Visualization and quantitative analysis of nanoparticles in the respiratory tract by transmission electron microscopy

Table 2 Synthetic data set in which nanoparticles are non-randomly distributed in different pulmonary tissue compartments. The hypothetical data were generated to provide an example of particles mainly taken up by macrophages or retained inside the lumen of the alveolar ducts/alveoli.

Compartment	N _O	P	N_E	RDI	X²	Fraction of total X² [%]
Conductive airway (lumen)	5	150	61.86	0.08	52.26	2.76
Alveolus (lumen)	527	1125	463.94	1.14	8.57	0.45
Macrophages	50	3	1.24	48.76	1781.45	94.22
Epithelial cell	12	38	15.67	0.77	0.86	0.05
Interstitium	13	34	14.02	0.93	0.07	0.004
Endothelial cell	12	38	15.67	0.77	0.86	0.05
Residual	0	113	46.6	0	46.6	2.46
Total	619	1501	619	1	1890.67	100

Note. With 6 degrees of freedom (7-1 compartments × 2-1 groups) and a total chi-squared value 1890.67 the null-hypothesis of random particle distribution has to be rejected with p < 0.001. The alveolar macrophages are the only compartment that fulfils the criteria for preferential particle localization: RDI > 1 and the partial chi-squared contributes substantially (more than 10%) to the non-randomness of the distribution, i.e. the total chi-squared [34, 103]. However, although the nanoparticles are preferentially located in the macrophages it is interesting to note that they deposit mainly in the alveolar region and are not found in the lumen of the blood vessels which are contained in the compartment residual. Abbreviations: N_O = Number of observed particles; N_E = Number of expected particles; P = Number of observed points; RDI = Relative deposition index; X² = Chi squared values.

ISSN: 1743-8977