively deliver these biomacromolecules and the oral route has the disadvantage of the harsh stomach environment that results in degradation. By comparison, the pulmonary route offers several advantages for both local and systemic delivery such as; a large surface area, a thin epithelium, dense vasculature, less enzymatic activity and is non-invasive. Various polymers have been investigated for the particulate delivery of macromolecules providing increased stability, sustained release and the potential for targeted delivery; the most common being Poly lactic-co-glycolic acid (PLGA). Nanoparticles (NPs) have shown potential for the delivery of macromolecules to tissues and cells but are too small to be deposited in the lung via inhalation. They can be incorporated into nanocomposite microcarriers (NCMC) for dry powder inhalation (DPI).
As an alternative to PLGA we have utilised poly(glycerol adipate-co-ω-pentadecalactone), PGA-co-PDL, to prepare NPs followed by spray drying to produce NCMPssuitable for dry powder inhalation. The properties of both NPs and NCMPs were optimized for different applications using Taguchi’s design of experiment and loaded with, for example; proteolytic enzymes, pneumococcal vaccine and miRNA.
NPs were prepared using an oil-in-water single emulsion solvent evaporation method followed by adsorption of the biomacromolecule from solution or the biomacromolecules were directly encapsulated using a double oil-in-water-in-oil method. NPs were characterised in terms of size, charge and drug loading and then spray-dried in an aqueous suspension of L-leucine (1:1.5) using a Büchi-290 mini-spray dryer. The resultant NCMPs were characterised for toxicity, aerosolization, in vitro release study, stability and activity.
Typically, NPs with adsorbed protein were of between 120 and 150nm in size and with encapsulated protein were around 200- 220nm; both suitable for targeting lung cells. Typically,10-20μg of a model protein (BSA) was adsorbed per mg of NPs and 40μg/mg was encapsulated, dependant on the conditions used. Spray-drying with L-leucine resulted in a 50% yield of NCMPs with a fine particle fraction (FPF%) dae<4.46 μm of around 75% and a mass median aerodynamic diameter (MMAD) of 1 -3μm suggesting deposition will be in the broncho-alveolar region of the lung. Cell viability was typically between 70-85% (A549 cell line) at 1.25 mg/ml concentration after 24 h treatment. SDS-PAGE and CD confirmed the primary and secondary structure of the released BSA was mainly conserved.
For the pneumococcal surface protein A (PspA) study, the activity of the PspA vaccine was confirmed using the lactoferrin binding assay. Similarly, internalization of mi-146A loaded cationic NPs to treat COPD was observed in adenocarcinomic human alveolar basal epithelial and alveoli cell lines using confocal microscopy. The miR146a delivered had a dose dependent effect on target gene repression (IRAK1). These examples demonstrate the potential of PGA-co-PDL NPs as a pulmonary delivery system for vaccination and to treat lung disease.
Takeaway Notes During this talk the following information will be provided.
• The synthesis, modification and application of a new polymer, PGA-co-PDL for drug delivery
• A technique for the encapsulation or adsorption of biomacromolecules onto polymeric NPs
• A technique for the incorporation of the NPs into a microcarrier for pulmonary delivery
• Examples of applications of this delivery system
• This NCMP drug delivery system can potentially be utilized for the delivery of a variety of biomacromolecules and small drug molecules via DPI either to the lung or potentially via the nasal route. We are happy to collaborate on such projects using this technology for alternative applications.