Condensational particle growth device for reliable cell exposure at the air–liquid interface to nanoparticles

Figures & data

Figure 1. (a) Schematic of condensational particle growth in DAVID. Four growth tubes each with one jet are shown in the schematic for simplicity, though there are eight tubes with four jets each. (b) Custom ALI cell culture, and (c) exposure dishes to interface in DAVID.

Figure 2. Schematic diagram of the testing setup used to assess the mass deposition of nanoparticles on membrane supports in DAVID by fluorescence. Uranine aerosol droplets are generated by a nebulizer, dried to nanoparticles, and deposited on membrane supports by condensational particle growth in DAVID.

Table 1. Count mean and median diameters of the droplets exiting the nebulizer (before dilution drier) and after condensational growth at operational flow rates of 4–8 LPM as measured by Aerodynamic Particle Sizer.

	Count mean diameter (µm)	Count median diameter (µm)	d50 (μm)
Nebulizer Droplet	4.09 ± 0.08	3.79 ± 0.08
4 LPM	6.34 ± 0.17	6.93 ± 0.13	1.80
6 LPM	5.43 ± 0.12	5.72 ± 0.11	1.47
8 LPM	5.00 ± 0.10	5.27 ± 0.09	1.27

The cutoff droplet diameter with 50% collection efficiency (d₅₀) was calculated based on Equation (3)(3) $$\eta =\frac{1}{1+{\left(\frac{d_{50}}{d_p}\right)}^2}$$(3) . Background particles present in room were used as the aerosol for condensational growth to determine the count mean diameter at full capacity.

Table 2. Test aerosol production settings for the Collison nebulizer and dilution dryer and the product properties (particle concentration, count mean and median particle diameters, geometric standard deviation [GSD], mass median diameter, and diameter of average mass).

	Flow rate (LPM)		Total concentration	Count diameter (nm)			Mass diameter (nm)
Condition	Collison nebulizer	Dilution dryer	#/cm^3	Mean	Median	GSD	Median diameter	Diameter average mass
Low	5	15	62,000	57.2	43.3	2.25	287	107
Medium	7	15	130,000	55.1	39.9	2.12	221	93.9
High	9	15	210,000	55.6	41.4	2.04	192	89.1

Figure 3. Mass deposition on membranes determined by fluorescence for operational flow rates in DAVID of (a) 4 LPM, (b) 6 LPM, and (c) 8 LPM at the three nanoparticle concentrations, and for the (d) low (e) medium, and (F) high particles concentrations for the three operational flow rates tested. In all of the graphs, the non-black markers are the mean of the four membranes in the experimental trial, and the black markers represent the mean of the replicate experimental trials with error bars representing the standard error. An example of deposition of the uranine droplets on the membranes in the exposure dish is overlaid in (d).

Table 3. The average coefficients of variation (CoV) of the replicate trials for the low (L), medium (M), and high (H) aerosol conditions and three operational flow rates at four exposure times.

Flow rate (LPM)	Time (m)	Aerosol condition
		L	M	H
4 LPM	5	0.357	0.180	0.112
	10	0.116	0.073	0.072
	15	0.121	0.153	0.069
	20	0.093	0.084	0.053
6 LPM	5	0.649	0.059	0.085
	10	0.310	0.066	0.052
	15	0.173	0.065	0.077
	20	0.093	0.084	0.053
8 LPM	5	N/A	0.085	0.221
	10	N/A	0.065	0.170
	15	N/A	0.078	0.074
	20	N/A	0.099	0.147

Figure 4. Count and mass particle size distributions of the fluorescent test aerosol from nebulizer under three flow conditions with constant 15 LPM dilution drying air. Flow rates for nebulization at low, medium, and high conditions were 5 LPM, 7 LPM, and 9 LPM, respectively. The different nebulizer flow rates produced aerosol concentrations of 62,000, 130,000, and 210,000 particles/cm³. Circular markers represent the count and other shapes represent the mass size distributions, respectively. Error bars represent standard deviation of eight SMPS scans.

Figure 5. Lactate dehydrogenase (LDH) viability assessment of cells exposed to clean HEPA filtered air at 4 and 6 LPM operational flow rates in DAVID and with no flow (control). Error bars represent the standard error for an n = 3.