(T1430-04-19) Characterization of Aerosolized Droplets Using a 3D Printed Device for Small Animal Nose-to-Brain Drug Administration

Purpose: Diseases of the central nervous system are challenging to treat because most drugs fail to bypass the blood brain barrier (BBB). Intranasal delivery is a promising drug delivery strategy with the potential to bypass the BBB through nose-to-brain (N2B) transport along perivascular and perineuronal pathways. The particle size of the aerosolized mist is a prime important factor in reaching the olfactory region for N2B delivery, as particles greater than 10 µm are likely to be trapped by mucus. The purpose of this study was to evaluate the effects of aerosolizer design and delivery variables on aerosol droplet size, including the effect of PBS solution and 100 nm PLGA-PEG nanoparticle dispersion. We hypothesize that aerosolizer design factors (fig 1) and solution properties will have a significant effect on the particle size of the aerosolized mist as evaluated using optical microscopy. We will be able to select the most suitable design parameters for intranasal delivery of drug-loaded nanoparticles in future animal studies.

Methods: A polylactide polymer-based 3D-printed aerosolizer was modified from the original design by Piazza et al. (2014). The aerosolizer nozzle was small enough to fit the nasal cavity of a rat, with an air compressor connected to tubing for forced pressure delivery of the drug, and a rudimentary controller box which was used to regulate actuation air pressure and duration (fig 1). Aerosolizer design was modified to study the effect of nozzle length, drug loading reservoir size, solution type, distance from the nozzle orifice, and actuation pressure on the mean particle diameter. Microscope slides were coated with a thin layer of paraffin oil and white petrolatum (1.5:1). The slide was mounted a fixed distance from the aerosolizer nozzle tip, and the aerosolizer was loaded with 20 µL of either, a) 0.01% Tween 80 PBS solution or b) nanoparticle dispersion containing 100 nm PLGA-PEG nanoparticles in saline. The solution/dispersion was aerosolized onto the coated surface of the slide to produce a 2-D plume of droplets. The slide was placed onto a Leica DMi1 inverted microscope for viewing at 5x magnification, and images were taken at 0, 2, 6, 10, and 14 mm away from the center of the slide in either direction to capture variation in particle size across the diameter of the radially symmetrical plume. Images were uploaded into ImageJ, binarized, and analyzed using the “Particle Analysis” function to return droplet areas. Average droplet size and standard deviation was calculated for each image using MATLAB. A one or two-way ANOVA followed by Tukey’s test, or a t-test, was performed to determine whether variables significantly affected mean particle size.

Results: The mean particle size differed significantly between aerosolizer designs using both 0.01% Tween 80 PBS (f(3, 118492) = 232.56, p < 0.001) and PLGA-PEG nanoparticle dispersions (f(3, 153955) = 74.41, p < 0.001). A one mm increase in nozzle tip length caused mean droplet diameter to increase by 0.34 µm in PBS (p < 0.001) and 0.17 µm in nanoparticle dispersion (p = 0.004). Removing the reservoir in the rear of the aerosolizer led to decreases in mean particle diameter of 0.39 µm in PBS (p < 0.001) and 0.78 µm in nanoparticle dispersion (p < 0.001). A two-way ANOVA revealed that solution/dispersion type (f(1, 272447) = 157.23, p < 0.001) also affects mean droplet diameter in addition to aerosolizer design (f(3, 272447) = 72.19, p < 0.001), with a statistically significant interaction between the two factors (f(3, 272447) = 209.78, p < 0.001). An analysis of extrinsic factors revealed that actuation air pressure and distance from the point of actuation also affect mean particle diameter. A one-way ANOVA detected statistically significant differences between delivery pressures of 14, 17, and 20 psi (f(2, 133602) = 85.31, p < 0.001). Average particle size increased by 0.13 µm when the pressure was increased from 14 to 17 psi (p = 0.004) before decreasing by 0.49 µm at 20 psi (p < 0.001). A two-tailed, unpaired student’s t-test assuming unequal variances found a significant decrease of particle size of 0.44 µm when distance from the point of actuation was increased from 11.0 to 27.7 mm.

Conclusion: We evaluated the effects of solution/dispersion properties of PBS or 100 nm nanoparticles and aerosolizer design factors on the average particle size of aerosolized mist. We observed that 100 nm nanoparticles produced a significantly different mean particle size compared to PBS containing Tween 80. It was also evidenced that shorter nozzle length, absence of a reservoir, and higher air pressure produced smaller particle sizes. The smallest mean droplet diameter (5.25 µm) was obtained with 1.5 mm inner diameter, 6 mm nozzle length, straight nozzle, 20 psi air pressure and no reservoir using 20 µL of nanoparticle dispersion at a distance of 27.7 mm. For further studies, we plan to use this aerosolizer in N2B delivery of drug-loaded nanoparticles.

References: [1] Piazza et al., “Haloperidol-loaded intranasally administered lectin functionalized poly(ethylene glycol)–block-poly(d,l)-lactic-co-glycolic acid (PEG–PLGA) nanoparticles for the treatment of schizophrenia,” European Journal of Pharmaceutics and Biopharmaceutics, vol. 87, no. 1, pp. 30–39, May 2014, doi: 10.1016/j.ejpb.2014.02.007.

Acknowledgements: HB acknowledges the financial support from the Life Health Sciences Institute at IUPUI to pursue this research.


Representative aerosolizer with the nozzle diameter, length, and transition type indicated, as well as the absence of a reservoir.


Effects of aerosolizer design and extrinsic delivery properties on mean particle diameter


Effects of delivery solution on mean particle diameter