intranasal-delivery-mrna-polyplexes-via-rayleigh-breakup-aerosols-an

Intranasal Delivery of mRNA Polyplexes via Rayleigh Breakup Aerosols: An <em>In Vitro</em> Method for Nasal Deposition and Functional Testing

Intranasal delivery of mRNA therapeutics is a promising strategy for vaccination and treating respiratory diseases, offering direct immune activation at ...

King's College London

Two main challenges are associated with current spray-dried microparticles for inhalation, including the enhancement of aerosolization performance of microparticles and the creation of sustained drug release for continuous treatment on-site. For achieving these purposes, pullulan was explored as a novel excipient to prepare spray-dried inhalable microparticles (with salbutamol sulphate, SS, as a model drug), which were further modified by additives of leucine (Leu), ammonium bicarbonate (AB), ethanol and acetone. It was demonstrated that all pullulan-based spray-dried microparticles had improved flowability and enhanced aerosolization behavior, with the fine particle (<4.46 µm) fraction of 42.0-68.7% w/w, much higher than 11.4% w/w of lactose-SS. Moreover, all modified microparticles showed augmented emitted fractions of 88.0-96.9% w/w, over 86.5% w/w of pullulan-SS. The pullulan-Leu-SS and pullulan-(AB)-SS microparticles demonstrated further increased fine particle (<1.66 µm) doses of 54.7 µg and 53.3 µg respectively, surpassing that (49.6 µg) of pullulan-SS, suggesting an additionally increased drug deposition in the deep lungs. Furthermore, pullulan-based microparticles revealed sustained drug release profiles with elongated time (60mins) over the control (2mins). Clearly, pullulan has a great potential to construct dual functional microparticles for inhalation with improved pulmonary delivery efficiency and sustained drug release on-site.

Dual functional pullulan-based spray-dried microparticles for controlled pulmonary drug delivery.

The bioaerogel microparticles have been recently developed for respiratory drug delivery and attract fast increasing interests. These highly porous microparticles have ultralow density and hence possess much reduced aerodynamic diameter, which favour them with greatly enhanced dispersibility and improved aerosolisation behaviour. The adjustable particle geometric dimensions by varying preparation methods and controlling operation parameters make it possible to fabricate bioaerogel microparticles with accurate sizes for efficient delivery to the targeted regions of respiratory tract (i.e. intranasal and pulmonary). Additionally, the technical process can provide bioaerogel microparticles with the opportunities of accommodating polar, weak polar and non-polar drugs at sufficient amount to satisfy clinical needs, and the adsorbed drugs are primarily in the amorphous form that potentially can facilitate drug dissolution and improve bioavailability. Finally, the nature of biopolymers can further offer additional advantageous characteristics of improved mucoadhesion, sustained drug release and subsequently elongated time for continuous treatment on-site. These fascinating features strongly support bioaerogel microparticles to become a novel platform for effective delivery of a wide range of drugs to the targeted respiratory regions, with increased drug residence time on-site, sustained drug release, constant treatment for local and systemic diseases and anticipated better-quality of therapeutic effects.

Particulate bioaerogels for respiratory drug delivery.

Mucoadhesive microparticles for oromucosal drug delivery offer several advantages, including intimate contact with the mucosa, delivery to less accessible regions, extended residence time, sustained drug release, reduced irritation, and improved patient compliance. In this study, pullulan was used to prepare mucoadhesive spray-dried microparticles for delivering benzydamine hydrochloride (BZH) to oral mucosa. The BZH-pullulan spray-dried microparticles had a mean size of <25 μm with an angle of repose values between 25.8-36.6°. Pullulan markedly extended drug-release time to >180 min, ~9 times greater than the duration (i.e., 20 min) reportedly achieved by chitosan. Kinetic analysis showed the drug-release rate was concentration dependent and jointly controlled by drug diffusion and polymer chain relaxation. Further, pullulan was mucoadhesive and was able to retain up to 78.8% w/w of microencapsulated gold nanoparticle probes at the mucosal membrane. These data strongly suggest that BZH-pullulan microparticles have great potential for oromucosal drug delivery, by providing elongated residence time in situ and sustained drug release for the treatment of local diseases.

Pullulan-Based Spray-Dried Mucoadhesive Microparticles for Sustained Oromucosal Drug Delivery.

The nasal delivery of mRNA vaccines attracts great interests in both academia and industry. While the lipid nanoparticle (LNP)-mRNA complexes are vulnerable and need a subtle process for aerosolisation. In this study, a new nasal atomizer, based on the working rationale of Rayleigh breakup, was employed to aerosolise LNP-mRNAs. The data revealed no statistical differences in physiochemical properties before and after aerosolisation, strongly suggesting LNP-mRNAs be well preserved upon aerosolisation by Rayleigh breakup technology. Additionally, these Rayleigh breakup droplets showed a physical size of ∼25 µm in mean with a narrow size distribution (Span: 1.24) and demonstrated a large portion (70-80 % w/w) greater than 10 µm in aerodynamic diameter, strongly suggesting a predominate deposition in the upper airway and designating a great appropriateness for nasal drug delivery. Furthermore, the recently developed Alberta Idealized Nasal Inlet (AINI) was utilized to evaluate the regional nasal deposition of LNP-mRNA aerosols. It was demonstrated that, at the administration angle of 45°, the major deposition of mRNAs (>50 % w/w) was in the target region of turbinates. The inhalation airflow at 7.5 L/min can maximize the targeted delivery of mRNA (∼64 % w/w) and minimize the undesirable depositions in other segments. This study provides a new approach to aerosolise LNP-mRNAs with undisturbed stabilities for targeted nasal vaccine delivery.

Targeted nasal delivery of LNP-mRNAs aerosolised by Rayleigh breakup technology.

The delivery of lipid nanoparticle (LNP)-mRNAs to the lungs attracts fast increasing interests for vaccination, as the mucosal immunity in the airway can prevent the establishment of an infection rather than only reduce the level of infection associated with systemic immunity triggered via intramuscular injection. The vibrating mesh nebuliser was well utilized to atomize inhalation solutions/suspensions for pulmonary delivery hence employed in this study for aerosolising LNP-mRNAs. In comparison with pre-aerosolised LNP-mRNAs, the post-aerosolised vectors demonstrated a significant increase (t-test, unpaired, p < 0.05) in particle size (215-363 nm vs. 116-130 nm), polydispersity index (PDI: > 0.33 vs. < 0.27), zeta potential (ZP: 11-14 mV vs. 2.6-7.7 mV), and encapsulation efficiency (EE: ∼99 % w/w vs. ∼91 % w/w), indicating a structural alteration upon high-frequency mesh vibration (HFMV). The particle sizes of LNP-mRNAs were further enlarged upon inertial impaction, and the size increments were dependent on the velocities of airflow for impaction and the N/P ratios. The aerosolised mists were fine, with >54 % w/w deposited in lower respiratory tract and >28.5 % w/w further delivered to alveolar regions. Further, a model was created to elucidate the variations of physicochemical properties for LNP-mRNAs upon HFMV and inertial impaction, and it disclosed that the fluidity and shear-induced fusion of LNPs were the fundamental reasons to cause these unfavourable changes particularly the size enlargement. These insights reveal that the effective development of inhaled LNP-mRNAs will rely on shear-less devices, formulation optimizations, inhalable dry powders, and their potential combinations.

Pulmonary delivery of LNP-mRNAs aerosolised by vibrating mesh nebulizer: An emphasis on variations and in-depth analyses of physicochemical properties.

Article	Year
Dual functional pullulan-based spray-dried microparticles for controlled pulmonary drug delivery. International journal of pharmaceutics\| PubMed ID: 37207859	2023
Particulate bioaerogels for respiratory drug delivery. Journal of controlled release : official journal of the Controlled Release Society\| PubMed ID: 38641021	2024
Pullulan-Based Spray-Dried Mucoadhesive Microparticles for Sustained Oromucosal Drug Delivery. Pharmaceutics\| PubMed ID: 38675121	2024
Targeted nasal delivery of LNP-mRNAs aerosolised by Rayleigh breakup technology. International journal of pharmaceutics\| PubMed ID: 39933606	2025
Pulmonary delivery of LNP-mRNAs aerosolised by vibrating mesh nebulizer: An emphasis on variations and in-depth analyses of physicochemical properties. International journal of pharmaceutics\| PubMed ID: 40446870	2025

Hao-Ying Li

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