Z39 - Muco-Penetrative Nanoparticle Platform for Tobramycin Delivery in Cystic Fibrosis Lung Infection

Saturday, October 11, 2025

10:00 AM - 11:00 AM PDT

Location: Exhibit Hall F, G & H

Presenting Author(s)

Calista Adler, BA/BE

Undergraduate
Dartmouth College, United States

Co-Author(s)

AW

Alexandra Will

Undergraduate Researcher
Dartmouth College, United States
NN

Neva Nemanic

Undergraduate Researcher
Dartmouth College, United States

Primary Investigator(s)

Katherine Hixon

Principle Investigator
Dartmouth College, Thayer School of Engineering
Hanover, New Hampshire, United States

Introduction: : Cystic fibrosis (CF) is a genetic disorder caused by mutations in the CF transmembrane conductance regulator (CFTR) gene, leading to inflammation, airway obstruction, and chronic lung infections. The most common pathogens, Pseudomonas aeruginosa (P. aeruginosa) and Staphylococcus aureus (S. aureus), specifically contribute to lung inflammation and impaired immune response [1]. In healthy lungs, chloride ions hydrate mucus; however, in CF, CFTR mutations impair chloride transport, leading to dehydrated, highly viscous mucus with lower pH, reduced pore size, and hyper-concentrated salts [2]. The current primary treatment approach for CF is antibiotic therapy tailored to the specific bacterial culture. However, a major challenge in delivering these antibiotics is mucus viscosity which hinders diffusion, making it difficult for drugs to reach all infection areas. As a result, there is an urgent need to develop new drug delivery methods to facilitate dispersal throughout the mucus. Polymeric nanoparticles offer a promising platform to improve drug delivery and ultimately allow for sustained drug release, biodegradability, biocompatibility, and improved therapeutic efficacy. Tobramycin (TOB) is an antibiotic that is commonly used to treat P. aeruginosa through long-term inhalable CF therapy [3]. Mannitol is a sugar alcohol that acts as a diuretic and has been proven to facilitate the hydration of mucus, thereby increasing mucociliary clearance [4]. We hypothesize that sodium alginate (SA) nanoparticles that i) contain TOB and ii) are coated in mannitol will enable tailorable, localized drug delivery to decrease mucus viscosity, increase mucociliary clearance, and improve drug diffusion to mitigate lung infection in CF patients.

Materials and

Methods: : SA nanoparticles were fabricated via emulsion polymerization, a scalable method, using a water-based 1% SA solution with 180 mg of hypromellose (HPMC) stabilizer and varying concentrations of TOB (50, 100, 150, 200, 250, and 300 µg/mL). This solution was then added to an iso-octane oil-based phase containing 5% Span80 surfactant, and where the immiscible phases were stirred at high speed to induce nanoparticle formation. Next, 10 mL each of 10% Tween80 surfactant, 0.7 M calcium chloride solution, and100% ethanol were sequentially added to stabilize and separate the particles from the oil phase. The resulting mixture was centrifuged, air-dried, resuspended in 5% mannitol, flash-frozen in liquid nitrogen, and lyophilized to yield mannitol-coated TOB-loaded SA nanoparticles. Scanning electron microscopy (SEM) was used to quantify particle size and morphology at 12, 20, and 30kx. To quantify particle degradation and controlled release, 5 mg of Rhodamine B was pre-added to the SA solutions and absorbance measured (554 nm) over 12 days. Preliminary bacterial clearance testing of free TOB on P. aeruginosa was performed to confirm antibiotic efficacy, based on measured optical density. Ongoing work is focused on filtering the nanoparticles (0.45 and 5 µm) to test specific varying size ranges and a TOB ELISA to measure nanoparticles encapsulation efficiency. A mucus viscosity study is also being used to evaluate the efficacy of mannitol in hydrating regions surrounding the nanoparticles. Finally, an aerosolization assay using a cascade impactor will visualize particle dispersal through air into collection cups, which directly quantify particle distribution for CF lungs.

Results, Conclusions, and Discussions:: This study demonstrates that mannitol-coated sodium alginate nanoparticles encapsulating TOB represent a promising strategy for overcoming the drug delivery barriers posed by the hyperviscous mucus environment in CF. The 1% SA nanoparticles containing TOB without mannitol were successfully formed through emulsion polymerization (Figure 1). Particle sizes quantified by SEM ranged from 31 nm to 1.4 µm with no statistically significant difference in size with increasing concentrations of TOB (p>0.05; Figure 2). Preliminary bacterial clearance testing of free TOB showed that during a 16-hour period, all concentrations of TOB (50–300 µg/mL) except for 100 µg/mL showed no bacterial growth, demonstrated by a low optical density of 0.086. Notably, 100 µg/mL of TOB showed a gradual increase in turbidity over time, mimicking the same increase as the P. aeruginosa bacterial control which reached an optical density of 0.376. This suggests that there was likely an error in the amount of TOB added considering that both 50 and 150 µg/mL TOB samples demonstrated high bacterial clearance. Notably, the addition of 5% mannitol resulted in the formation of crystalline structures engulfing the SA nanoparticles (Figure 3). This observation suggests that a lower concentration of mannitol must be necessary to achieve a thin, uniform coating of the SA particles. Importantly, once administered, these mannitol coatings are expected to interact with the mucus, hydrating and dissolving upon contact. This would leave behind uncoated nanoparticles capable of degrading and releasing the encapsulated drug at the target site. To enhance clinical relevance, additional analyses are being conducted to evaluate size-specific delivery efficiency, drug encapsulation, and the role of mannitol in mucus hydration. These studies aim to optimize diffusion, release kinetics, and aerosol performance for pulmonary application. These results demonstrate that emulsion-based fabrication can effectively produce nanoparticles suitable for targeted drug delivery. This platform has the potential to improve antibiotic retention in the lungs, enhance mucociliary clearance, facilitate mucus penetration, and ultimately reduce the burden of chronic infection in CF patients. As a less-invasive therapeutic strategy, this approach complements ongoing efforts to develop controlled drug delivery systems for CF.

Acknowledgements and/or References (Optional): : [1] Souche, A., et al. “How Staphylococcus aureus and Pseudomonas aeruginosa Hijack the Host Immune Response in the Context of Cystic Fibrosis.” International Journal of Molecular Sciences, vol. 24, no. 7, 2023, p. 6609. PMC, doi:10.3390/ijms24076609.

[2] Anjum, Md Meraj, et al. “Overcoming Barriers in Cystic Fibrosis Therapy through Inhalational Lipid Nanoparticles: Challenges and Advances.” Journal of Drug Delivery Science and Technology, vol. 89, 2023, 105068. ScienceDirect, doi:10.1016/j.jddst.2023.105068.

[3] Shteinberg, M., and Elborn, J. S. “Use of Inhaled Tobramycin in Cystic Fibrosis.” Advances in Therapy, vol. 32, no. 1, 2015, pp. 1–9. doi:10.1007/s12325-015-0179-3.

[4] Nevitt, Sarah J., et al. "Inhaled Mannitol for Cystic Fibrosis." Cochrane Database of Systematic Reviews, vol. 5, 2020, article CD008649. PMC, doi:10.1002/14651858.CD008649.pub4.